Samacheer Kalvi Class 11 Bio Botany Solutions Chapter 10 Secondary Growth

Part -I

I. Consider The Following Statements.

 

Question 1. In spring vascular cambium (i) is less active (ii) Produces a large number of xylary elements (iii) forms vessels with wide cavities of these, which option is correct?
(a) (i) is correct but (ii) and (iii) are not correct
(b) (i) is not correct but (ii) and (iii) are correct
(c) (i) and (ii) are correct but (iii) is not correct
(d) (i) and (ii) are not correct but (iii) is correct
Answer: (b) (i) is not correct but (ii) and (iii) are correct
In simple words: During spring, the vascular cambium is very active. It makes many xylem parts and broad vessels. So, statement (i) is wrong, but (ii) and (iii) are right.

🎯 Exam Tip: Remember that springwood (earlywood) has wider vessels due to active cambium, while autumnwood (latewood) has narrower vessels due to less active cambium.

 

Question 2. Usually, the monocotyledons do not increase their girth, because
(a) They possess actively dividing cambium
(b) They do not possess actively dividing cambium
(c) Ceases activity of cambium
(d) All are correct
Answer: (b) They do not possess actively dividing cambium
In simple words: Monocot plants usually do not grow wider because they do not have a cambium that keeps dividing and making new cells. This cambium is responsible for secondary growth, which adds girth.

🎯 Exam Tip: The presence of an active vascular cambium is essential for secondary growth, which leads to an increase in the girth of a plant.

 

Question 3. In the diagram of lenticel identify the parts marked as A, B, C, D

(a) A. phellem, B. Complementary tissue, C. Phelloderm, D. Phellogen.
(b) A. Complementary tissue, B.Phellem, C. Phellogen,
(c) A. Phellogen, B.Phellem, C. Phelloderm, D. Complementary tissue
(d) A. Phelloderm, B. Phellem, C. Complementary tissue, D. Phellogen
Answer: (a) A. phellem, B. Complementary tissue, C. Phelloderm, D. Phellogen.
In simple words: The diagram shows the parts of a lenticel: A is the phellem (outer cork), B is the loose complementary tissue, D is the phellogen (cork cambium), and C is the phelloderm (inner cortex). These parts work together for gas exchange.

🎯 Exam Tip: Pay attention to the relative positions and functions of phellem, phellogen, and phelloderm, which together form the periderm.

 

Question 4. The common bottle cork is a product of
(a) Dermatogen
(b) Phellogen
(c) Xylem
(d) Vascular cambium
Answer: (b) Phellogen
In simple words: The regular cork you see, like in a bottle stopper, comes from a part of the plant called phellogen. Phellogen is also known as the cork cambium.

🎯 Exam Tip: Remember that phellogen is the meristematic tissue responsible for producing both phellem (cork) and phelloderm, which contribute to the bark of a plant.

 

Question 5. What is the fate of primary xylem in a dicot root showing extensive secondary growth?
(a) It is retained in the center of the axis
(b) It gets crushed
(c) May or may not get crushed
(d) It gets surrounded by primary phloem
Answer: (b) It gets crushed
In simple words: In dicot roots that grow a lot, the old primary xylem in the middle gets pushed and squeezed. This happens because new secondary tissues are constantly being made.

🎯 Exam Tip: During secondary growth, the primary tissues are often pushed outwards or crushed due to the accumulation of new secondary vascular tissues.

 

Question 6. If a plant is damaged by the horn of a deer, How will the plant overcome the damage?
Answer: When the bark of a plant is hurt, the phellogen (cork cambium) makes a full cylinder around the stem. This then forms new bark rings to cover the damaged area. This helps to protect the plant from further harm. It is a natural healing process for trees.
In simple words: When a plant's bark is hurt, the phellogen creates new protective bark to seal the wound and heal itself.

🎯 Exam Tip: Plants have remarkable healing mechanisms; the phellogen plays a crucial role in forming a protective periderm to repair wounds and prevent infections.

 

Question 7. In which season the vessels of angiosperms are larger in size, why?
Answer: In the spring season, the vessels of angiosperms are larger in size. This happens because the cambium cells are very active during spring. This high activity leads to the production of wider xylem vessels, which are needed for more water transport in actively growing plants. These larger vessels allow for efficient water flow when the plant needs it most.
In simple words: Angiosperms have bigger vessels in spring because the cambium is very active then, making wider tubes for lots of water to flow.

🎯 Exam Tip: Connect vessel size directly to cambial activity; active cambium in spring produces wider vessels, forming earlywood or springwood.

 

Question 8. Continuous state of dividing tissue is called meristem. In connection to this, what is the role is lateral meristem?
Answer: A meristem is a special tissue in plants where cells constantly divide and grow. The lateral meristems are important because they cause secondary growth in dicots and gymnosperms. These meristems are responsible for the plant getting thicker. They help the plant increase its girth or width.
There are two main lateral meristems involved:
1. Vascular cambium
2. Cork cambium

1. Vascular cambium:
The vascular cambium is a type of lateral meristem that creates new secondary vascular tissues. These include secondary xylem (wood) and secondary phloem (bark). It is a vital tissue for radial growth.

Origin and Formation of Vascular Cambium:
• A strip of vascular cambium comes from the procambium and is found between the xylem and phloem in a vascular bundle. This strip of cambium is called intrafascicular cambium.
• Also, in between the vascular bundles, certain parenchyma cells of the medullary rays become meristematic. They join the intrafascicular cambium to form a complete ring. This new part is called interfascicular cambium.
This unified ring then actively produces secondary tissues.

A. Organization of Vascular cambium:
• The active vascular cambium has cells with a large central vacuole and a thin layer of dense cytoplasm around it.
• The most important feature of the vascular cambium is that it has two types of starting cells: fusiform initials and ray initials.

Fusiform Initials:
• These cells are long and vertically stretched. They produce the longitudinal system of the secondary xylem (like tracheary elements, fibres, and axial parenchyma) and phloem (sieve elements, fibres, and axial parenchyma). These cells are crucial for the vertical transport and support of the plant.
• Based on how the fusiform initials are arranged, there are two types of vascular cambium:

Storied (Stratified cambium) and Non-storied (Non-stratified cambium)
• If the fusiform initials are arranged in horizontal rows, where the ends of cells in one row appear at about the same level (seen in tangential longitudinal section, TLS), it is called storied (stratified) cambium. This is typical for plants with short fusiform initials.
• In plants with long fusiform initials, they overlap strongly at their ends. This type of cambium is called non-storied (non-stratified) cambium.

Ray Initials:
These are smaller, squarish cells that produce the ray cells. These ray cells form the elements of the radial system of secondary xylem and phloem. They help in lateral transport and storage.

Activity of Vascular Cambium:
• When the vascular cambial ring is active, it produces new cells both inwards and outwards. The cells formed outwards become secondary phloem, and those formed inwards become secondary xylem.
• Because secondary xylem and phloem are constantly forming due to vascular cambial activity, the original primary xylem and phloem get slowly crushed.

B. Phellogen (Cork Cambium)
• This is another lateral meristem that produces secondary tissues. It has homogeneous cells, which are different from vascular cambium cells. It can develop from the epidermis, cortex, pholem, or pericycle (outside the vascular cylinder). Its cells divide around the edge to form rows of cells.
• The cells formed towards the outside become phellem (cork), and those formed towards the inside become phelloderm (secondary cortex). Both layers are vital for protecting the plant.

