Q: Q1. What is meant by modification of root? What type of modification of root is found in the:\n(a) Banyan tree\n(b) Turnip\n(c) Mangrove tree

### What is meant by modification of root?\nRoots in most plants are primarily involved in absorption of water and minerals from the soil and providing anchorage to the plant parts. However, in some plants, roots change their shape and structure and get modified to perform functions other than absorption and anchorage. These functions include storage of food, mechanical support, and respiration. This alteration in the form and function of roots is known as root modification.\n\n### Types of root modification found in:\n\n**(a) Banyan tree (Ficus benghalensis): Prop Roots**\nIn the Banyan tree, large, pillar-like adventitious roots arise from the branches and grow vertically downwards into the soil. Once they reach the soil, they fix themselves and provide additional mechanical support to the massive, spreading branches of the tree. These roots are called prop roots. They are a type of adventitious root modification for support.\n\n**(b) Turnip (Brassica rapa): Fusiform Root**\nTurnip exhibits a modification of the tap root system for food storage. The tap root becomes swollen and fleshy, taking on a fusiform (spindle-shaped) appearance, which is broad in the middle and tapers towards both ends. This swollen part stores reserve food material. It is a type of tap root modification for storage.\n\n**(c) Mangrove tree (e.g., Rhizophora, Avicennia): Pneumatophores**\nMangrove trees grow in marshy, saline areas where the soil is waterlogged and poorly aerated (lacks oxygen). To cope with this condition, some branches of the tap root grow vertically upwards out of the soil and water into the air. These roots are called pneumatophores. They possess numerous small pores called lenticels on their surface, which facilitate the exchange of gases for respiration. This is a modification of the tap root for respiration.

Q: Q5. Write floral formula of a actinomorphic, bisexual, hypogynous flower with five united sepals, five free petals, five free stamens and two united carpels with superior ovary.

The floral formula for the described flower is:\n\n**⊕ ⚥ K₍₅₎ C₅ A₅ G₍₂₎**\n\n**Explanation of symbols:**\n* **⊕ (Actinomorphic):** Represents radial symmetry.\n* **⚥ (Bisexual):** Indicates that the flower has both male (androecium) and female (gynoecium) reproductive organs.\n* **K₍₅₎ (Calyx):** 'K' stands for calyx (sepals). The subscript '5' indicates five sepals. The parentheses '₍ ₎' around '5' denote that the sepals are united (gamosepalous).\n* **C₅ (Corolla):** 'C' stands for corolla (petals). The subscript '5' indicates five petals. The absence of parentheses signifies that the petals are free (polypetalous).\n* **A₅ (Androecium):** 'A' stands for androecium (stamens). The subscript '5' indicates five stamens. The absence of parentheses signifies that the stamens are free.\n* **G₍₂₎ (Gynoecium):** 'G' stands for gynoecium (carpels/pistil). The subscript '2' indicates two carpels. The parentheses '₍ ₎' around '2' denote that the carpels are united (syncarpous). The bar under 'G' (Gynoecium) indicates a superior ovary (hypogynous flower).

Q: Q7. Draw the labelled diagram of the following:\n(a) L.S. of a flower\n(b) Vertical section of maize grain

**(a) L.S. of a flower:**\nThe diagram should show a longitudinal section of a typical bisexual flower, clearly illustrating the following parts with appropriate labels:\n1. **Pedicel:** The stalk of the flower.\n2. **Thalamus (Receptacle):** The swollen tip of the pedicel on which floral organs are borne.\n3. **Sepals (Calyx):** The outermost whorl, typically green and leaf-like, protecting the bud.\n4. **Petals (Corolla):** The second whorl, often brightly coloured to attract pollinators.\n5. **Stamen (Androecium):** The male reproductive part, consisting of:\n * **Anther:** Contains pollen grains.\n * **Filament:** Stalk supporting the anther.\n6. **Pistil/Carpel (Gynoecium):** The female reproductive part, consisting of:\n * **Stigma:** Receptive tip for pollen.\n * **Style:** Stalk connecting stigma to ovary.\n * **Ovary:** Swollen basal part containing ovules.\n * **Ovule:** Contains the female gamete.\n\n**(b) Vertical section of maize grain:**\nThe diagram should show a longitudinal section of a maize (monocot) grain, clearly illustrating the following parts with appropriate labels:\n1. **Pericarp:** The fruit wall, fused with the seed coat.\n2. **Aleurone layer:** Proteinaceous layer surrounding the endosperm, typically 1-3 cells thick.\n3. **Endosperm:** The large, starchy food storage tissue.\n4. **Scutellum:** A single, shield-shaped cotyledon, located laterally to the embryonal axis, which absorbs food from the endosperm.\n5. **Embryonal axis:** Consists of:\n * **Plumule:** Embryonic shoot, covered by a protective sheath called **coleoptile**.\n * **Radicle:** Embryonic root, covered by a protective sheath called **coleorhiza**.\n * **Root cap:** Protective covering over the root tip.

Q: Q10. Define placentation. Describe the different types of placentation found in flowering plants.

