GSEB Class 11 Biology Solutions Chapter 5 Morphology of Flowering Plants

 

Question 1. What is meant by modification of root? What type of modification of the root is found in the:
1. Banyan tree
2. Turnip
3. Mangrove trees
Answer: Root modification means a change in the root's usual form or function. Roots typically absorb water and nutrients, but sometimes they adapt to perform other important tasks, such as storing food or providing extra support.
1. Banyan tree: These trees have Prop or Pillar roots. These are pillar-like adventitious roots that grow from the strong horizontal branches of a Banyan tree (Ficus benghalensis, also called Bargad). At first, these roots are in the air and absorb moisture from it.
2. Turnip: This vegetable has Napiform (pitcher-shaped) fleshy taproots. They are almost round or top-shaped and become narrow very quickly at the end. For example, the Turnip (Brassica repa) itself.
3. Mangrove trees: These trees have Pneumatophores, also known as respiratory or breathing roots. These are aerial roots or aerophores found in mangrove plants, which grow in marshy areas near the seashores. Examples include Rhizophora, Sonneratia, Avicennia, and Heritiera.
In simple words: Roots change their usual shape and job. Banyan trees have big prop roots for support, turnips have fat napiform roots for storing food, and mangrove trees have special breathing roots called pneumatophores to get air in wet soil.

Exam Tip: When asked about root modifications, always mention the plant, the specific name of the modified root, and its primary function (e.g., support, food storage, gas exchange).

 

Question 2. Justify the following statements on the basis of external features:
1. Underground parts of a plant are not always roots.
2. The flower is a modified shoot
Answer:
1. Underground parts of a plant are not always roots: In some plants, stems stay underground to carry out extra tasks, like food storage and vegetative propagation. For instance, Potatoes are a changed form of an underground stem, not a root.
2. A flower is a modified shoot: When the stem takes on the job of general reproduction, it changes into a flower. Because of this, a flower is often considered a modified root.
In simple words: Not all plant parts under the ground are roots; some are modified stems, like potatoes. A flower is actually a changed stem that's adapted for reproduction.

Exam Tip: To justify statements about plant modifications, always provide a clear reason and a specific plant example to support your explanation.

 

Question 3. How is a pinnately compound leaf different from a palmately compound leaf?
Answer: In a pinnately compound leaf, many small leaflets are found on a shared central stalk, called the rachis. This rachis acts like the middle vein of the leaf, as seen in Gulmohar. In contrast, in palmately compound leaves, the leaflets all attach at a single spot, which is the end of the petiole, like in silk cotton.
In simple words: Pinnate leaves have leaflets arranged along a central stem, like a feather. Palmate leaves have all their leaflets coming from one single point, like fingers on a hand.

Exam Tip: Clearly state the arrangement of leaflets for each type and provide a common example for better understanding.

 

Question 4. Explain with suitable examples of the different types of phyllotaxy.
Answer: Phyllotaxy refers to the specific way leaves are arranged on a plant's stem or branch. This arrangement typically comes in three main forms: alternate, opposite, and whorled.

• An alternate arrangement of leaves: In this phyllotaxy type, a single leaf grows at each node, with leaves appearing one after another along the stem. Examples include China rose, mustard, and sunflower plants.
• Opposite arrangement of leaves: In this type, a pair of leaves grows at each node, positioned directly across from each other. Examples are Calotropis and guava plants.
• Whorled Arrangement of leaves: This happens if more than two leaves grow at a single node and form a circle or ring. This is seen in Alstonia.

In simple words: Phyllotaxy is how leaves are placed on a stem. It can be alternate (one leaf per spot, like a spiral), opposite (two leaves per spot, facing each other), or whorled (more than two leaves in a ring around the stem).

Exam Tip: When explaining phyllotaxy, define each type clearly, describe the leaf arrangement, and provide a distinct example for each category to score full marks.

