question_answer 44)

      In the diagram given below, show the path of a pollen tube from the pollen on the stigma into the embryo sac. Name the components of egg apparatus.

Answer:

                    Following compatible pollination, the pollen grain germinates on the stigma to produce apollen tube through one of the germ pores. The contents of the pollen grain (2 mole nuclei)move into the pollen tube. Pollen tube grows through the tissues of the stigma and reachesthe ovary. After reaching the ovary, pollen tube, entersthe ovule through the micropyle and thenentersthe embryo sac by passing into one of the synergids through the fill form apparatus.It leadsto the degeneration of that synergid. The pollen tube breaks to release its contents (2 male nuclei). Out of the two male gametesone fuses with egg and the other fuses with central cell and fertilize. Longitudinal section of a flower showing path of pollen tube growth The component cells of the egg-apparatus in an embryo sac include, two synergids, one egg cell and the filiform apparatus.