The flower — the generative reproductive organ
A flower is the sexual reproductive organ of angiosperms, a modified shortened shoot. Fruit and seeds form from it. The flower is attached to the shoot by a peduncle; the widened tip of the peduncle, the receptacle, carries all the flower parts. The perianth consists of the calyx (green sepals) and the corolla (usually coloured petals); it protects the stamens and pistil until the flower opens. A stamen has an anther and a filament; pollen ripens in the anther. The pistil sits in the centre of the flower and has an ovary, style and stigma: the stigma catches pollen, the ovary holds the ovules, and after fertilization the ovary becomes the fruit. In a flower formula parts are given by initial letters and numbers: Gk — sepals, Gt — petals, Ch — stamens, U — pistil, Og — simple perianth; brackets show fused parts, ∞ means many. For example, the plum flower: Gk₅ Gt₅ Ch∞ U₁.
| Part | Made of |
|---|---|
| Flower stalk | receptacle at its tip |
| Perianth | calyx, corolla |
| Stamen | anther, filament |
| Pistil | stigma, style, ovary |
Laboratory 4: with tweezers separate the flower parts one by one (cherry, tulip, shepherd’s purse or a houseplant flower), stick them in the notebook (sepals, petals, stamens, pistil); view the anther and stigma under a magnifier; write the flower formula. Safety: pupils with pollen allergy should cover nose and mouth or not take part; do not touch unknown or poisonous flowers; do not taste flowers; wash hands afterwards.