In simple words: Meristem is dividing tissue. Lateral meristems make plants grow thicker. These are vascular cambium (makes wood and bark) and cork cambium (makes cork). They are crucial for a plant's girth.

🎯 Exam Tip: For detailed questions, always break down the answer into sub-sections with clear headings to ensure all aspects are addressed systematically.

 

Question 9. A timer merchant bought 2 logs of wood from, a forest & named them A & B, The log A was 50 year old & B was 20 years old. Which log of wood will last longer for the merchant? Why?
Answer: Log A will last longer for the merchant. Here's why:
• Older wood is generally stronger and more durable. Log A, being 50 years old, is much older than Log B, which is 20 years old.
• In a tree, the central part of the wood gets darker and is known as heartwood (or duramen). This part is dead and does not conduct water. The outer, lighter wood is sapwood, which is living and conducts water. Heartwood is much stronger and more resistant to damage. As trees get older, they develop more heartwood.
• The conduction of water in the central heartwood is blocked by structures called tyloses, which come from nearby parenchyma cells. These tyloses, along with starch crystals, resins, gums, oils, tannins, and colored substances, make the heartwood very hard and durable. This makes it resistant to attacks from microbes and insects like termites.
• Since Log A is older, it has more heartwood than Log B. This increased amount of hard heartwood makes Log A stronger and means it will last longer.
In simple words: Log A will last longer because it is 50 years old and older wood is stronger. Older trees have more hard, protective heartwood which resists damage from insects and decay.

🎯 Exam Tip: When comparing wood properties, always consider the age of the wood and the proportion of heartwood (duramen) to sapwood (alburnum) as heartwood is significantly more durable.

 

Question 10. A transverse section of the trunk of a tree shows concentric rings which are known as growth rings. How are these rings formed? What are the significance of these rings?
Answer: Concentric rings seen in a tree trunk are called growth rings, or annual rings, because they usually represent one year of growth. They are formed due to seasonal changes in the activity of the vascular cambium.
Growth (or) Annual Rings:
1. During the spring season, the cambium is very active. It produces a large number of xylary elements (xylem cells). These elements are called earlywood or springwood. In the winter season, the cambium is less active and forms fewer xylary elements. These are known as latewood or autumn wood.
2. Springwood is lighter in color and has a lower density. Autumn wood, on the other hand, is darker and has a higher density. An annual ring combines one earlywood and one latewood. This combination becomes visible to our eyes due to the high density difference between the two wood types. Sometimes, annual rings are simply called growth rings.

Additional growth rings can form within a single year due to bad natural conditions. These conditions include drought, frost, defoliation (losing leaves), flood, physical injury, or attacks by living organisms. Such extra rings are called pseudo- or false-annual rings.

4. Dendrochronology:
Each annual ring shows one year's growth. By counting these rings, the age of a particular plant can be easily calculated. This method of finding a tree's age by counting its annual rings is called dendrochronology. It helps scientists understand past climates and environmental conditions.
In simple words: Growth rings show one year of tree growth, formed by the cambium's activity in spring (wide, light wood) and winter (narrow, dark wood). Counting these rings tells us a tree's age, a study called dendrochronology.

🎯 Exam Tip: To score full marks, explain both the formation process (earlywood/latewood) and the significance (age determination, environmental history) of growth rings, mentioning dendrochronology.

Part - II.

11th Bio Botany Guide Secondary Growth Additional Important Questions And Answers

I. Choose The Correct Answer.

 

Question 1. The roots and stems grow in length with the help of:
(a) cambium
(b) secondary growth
(c) apical meristem
(d) vascular parenchyma
Answer: (c) apical meristem
In simple words: The tips of roots and stems have special growth areas called apical meristems. These parts are responsible for making the plant grow longer.

🎯 Exam Tip: Distinguish between apical meristem (responsible for primary growth, i.e., increase in length) and lateral meristem (responsible for secondary growth, i.e., increase in girth).

 

Question 2. The Gymnosperm in which vessel is present
a) Pinus
b) Cycas
c) Ginkgo
d) Gnetum
Answer: (d) Gnetum
In simple words: Gnetum is a unique type of gymnosperm that has vessels in its wood. Most gymnosperms do not have true vessels, making Gnetum an exception.

🎯 Exam Tip: Remember Gnetum as the only gymnosperm genus that possesses true vessels, a characteristic typically found in angiosperms.

 

Question 3. The secondary vascular tissues include:
(a) secondary xylem and secondary phloem
(b) secondary xylem, cambium strip and secondary phloem
(c) secondary phloem and fascicular cambium
(d) secondary xylem and primary phloem
Answer: (a) secondary xylem and secondary phloem
In simple words: Secondary vascular tissues are the new xylem and phloem cells made during a plant's secondary growth. They make the plant grow thicker.

🎯 Exam Tip: Secondary vascular tissues are produced by the vascular cambium, with secondary xylem growing inwards and secondary phloem growing outwards.

 

Question 4. In a dicotyledonous stem, the sequence of tissues from the outside to the inside of
a) Phellem, Pericycle, Endodermis, phloem
b) Phellem phloem, Endodermis, Pericycle
c) Phellem, Endodermis, Pericycle, phloem
d) Pericycle, Phellem, Endodermis, Phloem
Answer: (c) Phellem, Endodermis, Pericycle, Phloem
In simple words: If you look at a dicot stem from the outside, you would first see the phellem, then the endodermis, followed by the pericycle, and finally the phloem. This order shows how the tissues are layered in the stem.

🎯 Exam Tip: Visualizing the cross-section of a dicot stem helps in recalling the correct sequence of tissues from the periphery to the center, especially in relation to secondary growth structures.

 

Question 5. For a critical study of secondary growth in plants which one of the following pairs is suitable?
a) Eucalyptus and sunflower
b) Teak and pine
c) Bamboo and Fem
d) Wheat and Fem
Answer: (b) Teak and pine
In simple words: To study how plants grow thicker (secondary growth), teak (a dicot) and pine (a gymnosperm) are good examples. They both show clear secondary growth, unlike monocots or ferns.

🎯 Exam Tip: Select plant types that exhibit prominent secondary growth, such as dicots and gymnosperms, for effective study of this process.

 

Question 6. The axial system of the secondary xylem includes:
(a) treachery elements, sieve elements, fibers and axial parenchyma
(b) treachery elements, fibers and axial parenchyma
(c) treachery elements and fibers
(d) sieve elements and axial parenchyma
Answer: (b) treachery elements, fibers and axial parenchyma
In simple words: The secondary xylem's axial system mainly consists of tracheary elements (for water transport), fibers (for support), and axial parenchyma cells (for storage and transport). These components work together to form the wood.

🎯 Exam Tip: Focus on the main cellular components of secondary xylem – tracheary elements, fibers, and parenchyma – which form its axial (vertical) system.

 

Question 7. Tissues considered in an annual ring is/are
a) Secondary xylem and phloem
b) Primary xylem and phloem
c) Secondary xylem only
d) Primary phloem and secondary xylem
Answer: (c) Secondary xylem only
In simple words: An annual ring is formed mainly by the new secondary xylem cells produced in one year. This ring, also known as a growth ring, helps determine the age of the tree.

🎯 Exam Tip: Annual rings are distinct layers of secondary xylem that reflect seasonal growth patterns, primarily due to changes in vascular cambium activity.

 

Question 8. Ray cells are present between:
(a) primary xylem and phloem
(b) primary xylem and secondary xylem
(c) secondary xylem and secondary phloem
(d) secondary phloem and cambium
Answer: (c) secondary xylem and secondary phloem
In simple words: Ray cells, which help in side-to-side transport and storage, are found between the secondary xylem and secondary phloem. They form part of the radial transport system in the stem.

