Question

Question 5 Define the following terms:

(a) Aestivation

(b) Placentation

(c) Actinomorphic

(d) Zygomorphic

(e) Superior ovary

(f) Perigynous flower

(g) Epipetalous Stamen

Class XI Biology Chapter - Morphology of Flowering Plants Page 83

Answer 1

1) Aestivation - It is the mode of arrangement of sepals or petals in a floral bud with respect to the other member of the same whorl is Called as Aestivation.There are 5 types of aestivation. These are :-

★Valvate
★Twisted
★Imbricate
★Vexillary
★Quincuncial

2)Placentation - The ovules are attached on one more cushion like structure which is known as Placentation.Or in other words the arrangement of ovules within the ovary is known as placentation. There are 6 types of placentation. for example :-

★Marginal
★Parietal
★Axile
★Central
★Basal
★Superficial

3) Actinomorphic - It is also known as Radial or regular symmetry. When a flower can be divided into 2 equal parts by any of the vertical axises or plane that passes through the centre then it is called as Actinomorphic. Examples - Mustard , Dhatura etc.

4) Zygomorphic - When a flower can be divided into 2 equal halves by any one plane only then it is said to be Zygomorphic. Examples - Pea , bean etc.

5) Superior ovary - When petals , sepals and stamens are situated below the ovary then the flower is called as Superior ovary. Examples - Mustard , China rose etc

6) Perigynous flower - In it thalamus grows upwardly forming a cup shaped structure.On the margin of the thalamus flower parts are attached except gynoecium which lies at the basal part. So in this condition gynoecium is situated below the other floral parts. Examples - Rose etc.

Epipetalous stamen - Stamen that are attached to the petals.

Answer 2

Answer:

The following are the definitions of the terms given :

(a) Aestivation

It is the sepals' arrangement in the floral but concerning other members of the same whorl. The different types of aestivation include twisted, valvate, imbricate and vexillary.

(b) Placentation

It is the arrangement of the ovule within the ovary. They are of the following types : Marginal, Axile, Parietal, Basal and Free central.

(c) Actinomorphic

Flowers which can be divided into two halves by any vertical planes are called as actinomorphic flowers. Ex : Chilli.

(d) Zygomorphic

The flower which has bilateral symmetry and can be divided by two halves only in one plane is called zygomorphic flower. Ex : Gulmohur.

(e) Superior ovary

In hypogynous flower gynoecium occupies the highest position while the other parts remain below it. Ovary in such a flower is known as superior ovary. Ex : Brinjal.

(f) Perigynous flower

A perigynous flower is the one in which gynoecium is situated in the centre and the other parts of the flower are located on the rim of the thalamus. Ovary is half inferior. Ex : Rose.

(g) Epipetalous Stamen

Instead of directly being inserted over the thalamus, it has a stamen which is borne over a petal. Such stamen is called as epipetalous stamen. Ex : Brinjal.