Question

Ray florets of sunflower are –
A. Asexual
B. Unisexual
C. Bisexual
D. Actinomorphic

Answer 1

Hint: Inflorescence is the arrangement of flowers on shoots or axes. Three types of inflorescence can be seen:
(a) Racemose.
(b) Cymose.
(c) Special type.

Complete Answer:
Sunflower (Helianthus annuus) belongs to the Asteraceae family. The inflorescence of sunflowers is capitulum (head).
Capitulum is a modified racemose in which the main axis is flattened, called receptacle. Receptacles bear many small sessile flowers called florets. Florets are arranged in centripetal manner i.e. younger flowers are present towards the centre and older towards periphery.

There are two types of florets:
(a) Disc floret – The flowers which are present in the centre. They are actinomorphic and bisexual.
(b) Ray florets – The flowers which are at the periphery. They are zygomorphic and asexual, hence are sterile. Ray florets are flowers with long, strap-like petals outside.

Additional information:
- Sunflower is grown as a crop for its edible oil mainly. The name sunflower was derived from the flower's head’s shape, which is similar to the sun.
- Heliotropism (movement towards sun) is shown by immature flowers when flowers are young. As the flower matures the heliotropism stops.
- Sunflowers have epigynous flowers i.e. have inferior ovary, it is not visible from outside and it is fully covered by thalamus.

The correct option is A.

Note: Pollination is sunflower is of two types – self-pollination and cross pollination. Sunflower seeds have nutritive value – they are rich in vitamin E that are fat soluble antioxidants.