🎯 Exam Tip: Remember that ray cells are part of the radial system of the secondary vascular tissues, linking the xylem and phloem for lateral transport and storage.

 

Question 9. Interfascicular cambium is a
a) Primary meristematic tissue
b) Primordial meristem
c) Type of protoderm
d) Secondary meristematic tissue
Answer: (d) Secondary meristematic tissue
In simple words: Interfascicular cambium is a type of meristem that develops later in the plant's life. It is formed from mature cells becoming meristematic again, which makes it a secondary meristem.

🎯 Exam Tip: Distinguish between primary meristems (like apical meristem) that cause growth from the start and secondary meristems (like interfascicular cambium and cork cambium) that contribute to girth increase later on.

 

Question 10. Interfascicular cambium develops from the cells of
a) Xylem parenchyma
b) endodermis
c) Pericycle
d) Medullary rays
Answer: (d) Medullary rays
In simple words: The interfascicular cambium, which helps in secondary growth, is formed from the cells of the medullary rays. These cells become active and connect the fascicular cambium.

🎯 Exam Tip: Understanding the origin of interfascicular cambium from medullary ray cells is key to comprehending the formation of a continuous cambial ring.

 

Question 11. Which of the statement is not correct?
(a) In temperate regions, the cambium is very active in the winter season.
(b) In temperate regions, the cambium is very active in the spring season.
(c) In temperate regions, the cambium is less active in the winter season.
(d) In temperate regions earlywood is formed in the spring season.
Answer: (a) In temperate regions, the cambium is very active in the winter season.
In simple words: The statement that cambium is very active in winter in temperate regions is incorrect. Cambium is mostly dormant or less active in winter, and becomes very active in spring to support new growth.

🎯 Exam Tip: Remember that cambial activity is highly influenced by seasonal changes, being most active during favorable conditions like spring and least active in harsh conditions like winter.

 

Question 12. At maturity, the sieve plates become impregnated with
a) Cellulose
b) Pectin
c) Suberin
d) Callose
Answer: (d) Callose
In simple words: When sieve plates in plants mature or are injured, they get filled with a substance called callose. This helps to seal off the sieve tubes.

🎯 Exam Tip: Callose deposition is a crucial process in sieve tube elements, playing roles in sealing damaged sieve plates and regulating nutrient flow.

 

Question 13. You are given a fairly old piece of dicot stem and a dicot root, which of the following anatomical structures will you distinguish between the two?
a) Secondary xylem
b) Secondary phloem
c) Protoxylem
d) Cortical cells
Answer: (c) Protoxylem
In simple words: The arrangement of protoxylem, the first-formed xylem, is different in dicot stems and roots. In stems, it is found towards the center (endarch), while in roots, it is found towards the outside (exarch). This difference helps tell them apart.

🎯 Exam Tip: The position of protoxylem (endarch in stem, exarch in root) is a reliable anatomical feature for distinguishing between dicot stems and roots.

 

Question 14. determination of the age of a tree by counting the annual rings is called:
(a) chronology
(b) dendrochronology
(c) palaeology
(d) phenology
Answer: (b) dendrochronology
In simple words: The scientific method of figuring out how old a tree is by counting its annual growth rings is called dendrochronology. These rings record yearly growth patterns.

🎯 Exam Tip: Understand that dendrochronology is not just about counting rings, but also about analyzing their patterns to gain insights into past climate and environmental conditions.

 

Question 15. Which one of the following is dead and works efficiently?
a) Sieve tube
b) Companian cells
c) Vessels
d) Both (b) and (c)
Answer: (c) Vessels
In simple words: Vessels are tubes that carry water in plants. They are made of dead cells, but they work very well to move water from the roots to the leaves.

🎯 Exam Tip: Remember that xylem elements like vessels and tracheids are dead at maturity to efficiently conduct water, forming a continuous pipeline in the plant.

 

Question 16. Which one of the following pairs is an example for meristematic tissue
a) Phellogen and phelloderm
b) Phellogen and Fascicular cambium
c) Procambium and phelloderm
d) Interfascicular cambium and phellem
Answer: (b) Phellogen and Fascicular cambium
In simple words: Phellogen (cork cambium) and fascicular cambium (part of the vascular cambium) are both active growth tissues in plants. They constantly produce new cells, showing they are meristematic.

🎯 Exam Tip: Meristematic tissues are actively dividing cells; identify terms like cambium (vascular, fascicular, interfascicular, cork/phellogen) as key examples.

 

Question 17. In fully developed tyloses:
(a) only starchy crystals are present
(b) resin and gums only are present
(c) oil and tannins are present
(d) starchy crystals, resins, gums, oils, tannins, or colored substances are present
Answer: (d) starchy crystals, resins, gums, oils, tannins, or colored substances are present
In simple words: When tyloses are fully formed, they fill with various materials. These include starches, resins, gums, oils, tannins, or other colored substances. These fillings contribute to the strength and durability of heartwood.

🎯 Exam Tip: Tyloses are outgrowths that block xylem vessels in heartwood, filled with various organic compounds that contribute to the wood's hardness and resistance to decay.

 

Question 18. Which wood is also known as Non-porous
a) Softwood
b) Heartwood
c) Hardwood
d) Sapwood
Answer: (a) Softwood
In simple words: Softwood, typically from coniferous trees, is also called non-porous wood. This is because it lacks the large vessels found in hardwood that appear as pores in a cross-section.

🎯 Exam Tip: Non-porous wood is characteristic of gymnosperms, primarily composed of tracheids, while porous wood (hardwood) is typical of angiosperms with vessels.

 

Question 19. Which of the statement is not correct?
(a) Sapwood and heartwood can be distinguished in the secondary xylem
(b) Sapwood is paler in colour
(c) Heartwood is darker in colour
(d) The sapwood conducts minerals, while the heartwood conduct water
Answer: (d) The sapwood conducts minerals, while the heartwood conduct water
In simple words: The incorrect statement is that heartwood conducts water. Heartwood is non-functional dead tissue for conduction. Only sapwood, the living outer part of the wood, actively transports water and dissolved minerals.

🎯 Exam Tip: Remember that sapwood is the physiologically active, water-conducting part of the xylem, while heartwood is its dead, non-conducting core, providing structural support.

 

Question 20. Removal of a ring of wood tissue outside the vascular cambium from the tree trunk kills it because
a) Water cannot move up
b) Food does not travel down and root become starved
c) Shoot apex become starved
d) All of the options
Answer: (b) Food does not travel down and root become starved
In simple words: If you remove a ring of tissue outside the vascular cambium (like in girdling), you cut off the phloem. Since phloem carries food from leaves to roots, the roots will starve and die, eventually killing the tree.

🎯 Exam Tip: Girdling experiments demonstrate the vital role of phloem in translocating food (sugars) from the leaves to the roots and other non-photosynthetic parts of the plant.

 

Question 21. The trees growing in the desert will
(a) Show alternate rings of xylem and sclerenchyma
(b) Have only conjunctive tissue and phloem formed by the activity of cambium
(c) do show distinct annual rings
(d) do not show distinct annual rings
Answer: (d) do not show distinct annual rings
In simple words: Trees in deserts grow in very unstable conditions, so they do not form clear yearly growth rings. This makes it hard to tell their age by counting rings.

🎯 Exam Tip: Remember that distinct annual rings are formed in regions with clear seasonal changes, like temperate zones, due to varying cambial activity.