### Definition of Placentation\n\n**Placentation** refers to the arrangement of ovules within the ovary. The part of the ovary where ovules are attached is called the placenta. Placentation is a significant taxonomic character used in the classification of flowering plants.\n\n### Types of Placentation\n\nThere are several types of placentation found in flowering plants, each characterized by a distinct arrangement of ovules:\n\n1. **Marginal Placentation:**\n * **Description:** In this type, the placenta forms a ridge along the ventral suture of the ovary. The ovules are borne on this ridge, forming two rows. The ovary is typically unilocular (single-chambered).\n * **Occurrence:** Characteristic of the family Fabaceae (e.g., pea, gram, bean).\n\n2. **Axile Placentation:**\n * **Description:** The placenta is axial, and the ovules are attached to it in a multilocular (many-chambered) ovary. The septa (partitions) divide the ovary into chambers, and the ovules are borne on the central axis.\n * **Occurrence:** Found in China rose, tomato, lemon.\n\n3. **Parietal Placentation:**\n * **Description:** The ovules develop on the inner wall of the ovary or on the peripheral part. The ovary is typically unilocular, but it may become two-chambered due to the formation of a false septum (replum).\n * **Occurrence:** Seen in mustard, Argemone.\n\n4. **Free Central Placentation:**\n * **Description:** The ovules are borne on a central axis, and the septa are absent. The ovary is unilocular. This type arises from axile placentation where the septa degenerate.\n * **Occurrence:** Found in Dianthus, Primrose.\n\n5. **Basal Placentation:**\n * **Description:** The placenta develops at the base of the ovary, and a single ovule is attached to it. The ovary is unilocular.\n * **Occurrence:** Characteristic of the family Asteraceae (e.g., sunflower, marigold).

Question 1

Q1. What is meant by modification of root? What type of modification of root is found in the:
(a) Banyan tree
(b) Turnip
(c) Mangrove tree

Accepted Answer

### What is meant by modification of root?
Roots in most plants are primarily involved in absorption of water and minerals from the soil and providing anchorage to the plant parts. However, in some plants, roots change their shape and structure and get modified to perform functions other than absorption and anchorage. These functions include storage of food, mechanical support, and respiration. This alteration in the form and function of roots is known as root modification.

### Types of root modification found in:

**(a) Banyan tree (Ficus benghalensis): Prop Roots**
In the Banyan tree, large, pillar-like adventitious roots arise from the branches and grow vertically downwards into the soil. Once they reach the soil, they fix themselves and provide additional mechanical support to the massive, spreading branches of the tree. These roots are called prop roots. They are a type of adventitious root modification for support.

**(b) Turnip (Brassica rapa): Fusiform Root**
Turnip exhibits a modification of the tap root system for food storage. The tap root becomes swollen and fleshy, taking on a fusiform (spindle-shaped) appearance, which is broad in the middle and tapers towards both ends. This swollen part stores reserve food material. It is a type of tap root modification for storage.

**(c) Mangrove tree (e.g., Rhizophora, Avicennia): Pneumatophores**
Mangrove trees grow in marshy, saline areas where the soil is waterlogged and poorly aerated (lacks oxygen). To cope with this condition, some branches of the tap root grow vertically upwards out of the soil and water into the air. These roots are called pneumatophores. They possess numerous small pores called lenticels on their surface, which facilitate the exchange of gases for respiration. This is a modification of the tap root for respiration.

Question 2

Q2. Draw the labelled diagram of the following:
(a) Gram seed
(b) V.S. of maize seed

Accepted Answer

### (a) Gram seed (Dicotyledonous seed)
**Description of the labelled diagram:**
The diagram should show an external view of a gram seed and a longitudinal section (L.S.) of a gram seed.

**External view:**
*   **Seed coat:** The outer protective covering.
*   **Hilum:** A scar on the seed coat, representing the point of attachment to the fruit.
*   **Micropyle:** A small pore located just above the hilum, through which water enters the seed during germination.
*   **Raphe:** A ridge formed by the fusion of the funiculus with the ovule wall (often less prominent in gram).

**Longitudinal Section (L.S.):**
*   **Seed coat:** The outer protective layer.
*   **Embryo:** Consisting of:
    *   **Embryonal axis:** The central axis from which the plumule and radicle arise.
    *   **Cotyledons (two):** Large, fleshy structures that store food for the developing embryo. They are attached to the embryonal axis.
    *   **Plumule:** The embryonic shoot, located at one end of the embryonal axis, between the cotyledons. It develops into the shoot system.
    *   **Radicle:** The embryonic root, located at the other end of the embryonal axis. It develops into the root system.

### (b) V.S. of maize seed (Monocotyledonous seed)
**Description of the labelled diagram:**
The diagram should show a vertical section (V.S.) of a maize seed.

*   **Pericarp and Seed coat:** Fused together to form a protective layer.
*   **Aleurone layer:** A proteinaceous layer forming the outermost layer of the endosperm, separating it from the embryo.
*   **Endosperm:** The large, central part of the seed, storing food (mainly starch). It is the primary storage tissue in maize.
*   **Embryo:** Small and located in the lower portion of the seed, embedded in the endosperm. It consists of:
    *   **Scutellum:** A single, large, shield-shaped cotyledon that is pressed against the endosperm and helps in the absorption of food from the endosperm.
    *   **Embryonal axis:** Comprising:
        *   **Plumule:** The embryonic shoot, covered by a protective sheath called **coleoptile**.
        *   **Radicle:** The embryonic root, covered by a protective sheath called **coleorhiza**.

**Key differences to highlight:** Gram seed is dicotyledonous and non-endospermic (food stored in cotyledons), while maize seed is monocotyledonous and endospermic (food stored in endosperm).