 

Question 5. Define the following terms:
1. Aestivation
2. Placentation
3. Actinomorphic
4. Zygomorphic
5. Superior ovary
6. Perigynous flower
7. Epipetalous stamen
Answer:
1. Aestivation: This is the specific way that sepals or petals are arranged inside a flower bud, with respect to other parts of the same layer or whorl, before the flower opens.
2. Placentation: This term refers to the arrangement of ovules inside the ovary of a flower.
3. Actinomorphic: A flower is called actinomorphic when it can be divided into two similar radial halves by any vertical plane that passes through its center. Examples include mustard, Datura, and Chilli.
4. Zygomorphic: A flower is called zygomorphic when it can only be divided into two similar halves by a single particular vertical plane. Examples include pea, Gulmohar, bean, and Cassia.
5. Superior ovary: Also known as a Hypogynous flower. In this type, the gynoecium (female reproductive part) sits in the highest position, while all other flower parts are located below it. The ovary in such flowers is thus called superior. Examples are mustard, China rose, and brinjal.
6. Perigynous flower: If the gynoecium is located in the center and other flower parts are situated on the edge of the thalamus at nearly the same height, it is called perigynous. Here, the ovary is considered half inferior. Examples include plum, rose, and peach.
7. Epipetalous stamen: This term describes stamens (male reproductive parts) that are connected to the petals of the flower. An example is brinjal.
In simple words: Aestivation is petal arrangement in a bud. Placentation is how ovules are placed in the ovary. Actinomorphic flowers are radially symmetrical (like a star), zygomorphic are bilaterally symmetrical (like a butterfly). A superior ovary sits above other parts, a perigynous flower has an ovary at the same level as others, and epipetalous stamens are fused to petals.

Exam Tip: When defining terms, use concise language. For biological terms, it's often helpful to include a brief example to illustrate the concept clearly.

 

Question 6. Differentiate between
1. Racemose and cymose inflorescence
2. Fibrous root and adventitious root
3. Apocarpous and syncarpous ovary
Answer:
1. Differences between Racemose and Cymose Inflorescence:
Racemose: In this type, the main axis continues to grow, and flowers develop sideways in an acropetal order (youngest flowers at the top). The main axis does not end in a flower. This is further divided into:

• Raceme
• Catkin
• Spike
• Spadix
• Corymb
• Umbel or capitulum

Branches grow indefinitely, and further branches emerge from the sides in an acropetal (bottom to top) pattern.
Cymose: In this type, the main axis ends in a flower, which stops its growth. Subsequent flowers develop from lateral branches in a basipetal order (youngest flowers at the bottom). This is further divided into:

• Mono-dichasial cyme
• Dichasial cyme
• Polychasial cyme

The branches emerge from terminal buds and stop growing after a period. Lateral branches then grow much strongly and spread out like a dome.

2. Differences between Fibrous Root and Adventitious Root:
Fibrous root: In monocotyledonous plants, the primary root lives for a short time and is then replaced by many roots. These roots grow from the base of the stem, forming a fibrous root system, as seen in wheat plants.
Adventitious root: In some plants, such as grass and banyan trees, roots grow from parts of the plant other than the radicle (the primary embryonic root). These roots are called adventitious roots.

3. Differences between Apocarpous Ovary and Syncarpous Ovary:
Apocarpous Ovary: This occurs when a flower has more than one carpel, and these carpels remain separate or free from each other, as observed in lotus and rose. Such an ovary is called an apocarpous ovary.
Syncarpous Ovary: This occurs when carpels are joined or fused together, as seen in mustard and tomato. After fertilization, the ovules inside this ovary develop into seeds, and the entire ovary grows into a fruit.
In simple words: Racemose flowers grow from the bottom up, with the main stem still growing, while cymose flowers grow from the top down, with the main stem ending in a flower. Fibrous roots branch out from the stem base, but adventitious roots grow from other plant parts. Apocarpous ovaries have separate carpels, and syncarpous ovaries have fused carpels.

Exam Tip: For differentiation questions, always present differences clearly side-by-side or in separate, well-defined points, using precise botanical terms and examples for each category.