 

Question 22. Canada balsam is produced from:
(a) Pisum sativum
(b) the resin of Arjuna plant
(c) Abies balsamea
(d) the root of Vinca rosea
Answer: (c) Abies balsamea
In simple words: Canada balsam is a special sticky liquid that comes from the Abies balsamea tree. It's often used to glue things together, especially in science.

🎯 Exam Tip: Associate specific plant products with their botanical sources, as these are common factual recall questions in botany.

 

Question 23. Choose the living cells from the given
(I) Phellem
(II) Phloem
(III) Phellogen
(IV) Xylem parenchyma
(a) (I) (II) & (III)
(b) (II) (III) & (IV)
(c) (I) (III) & (IV)
(d) (I) (II) & (IV)
Answer: (b) (II) (III) & (IV)
In simple words: Phloem, phellogen, and xylem parenchyma are all types of living cells found in plants, performing various important functions. Phellem (cork) is made of dead cells.

🎯 Exam Tip: Distinguishing between living and non-living tissues in plants is fundamental. Cork (phellem) is a common example of dead, protective tissue.

 

Question 24. When we peel the skin of a potato tuber we remove
(a) Periderm
(b) Epidermis
(c) Cuticle
(d) Sapwood
Answer: (a) Periderm
In simple words: The outer layer of a potato that we peel off is called the periderm. It acts like the skin of the potato, protecting it.

🎯 Exam Tip: Recognize common examples of plant structures, like the potato periderm, which serves a protective function similar to bark on a stem.

 

Question 25. Phelloderm is otherwise called as:
(a) primary cortex
(b) corkwood
(c) secondary cortex
(d) rhytidome
Answer: (c) secondary cortex
In simple words: Phelloderm is just another name for the secondary cortex, which is a layer of cells inside the cork cambium in plants. It provides extra protection and support.

🎯 Exam Tip: Learn the alternative names for plant tissues, as examiners often use them interchangeably to test your comprehensive knowledge.

 

Question 26. The waxy substance that makes cork cells impervious and is deposited on their walls is:
(a) Cutin
(b) Suberin
(c) Eignin
(d) Hemicellulose
Answer: (b) Suberin
In simple words: Cork cells have a special waxy substance called suberin on their walls. This makes them waterproof and helps protect the plant from losing too much water.

🎯 Exam Tip: Suberin is a key component of cork and periderm, highlighting the plant's adaptation for protection and water retention.

 

Question 27. The antimalarial compound quinine is, extracted from:
(a) seeds of cinchona
(b) bark of cinchona
(c) leaves of cinchona
(d) flowers of cinchona
Answer: (b) bark of cinchona
In simple words: Quinine, a medicine used to fight malaria, comes from the bark of the cinchona tree. This shows how plants can provide important medicines.

🎯 Exam Tip: Be aware of medicinal plants and the specific parts from which important compounds are extracted. This is a common applied botany question.

 

Question 28. Annual rings are distinct in plants growing in
(a) Tropical regions
(b) Arctic regions
(c) Grasslands
(d) Temperate region
Answer: (d) Temperate region
In simple words: Plants in places with clear seasons, like temperate regions, grow faster in spring and slower in winter. This difference creates distinct annual rings, helping us count their age.

🎯 Exam Tip: Distinct annual rings are a direct result of seasonal variations influencing cambial activity; therefore, regions with pronounced seasons will exhibit them.

 

Question 29. Which of the following are components of the bark?
(I) Cortex
(II) Periderm
(III) Pith
(IV) Secondary phloem
(a) (I) (II) & (III)
(b) (II) (III) & (IV)
(c) (I) (III) & (IV)
(d) (I) (II) & (IV)
Answer: (d) (I) (II) & (IV)
In simple words: The bark of a tree includes the cortex, periderm, and secondary phloem. The pith is located in the very center of the stem, so it is not part of the bark.

🎯 Exam Tip: Remember that bark refers to all tissues external to the vascular cambium, which includes secondary phloem, cortex, and periderm, but not the pith.

 

Question 30. Rubber is obtained from:
(a) Bombax mori
(b) Hevea brasiliensis
(c) Quercus suber
(d) Morus rubra
Answer: (b) Hevea brasiliensis
In simple words: Natural rubber, which is used to make many things like tires and balloons, comes from the rubber tree, scientifically known as Hevea brasiliensis. The milky liquid inside is collected and processed.

🎯 Exam Tip: Know the economic importance of plants and their products, as well as the specific species they are derived from.

 

Question 31. Wood actually means
(a) Primary xylem
(b) Secondary xylem
(c) Primary phloem
(d) Secondary phloem
Answer: (b) Secondary xylem
In simple words: When we talk about wood, we are usually referring to the secondary xylem. This tissue is formed from the growth of the vascular cambium and is responsible for transporting water and nutrients, making up the bulk of a tree trunk.

🎯 Exam Tip: Understand the origin of wood in the context of secondary growth; it is primarily formed by the activity of the vascular cambium, producing secondary xylem.

 

Question 32. When a plant is wounded, the wound is healed by the formation of new cells, by the activity of
(a) Primary meristem
(b) Apical meristem
(c) Secondary meristem
(d) Intercalary meristem
Answer: (c) Secondary meristem
In simple words: When a plant gets hurt, special cells called secondary meristems start working to create new cells. These new cells help to cover the wound and repair the damage.

🎯 Exam Tip: Recognize that secondary meristems are key players in wound healing and secondary growth, forming protective and repair tissues.

 

Question 33. Commercial cork is obtained from
(a) Oak
(b) Silver oak
(c) Pine
(d) Ficus
Answer: (a) Oak
In simple words: The cork that is used to make bottle stoppers and other products comes from certain types of oak trees. This material is harvested from the bark of these trees.

🎯 Exam Tip: Cork is a product of the phellogen (cork cambium) and is most famously harvested from the cork oak tree, *Quercus suber*.

II. Match Correctly And Choose The Right Answer

 

Question 1. Match the following.
I) Spicy bark – A Turpentine
II) Ornamental Antique – B Quinine
III) Active drug – C Cinnamon
IV) Thinner and solvent – D Amber
(a) B-A-D-C
(b) C-A-B-D
(c) D-C-A-B
(d) C-D-B-A
Answer: (d) C-D-B-A
In simple words: This match means: Spicy bark is Cinnamon. Ornamental Antique is Amber. Active drug is Quinine. Thinner and solvent is Turpentine. Each item is correctly paired with its matching property or substance.

🎯 Exam Tip: For matching questions, systematically go through each item and its corresponding options to ensure all pairs are logically connected as per biological context.

 

Question 2. Match the following.
I) Phellogen – A. Cork
II) Phelloderm – B. Cork cambium
III) Phellem – C. Lack suberin
IV) Phelloids – D. Secondary cortex
(a) B-D-A-C
(b) D-B-C-A
(c) B-D-C-A
(d) D-B-A-C
Answer: (a) B-D-A-C
In simple words: This match correctly pairs Phellogen with Cork cambium, Phelloderm with Secondary cortex, Phellem with Cork, and Phelloids with cells that lack suberin. Each component is correctly identified with its other name or characteristic.

🎯 Exam Tip: Understanding the relationships and alternative names for the components of the periderm (phellogen, phellem, phelloderm) is essential for such matching questions.

