CBSE Class 11 Biology Anatomy Of Flowering Plants Notes

6. Anatomy of Flowering Plants

POINTS TO REMEMBER :

• Study of internal structure of plant is called anatomy.

• In plants cells are the basic unit.

• Cells organized into tissues and tissues organized into organs.

THE TISSUES :

• A group of cells having common origin and perform one function.

• Plant tissues are classified into two types:-

o Meristematic tissue.

o Permanent tissue

Meristematic tissues :

• Growth in plants is restricted to specific regions with active cell division called meristems.

• Different types of meristems are:-

o Apical meristem:

• Occurs in the shoot and root tips.

• Primary meristem

• Increase the length of plant

o Intercalary meristem :

• Present in-between mature tissues.

• Primary meristem

• Occurs in grasses and regenerate parts removed by grazing.

o Lateral meristem:

• Occurs in the mature regions of roots and shoots.

• Also known as secondary meristem.

• Responsible for producing secondary tissues.

• Fascicular vascular cambium, interfascicular cambium and cork cambium are example of lateral meristem.

• Axillary bud :

o During formation of leaves and elongation of stem, some cells ‘left behind’ from shoot apical meristem, constitute the axillary bud.

o Present in the axils of leaves and are capable for forming a branch or a flower.

Permanent tissues :

• Cells produced from primary or secondary meristem stop dividing and differentiated structurally and functionally, termed as permanent cells.

• A group of permanent cell constitutes the permanent tissues.

• Permanent tissues having similar in structure and function are called simple tissues.

• Permanent tissues having many different types of cells are called complex tissues.

Simple tissues :

• Simple tissues made of only one type of cells. 

Parenchyma :

• Forms major component within organs.

• Cells are isodiametric.

• Thin cell wall made of cellulose.

• Cells may be spherical, oval, round, polygonal or elongated shape.

• Cells are closely packed or have small intercellular space.

• Perform various functions such as photosynthesis, storage, secretion.

Collenchyma :

• Found either in homogeneous layer of in patches.

• Cell wall thickened in the corner due to deposition of cellulose, hemicelluloses and pectin.

• Cells are oval, spherical or polygonal in shape

• Often contain chloroplasts.

• No intercellular spaces.

• Provide mechanical support to the growing part of the plant such as young stem and petiole of a leaf.

Sclerenchyma :

• Consists of long, narrow cells

• Cell wall is thick and lignified.

• Cell wall with few or numerous pits.

• Cells are usually dead and without protoplast.

• Provides mechanical support to the organs.

• Sclerenchymas are of two types on the basis of origin, form, structure.

Fibres :

• Thick walled

• Elongated and pointed cells

• Generally occurs in group in various parts of the plant.

Sclereids :

• Spherical, oval or cylindrical in shape.

• Highly thickened dead cells with very narrow cavities (lumen).

• Commonly found in fruit walls of nuts; pulp of guava, pear and sapota; seed coats of legumes and leaves of tea.

Complex tissues :

• Made of more than one type of cells and these work together as a unit.

• Xylem and phloem constitute the complex tissues in plants.

Xylem :
• Functions as conducting tissues for water and minerals from roots to stem and leaves.
• Provides mechanical support to the plant.
• It consists of four different kinds of elements:-
o Tracheids
o Vessels
o Xylem fibres and
o Xylem parenchyma.

• Tracheids :
o Elongated or tube like cells.
o Thick and lignified walls and tapering ends.
o Cells are dead and without protoplasm.
o Inner layers of cell walls have thickenings which vary in forms.

• Vessels.
o Is a long cylindrical tube-like structure made up of many cells called vessel members.
o Each with lignified walls and a large central cavity.
o Cells are devoid of protoplasm.
o Vessel members are interconnected through perforations in their common walls.
o Presences of vessels are the characteristics of the angiosperm.

• Xylem fibres :
o Have highly thickened walls and obliterated central lumen.
o Either septate or aseptate.

• Xylem Parenchyma :
o Cells are living and thin-walled.
o Cell walls are made up of cellulose.
o They stored food materials in the form of starch or fat.
o Also store materials like tannins.
o The radial conduction of water takes place by the ray parenchymatous cells.

• The primary xylem is of two types-
o Protoxylem
o Metaxylem.
• The first formed xylem elements are called protoxylem.
• The later formed primary xylem is called metaxylem.
• Endarch: the protoxylem lies towards pith and metaxylem towards the periphery of the organ ( in stem)
• Exarch: in root the protoxylem lies towards periphery and metaxylem lies towards the centre.

