Morphology of flowering plants is the study of their external structure and form. This chapter delves into the various parts of a flowering plant, from the root system to the reproductive units.
Root System:
- Taproot: A single, main root that grows vertically downward (e.g., carrot).
- Fibrous Root System: Numerous, thread-like roots that grow in all directions (e.g., wheat).
- Adventitious Roots: Roots that arise from any part of the plant other than the radicle (e.g., aerial roots, prop roots).
Shoot System:
- Stem: The main axis of the plant, supporting the leaves, flowers, and fruits.
- Leaves: The photosynthetic organs of the plant, typically green and containing chlorophyll.
- Flowers: The reproductive units of a flowering plant, consisting of petals, sepals, stamens, and carpels.
- Fruits: The ripened ovaries of a flower, containing seeds.
Flower Structure:
- Calyx: The outermost whorl of sepals, usually green and protective.
- Corolla: The second whorl of petals, often brightly colored to attract pollinators.
- Androecium: The male reproductive whorl, consisting of stamens (filament and anther).
- Gynoecium: The female reproductive whorl, consisting of carpels (ovary, style, and stigma).
Fruits and Seeds:
- Fruits: The ripened ovaries, containing seeds. They can be fleshy or dry.
- Seeds: The reproductive units of a plant, containing the embryo and endosperm (nutrient storage tissue).
Seed Germination: The process by which a seed develops into a new plant.
Key Points:
- The morphology of flowering plants is adapted to their specific environments and functions.
- Understanding plant morphology is essential for identifying and classifying plants, as well as for agricultural and horticultural practices.
- The study of plant morphology provides insights into the evolutionary relationships between different plant groups.
Exercise
1. How is a pinnately compound leaf different from a palmately compound leaf?
Ans :
Pinnately compound and palmately compound leaves are two different types of compound leaves, which are leaves divided into multiple leaflets.
Pinnately compound leaf:
- The leaflets are arranged along a central axis or petiole like the feathers on a pinnate.
- The central axis can be unipinnate (with a single row of leaflets) or bipinnate (with two rows of leaflets).
- Examples of pinnately compound leaves include rose, neem, and mango.
Palmately compound leaf:
- The leaflets radiate from a single point at the end of the petiole, resembling the fingers of a palm.
- The number of leaflets varies, but it’s often five or seven.
- Examples of palmately compound leaves include castor, silk cotton, and neem.
2. Explain with suitable examples the different types of phyllotaxy.
Ans :
- Alternate:
- Arrangement: One leaf arises from each node, alternating with the leaves on adjacent nodes.
- Examples: Sunflower, mango, rose
- Opposite:
- Arrangement: Two leaves arise from each node, opposite each other.
- Examples: Hibiscus, jasmine, tulsi
- Whorled:
- Arrangement: More than two leaves arise from each node, arranged in a whorl.
- Examples: Nerium (oleander), Calotropis (milkweed)
3. Define the following terms:
(a) aestivation (b) placentation (c) actinomorphic (d) zygomorphic (e) superior ovary (f) perigynous flower (g) epipetalous stamen
Ans :
a) Aestivation: It can be valvate, imbricate, twisted, or quincuncial.
(b) Placentation: The arrangement of ovules within an ovary. It can be marginal, basal, parietal, axile, or free-central.
(c) Actinomorphic: A flower that can be divided into two equal halves along any plane passing through the center.
(d) Zygomorphic: A flower that can be divided into two equal halves only along one specific plane.
(e) Superior Ovary: An ovary that is positioned above the attachment point of the petals and sepals.
(f) Perigynous Flower: A flower in which the sepals, petals, and stamens are fused to form a cup-like structure around the ovary.
(g) Epipetalous Stamen: A stamen that is attached to the petal.