 

Question 3. Match the following.
I) Sapwood – A. Softwood
II) Heartwood – B. Hardwood
III) Porous wood – C. Albumum
IV) Nonporous wood – D. Duramen
(a) A-C-D-B
(b) C-D-A-B
(c) C-D-B-A
(d) D-C-B-A
Answer: (c) C-D-B-A
In simple words: This match means: Sapwood is also called Albumum. Heartwood is also called Duramen. Porous wood is generally Hardwood. Nonporous wood is generally Softwood. All the pairs are correct terms or characteristics.

🎯 Exam Tip: Familiarize yourself with synonyms for wood types, such as sapwood (alburnum) and heartwood (duramen), as they are frequently used in botanical terminology.

III Identify True Or False And From The Given Option Choose The Right Answer:

 

Question 1. Identify the correct combination of True/False statements.
A) In pinus wood is Non-porous
B) In Morns wood is porous
C) In Quercus the wood is Diffuse porous
D) In Acer the wood is Ring porous
(a) A&D True B&C False
(b) A & B True C & D False
(c) A & C True B & D False
(d) A&B False C &D True
Answer: (b) A & B True C & D False
In simple words: Pine wood does not have pores, and mulberry wood has pores. Oak wood is usually ring porous, not diffuse porous. Maple wood is usually diffuse porous, not ring porous. So, statements A and B are correct, while C and D are incorrect.

🎯 Exam Tip: Know the characteristics of wood types (porous/non-porous, ring porous/diffuse porous) and common examples of trees associated with each type.

 

Question 2. Arrange the given plants in order from more distinct Annual rings to least distinct Annual rings.
(a) Seashore plants, Desert plants, Tropical plants & Temperature plants
(b) Temperature plants, Tropical plants, Desert plants, Seashore plants
(c) Tropical plants, Desert plants, Temperature plants, Seashore plants
(d) Temperature plants, Seashore plants, Tropical plants, Desert plants
Answer: (d) Temperature plants, Seashore plants, Tropical plants, Desert plants
In simple words: Plants growing in temperate places have the clearest yearly growth rings because their seasons change a lot. Seashore plants have less distinct rings, followed by tropical plants with even less clear rings, and desert plants have the least distinct rings due to irregular growth patterns.

🎯 Exam Tip: The clarity of annual rings is directly linked to the regularity and distinctness of seasonal changes, with temperate zones having the most pronounced seasonality.

 

Question 3. In wood, the Annual rings become clearly evident to our eyes due to
(a) The high density and dark coloured of latewood or Autumn wood
(b) The low density and light coloured early wood or springwood
(c) The high density and dark coloured early wood or springwood
(d) The low density and light coloured latewood or Autumn wood
Answer: (a) The high density and dark coloured of latewood or Autumn wood
In simple words: Annual rings are easy to see because the wood grown later in the year (autumn wood) is dark and packed tightly. This strong contrast with the lighter, looser wood from springtime makes the rings stand out.

🎯 Exam Tip: Annual rings are visible due to the contrast in cell size and wall thickness between earlywood (springwood) and latewood (autumn wood), which results in differences in color and density.

 

Question 4. Column I and Column II – Match them correctly and Find out the right option.

Which of the following combination is correct?
(a) A – 2, 4, 7, 8 B- 1,3, 5,6
(b) A – 1, 2, 7,8 B- 3,4,5, 6
(c) A – 1, 3, 5, 6 B- 2, 4, 7, 8
(d) A – 1,3,7, 8 B – 2, 4, 5, 6
Answer: (b) A – 1, 2, 7,8 B- 3,4,5, 6
In simple words: Springwood is lighter, has high density, fewer xylem elements, and small vessel cavities. Autumn wood is darker, has low density, more xylem elements, and wider vessel cavities. This difference in characteristics helps to form annual growth rings.

🎯 Exam Tip: This question might challenge conventional biological facts regarding wood density and vessel size. Always confirm the expected answer based on the provided options in the exam context, even if it contradicts general knowledge. In general biology, springwood has low density and wide vessels.

IV. Assertion And Reason

 

Question 1. ASSERTION: – A All tissues lying inside the Vascular Cambium are called as Bark REASON -R: Bark is made up of Phellogen. Phellem and Phelloderm Cortex, primary and secondary phloem
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true, but R is not the correct explanation of A
(c) A is true but 'R' is false
(d) A is false and 'R' is true
(e) Both A and 'R' are false
Answer: (d) A is false and 'R' is true
In simple words: The first statement (Assertion A) is incorrect because bark is actually found outside the vascular cambium, not inside. The second statement (Reason R) is correct because bark is indeed made up of several layers like phellogen, phellem, phelloderm cortex, and phloem.

🎯 Exam Tip: Clearly differentiate between internal and external plant structures relative to the vascular cambium to correctly identify components like bark and wood.

 

Question 2. ASSERTION: -A In angiosperms, the conduction of water is more efficient because their xylem has vessels REASON – R: Conduction of water by vessel element is an active process in which energy is supplied by xylem parenchyma with a large number of Mitochondria
(a) Both A and R are true and 'R' is the correct explanation of A
(b) Both A and R are true, but R is not the correct explanation of A
(c) A is true but 'R' is false
(d) A is false and 'R' is true
Answer: (a) Both A and R are true and 'R' is the correct explanation of A
In simple words: Angiosperms can move water very well because their xylem contains vessels, which are efficient tubes for water transport. This efficient movement happens because the vessel elements, with help from xylem parenchyma and their many mitochondria, actively push the water.

🎯 Exam Tip: Focus on understanding the role of vessels in angiosperm water transport and the energy involvement of parenchyma, as described in the provided statements.

 

Question 3. ASSERTION: -A. All the endodermal cells of the root do not contain Casparian thickenings on their radial and transverse walls. REASON-R: Passage cells are found in the root endodermis, which conducts water in to the xylem
(a) Both A and R are true and 'R' is the correct explanation of A
(b) Both A and R are true, but R is not the correct explanation of A
(c) A is true but 'R' is false
(d) A is false and 'R' is true
Answer: (a) Both A and R are true and 'R' is the correct explanation of A
In simple words: It is true that not all endodermal cells in a root have thick Casparian strips. This is because some special passage cells exist in the endodermis, and their job is to help water move directly into the xylem, explaining why not all cells need the strips.

🎯 Exam Tip: Remember the specific function of passage cells in the endodermis; they are crucial for allowing water movement past the Casparian strips into the stele.

 

Question 4. ASSERTION:-A Cambium is a lateral meristem and causes growth in width REASON-R Cambium is made up of fusiform and ray initials in stem
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true, but R is not the correct explanation of A
(c) A is true but 'R' is false
(d) A is false and 'R' is true
Answer: (b) Both A and R are true, but R is not the correct explanation of A
In simple words: The cambium is indeed a lateral meristem that helps plants grow wider, and it is also true that the cambium is made of fusiform and ray initials. However, knowing what the cambium is made of does not explain why it makes the plant grow wider; those are two separate facts.

🎯 Exam Tip: Distinguish between a statement of fact and a correct explanation. Both assertion and reason can be true independently, but the reason might not clarify the assertion.

 

Question 5. ASSERTION: – A The lenticel is meant for gaseous exchange. REASON-R Lenticel checks excessive evaporation of water.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not the correct explanation of A
(c) A is true but 'R' is false
(d) A is false and 'R' is true
Answer: (b) Both A and R are true but R is not the correct explanation of A
In simple words: Lenticels are pores that help plants breathe by exchanging gases. They also help stop too much water from evaporating. While both statements are true, the reason does not explain how lenticels help with gas exchange.

🎯 Exam Tip: Be precise about the primary function of structures like lenticels (gas exchange) and also recognize secondary effects (some water loss, but overall bark checks major loss).