 

Question 7. Draw the labeled following:
1. Gram seed
2. V.S. maize seed
Answer:

In simple words: This question asks for drawings of a gram seed and a maize seed, showing all their different parts. The images illustrate the exterior and interior structures with their labels.

Exam Tip: For diagrams, ensure clear, accurate labels for all essential parts. Practice drawing these seeds from memory to improve recall during exams.

 

Question 8. Describe modifications of the stem with suitable examples.
Answer: Stems can change their form to perform various functions beyond their primary role. Here are some key modifications:
Food storage: Stems are modified to carry out different tasks. Underground stems of plants like potato, ginger, turmeric, Samarkand, and colocasia are changed to store food. They also serve as organs for perennation, helping the plant survive difficult growth conditions.
Tendrils: Stem tendrils grow from axillary buds. These are thin and coiled structures that help plants to climb, such as gourds (cucumber, pumpkins, watermelon) and grapevines.
Thorns: Axillary buds on stems can also change into hard, straight, and pointed thorns. Thorns are found in many plants, including citrus and Bougainvillea. They help protect plants from animals that might eat them. Some plants in dry areas change their stems into flat (Opuntia) or fleshy cylindrical (Euphorbia) shapes. These modified stems contain chlorophyll and perform photosynthesis.
Vegetative Reproduction: Underground stems of certain plants, like grass and strawberry, spread to new areas. When the older parts die, new plants emerge. In plants like mint and jasmine, a thin lateral branch grows from the base of the main stem. After growing in the air for some time, it arches downward to touch the ground. In aquatic plants like Pistia and Eichhornia, a lateral branch with short internodes and a rosette of leaves and a cluster of roots is present at each node. In banana and pineapple, the lateral branches grow from the base and underground part of the main stem, move horizontally beneath the soil, and then come out diagonally upward to form leafy shoots.

In simple words: Stems can change their form to do different jobs. Some stems grow underground to save food, like potatoes. Others become thin tendrils to help plants climb, like grapevines. Some turn into sharp thorns for protection, like in citrus plants. Also, some stems help plants reproduce by spreading out and making new plants, such as grass or strawberries.

Exam Tip: When describing stem modifications, always mention the specific type of modification, its function, and a clear example of a plant that exhibits it.

 

Question 9. Take one flower each of the families Fabaceae and Solanaceae and write its semi-technical description. Also, draw their floral diagram after studying them.
Answer:
(a) Fabaceae: This family was previously known as Papilionoideae, a sub-family of the Leguminosae family. It is widely found across the globe.
Vegetative characters: These plants can be trees, shrubs, or herbs. Their roots often have nodules. Leaves are alternate, either pinnately compound or simple, with a swollen leaf base (pulvinate), stipules, and reticulate venation.
Floral characters:
Inflorescence: Racemose
Flower: Bisexual, zygomorphic (bilaterally symmetrical), with a calyx. Sepals are five and joined (gamosepalous).
Corolla: Petals are five and separate (polypetalous), papilionaceous (butterfly-like), consisting of one large posterior standard petal, two lateral wings, and two anterior ones that form a keel (enclosing the stamens and pistil).
Androecium: Stamens are ten, diadelphous (in two bundles), with dithecous anthers (two pollen sacs).
Gynoecium: The ovary is superior, made of a single carpel, unilocular (one chamber) with many ovules, and a single style. Fruit is a legume, and seeds are one to many, non-endospermic.
Economic importance: Many plants in this family are sources of pulses (gram, arhar, sem, moong, soybean), edible oil (soybean, groundnut), dyes (Indigofera), fibers (sun hemp), fodder (sesbania Trifolium), ornamentals (lupin, sweet pea), and medicine (muliathi).