Question 3

Q3. Describe the various types of placentation found in flowering plants.

Accepted Answer

### Placentation
Placentation refers to the arrangement of ovules within the ovary. The part of the ovary where ovules are attached is called the placenta. The type of placentation is an important characteristic used in the classification of flowering plants. The main types of placentation are:

1.  **Marginal Placentation:**
    *   **Description:** The placenta forms a ridge along the ventral suture of the ovary, and the ovules are borne on this ridge in two rows.
    *   **Ovary Type:** Typically found in monocarpellary ovaries (ovary with a single carpel).
    *   **Example:** Pea (Pisum sativum), Bean.

2.  **Axile Placentation:**
    *   **Description:** The ovary is multilocular (chambered), and the placenta is axial. The ovules are attached to the central axis in each locule.
    *   **Ovary Type:** Found in multicarpellary, syncarpous ovaries (multiple carpels fused).
    *   **Example:** China rose (Hibiscus rosa-sinensis), Tomato (Solanum lycopersicum), Lemon (Citrus limon).

3.  **Parietal Placentation:**
    *   **Description:** The ovules develop on the inner wall of the ovary or on peripheral parts. The ovary is typically one-chambered but becomes two-chambered due to the formation of a false septum (replum).
    *   **Ovary Type:** Found in multicarpellary, syncarpous ovaries.
    *   **Example:** Mustard (Brassica campestris), Argemone (Argemone mexicana).

4.  **Free Central Placentation:**
    *   **Description:** The ovules are borne on a central axis, and there are no septa (partitions) in the ovary. The ovary is unilocular.
    *   **Ovary Type:** Found in multicarpellary, syncarpous ovaries.
    *   **Example:** Dianthus (Carnation), Primrose (Primula).

5.  **Basal Placentation:**
    *   **Description:** The placenta develops at the base of the ovary, and a single ovule is attached to it.
    *   **Ovary Type:** Found in monocarpellary or multicarpellary, syncarpous ovaries, typically unilocular.
    *   **Example:** Sunflower (Helianthus annuus), Marigold (Tagetes erecta).

These different arrangements ensure efficient development and dispersal of seeds.

Question 4

Q4. Differentiate between the following:
(a) Racemose and cymose inflorescence
(b) Fibrous root and adventitious root
(c) Apocarpous and syncarpous ovary

Accepted Answer

### (a) Racemose and Cymose Inflorescence

### (b) Fibrous root and Adventitious root

| Feature             | Fibrous Root System                                  | Adventitious Root System                             |
| :------------------ | :--------------------------------------------------- | :--------------------------------------------------- |
| **Origin**          | Arises from the base of the stem                     | Arises from parts of the plant other than the radicle (e.g., stem, branches, leaves) |
| **Primary root**    | The primary root is short-lived and is replaced by a cluster of roots. | Primary root may or may not be present; if present, it is not the main root system. |
| **Structure**       | Consists of a cluster of thin, fibrous roots of similar size. | Can be of various forms (e.g., prop roots, stilt roots, climbing roots, storage roots). |
| **Occurrence**      | Characteristic of monocotyledonous plants.           | Found in both monocots and dicots, often as modifications. |
| **Function**        | Primarily anchorage and absorption.                  | Primarily for support, storage, or other specialized functions (e.g., respiration). |
| **Examples**        | Wheat, Rice, Maize, Onion                            | Banyan (prop roots), Maize/Sugarcane (stilt roots), Monstera (climbing roots), Sweet potato (storage roots) |

*Note: All fibrous roots are adventitious roots, but not all adventitious roots are fibrous. Fibrous roots are a specific type of adventitious root system where the primary root is short-lived and replaced by a cluster of roots from the stem base. Adventitious roots are a broader category originating from any part other than the radicle.*

### (c) Apocarpous and Syncarpous Ovary

Question 5

Q5. Write floral formula of a actinomorphic, bisexual, hypogynous flower with five united sepals, five free petals, five free stamens and two united carpels with superior ovary.

Accepted Answer

The floral formula for the described flower is:

**⊕ ⚥ K₍₅₎ C₅ A₅ G₍₂₎**

**Explanation of symbols:**
*   **⊕ (Actinomorphic):** Represents radial symmetry.
*   **⚥ (Bisexual):** Indicates that the flower has both male (androecium) and female (gynoecium) reproductive organs.
*   **K₍₅₎ (Calyx):** 'K' stands for calyx (sepals). The subscript '5' indicates five sepals. The parentheses '₍ ₎' around '5' denote that the sepals are united (gamosepalous).
*   **C₅ (Corolla):** 'C' stands for corolla (petals). The subscript '5' indicates five petals. The absence of parentheses signifies that the petals are free (polypetalous).
*   **A₅ (Androecium):** 'A' stands for androecium (stamens). The subscript '5' indicates five stamens. The absence of parentheses signifies that the stamens are free.
*   **G₍₂₎ (Gynoecium):** 'G' stands for gynoecium (carpels/pistil). The subscript '2' indicates two carpels. The parentheses '₍ ₎' around '2' denote that the carpels are united (syncarpous). The bar under 'G' (Gynoecium) indicates a superior ovary (hypogynous flower).

