Q.Draw a neat, labelled diagram of a typical bisexual angiosperm flower and name its four whorls, stating one function of each whorl.

From outermost to innermost the whorls are: (1) calyx, made of sepals, usually green, protects the bud; (2) corolla, made of petals, usually coloured, attracts pollinators; (3) androecium, made of stamens, the male reproductive whorl that produces pollen; (4) gynoecium, made of one or more carpels, the female reproductive whorl containing the ovary, style and stigma.

A typical bisexual angiosperm flower is a modified shoot in which four distinct whorls are borne in concentric rings on a shortened axis, the thalamus or receptacle.

The outermost whorl is the calyx, composed of sepals, which are usually green and leaf-like; its principal function is to protect the other floral parts, especially while the flower is still in bud. Next is the corolla, composed of petals, which are usually large, thin and brightly coloured (or white) and whose function is to attract pollinating agents such as insects and birds, sometimes aided by scent and nectar.

Within the corolla lies the androecium, the male reproductive whorl, made up of stamens; each stamen consists of a filament and an anther, and the whorl's function is to produce microspores that develop into pollen grains bearing the male gametes. At the very centre lies the gynoecium, the female reproductive whorl, made up of one or more carpels forming the ovary, style and stigma; its function is to bear the ovules within the ovary and to receive pollen on the stigma, leading eventually to fertilisation and seed/fruit formation.

(A labelled diagram would show, in longitudinal section: the thalamus at the base, sepals and petals arranged around the outside, stamens with anther and filament around the centre, and the pistil/carpel with stigma, style and ovary containing ovules at the very centre.)

Recall the flower as a modified shoot bearing four whorls in a fixed sequence on the thalamus; state each whorl's composition and its single main function.

Confusing calyx with corolla when sepals are coloured (as in some ornamentals); forgetting that androecium and gynoecium, not calyx/corolla, are the true reproductive (fertile) whorls.