Floral Formula: \( \% \text{ K}_{(5)} \text{ C}_{1+2(2)} \text{ A}_{(9)+1} \underline{\text{G}}_1 \)

(b) Solanaceae: This is a large family commonly known as the 'potato family'. It is extensively found in tropical, subtropical, and even temperate regions.
Vegetative characters: Plants are mostly herbs, shrubs, and small trees. The stem is herbaceous, rarely woody, aerial, erect, cylindrical, branched, solid or hollow, hairy or smooth. Potatoes have an underground stem (Solanum tuberosum).
Leaves: Alternate, simple, rarely pinnately compound, without stipules; venation is reticulate.
Floral characters:
Inflorescence: Solitary, axillary, or cymose, as in Solanum.
Flower: Bisexual, actinomorphic (radially symmetrical).
Calyx: Sepals are five, united, persistent, with valvate aestivation.
Corolla: Petals are five, united, with valvate aestivation.
Androecium: Stamens are five, epipetalous (attached to petals).
Gynoecium: Carpels are two, syncarpous (fused); the ovary is superior, bilocular (two chambers), and the placenta is swollen with many ovules.
Fruits: Berry or capsule.
Seeds: Many, with endosperms.
Economic Importance: Many plants in this family provide food (tomato, brinjal, potato), spice (chili), medicine (belladonna, ashwagandha), are used as fumigants (tobacco), and as ornamentals (petunia).

Floral Formula: \( \text{⊕ } \text{K}_{(5)} \text{ C}_{(5)} \text{ A}_5 \underline{\text{G}}_{(2)} \)
In simple words: This question asks us to describe a flower from the Fabaceae family and another from the Solanaceae family, including their features and a drawing of their floral arrangement. Fabaceae flowers have special petals, while Solanaceae flowers are regular. Both descriptions include how their leaves, stems, and reproductive parts look, along with their floral formulas.

Exam Tip: For family descriptions, systematically list vegetative and floral characters, paying attention to specific terms like "zygomorphic," "papilionaceous," "epipetalous," and "syncarpous." Always remember to include the floral formula and a clear floral diagram for full marks.

 

Question 10. Describe the various types of placentations found in flowering plants.
Answer: Placentation refers to the specific arrangement of ovules within the ovary of a flower. There are several different types:
(a) Marginal: In marginal placentation, the placenta creates a ridge along the ventral seam of the ovary. The ovules grow on this ridge, forming two distinct rows, as seen in a pea pod.
(b) Axile: This occurs when the placenta is located in the central axis, and the ovules are attached to it in an ovary that has multiple chambers (multilocular). Examples include China rose, tomato, and lemon.
(c) Parietal: In parietal placentation, the ovules grow on the inner wall of the ovary or on its outer edge. The ovary has only one chamber but appears two-chambered because of a false septum. Examples are mustard and argemone. When ovules grow on a central axis without any septa, as in Dianthus and Primrose, the placentation is called free central.
(d) Basal: In basal placentation, the placenta grows at the base of the ovary, and only a single ovule is attached there. This type is found in sunflower and marigold.

In simple words: Placentation describes how ovules are arranged inside a flower's ovary. Marginal placentation has ovules along one edge, like peas. Axile has them on a central stalk in a divided ovary. Parietal has them on the inner walls of an undivided ovary. Basal has one ovule at the very bottom. Free central has ovules on a central column but no dividing walls.

Exam Tip: When describing placentation, always specify the ovule attachment location and the ovary's chamber structure. Provide distinct plant examples for each type.

 