Question 6

Q6. Define the following terms:
(a) Aestivation
(b) Placentation
(c) Actinomorphic
(d) Zygomorphic
(e) Superior ovary
(f) Perigynous flower
(g) Epipetalous stamen

Accepted Answer

(a) **Aestivation:** The mode of arrangement of sepals or petals in a floral bud with respect to the other members of the same whorl is called aestivation. Common types include valvate, twisted, imbricate, and vexillary.

(b) **Placentation:** The arrangement of ovules within the ovary is known as placentation. It is a characteristic feature used in the classification of flowering plants. Different types include marginal, axile, parietal, free central, and basal.

(c) **Actinomorphic:** When a flower can be divided into two equal radial halves by any radial plane passing through the centre, it is said to be actinomorphic or radially symmetrical. Examples include mustard, datura, and chilli.

(d) **Zygomorphic:** When a flower can be divided into two similar halves only in one particular vertical plane, it is said to be zygomorphic or bilaterally symmetrical. Examples include pea, gulmohur, bean, and cassia.

(e) **Superior ovary:** An ovary is said to be superior when it is positioned above the attachment points of the other floral parts (sepals, petals, and stamens). In this condition, the flower is described as hypogynous. Examples include mustard, China rose, and brinjal.

(f) **Perigynous flower:** In a perigynous flower, the ovary is situated in the centre, and other floral parts (sepals, petals, and stamens) are located on the rim of the thalamus, almost at the same level. The ovary is considered half-inferior. Examples include plum, rose, and peach.

(g) **Epipetalous stamen:** When stamens are attached to the petals, they are called epipetalous. This condition is commonly observed in the family Solanaceae, for example, brinjal.

Question 7

Q7. Draw the labelled diagram of the following:
(a) L.S. of a flower
(b) Vertical section of maize grain

Accepted Answer

**(a) L.S. of a flower:**
The diagram should show a longitudinal section of a typical bisexual flower, clearly illustrating the following parts with appropriate labels:
1.  **Pedicel:** The stalk of the flower.
2.  **Thalamus (Receptacle):** The swollen tip of the pedicel on which floral organs are borne.
3.  **Sepals (Calyx):** The outermost whorl, typically green and leaf-like, protecting the bud.
4.  **Petals (Corolla):** The second whorl, often brightly coloured to attract pollinators.
5.  **Stamen (Androecium):** The male reproductive part, consisting of:
    *   **Anther:** Contains pollen grains.
    *   **Filament:** Stalk supporting the anther.
6.  **Pistil/Carpel (Gynoecium):** The female reproductive part, consisting of:
    *   **Stigma:** Receptive tip for pollen.
    *   **Style:** Stalk connecting stigma to ovary.
    *   **Ovary:** Swollen basal part containing ovules.
    *   **Ovule:** Contains the female gamete.

**(b) Vertical section of maize grain:**
The diagram should show a longitudinal section of a maize (monocot) grain, clearly illustrating the following parts with appropriate labels:
1.  **Pericarp:** The fruit wall, fused with the seed coat.
2.  **Aleurone layer:** Proteinaceous layer surrounding the endosperm, typically 1-3 cells thick.
3.  **Endosperm:** The large, starchy food storage tissue.
4.  **Scutellum:** A single, shield-shaped cotyledon, located laterally to the embryonal axis, which absorbs food from the endosperm.
5.  **Embryonal axis:** Consists of:
    *   **Plumule:** Embryonic shoot, covered by a protective sheath called **coleoptile**.
    *   **Radicle:** Embryonic root, covered by a protective sheath called **coleorhiza**.
    *   **Root cap:** Protective covering over the root tip.

Question 8

Q8. Write floral formula of an actinomorphic, bisexual, hypogynous flower with five united sepals, five free petals, five free stamens and two united carpels with superior ovary and ax

Accepted Answer

To write the floral formula, we use specific symbols to represent different floral characteristics. Let's break down the given description and assign the corresponding symbols:

1.  **Actinomorphic:** Represented by a circle with a plus sign inside ($\oplus$). This indicates radial symmetry.
2.  **Bisexual:** Represented by the male and female symbols combined ($	ext{♂♀}$). This indicates the presence of both stamens and carpels in the same flower.
3.  **Five united sepals:** Sepals are represented by 'K' (for Calyx). Since there are five and they are united, it is written as K(5). The parenthesis indicates fusion.
4.  **Five free petals:** Petals are represented by 'C' (for Corolla). Since there are five and they are free, it is written as C5.
5.  **Five free stamens:** Stamens are represented by 'A' (for Androecium). Since there are five and they are free, it is written as A5.
6.  **Two united carpels with superior ovary:** Carpels are represented by 'G' (for Gynoecium). Since there are two and they are united, it is written as G(2). The superior ovary is indicated by a line placed *under* the 'G'.
7.  **Hypogynous flower:** This condition directly relates to the superior ovary, where the ovary is at the top, and other floral parts are below it. This is already covered by the superior ovary notation.
8.  **Axile placentation:** This describes the arrangement of ovules within the ovary. While it's an important characteristic, it is typically not directly represented in the standard floral formula symbols but is a feature of the gynoecium, often associated with a multilocular, syncarpous ovary (G(2) in this case).

Combining these symbols, the floral formula is:

**$\oplus 	ext{♂♀ K(5) C5 A5 G(2)}$**

Question 9

Q9. Describe the arrangement of floral members in relation to their insertion on thalamus.

