Question

Give reasons why:
(i) Most zygotes in angiosperms divide only after certain amount of endosperm is formed.
(ii) Groundnut seeds are exalbuminous and castor seeds are albuminous.
(iii) Micropyle remains as a small pore in the seed coat of a seed.
(iv) Integuments of an ovule harden and the water content is highly reduced, as the seed matures.
(v) Apple and cashew are not called true fruits.

Answer 1

(i)Formation of angiosperms ensures supply of nutrients to the embryo.
(ii) In groundnut food is stored in cotyledon and seeds have no residual endosperm as R is completely used up during embryo development. The castor seeds retain part of endosperm as it is not completely used up during embryo development.
(iii)This facilitates entry of oxygen and water during seed germination
(iv) The seed coat hardens and moisture content of seeds is reduced considerably to enable the seed to remain viable for a long time during storage
(v) Because in these fruits, the thalamus also contributes to fruit formation