Question 11. What is a flower? Describe the parts of a typical angiosperm flower.
Answer: A flower serves as the reproductive unit in angiosperms (flowering plants). Its main purpose is sexual reproduction.
A typical flower consists of four different kinds of whorls (circles of parts), arranged one after another on the swollen end of the stalk or pedicel. This swollen end is known as the thalamus or receptacle. These whorls are the calyx, corolla, androecium, and gynoecium. The calyx and corolla are considered accessory organs because they protect the reproductive parts, while the androecium and gynoecium are the actual reproductive organs. In some flowers, like lily, the calyx and corolla are not separate and are together called the perianth. A flower with both androecium and gynoecium is called bisexual. If a flower has only stamens (male parts) or only carpels (female parts), it is unisexual.
In terms of symmetry, a flower can be actinomorphic (radial) or zygomorphic (bilateral). A flower is actinomorphic, like mustard, datura, or chili, if it can be divided into two equal radial halves by any radial plane passing through its center. If a flower can only be divided into two similar halves by just one particular vertical plane, it is zygomorphic, as seen in pea, Gulmohar, bean, or cassia. A flower is considered asymmetric (irregular) if it cannot be divided into two similar halves by any vertical plane through its center, such as in canna.
A flower might be trimerous, tetramerous, or pentamerous if its floral parts are in multiples of 3, 4, or 5, respectively. Flowers with bracts (small, reduced leaves at the base of the pedicel) are called bracteate, and those without bracts are ebracteate.
Based on how the calyx, corolla, and androecium are positioned in relation to the ovary and thalamus, flowers are classified as hypogynous, perigynous, and epigynous. In a hypogynous flower, the gynoecium occupies the highest position, with other parts located below it. The ovary in such flowers is called superior, as in mustard, China rose, and brinjal.
If the gynoecium is in the center and other flower parts are at almost the same level on the rim of the thalamus, it is called perigynous. Here, the ovary is considered half inferior, as in plum, rose, and peach. In epigynous flowers, the edge of the thalamus grows upward, completely surrounding and fusing with the ovary. The other parts of the flower grow above the ovary. Thus, the ovary is called 'inferior,' as seen in flowers like guava and cucumber, and the ray florets of sunflower.
In simple words: A flower is how flowering plants reproduce. It has four main parts: the calyx (sepals), corolla (petals), androecium (male part), and gynoecium (female part). Flowers can be symmetrical in different ways (radial or bilateral) and their parts can be arranged above, around, or below the ovary.

Exam Tip: Structure your answer by first defining a flower, then describing its main parts (whorls), followed by symmetry types, and finally, the position of the ovary relative to other floral organs. Provide examples for clarity in each section.

 

Question 12. How do the various leaf modifications help plants?
Answer: Leaves often change their shape and function to do jobs other than photosynthesis. These changes help plants in various ways:
Leaves are changed into tendrils for climbing, as seen in peas, allowing the plant to grow upward and access more sunlight. They can also transform into spines for protection against animals that might eat them, as in cacti. The thick, fleshy leaves of onions and garlic store food, which helps the plant survive and grow. In some plants, like Australian acacia, the leaves are small and short-lived, but their petioles (leaf stalks) expand and turn green to make food. Specialized insectivorous plants, such as pitcher plants and Venus fly traps, have modified leaves that help them catch and digest insects, especially in nutrient-poor soils.

In simple words: Leaves change to help plants survive. They can become tendrils for climbing, sharp spines for protection, fleshy for storing food, or even special traps to catch insects.

Exam Tip: Focus on linking each modification to a specific survival advantage or function, and use clear examples to support your points.

 

Question 13. Define the term inflorescence. Explain the basis for the different types of inflorescence in flowering plants.
Answer: Inflorescence is the specific arrangement of flowers on the floral axis. The way flowers are organized on a plant stems from how the plant's main growing tip (apex) behaves.
The different types of inflorescence are based on whether the main apex changes into a flower or continues to grow. This fundamental distinction gives rise to the two primary types of inflorescence: racemose and cymose.
Racemose Inflorescence: In this type, the main axis continues to grow without ending in a flower. Flowers develop laterally in an acropetal succession, meaning the older flowers are at the base and the younger ones are towards the apex. The continued growth of the main axis allows for an indefinite number of flowers.
Cymose Inflorescence: In contrast, in cymose inflorescence, the main axis terminates in a flower, which stops its growth. Subsequent flowers develop from lateral branches. This growth pattern results in a basipetal succession, where the younger flowers are at the base and the older ones are at the apex. This type of inflorescence typically produces a limited number of flowers due to the arrested growth of the main axis.

In simple words: Inflorescence is how flowers are arranged on a stem. The main difference in types is whether the stem keeps growing (racemose, like a never-ending bouquet) or stops growing with a flower at its tip (cymose, like a finished flower at the end of a branch).

