Explain the process of fertilization in plants .

Explanation

(i) Pollen grains reach the right stigma and begin to germinate .
(ii) Pollen grain forms a small tube -like structure called pollen tube which emerges through the germ pore . The contents of the pollen grain move into the tube .
(iii) Pollen tube grows through the tissues of the stigma and style and finally the ovule through the mictropyle .
(iv ) Vegetative cell degenerates and the generative cell divides to form two sperms ( or male gametes .)
(v ) Tip of pollen tube bursts and the two sperms enter the embryo sac .

(vi ) One sperm fuses with the egg ( syngamy ) and forms a diploid zygote .
(vii ) The other sperm fuses with the secondary nucleus ( triple fusion ) to form the primary endosperm nucleus which is triploid in nature . since two types of fusion syngamy and triple fusion take place in an embryo sac the process is termed as double fertillization .
(viii ) After triple fusion , primary endosperm nucleus develops into an endosperm
( ix ) Endosperm provides food to the developing embryo .
(x ) Later the synergids and antipodal cells degenerate .