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1. Define Actinomorphic.

When a flower can be divided into equal  radial halves in any radial plane passing through the centre, it is said to be actinomorphic, example., Mustard, Datura etc.
2. How is a pinnately compound leaf different from a palmately compound leaf ?
The compound leaves may be of two types as pinnately compound leaf and palmately compound leaf. In pinnately compound leaf, a number of leaflets are present on a common axis, the rachis, which represents the midrib of the leaf as in neem. Pinnately compound leaf may be of different types as unipinnate, bipinnate, tripinnate and decompound. In palmately compound keaf, the leaflets are attached at a common point, i.e., at the tip of petiole, as in silk cotton. Palmately compound leaf may be of different types as unifoliate, bifoliate, trifoliate, quadrifoliate and multifoliate.
3. Define Placentation
The arrangement of ovules within the ovary is known as placentation.The placentation are of different types namely, marginal, axile, parietal, basal, and free central.
4. Define the term inflorescence. Explain the basis for the different types inflorescence in flowering plants.
The arrangement of flowers on the floral axis is termed as inflorescence. A flower is a modified shoot wherein internodes do not elongate and the axis gets condensed. The apex produces different kinds of floral appendages laterally at successive nodes instead of leaves. When a shoot tip transforms into a flower, it is always solitary. Depending on whether the apex gets converted into a flower or continues to grow,  two major types of inflorescence are defined – racemose and cymose. In racemose type of inflorescence the main axis continues to grow, the flowers are borne laterally in an acropetal succession. In cymose type of inflorescencethe main axis terminates in a flower, hence is limited in growth. The flowers are borne in a basipetal order.
5. What is a flower ? Describe the parts of a typical angiosperm flower.
The flower is the reproductive unit in the angiosperms. It is meant for sexual reproduction. A typical flower has four different kinds of whorls arranged successively on the swollen end of the talk or pedicel, called thalamus or receptacle. These are calyx, corolla, androecium and gynoecium.
Calyx and corolla are accessory organs, while androecium and gynoecium are reproductive organs. In some flowers like Lily, the calyx and corolla are not distinct and are termed as perianth.
Calyx: The calyx is the outermost whorl of the flower and the members are called sepals. Generally, sepals are green, leaf like and protect the flower in the bud stage. The calyx may be gamosepalous (sepals united) or polysepalous (sepals free).
Corolla: Corolla is composed of petals. Petals are usually brightly coloured to attract insects for pollination. Like calyx, corolla may also be free(gamopetalous) or united (polypetalous). The shape and colour of corolla vary greatly in plants. Corolla may be tubular, bell-shaped, funnel-shaped or wheel-shaped.
Androecium: Androecium is composed of stamens. Each stamen which represents the male reproductive organ consists of a stalk or a filament and an anther. Each anther is usually bilobedand each lobe has two chambers, the pollen sacs. The pollen grains are produced in pollen-sacs. A sterile stamen is called staminode.
Gynoecium: Gynoecium is the female reproductive part of the flower and is made ip of one or more carpel. A carpel consists of three parts namely stigma, style and ovary. Ovary is the enlarged basal part, on which lies the elongated tube, the style. The style connects the ovary to the stigma. The stigma is usually at the tip of the style and is the receptivesuface for pollen grains. Each ovary bears one or more ovules attached to a flattened, cushion-like placenta. When more than one carpel is present, they may be free(as in lotus and rose) and are called apocarpous. They are termed syncarpous when carpel are fused, as in mustard and tomato. After fertilization, the ovules develop into seeds and the ovary matures into a fruit.
6. Define Aestivation.
The mode of arrangement of sepals and petals in floral bud with respect to other members of the same whorl is known as aestivation. The main type of aestivation are valvate, twisted, imbricate and vexillary.
7. Justify the following statements on the basis of external features:
(i) Underground parts of a plant are not always roots.
(ii) Flower is a modified shoot.
(i) Underground parts of plant are not always roots because sometimes the stem is also modified into various forms to perform different functions of storage, synthesis, vegetative propagation, perennation, etc. Underground modifications of stems are tuber, rhizome, corm and bulb.
(ii) Flower is the reproductive part of the angiospermic plant and is defined as the modified shoot with highly condensed internodes and leaves modified variously to perform different functions. Calyx, corolla, androecium and gynoecium are the four whorls or parts of a typical flower.

8. Differentiate between apocarpous and syncarpous ovary


Apocarpous ovary

      Syncarpous ovary


The ovary belongs to a single free carpel

The ovary belongs to a single pistil


The flower has several free ovaries

There is a single ovary


It is always unilocular

It may be unilocular or multilocular


On maturity it forms fruitlet of aggregate type

On maturity it forms a simple fruit.

9. Define Epipetalous stamen.
When stamens are attached to the petals, they are epipetalous, example., brinjal.
10. Define Perigynous flowers.
If gynoecium is situated in the centre and other parts of the flower are located on the rim of the thalamus almost at the same level, it is called pergynous. Here ovary is half superior, example., peach, plum.

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Plus 1 Biology Science
Tamil Nadu (English Medium)

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