4. Differentiate between
(a) Racemose and cymose inflorescence (b) Apocarpous and syncarpous ovary
Ans :
(a) Racemose and cymose inflorescence
| Feature | Racemose Inflorescence | Cymose Inflorescence |
| Growth Pattern | Indeterminate growth, new flowers continue to develop at the tip | Determinate growth, oldest flowers are at the tip and new flowers develop laterally |
| Order of Flowering | Oldest flowers at the base, youngest at the tip | Oldest flowers at the tip, youngest at the base |
| Example | Raceme, spike, corymb, panicle | Cyme, scorpioid cyme, thyrse |
(b) Apocarpous and syncarpous ovary
| Feature | Apocarpous Ovary | Syncarpous Ovary |
| Carpels | Multiple free carpels | Carpels fused together |
| Ovules | Each carpel has its own ovary and ovules | Ovules are united in a single ovary |
| Fruit Formation | Each carpel forms a separate fruitlet | A single fruit forms from the fused carpels |
| Example | Strawberry, buttercup | Tomato, pea, rose |
5. Draw the labelled diagram of the following: (i) gram seed (ii) V.S. of maize seed
Ans :
(i) gram seed
(ii) V.S. of maize seed
6. Take one flower of the family Solanaceae and write its semi-technical description. Also draw their floral diagram.
Ans :
Solanum nigrum (Black Nightshade)
Floral Description:
- Flower: Complete, bisexual, actinomorphic.
- Calyx: Five sepals, united, persistent, valvate aestivation.
- Corolla: Five petals, united, valvate aestivation, white or greenish-white.
- Androecium: Five stamens, epipetalous, didynamous.
- Fruit: Berry, usually black or purple.
- Seeds: Numerous, endospermic.
7. Describe the various types of placentations found in flowering plants.
Ans :
There are several different types of placentation found in flowering plants:
- Marginal:
- Ovules are positioned along the edge of the ovary.
- Example: Pea, bean
- Axile:
- Ovules are attached to the central axis of the ovary, which is formed by the fused carpels.
- Example: Tomato, cotton
- Parietal:
- Ovules are connected to the inner lining of the ovary.
- Example: Cucumber, mustard
- Free-central:
- Ovules are free and attached to a central column in the ovary.
- Example: Primrose, Dianthus
- Basal:
- Ovules are anchored to the base of the ovary.
- Example: Sunflower, marigold
8. What is a flower? Describe the parts of a typical angiosperm flower
Ans :
A flower is the reproductive organ of a flowering plant. It is where the process of pollination and fertilization takes place, leading to the production of seeds and fruits.
Parts of a Typical Angiosperm Flower:
- Petals: Colorful structures that attract pollinators.
- Sepals: Green, leaf-like structures that protect the flower bud.
- Stamens: Male reproductive organs consisting of:
- Filament: The stalk that supports the anther.
- Anther: The part that produces pollen grains.
- Carpel: Female reproductive organ consisting of:
- Stigma: The sticky tip that receives pollen.
- Ovary: The enlarged base that contains the ovules.
9. Define the term inflorescence. Explain the basis for the different types inflorescence in flowering plants.
Ans :
Inflorescence refers to the pattern in which flowers are arranged on a plant. It refers to the way flowers are grouped or clustered together on a stem.
Basis for Different Types of Inflorescence:
Inflorescences can be classified based on several factors, including:
- Growth pattern:
- Indeterminate: New flowers continue to develop at the tip of the inflorescence.
- Determinate: The oldest flowers are at the tip, and new flowers develop laterally.
- Arrangement of flowers:
- Racemose: Flowers are arranged in a linear or unbranched fashion.
- Cymose: Flowers are arranged in a branched fashion, with the oldest flowers at the base and the youngest at the tip.
- Presence or absence of bracts:
- Bracts are modified leaves that support or protect the flowers.
- Type of flowers:
- Whether the flowers are solitary or grouped together.
10. Describe the arrangement of floral members in relation to their insertion on thalamus.
Ans :
The arrangement of floral members in relation to their insertion on the thalamus is known as floral insertion. There are three main types of floral insertion:
- Perigyny:
- The ovary is semi-inferior, meaning it is partially embedded in the thalamus.
- The sepals, petals, and stamens are fused to form a cup-like structure around the ovary.
- Examples: Plum, peach, cherry
- Epigyny:
- The ovary is inferior, meaning it is completely embedded in the thalamus.
- Examples: Cucumber, pumpkin, apple
