Question

Please explain in your own words at least five sentences

1 double fertilization in angiosperms.

2 mechanism for opening and closing of guard cells.

Answer 1

1. double fertilization in angiosperm

pollen tube enters in embryo sac through micropylar site. before entry of pollentube in embryo sac, antipodal cell degenerate, one synerged degenerated and another synergies degenerating..

* pollen tube enters in embryo sad through degenerating synergies.

* pollen tube burst on degenerating synergies and release male gamete in central cell.

*after release male gamete, degenerating synergies is completely degenerate.

*out of two male gamete, one male gamete fertilise egg cell and another male gamete fertilise polar nuclei. two male gamete fertilise two different nuclei. this phenomena is called DOUBLE. FERTILIZATION.

2. Mechanism for opening and closing of guard cell

* according to classical theory, during day time starch converted in to sugar.

* sugar insoluble in water.

* osmotic concentration Guard cell increased.

* water enter inside guard cell, guard cell become turgid sonata open.

* during night time, sugar converted in to starch.

* starch is insoluble in water. , osmotic concentration of guard cell decreases. water come out from guard cell, guard cell become flaccid ,then, stomata open.