Question

explain double fertilisation in plant..

Answer 1

DOUBLE FERTILIZATION IN PLANTS..

Double fertilization is a phenomenon that occurs in flowering plants i.e. Angiosperms. After pollination, when pollen grain falls on stigma, it forms a pollen tube that travels all the way through style to reach ovary. Most successful pollen tube reaches embryo sac of ovule & fuses with it. Inside pollen tube, there are 2 sperm cells which are released in embryo sac. One of them fertilizes the egg to form zygote & the second one fertilizes with two polar nuclei to form secondary nucleus (triple fusion). After double fertilization the fertilized ovary is able to form fruit & seed. It is because of double fertilization that seed forms endosperm which nurtures the growing embryo. The process of double fertilization has played significant role in evolution of flowering plants.

Answer 2

༊*·˚Double Fertilisation in plants :-

• The process of fusion of male gamete  with the female gamete to form the  diploid zygote (2n) is known as  fertilisation.

• The fusion of one male gamete with egg  and that of another male gamete with a  secondary nucleus is called double  fertilisation.

• It is the characteristic feature of only  angiosperms.

• All angiosperms are characterised by a  unique process called double fertilisation.

• Double fertilisation is significant because  it involves the use of both the male  gametes produced by a pollen grain.

• This avoids the chances of polyembryony  and increases the chances of survival of the future plant.

• It consists of two fusions and results in  the formation of two products.

• First fertilisation restores diploidy in the  life cycle.

• The diploid zygote develops into an  embryo which subsequently develops  into a new plant.

• Second fertilisation product, triploid PEN  (Primary endosperm nucleus) develops  to form a nutritive tissue called  endosperm for developing an embryo.