Accepted Answer

The position of the floral parts (sepals, petals, and stamens) in relation to the ovary on the thalamus (receptacle) is a crucial characteristic used in classifying flowering plants. Based on this arrangement, flowers are primarily classified into three types:

### 1. Hypogynous Flower

*   **Description:** In a hypogynous flower, the gynoecium (ovary) occupies the highest position on the thalamus, while the other floral parts (sepals, petals, and stamens) are situated below it. The thalamus is typically conical or convex.
*   **Ovary Position:** The ovary in a hypogynous flower is described as **superior**.
*   **Examples:** Mustard, China rose, Brinjal.

### 2. Perigynous Flower

*   **Description:** In a perigynous flower, the gynoecium is situated in the centre, and the other floral parts are located on the rim of the thalamus, which grows upwards to form a cup-shaped structure. The floral parts are thus at almost the same level as the ovary.
*   **Ovary Position:** The ovary in a perigynous flower is described as **half-inferior**.
*   **Examples:** Plum, Rose, Peach.

### 3. Epigynous Flower

*   **Description:** In an epigynous flower, the margins of the thalamus grow upwards, completely enclosing the ovary and getting fused with its wall. The other floral parts arise above the ovary.
*   **Ovary Position:** The ovary in an epigynous flower is described as **inferior**.
*   **Examples:** Guava, Cucumber, Ray florets of sunflower.

Question 10

Q10. Define placentation. Describe the different types of placentation found in flowering plants.

Accepted Answer

### Definition of Placentation

**Placentation** refers to the arrangement of ovules within the ovary. The part of the ovary where ovules are attached is called the placenta. Placentation is a significant taxonomic character used in the classification of flowering plants.

### Types of Placentation

There are several types of placentation found in flowering plants, each characterized by a distinct arrangement of ovules:

1.  **Marginal Placentation:**
    *   **Description:** In this type, the placenta forms a ridge along the ventral suture of the ovary. The ovules are borne on this ridge, forming two rows. The ovary is typically unilocular (single-chambered).
    *   **Occurrence:** Characteristic of the family Fabaceae (e.g., pea, gram, bean).

2.  **Axile Placentation:**
    *   **Description:** The placenta is axial, and the ovules are attached to it in a multilocular (many-chambered) ovary. The septa (partitions) divide the ovary into chambers, and the ovules are borne on the central axis.
    *   **Occurrence:** Found in China rose, tomato, lemon.

3.  **Parietal Placentation:**
    *   **Description:** The ovules develop on the inner wall of the ovary or on the peripheral part. The ovary is typically unilocular, but it may become two-chambered due to the formation of a false septum (replum).
    *   **Occurrence:** Seen in mustard, Argemone.

4.  **Free Central Placentation:**
    *   **Description:** The ovules are borne on a central axis, and the septa are absent. The ovary is unilocular. This type arises from axile placentation where the septa degenerate.
    *   **Occurrence:** Found in Dianthus, Primrose.

5.  **Basal Placentation:**
    *   **Description:** The placenta develops at the base of the ovary, and a single ovule is attached to it. The ovary is unilocular.
    *   **Occurrence:** Characteristic of the family Asteraceae (e.g., sunflower, marigold).

Question 11

Q11. Describe the various types of placentation found in flowering plants.

Accepted Answer

Placentation refers to the arrangement of ovules within the ovary. The placenta is the parenchymatous cushion inside the ovary to which the ovules are attached. The type of placentation is an important taxonomic character in flowering plants.

**Types of Placentation:**

1.  **Marginal Placentation:**
    *   **Description:** The placenta forms a ridge along the ventral suture of the unilocular (single-chambered) ovary. The ovules are borne on this ridge in two rows. The ovary is typically monocarpellary (formed from a single carpel).
    *   **Example:** Pea (Pisum sativum), Bean, Gram.

2.  **Axile Placentation:**
    *   **Description:** This type of placentation is found in multicarpellary (formed from two or more carpels), syncarpous (fused carpels) ovaries. The ovary is multilocular (chambered) due to the fusion of the margins of the carpels and the formation of septa. The placenta is axial, and the ovules are attached to it in each locule.
    *   **Example:** China rose (Hibiscus rosa-sinensis), Tomato, Lemon, Orange.

3.  **Parietal Placentation:**
    *   **Description:** This occurs in multicarpellary, syncarpous ovaries which are typically unilocular (single-chambered) but may become bilocular due to the formation of a false septum (replum). The ovules develop on the inner wall of the ovary or on peripheral parts. The carpels are fused at their margins, and the placentae are located on the fused margins.
    *   **Example:** Mustard (Brassica campestris), Argemone, Papaya, Cucumber.

4.  **Free Central Placentation:**
    *   **Description:** This type is found in multicarpellary, syncarpous ovaries that are unilocular. The ovules are borne on a central axis, and the septa are absent. The central axis is not connected to the ovary wall.
    *   **Example:** Dianthus (Carnation), Primrose.

5.  **Basal Placentation:**
    *   **Description:** This occurs in unilocular ovaries. The placenta develops at the base of the ovary, and a single ovule is attached to it. The ovary is typically monocarpellary or multicarpellary syncarpous.
    *   **Example:** Sunflower (Helianthus annuus), Marigold (Tagetes erecta), Wheat, Rice.

These different types of placentation ensure efficient development and dispersal of seeds, reflecting adaptations to various reproductive strategies in flowering plants.

Question 12

Q12. What is a flower? Describe the parts of a typical angiosperm flower.