 

Question 6. ASSERTION:-A Heartwood is more durable REASON – R Heartwood contains organic compounds like tannins, resins, oil, gums, aromatic substances and essential oils help to resist microbial and termites attack.
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true, but R is not the correct explanation of A
(c) A is true but 'R' is false
(d) A is false and 'R' is true
Answer: (a) Both A and R are true and R is the correct explanation of A
In simple words: Heartwood is very strong and lasts a long time because it has special chemicals like tannins and oils. These chemicals protect it from germs and bugs, which explains why heartwood is so durable.

🎯 Exam Tip: Understand that the chemical composition of heartwood directly contributes to its durability and resistance to decay, making it valuable.

V. 2 Marks Questions

 

Question 1. Distinguish between Primary and Secondary growth.
Answer:
**Primary growth:**
1. The roots and stem grow longer with the help of the apical meristem.
2. This is known as longitudinal growth.
3. For example, it occurs in angiosperms and gymnosperms.
**Secondary growth:**
1. The roots and stem get thicker or wider with the help of the lateral meristem.
2. This is also known as latitudinal growth or growth in girth.
3. For example, it occurs in most angiosperms, including some monocots and gymnosperms. Both types of growth are essential for the plant's overall development and survival.
In simple words: Primary growth makes plants taller and roots longer, while secondary growth makes stems and roots thicker. Both happen using different parts of the plant's growth tissue.

🎯 Exam Tip: Clearly state the meristem involved (apical for primary, lateral for secondary), the direction of growth (length for primary, girth for secondary), and provide relevant examples for full marks.

 

Question 2. Mention the two Lateral meristems responsible for secondary growth.
Answer: The secondary growth in dicots and gymnosperms is caused by two lateral meristems: The vascular cambium helps form new xylem and phloem, which makes the stem thicker.
1. Vascular cambium and
2. Cork cambium
In simple words: Secondary growth, which makes plants thicker, happens because of two special tissues: vascular cambium and cork cambium.

🎯 Exam Tip: Remember that secondary growth, leading to an increase in plant girth, is specifically controlled by lateral meristems, not apical meristems.

 

Question 3. Define interfascicular cambium?
Answer: The interfascicular cambium is formed when a few parenchyma cells from the medullary rays, located between the vascular bundles, become meristematic. These cells align with the fascicular cambium to create strips of vascular cambium. This extended cambial ring helps the plant grow wider.
In simple words: Interfascicular cambium is a part of the growth ring that forms between the main vascular bundles, helping the plant stem get wider.

🎯 Exam Tip: Specify its origin (medullary rays becoming meristematic) and its location (between vascular bundles) to accurately define interfascicular cambium.

 

Question 4. Fill in the blanks

Answer:In simple words: This table shows how different plants give us useful products like Canada balsam for slides, Gum Arabic for painting, cork for bottles, and hematoxylin as a dye for science.

🎯 Exam Tip: When filling tables, ensure all blanks are addressed and that the botanical names, common products, and uses are correctly matched, checking for any missing information.

 

Question 5. Distinguish between the stratified cambium and Non-stratified cambium.
Answer:
**Stratified cambium:** Plants with short fusiform initials produce a storied cambium, where the initials are arranged in horizontal layers.
**Non-stratified cambium:** Plants with long fusiform initials produce a non-storied cambium, where the initials strongly overlap at their ends. Both types are important for the secondary growth of plants.
In simple words: In stratified cambium, the cells are neatly stacked in rows. In non-stratified cambium, the cells are long and overlap each other instead of being in neat rows.

🎯 Exam Tip: Focus on the arrangement of fusiform initials (horizontal tiers for stratified, overlapping for non-stratified) as the key distinguishing feature.

 

Question 6. Why does porous wood appear harder and more commercially important?
Answer: Porous wood, commonly known as hardwood, contains xylem vessels that appear as pores in a cross-section. As the tree ages, especially in the heartwood, many of these vessels become blocked by structures called tyloses, which are filled with gums, resins, tannins, and oils. This deposition makes the wood denser, harder, and more durable, thus increasing its commercial value. The presence of these substances helps the wood resist decay and insect attacks.
In simple words: Porous wood (hardwood) gets tough because its old parts fill up with sticky substances that make it dense and strong. This makes it last longer and more useful for people to buy and use.

🎯 Exam Tip: The hardness and commercial value of porous wood, particularly heartwood, are attributed to the deposition of various organic compounds and the formation of tyloses, which enhance durability.

 

Question 7. What is the source of turpentine? and What is its use?
Answer:
Turpentine is a resin obtained from the bark of conifers, such as pine trees.
Its uses include:
- It is used as a thinner for oil-based paints.
- It is also used as an organic solvent.
- It is used as a balm to relieve muscular pain. This versatile resin has various applications in industry and medicine.
In simple words: Turpentine comes from pine tree sap. It is used to thin paint, clean things, and help with muscle pain.

🎯 Exam Tip: When asked about plant products, always provide both the source (the plant name and part) and multiple common uses to demonstrate comprehensive knowledge.

 

Question 8. Distinguish between Periderm and Polyderm
Answer:
**Periderm:**
1. Secondary growth replaces the epidermis and primary cortex to form the periderm.
2. It consists of phellem (cork), phellogen (cork cambium), and phelloderm (secondary cortex).
3. An example is dicot stems and roots.
**Polyderm:**
1. It is a special type of protective tissue that has a suberized layer alternating with non-suberized cells in the periderm.
2. An example is the roots and underground stems of Rosaceae plants. The main difference lies in their cellular composition and specific protective mechanisms.
In simple words: Periderm is the usual outer protective skin that replaces the first skin of older plants, made of three layers. Polyderm is a special kind of periderm with alternating waterproof and non-waterproof layers, found in specific plants.

🎯 Exam Tip: Focus on the distinct structural differences: periderm is a three-layered protective tissue, while polyderm is a specific type of periderm with alternating cell layers.

 

Question 9. Define Rhytidome?
Answer: Rhytidome is a technical term for the outer dead bark. It consists of periderm and isolated cortical or phloem tissues formed during successive secondary growth. For example, it is seen in *Quercus* (oak) trees. This outermost layer provides significant protection to the inner, living tissues.
In simple words: Rhytidome is the very outer, dead bark of a tree. It includes all the old, protective layers that build up over time.

🎯 Exam Tip: Rhytidome is distinct from a single periderm layer; it represents multiple layers of periderm and associated dead tissues accumulated over time.

 

Question 10. What is the use of Canada balsam?
Answer: Canada balsam is an organic gum-like substance produced from the resin ducts of the *Abies balsamea* plant. It is primarily used as a permanent mounting medium for microscopic slide preparation. For instance, a 60-year-old specimen of a flatworm can be permanently mounted in Canada balsam to preserve it for study. Its clear property helps in viewing tiny details under the microscope.
In simple words: Canada balsam is a sticky liquid from a tree. It is used to stick tiny things onto glass slides so scientists can look at them clearly under a microscope.

🎯 Exam Tip: Its transparency and refractive index, similar to glass, make Canada balsam ideal for permanent microscopic slide preparations.

VI. 3 Mark Questions

 

Question 1. Distinguish between Primary and Secondary growth.
Answer:Primary growth refers to the increase in the length of plant roots and stems. This happens with the help of the apical meristem. It is also known as longitudinal growth and is found in angiosperms and gymnosperms. Growing upwards helps plants reach sunlight.
Secondary growth is when roots and stems get thicker. This is done by lateral meristems. It is also called latitudinal growth or growth in girth. Most angiosperms, and even some monocots and gymnosperms, show this type of growth.
In simple words: Primary growth makes plants taller, while secondary growth makes them wider.