Exam Tip: Define inflorescence clearly, then use the growth pattern of the main axis (indeterminate for racemose, determinate for cymose) as the primary basis for distinction. Illustrate with a simple sketch if possible.

 

Question 14. Write the floral formula of an actinomorphic, bisexual, hypogynous flower with five united sepals, five free petals, five free stamens, and two united carpels with the superior ovary and axile placentation.
Answer: The floral formula for an actinomorphic, bisexual, hypogynous flower with five united sepals, five free petals, five free stamens, and two united carpels with a superior ovary and axile placentation is:
\( \text{⊕ } \text{♂♀ } \text{K}_{(5)} \text{ C}_5 \text{ A}_5 \underline{\text{G}}_{(2)} \)
Here's what each symbol means based on the flower's description:
\( \text{⊕ } \): This symbol indicates that the flower is actinomorphic, meaning it has radial symmetry and can be divided into two equal halves by any vertical plane passing through the center.
\( \text{♂♀ } \): This symbol represents a bisexual flower, meaning it contains both male (stamens) and female (carpels) reproductive organs.
\( \text{K}_{(5)} \): 'K' stands for calyx (sepals). The subscript '(5)' shows that there are five sepals, and the parentheses indicate that these sepals are united or fused together.
\( \text{C}_5 \): 'C' stands for corolla (petals). The subscript '5' indicates there are five petals, and the absence of parentheses means these petals are free or separate.
\( \text{A}_5 \): 'A' stands for androecium (stamens). The subscript '5' means there are five stamens, and they are free.
\( \underline{\text{G}}_{(2)} \): 'G' stands for gynoecium (carpels). The underline below 'G' signifies a superior ovary (hypogynous condition). The subscript '(2)' indicates that there are two carpels, and the parentheses mean these carpels are united or fused, forming a single pistil.
In simple words: The floral formula describes a flower using symbols. \( \text{⊕} \) means it's radially symmetrical. \( \text{♂♀} \) means it has both male and female parts. \( \text{K}_{(5)} \) means five fused sepals. \( \text{C}_5 \) means five separate petals. \( \text{A}_5 \) means five separate stamens. \( \underline{\text{G}}_{(2)} \) means two fused carpels forming a superior ovary.

Exam Tip: When writing floral formulas, remember to use standard symbols for symmetry, sexuality, and floral parts. Pay close attention to parentheses for fusion and the underline/overline for ovary position to accurately represent the flower's characteristics.

 

Question 15. Describe the arrangement of floral members in relation to their insertion on the thalamus.
Answer: The way floral parts—calyx, corolla, and androecium—are arranged concerning the ovary on the thalamus allows flowers to be categorized into three main types:
(a) Hypogynous: In a hypogynous flower, the gynoecium (the female part) is positioned at the very top, taking the highest place. All other floral parts, such as the sepals, petals, and stamens, are situated below the ovary. Because of this arrangement, the ovary in hypogynous flowers is considered superior. Examples include mustard, China rose, and brinjal.
(b) Perigynous: If the gynoecium is located in the center of the flower, and the other floral parts are inserted on the rim (edge) of the thalamus at almost the same height as the ovary, it is called perigynous. In this type of arrangement, the ovary is said to be half inferior. Examples include plum, rose, and peach.
(c) Epigynous: In epigynous flowers, the margin of the thalamus (the receptacle) grows upward and completely surrounds the ovary, eventually fusing with it. Consequently, all other floral parts grow from above the ovary. Due to this arrangement, the ovary in epigynous flowers is considered inferior. Examples are guava, cucumber, and sunflower.
In simple words: Flowers are categorized by where their parts are attached to the central part (thalamus) relative to the ovary. In hypogynous flowers, the ovary is on top (superior). In perigynous flowers, the ovary is in the middle (half inferior). In epigynous flowers, the ovary is embedded below all other parts (inferior).

Exam Tip: When describing the positions of floral members, clearly explain the relative height of the ovary compared to other parts (sepals, petals, stamens). Use the terms 'superior,' 'half inferior,' and 'inferior' correctly and provide suitable plant examples for each category.