Accepted Answer

**What is a Flower?**
A flower is a modified shoot, specialized for sexual reproduction in angiosperms (flowering plants). It is the reproductive unit of an angiosperm, designed to facilitate pollination and fertilization, leading to the formation of fruits and seeds. Flowers are typically borne on a stalk called a pedicel and are attached to the main stem at a node. The apex of the pedicel is swollen to form the thalamus (or receptacle), on which the floral organs are arranged in successive whorls.

**Parts of a Typical Angiosperm Flower:**
A typical angiosperm flower consists of four main whorls, arranged concentrically on the thalamus. These whorls are generally categorized into accessory (non-essential) organs and reproductive (essential) organs.

**I. Accessory (Non-Essential) Organs:** These parts do not directly participate in reproduction but help in protection and attraction of pollinators.

1.  **Calyx:**
    *   **Description:** It is the outermost whorl of the flower, composed of units called **sepals**. Sepals are typically green, leaf-like structures.
    *   **Function:** Primarily protects the flower in its bud stage. In some cases, they may be brightly colored (petaloid) to attract pollinators.
    *   **Variations:** Sepals can be free (polysepalous, e.g., mustard) or fused (gamosepalous, e.g., cotton).

2.  **Corolla:**
    *   **Description:** It is the second whorl, located inner to the calyx, composed of units called **petals**. Petals are usually brightly colored, fragrant, and often have nectar glands.
    *   **Function:** Attracts insects and other animals for pollination. It also protects the inner reproductive organs.
    *   **Variations:** Petals can be free (polypetalous, e.g., rose) or fused (gamopetalous, e.g., petunia). The shape and color of corolla vary greatly in different plants.

*   **Perianth:** In some flowers (e.g., lily), the calyx and corolla are not distinct and are collectively called perianth. The units of perianth are called **tepals**.

**II. Reproductive (Essential) Organs:** These parts directly participate in sexual reproduction.

3.  **Androecium:**
    *   **Description:** It is the third whorl, located inner to the corolla, representing the male reproductive part of the flower. It is composed of units called **stamens**.
    *   **Structure of a Stamen:** Each stamen typically consists of two parts:
        *   **Filament:** A slender stalk that supports the anther.
        *   **Anther:** A bilobed structure at the tip of the filament, containing pollen sacs (microsporangia) where pollen grains (male gametophytes) are produced.
    *   **Variations:** Stamens can be free or fused (e.g., monoadelphous in China rose, diadelphous in pea, polyadelphous in citrus). They can also be attached to petals (epipetalous, e.g., brinjal) or perianth (epiphyllous/epitapalous, e.g., lily).

4.  **Gynoecium (Pistil):**
    *   **Description:** It is the innermost whorl, representing the female reproductive part of the flower. It is composed of one or more units called **carpels** (or pistils).
    *   **Structure of a Carpel:** Each carpel typically consists of three parts:
        *   **Ovary:** The swollen basal part containing one or more ovules. The ovules develop into seeds after fertilization.
        *   **Style:** A slender stalk connecting the ovary to the stigma.
        *   **Stigma:** The receptive tip of the carpel, which receives pollen grains during pollination.
    *   **Variations:** The gynoecium can be monocarpellary (single carpel, e.g., pea), or multicarpellary (multiple carpels). If multiple carpels are present, they can be free (apocarpous, e.g., lotus, rose) or fused (syncarpous, e.g., tomato, mustard).

These four whorls, when all present, constitute a complete flower. If any whorl is missing, the flower is called an incomplete flower.

Question 13

Q13. How is a compound leaf different from a simple leaf?

Accepted Answer

The primary difference between a simple leaf and a compound leaf lies in the nature of their lamina (leaf blade) and how it is divided.

| Feature             | Simple Leaf                                                                                             | Compound Leaf                                                                                                                              |
| :------------------ | :------------------------------------------------------------------------------------------------------ | :----------------------------------------------------------------------------------------------------------------------------------------- |
| **Lamina Incision** | The lamina is entire, or when incised, the incisions do not reach the midrib (in pinnate) or the petiole (in palmate). | The lamina is completely divided into two or more smaller, separate units called **leaflets**. The incisions reach the midrib or the petiole. |
| **Axillary Bud**    | An axillary bud is present in the axil of the petiole (at the base of the entire leaf stalk).            | An axillary bud is present in the axil of the petiole (at the base of the entire compound leaf), but **not** in the axil of the leaflets. |
| **Petiole**         | The lamina is directly attached to the petiole.                                                         | Leaflets are attached to a common axis (rachis in pinnate, or directly to the petiole in palmate). Each leaflet may have a small stalk called a petiolule. |
| **Shedding**        | The entire leaf (lamina + petiole) sheds as a single unit.                                              | Individual leaflets may shed, but the entire compound leaf (along with its rachis/petiole) sheds as a single unit.                         |
| **Examples**        | Mango, Guava, Banyan, China rose, Peepal.                                                               | Neem, Rose, Acacia (pinnately compound); Silk cotton, Cannabis (palmately compound).                                                       |

Question 14

Q14. Describe the arrangement of floral members in relation to their insertion on thalamus.