🎯 Exam Tip: Remember that apical meristems are at the tips (length), while lateral meristems are on the sides (width).

 

Question 2. Notes on Lenticels.
Answer:Lenticels are raised openings or pores that appear as scars on the surface of the bark of old stems and roots. They form during secondary growth in stems. In these areas, the phellogen is more active, forming a loose tissue of thin-walled parenchyma cells called complementary tissue. Lenticels are important for exchanging gases and allowing a small amount of transpiration, known as lenticular transpiration.
In simple words: Lenticels are small pores on bark that help the plant breathe and release a little water.

🎯 Exam Tip: Highlight that lenticels are for gas exchange and are formed due to phellogen activity, which differentiates them from stomata.

 

Question 3. Explain briefly about false annual rings.
Answer:False annual rings, also called pseudo- or false-annual rings, are extra growth rings that form within a single year. They develop because of difficult natural events like drought, frost, heavy leaf fall, floods, physical injury, or attacks by living things during the growing season. These challenges interrupt normal growth, causing more than one ring to form in that year.
In simple words: False annual rings are extra rings that grow in trees in one year due to bad weather or damage, not normal yearly growth.

🎯 Exam Tip: Remember to link false annual rings directly to "adverse natural calamities" or "stressful environmental conditions" rather than normal seasonal changes.

 

Question 4. Differences between Diffuse porous wood and Ring porous wood
Answer:Diffuse porous wood is found in places where the weather conditions stay the same. In this type of wood, the vessels are almost the same size in every annual ring and are spread out evenly throughout the wood. This even distribution helps in consistent water transport.
Ring porous wood, on the other hand, is found where the weather conditions change a lot. Here, the vessels vary in size, with some being wide and others narrow within a single annual ring. The vessels are not spread out evenly throughout the wood, which reflects the seasonal changes in growth.
In simple words: Diffuse porous wood has evenly sized vessels spread out, while ring porous wood has vessels of different sizes that are not evenly spread, depending on the climate.

🎯 Exam Tip: When distinguishing between wood types, always connect the structure of the vessels (size and distribution) to the climatic conditions where the tree grows.

 

Question 5. Differences between Porous Wood and Non - porous wood
Answer:Porous wood, also called Hardwood (e.g., Morus), is common in angiosperms. It is called porous because it contains vessels, which are a type of water-conducting tissue. These vessels look like tiny pores in the wood when viewed in cross-section.
Non-porous wood, or softwood (e.g., Pinus), is common in gymnosperms. It is called non-porous because it does not contain vessels. Instead, it relies on tracheids for water conduction, which are narrower and do not form distinct pores.
In simple words: Porous wood has vessels and is typical of flowering plants, while non-porous wood lacks vessels and is typical of conifers.

🎯 Exam Tip: Remember that the presence or absence of vessels is the key distinguishing feature between porous and non-porous wood, correlating with angiosperms and gymnosperms respectively.

 

Question 6. Differences between Sapwood (alburnum) and Heart Wood (duramen)
Answer:

In simple words: Sapwood is the living, outer, lighter part of the tree that carries water, while heartwood is the dead, central, darker part that gives strength and is more resistant to decay.

🎯 Exam Tip: Focus on the main differences: sapwood is live and transports water, while heartwood is dead and provides structural support and decay resistance.

 

Question 7. Distinguish between Phellem and Phelloderm.
Answer:

In simple words: Phellem is the outer, protective, dead layer (cork), while phelloderm is the inner, living layer that helps with food storage. Both are formed by the phellogen.

🎯 Exam Tip: Clearly state their position relative to the phellogen (outer/inner) and whether their cells are living/dead, compact/loose, and their primary function (protection/storage).

 

Question 8. Explain the term lenticel.
Answer:A lenticel is a raised opening or pore found on the epidermis or bark of stems and roots. It forms during secondary growth in stems. When the phellogen becomes very active in the region of a lenticel, it creates a mass of loosely arranged, thin-walled parenchyma cells. These cells are known as complementary tissue or filling tissue. Lenticels play a vital role in the exchange of gases between the plant and the atmosphere, as well as in a process called lenticular transpiration, where a small amount of water vapor is released. Their porous structure is key to their function.
In simple words: Lenticels are small, raised pores on tree bark that let the plant breathe and release water vapor.

🎯 Exam Tip: Define lenticels as pores, explain their formation by phellogen, identify complementary tissue, and state their dual function: gas exchange and lenticular transpiration.

 

Question 9. Mention the benefits of bark in a tree.
Answer:Bark offers several important benefits to a tree. It protects the plant from harmful parasitic fungi and insects, and it helps prevent water loss due to evaporation. Additionally, bark shields the tree from extreme changes in outside temperature. It acts as an insect repellent, is resistant to decay, fireproof, and is a source for various drugs and spices. The phloem cells within the bark help transport food throughout the plant, while the secondary cortical cells are used for storing nutrients. Bark is essential for the tree's survival and many practical uses.
In simple words: Bark protects the tree from bugs, disease, and weather; stops water loss; and helps move food. It also gives us useful products like drugs and spices.

🎯 Exam Tip: When listing benefits, categorize them into protective functions (pests, water, temperature), economic uses (drugs, spices), and physiological roles (food conduction, storage).

 

Question 10. Annual rings are not clear and distinct in desert trees and seashore plants – Justify.
Answer:Annual rings are not clear in desert trees and seashore plants because the climatic conditions in these regions remain mostly the same throughout the year. The formation of distinct annual rings depends on significant seasonal changes that influence the activity of the cambium. In deserts, conditions are consistently dry and hot, and at seashores, they are consistently humid and mild. Because there isn't a clear distinction between favorable and unfavorable growing seasons, the cambium activity doesn't vary much, leading to less distinct earlywood and latewood formation. This uniform environment results in growth rings that are hard to tell apart.
In simple words: Desert and seashore trees don't have clear annual rings because their weather stays much the same all year, so their growth doesn't change enough to show distinct rings.

🎯 Exam Tip: The key reason is the "lack of significant seasonal changes" influencing cambial activity, which prevents the clear differentiation of earlywood and latewood.

 

Question 11. A plant dies if the sapwood is damaged, but not with that of Heartwood – Give factual justification.
Answer:A plant dies if its sapwood is damaged because sapwood is the living part of the wood responsible for water conduction. It actively transports water and minerals from the roots to the rest of the plant. If sapwood is damaged or exposed, this vital water conduction is blocked, leading to rapid water loss, decay, tissue decomposition, and ultimately the death of the plant. In contrast, heartwood is the dead, central part of the wood that provides structural support but does not transport water. So, if heartwood is damaged, it doesn't affect the plant's water supply or other vital functions directly, and the plant can often survive. The sapwood's active role in nutrient and water transport is critical for survival.
In simple words: Sapwood is alive and carries water, so damaging it kills the plant. Heartwood is dead and just provides support, so damaging it does not kill the plant.

🎯 Exam Tip: The critical distinction is the physiological function: sapwood conducts water (vital), while heartwood provides support (non-vital for transport).

 

Question 12. What is Dendrochronology? Add a note on the significance of studying the growth rings.
Answer:Dendrochronology is the scientific method of determining the age of a tree by carefully counting its annual growth rings. Each annual ring represents one year of the tree's growth. By studying these rings, we can understand past climate and environmental conditions. This technique relies on the unique pattern of wider and narrower rings that correspond to favorable and unfavorable growing seasons.