Phloem :
• Transports food materials usually from leaves to other part of plant.
• It is composed of four elements:-
o Sieve tube elements.
o Companion cells.
o Phloem parenchyma.
o Phloem fibres.

• Sieve tube elements :
o Long tube like structure arranged longitudinally
o Associated with companion cells.
o End walls are perforated to form sieve plates.
o A mature sieve element possesses peripheral cytoplasm and a large vacuole but lacks nucleus.
o The function of sieve elements controlled by nucleus of companion cells.

• Companion cells :
o Specialized parenchymatous cells.
o Closely associated with sieve tube elements.
o Connected with sieve tube element by pit field.
o Helps in maintaining pressure gradient in the sieve tubes.

• Phloem parenchyma :
o Made up of elongated tapering cylindrical cells
o Have dense cytoplasm and nucleus.
o Cell wall made of cellulose and has pits through plasmodesmatal connections exist between the cells.
o Store food materials and other substances like resins and latex and mucilages.
o It is absent in monocotyledons.

• Phloem fibres :
o Also known as bast fibres.
o Made of sclerenchymatous cells.
o Absent in primary phloem but present in secondary phloem.
o Much elongated, unbranched and have pointed, needle like apices.
o Cell wall is quite thick.
o On maturity loose their protoplasm and become dead.
o Phloem fibres of jute, flax and hemp are used commercially.
• The first formed primary phloem consists of narrow sieve tubes and referred as protophloem.
• The later formed phloem has bigger sieve tubes and is referred to as metaphloem.

THE TISSUE SYSTEM :
• On the basis of their structure and location there are three types of tissue systems.
o Epidermal tissue system.
o Ground or fundamental tissue system.
o Vascular or conducting tissue system.

Epidermal tissue system :
• Forms the outermost covering of the whole plant body and comprises:
o Epidermal cells.
o Stomata
o Epidermal appendages like trichomes and hairs.
• Epidermis consists of single layer parenchymatous cells.
• Cells are elongated, compactly arranged, which form continuous layer.
• Epidermis is usually single layered.
• Outside the epidermis covered with waxy thick layer called cuticle.
• Cuticle absent in epidermis of root.
• Stomata are the structure present in the epidermis of leaf.
• Stomata regulate the process of transpiration and gaseous exchange.

Stomata :
• Each stoma composed of two bean shaped cell called guard cells.
• In grasses the guard cells are dumb-bell shaped.
• Outer wall of guard cell is thin and inner wall is thick.
• Guard cell possesses chloroplast and regulates the opening and closing of stomata.
• Epidermal cells in the vicinity of guard cell called subsidiary cells.
• Stomatal aperture, guard cells and subsidiary cells together called stomatal apparatus.
• The root hairs are unicellular elongations of the epidermal cells and help absorb water and mineral from the soil.

Trichomes :
• On stem the epidermal hairs are called trichomes.
• Trichomes are usually multicellular.
• May be branched or unbranched and soft or stiff.
• Sometimes secretory.
• Trichomes help in preventing water loss due to transpiration.

The ground tissue system :
• All the tissues except epidermis and vascular bundles constitute the ground tissue.

Important Questions for NCERT Class 11 Biology Anatomy of Flowering Plants

Ques. Phloem in gymnosperms lacks
(a) both sieve tubes and companion cells
(b) albuminous cells and sieve cells
(c) sieve tubes only (d) companion cells only.

Answer: A

Ques. Regeneration of damaged growing grass following grazing is largely due to
(a) lateral meristem          (b) apical meristem
(c) intercalary meristem    (d) secondary meristem.

Answer: C

Ques. Tracheids differ from other tracheary elements in
(a) having Casparian strips
(b) being imperforate (c) lacking nucleus
(d) being lignified. 

Answer: B

Ques. Meristematic tissue responsible for increase in girth of tree trunk is
(a) intercalary meristem      (b) lateral meristem
(c) phellogen                      (d) apical meristem.

Answer: B

Ques. Gymnosperms are also called soft wood spermatophytes because they lack
(a) cambium                      (b) phloem fibres
(c) thick-walled tracheids    (d) xylem fibres. 

Answer: D

Ques. Companion cells are closely associated with
(a) sieve elements            (b) vessel elements
(c) trichomes                    (d) guard cells. 

Answer: A

Ques. Function of companion cells is
(a) providing energy to sieve elements for active transport
(b) providing water to phloem
(c) loading of sucrose into sieve elements by passive transport
(d) loading of sucrose into sieve elements.

