NEET Biology Notes Morphology of Flowering Plants Flower
A flower is a modified shoot, which acts as reproductive unit in angiosperms. A typical flower has four different kinds of whorl arranged successfully on the swollen end of the stalk or pedicel called thalamus or receptacle, i.e. calyx, corolla, androecium and gynoecium.
Structure of Flower
The outermost whorl of floral parts is composed of sepals, collectively called the calyx, the next inner whorl composed of petals collectively called as corolla. Sepals and petals are the sterile parts of flower. The fertile parts are the androecium, (arises just inside the corolla and the pistil) and gynoecium (in the centre of the flower). Androecium is the collective term used for the male reproductive organs, the units of which are stamens and each stamen has an anther (pollen grain forming part), connective (cementing tissue ligases two adjacent anther sacs) and a stalk called filament (links the anther to thalamus).
fn some plants although two whorls (calyx and corolla) are present but they are not differentiated from one another. In such a case both whorls are called perianth and each part of the perianth is called tepal.
In some plants, e.g. sunflower the sepals are modified into hairy structure called pappus and helped in dispersal of fruits.
Gynoecium or pistil is also a collective term used for female reproductive organs, the units of which are called carpels and each carpel has a swollen ovary (bears ovules). A long stalk arising at the tip of ovary is called style and a pollen receptive terminal portion on the style is called stigma. Androecium and gynoecium are called essential floral whorls because they directly take part in reproduction, whereas calyx and corolla take part in reproduction indirectly, so they are called non-essential or accessory whorls.