Sunflower is not a flower, but it is a kind of inflorescence called capitulum in which the receptacle is flattened. It bears numerous sessile and small florets. The youngest floret is in the center and oldest lies at the periphery. Whole cluster of florets gets surrounded by bracts, known as involucre.
Two kinds of florets are recognised in sunflower
(i) Ray Florets Arranged on the rim of receptacle having distinct yellow and strap shaped petals. These florets are female, sterile and are always zygomorphic and may be arranged in one or more whorls.
(ii) Disc florets Grouped in the center, bisexual and actinomorphic.
