heredity and evolution — Science STD 10 — Question

Description : A flower is the shoot of the plant converted for the process of reproduction. It is developed from a bud. Corolla gives support to the flower and four layers are arranged on thalamus.
→ (1) Sepal Layer
(2) Petal Layer
(3) Stamen Layer
(4) Pistil Layer
(1) Sepal Layer : It is made up of sepals. They are the outermost layer. They protect the flower in budding stage but they do not participate in the process of reproduction.
(2) Petal Layer : It is the second layer. It attracts the vector for the process of pollination. It do not participate in the process of reproduction.
(3) Stamen Layer : It is the third layer. It takes part in the process of reproduction. Yellows colour pollen grains are formed from it which are useful in the process of fertilisation.
(4) Pistil Layer : It is the female reproductive part present in the centre of the flower. It contains ovary, style and stigma.
→ Stigma is sticky or with rough surface. It gives a place for pollen grains to stick.
Style is responsible for growing pollen tube. It connects ovary and style.
→ Ovary contains egg, which when fertilised get converted into fruit. After fertilisation egg get converted into seed.
→ The flower may be unisexual when it contains either stamen or pistil or bisexual when it contains both stamen and pistil.