Accepted Answer

The arrangement of floral members (sepals, petals, stamens, and carpels) on the thalamus (receptacle) in relation to the position of the ovary is a significant characteristic used in floral morphology and taxonomy. Based on the relative position of the calyx, corolla, and androecium with respect to the ovary on the thalamus, flowers are classified into three main types:

1.  **Hypogynous Flower (Superior Ovary):**
    *   **Description:** In a hypogynous flower, the gynoecium (ovary) occupies the highest position on the thalamus, while the other floral parts (sepals, petals, and stamens) are situated below it. The ovary is therefore said to be **superior**.
    *   **Arrangement:** The thalamus is typically convex or conical, and the ovary is seated at its apex. The other floral whorls arise from below the level of the ovary.
    *   **Examples:** Mustard, China rose, Brinjal, Sunflower, Lily.

2.  **Perigynous Flower (Half-Inferior Ovary):**
    *   **Description:** In a perigynous flower, the ovary is situated in the center, and the other floral parts are located on the rim of the thalamus, almost at the same level as the ovary. The thalamus forms a cup-shaped or saucer-shaped structure, and the ovary is partially enclosed within it.
    *   **Arrangement:** The ovary is neither completely superior nor completely inferior, hence it is sometimes referred to as **half-inferior**.
    *   **Examples:** Plum, Rose, Peach.

3.  **Epigynous Flower (Inferior Ovary):**
    *   **Description:** In an epigynous flower, the margins of the thalamus grow upwards, completely enclosing the ovary, and getting fused with its wall. The other floral parts (sepals, petals, and stamens) arise from the top of the ovary.
    *   **Arrangement:** The ovary is completely enclosed within the thalamus and appears to be below the attachment point of the other floral whorls. The ovary is therefore said to be **inferior**.
    *   **Examples:** Guava, Cucumber, Ray florets of sunflower.

These classifications are crucial for understanding floral evolution and are often used in identifying plant families.

Question 15

Q15. Define the following terms:
(a) Aestivation
(b) Placentation
(c) Actinomorphic
(d) Zygomorphic
(e) Superior ovary
(f) Perigynous flower
(g) Epipetalous stamen

Accepted Answer

**(a) Aestivation:**
**Definition:** Aestivation is the mode of arrangement of sepals or petals in a floral bud with respect to the other members of the same whorl. It describes how the petals or sepals overlap or touch each other before the flower opens.
**NEET Relevance:** High (definitions, types like valvate, twisted, imbricate, vexillary, and their examples are frequently asked).

**(b) Placentation:**
**Definition:** Placentation refers to the arrangement of ovules within the ovary. The placenta is the parenchymatous tissue inside the ovary to which the ovules are attached.
**NEET Relevance:** High (definitions, types like marginal, axile, parietal, free central, basal, and their examples are frequently asked).

**(c) Actinomorphic:**
**Definition:** An actinomorphic flower is a flower that can be divided into two equal radial halves by any radial plane passing through the center. Such flowers are radially symmetrical.
**Example:** Mustard, Datura, Chilli.
**NEET Relevance:** High (definitions, examples, and distinguishing from zygomorphic flowers are common).

**(d) Zygomorphic:**
**Definition:** A zygomorphic flower is a flower that can be divided into two similar halves only by a single specific vertical plane. Such flowers are bilaterally symmetrical.
**Example:** Pea, Gulmohar, Bean, Cassia.
**NEET Relevance:** High (definitions, examples, and distinguishing from actinomorphic flowers are common).

**(e) Superior ovary:**
**Definition:** A superior ovary is an ovary that is positioned above the attachment points of the other floral parts (sepals, petals, and stamens) on the thalamus. This condition is characteristic of hypogynous flowers.
**Example:** Mustard, China rose, Brinjal.
**NEET Relevance:** High (definitions, associated with hypogynous flowers, and examples are frequently asked).

**(f) Perigynous flower:**
**Definition:** A perigynous flower is one in which the gynoecium (ovary) is situated in the center, and the other floral parts (sepals, petals, and stamens) are located on the rim of the cup-shaped thalamus, almost at the same level as the ovary. The ovary in such flowers is considered half-inferior.
**Example:** Plum, Rose, Peach.
**NEET Relevance:** High (definitions, associated with half-inferior ovary, and examples are frequently asked).

**(g) Epipetalous stamen:**
**Definition:** An epipetalous stamen is a stamen that is attached to a petal. This condition indicates the fusion or adnation of stamens with petals.
**Example:** Brinjal, Datura, Petunia.
**NEET Relevance:** High (definitions, examples, and understanding adnation are frequently asked).

Question 16

Q16. Describe the various types of placentation found in flowering plants.

Accepted Answer

Placentation refers to the arrangement of ovules within the ovary. The placenta is the parenchymatous cushion inside the ovary to which the ovules are attached. The type of placentation is an important characteristic for classifying flowering plants. There are five main types of placentation:

### 1. Marginal Placentation
In this type, the placenta forms a ridge along the ventral suture of the ovary. The ovules are borne on this ridge, forming two rows. This type of placentation is characteristic of monocarpellary, unilocular ovaries. It is typically found in members of the family Fabaceae (peas, beans).

### 2. Axile Placentation
When the placenta is axial and the ovules are attached to it in a multilocular ovary, it is called axile placentation. The carpels fuse to form septa, dividing the ovary into multiple chambers (locules). The ovules are borne on the central axis where these septa meet. Examples include China rose, tomato, and lemon.