Answer: D

Ques. Which one of the following is not a lateral meristem?
(a) Intrafascicular cambium
(b) Interfascicular cambium
(c) Phellogen (d) Intercalary meristem

Answer: D

Ques. The chief water conducting elements of xylem in gymnosperms are
(a) vessels                      (b) fibres
(c) transfusion tissue       (d) tracheids. 

Answer: D

Ques. Transport of food material in higher plants takes place through
(a) companion cells          (b) transfusion tissue
(c) tracheids                    (d) sieve elements.

Answer: D

Ques. The length of different internodes in a culm of sugarcane is variable because of
(a) size of leaf lamina at the node below each internode
(b) intercalary meristem (c) shoot apical meristem
(d) position of axillary buds. 

Answer: B

Ques. A common structural feature of vessel elements and sieve tube elements is
(a) enucleate condition          (b) thick secondary walls
(c) pores on lateral walls       (d) presence of P-protein.

Answer: A

Ques. The apical meristem of the root is present
(a) only in radicals                  (b) only in tap roots
(c) only in adventitious roots   (d) in all the roots.

Answer: D

Ques. Chlorenchyma is known to develop in the
(a) cytoplasm of Chlorella
(b) mycelium of a green mould such as Aspergillus
(c) spore capsule of a moss
(d) pollen tube of Pinus. 

Answer: C

Ques. The cells of the quiescent centre are characterised by
(a) having dense cytoplasm and prominent nuclei
(b) having light cytoplasm and small nuclei
(c) dividing regularly to add to the corpus
(d) dividing regularly to add to tunica. 

Answer: B

Ques. Which of the following statements is true?
(a) Vessels are multicellular with wide lumen.
(b) Tracheids are multicellular with narrow lumen.
(c) Vessels are unicellular with narrow lumen.
(d) Tracheids are unicellular with wide lumen.

Answer: A

Ques. Axillary bud and terminal bud derived from the activity of
(a) lateral meristem    (b) intercalary meristem
(c) apical meristem     (d) parenchyma. 

Answer: C

Ques. Vessels are found in
(a) all angiosperms and some gymnosperm
(b) most of angiosperms and few gymnosperms
(c) all angiosperms, all gymnosperms and some pteridophyta
(d) all pteridophyta. 

Answer: B

Ques. At maturity, which of the following is non-nucleated?
(a) Palisade cell     (b) Cortical cell
(c) Sieve cell         (d) Companion cell 

Answer: C

Ques. Which of the following is not true about ‘sclereids’?
(a) These are groups of living cells.
(b) These are found in nut shells, guava pulp, pear.
(c) These are also called stone cells.
(d) These are form of sclerenchyma with fibres.

Answer: A

Ques. Which of the following plant cells will show totipotency?
(a) Sieve tubes     (b) Xylem vessels
(c) Meristem         (d) Cork cells 

Answer: C

Ques. Bordered pits are found in
(a) sieve cells             (b) vessel wall
(c) companion cells     (d) sieve tube wall.

Answer: B

Ques. An organised and differentiated cellular structure having cytoplasm but no nucleus is
(a) vessels               (b) xylem parenchyma
(c) sieve tubes         (d) tracheids. 

Answer: C

Ques. Angular collenchyma occurs in
(a) Cucurbita         (b) Helianthus
(c) Althaea            (d) Salvia. 

Answer: A

Ques. Collenchyma occurs in
(a) herbaceous climbers         (b) woody climbers
(c) climbing stems                 (d) water plants.

Answer: C

Ques. Collenchyma occurs in the stem and petioles of
(a) xerophytes         (b) monocots
(c) dicot herbs         (d) hydrophytes. 

Answer: C

Ques. Cork cambium and vascular cambium are
(a) parts of secondary xylem and phloem
(b) parts of pericycle (c) lateral meristem
(d) apical meristem.

Answer: C

Ques. Sieve tubes are suited for translocation of food because they possess
(a) bordered pits (b) no end walls
(c) broader lumen and perforated cross walls
(d) no protoplasm. 

Answer: C

Ques. Death of protoplasm is a pre-requisite for a vital function like
(a) transport of sap             (b) transport of food
(c) absorption of water        (d) gaseous exchange.

Answer: A

Ques. Organisation of stem apex into corpus and tunica is determined mainly by
(a) planes of cell division
(b) regions of meristematic activity
(c) rate of cell growth
(d) rate of shoot tip growth. 

Answer: A

Ques. Which meristem helps in increasing girth?
(a) Lateral meristem     (b) Intercalary meristem
(c) Primary meristem    (d) Apical meristem

Answer: A

Ques. Tunica corpus theory is connected with
(a) root apex          (b) root cap
(c) shoot apex        (d) secondary growth.

Answer: C

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