Question

explain the two ways by which seed develop without fertilization

Answer 1

The two ways by which embryo development occurs in plants without fertilisation are parthenogenesis and apomixis. However, development of seed without fertilisation is called apomixis.
The apomixis may take place in following two ways:
(1)Gametophytic apomixis
In this case the unfertilised egg cell gives rise to embryo without fertilisation.
(2)Sporophytic apomixis
In this case an embryo is formed directly from nucellus or integument tissue of ovule.

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