### 3. Parietal Placentation
In this type, the ovules develop on the inner wall of the ovary or on peripheral part. The ovary is typically one-chambered (unilocular) but may become two-chambered due to the formation of a false septum (replum). This is observed in mustard and Argemone.

### 4. Free Central Placentation
In free central placentation, the ovules are borne on a central axis, and the septa are absent. The ovary is unilocular. This type arises from axile placentation where the septa degenerate during development. Examples include Dianthus (carnation) and Primrose.

### 5. Basal Placentation
In basal placentation, the placenta develops at the base of the ovary, and a single ovule is attached to it. The ovary is unilocular. This is the most common type of placentation found in families like Asteraceae (sunflower, marigold) and Poaceae (grasses).

These different arrangements ensure efficient development and dispersal of seeds, reflecting adaptations to various reproductive strategies in flowering plants.

Question 17

Q17. What is a flower? Describe the parts of a typical angiosperm flower.

Accepted Answer

### What is a Flower?
A flower is a highly modified and condensed shoot specialized for sexual reproduction in angiosperms (flowering plants). It is typically borne on a stalk called a pedicel and consists of a condensed axis (thalamus or receptacle) on which floral leaves (sepals, petals, stamens, and carpels) are spirally or cyclically arranged. Flowers are the reproductive structures that produce gametes, facilitate fertilization, and develop into fruits containing seeds.

### Parts of a Typical Angiosperm Flower
A typical angiosperm flower consists of four concentric whorls, usually arranged on the thalamus (receptacle). These whorls are:

#### 1. Calyx (Accessory Whorl)
*   **Description:** The outermost whorl of the flower, composed of units called **sepals**. Sepals are typically green, leaf-like structures.
*   **Function:** Primarily protective, enclosing the other floral parts in the bud stage. They can also perform photosynthesis.
*   **Variations:** Sepals can be free (polysepalous) or fused (gamosepalous).

#### 2. Corolla (Accessory Whorl)
*   **Description:** The second whorl, located just inside the calyx, composed of units called **petals**. Petals are often brightly coloured, fragrant, and showy.
*   **Function:** To attract pollinators (insects, birds, etc.) for cross-pollination. They may also provide some protection to the inner reproductive organs.
*   **Variations:** Petals can be free (polypetalous) or fused (gamopetalous).

#### 3. Androecium (Essential/Reproductive Whorl)
*   **Description:** The third whorl, representing the male reproductive part of the flower. It is composed of units called **stamens**. Each stamen typically consists of two parts:
    *   **Filament:** A slender stalk that supports the anther.
    *   **Anther:** A bilobed structure at the tip of the filament, containing pollen sacs (microsporangia) where pollen grains (male gametophytes) are produced.
*   **Function:** Production and dispersal of pollen grains, which contain the male gametes.
*   **Variations:** Stamens can be free or united in various ways (e.g., monadelphous, diadelphous, polyadelphous).

#### 4. Gynoecium (Essential/Reproductive Whorl)
*   **Description:** The innermost and female reproductive part of the flower. It is composed of one or more units called **carpels** (also known as pistils). Each carpel typically consists of three parts:
    *   **Stigma:** The receptive tip, often sticky, that receives pollen grains.
    *   **Style:** A slender stalk connecting the stigma to the ovary.
    *   **Ovary:** The swollen basal part containing one or more ovules. The ovules develop into seeds after fertilization, and the ovary matures into a fruit.
*   **Function:** Production of ovules (containing female gametes), reception of pollen, and protection of developing seeds and fruit.
*   **Variations:** Carpels can be free (apocarpous) or fused (syncarpous). The position of the ovary relative to other floral parts can be superior, inferior, or half-inferior.

Together, these parts work in a coordinated manner to achieve the primary goal of sexual reproduction in flowering plants.

Question 18

Q18. Describe the various types of placentation found in flowering plants.

Accepted Answer

Placentation refers to the arrangement of ovules within the ovary. The placenta is the parenchymatous cushion inside the ovary to which the ovules are attached. The type of placentation is a significant characteristic used in the classification of flowering plants. There are five main types of placentation:

### 1. Marginal Placentation
In marginal placentation, the placenta forms a ridge along the ventral suture of the ovary. The ovules are borne on this ridge in two rows. The ovary is typically unilocular (single-chambered).
*   **Examples**: Pea, Gram, Bean (members of the Fabaceae family).

### 2. Axile Placentation
In axile placentation, the placenta is axial, and the ovules are attached to it in a multilocular (many-chambered) ovary. The septa (partitions) divide the ovary into several locules, and the ovules are borne on the central axis where these septa meet.
*   **Examples**: China rose (Hibiscus), Tomato, Lemon.

### 3. Parietal Placentation
In parietal placentation, the ovules develop on the inner wall of the ovary or on the peripheral part. The ovary is typically unilocular, but it may become two-chambered due to the formation of a false septum (also known as replum).
*   **Examples**: Mustard, Argemone.

### 4. Free Central Placentation
In free central placentation, the ovules are borne on a central axis, and the septa are absent. The ovary is unilocular. This type is believed to be derived from axile placentation where the septa have degenerated.
*   **Examples**: Dianthus (Carnation), Primrose.

### 5. Basal Placentation
In basal placentation, the placenta develops at the base of the ovary. A single ovule is attached to the base of the ovary. The ovary is unilocular.
*   **Examples**: Sunflower, Marigold (members of the Asteraceae family).

Chapter 5: Morphology of Flowering Plants