Significance of studying growth rings:

• The age of wood can be accurately calculated.
• The age can be verified using methods like radioactive carbon dating.
• Growth rings provide historical evidence for forensic investigations, climate studies, and ecological research.

In simple words: Dendrochronology is counting tree rings to find a tree's age. This helps us learn about past climates and for scientific studies.

🎯 Exam Tip: Define dendrochronology clearly as age determination by annual rings, and remember its significance for dating, environmental history, and forensic science.

 

Question 13. If 'A' is vascular cambium, then label other parts with reference to cambial activity.
Answer:The diagram shows a cross-section of a stem with various tissues formed by cambial activity. In this diagram: A - Vascular cambium
B - First formed phloem (Primary phloem)
C - First formed xylem (Primary xylem)
D - Second formed phloem (Secondary phloem)
E - Second formed xylem (Secondary xylem)
In simple words: This diagram shows how the vascular cambium (A) makes new phloem (D) and xylem (E) cells, while the older phloem (B) and xylem (C) are pushed aside.

🎯 Exam Tip: Remember the order of tissue formation: primary tissues are formed first, then the vascular cambium forms secondary tissues, pushing the primary tissues to the outer and inner sides.

 

Question 14. Cross-section of wood showing Annual rings.
Answer:The diagram displays a cross-section of a tree trunk, clearly showing the distinct annual rings, which indicate the tree's age and growth patterns.
A - Bark
B - Sapwood
C - Heartwood
D - Annual rings
In simple words: This picture shows a tree trunk cut open, where you can see the bark, the lighter sapwood, the darker heartwood, and the lines that are called annual rings.

🎯 Exam Tip: For this type of diagram, correctly identifying bark, sapwood, heartwood, and the annual rings is crucial, as they represent the main components of a woody stem.

 

Question 15. Identify the diagram & Label the parts.
Answer:The diagram shows the structure of Tyloses, which are balloon-like outgrowths from parenchyma cells into the vessel lumen. These structures block the vessels and prevent the flow of water.
A - Parenchyma cell
B - Tyloses
C - Vessel wall
D - Vessel Lumen
In simple words: This drawing shows tyloses, which are tiny balloons growing from a cell (A) into a wood tube (D), blocking it up (B).

🎯 Exam Tip: Understand that tyloses (B) are outgrowths from parenchyma cells (A) that block the vessel lumen (D) and are associated with heartwood formation and disease resistance.

 

Question 16. In the given diagram, the parts labelled are A, B, C, D identify the part correctly with respect to its function.
(a) A – Periderm for gaseous exchange
(b) C – Secondary cortex for protection
(c) B – Complementary tissues for gaseous exchange
(d) D – Phloem for food and hormone formation
Answer: (c) B – Complementary tissues for gaseous exchange
In simple words: The diagram shows a lenticel, and part B represents the complementary tissues which allow gases to pass through for plant breathing.

🎯 Exam Tip: For diagrams of lenticels, always associate the loosely arranged complementary tissue (often labeled B) with its primary function of gaseous exchange.

 

Question 17. Different stages of secondary growth in Dicot root
Answer:The diagram illustrates a cross-section of a dicot root undergoing secondary growth, showing the arrangement of different vascular tissues.
A - Cambial ring
B - Primary xylem
C - Secondary xylem
D - Primary phloem
E - Secondary phloem
In simple words: This diagram shows how a dicot root gets thicker. You can see the cambial ring (A) which makes new xylem (C) and phloem (E) cells, pushing the older xylem (B) and phloem (D) outwards.

🎯 Exam Tip: When interpreting secondary growth diagrams, clearly identify the cambial ring as the meristematic layer and distinguish between primary and secondary xylem/phloem based on their positions.

VII. 5 Mark Questions

 

Question 1. Distinguish between Phellem and Phelloderm.
Answer:

In simple words: Phellem is the dead, outer cork layer that protects, while phelloderm is the living, inner layer that stores food and water. Both are created by the phellogen.

🎯 Exam Tip: Always describe their relative positions, cell characteristics (living/dead, compact/loose), and primary functions to clearly differentiate phellem and phelloderm.

 

Question 2. Distinguish the significance of Cork and Bark
Answer:

Cork:

1. Cork includes only the phellem layer of the bark.
2. It is made up of suberin, a substance that makes it hydrophobic (water-repellent).
3. It is impermeable, floats well, is elastic, and has fire-retardant properties.
4. It is used for making bottle stoppers (e.g., from the bark of Quercus suber).

Bark:

1. Bark includes all tissues located outside the vascular cambium, which are the periderm, cortex, primary, and secondary phloem.
2. It has properties that repel insects, resist decay, and are fireproof.
3. It is used for drugs or spices.
4. Examples include the bark of Cinchona (used for antimalarial drugs) and the bark of Cinnamomum (used as a spice).

In simple words: Cork is just the outer protective, water-resistant part of the bark. Bark is a bigger part of the tree that includes cork and other layers, offering protection and many useful products like medicine and spices.

🎯 Exam Tip: Remember that cork is a component of bark, specifically the phellem, while bark encompasses all layers external to the vascular cambium, each with specific functions and uses.

 

Question 3. Differentiate between, the vascular cambial components Fusiform initials and Ray initials.
Answer:

Fusiform initials:

1. These are vertically elongated cells.
2. They give rise to the axial system of secondary tissues, which include secondary xylem and phloem.
3. Secondary xylem includes tracheary elements, fibers, and axial parenchyma.
4. Secondary phloem includes sieve elements.
5. Based on how fusiform initials are arranged, two types of vascular cambium are recognized: a) stratified cambium (storied) and b) non-stratified cambium (non-storied).

Ray initials:

1. These are horizontally elongated cells.
2. They give rise to the radial system of secondary xylem and phloem.
3. The radial system is made of rows of parenchymatous cells arranged at right angles to the longitudinal axis of xylem elements. These cells aid in horizontal transport.
4. Secondary phloem includes phloem rays, fibers, and axial parenchyma.

In simple words: Fusiform initials are long cells that make the main up-and-down tissues (xylem and phloem) of the tree, while ray initials are short cells that make the side-to-side tissues (rays) for transport across the stem.

🎯 Exam Tip: Differentiate them by their shape (vertical/horizontal), the system they form (axial/radial), and the secondary tissues they produce.

 

Question 4. Give an account of Primary & Secondary structure of Dicto Stern. (Flow chart)
Answer:The flow chart below illustrates the development from primary to secondary structure in a dicot stem, highlighting the roles of different cambial tissues.

In simple words: The primary structure grows first, then specific cells change into cambium (like the vascular cambium and cork cambium). These cambium tissues then make all the secondary structures that make the stem wider and protected.

🎯 Exam Tip: For flow charts, clearly show the origin of each cambium (fascicular, interfascicular, cork) and the specific secondary tissues (xylem, phloem, phellem, phelloderm, lenticels) they produce.

 

Question 5. Give an account of Any 5 Commercial barks their, properties and uses
Answer:Here are five commercial barks, along with their properties and uses, which are important in various industries.

In simple words: Different tree barks give us useful things: Cinchona bark provides quinine for malaria, cork oak bark gives stoppers, rubber trees give rubber, pine trees give turpentine, cinnamon bark gives spice, and acacia trees give gum Arabic.

🎯 Exam Tip: For questions about commercial barks, ensure you name the plant, its key property, and at least one significant use for full marks.