1.

Differentiate between ‘self-pollination’ and ‘cross-pollination’. Describe double fertilisation in plants.

Answer»
Self-pollination Cross-pollination
(i) Self-pollination occurs within a flower or between two flowers of the same plant.(i) Cross-pollination occurs between two flowers borne on different plants of the same species.
(ii) Flowers do not depend on other agencies for pollination.(ii) Agents such as insects, water and wind are required for pollination.
(iii) Pollen grains are produced in small numbers.(iii) Pollen grains are produced in large numbers.

During fertilisation in plants, the following events take place: 

(i) One of the male gamete fuses with the female gamete present in the embryo sac. 

(ii) The other male gamete fuses with the two polar nuclei in the embryo sac. The first fusion product gives rise to the zygote while the second one forms the endosperm. The process of two fusions occurring in the embryo sac is called double fertilisation.


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