Explain following terms :(a) Grafting(b) Apomixis(c) Polyembryony(d) Parthenocarpy

Answer:

(a) Grafting: an artificial method of vegetative propagation in which parts of two plants are joined so that they unite and grow as one plant. The rooted plant is the stock and the part inserted on it is the scion; the cambium of both must be in contact. It is used in mango, apple, citrus, rose etc. to combine desirable characters.

(b) Apomixis: the formation of seeds without fertilization (and usually without meiosis), so it is a form of asexual reproduction that mimics sexual reproduction. The embryo develops from a diploid egg or other cells of the ovule, e.g. in some grasses and Asteraceae. Apomictic seeds produce plants identical to the parent; it is useful for preserving hybrid vigour.

(c) Polyembryony: the occurrence of more than one embryo in a single seed, e.g. in Citrus (orange, lemon) and mango. Extra embryos may develop from nucellus or integument cells (adventive embryony), synergids, antipodals or by cleavage of the zygote.

(d) Parthenocarpy: the development of fruit without fertilization; such fruits are seedless, e.g. banana, pineapple, seedless grapes and watermelon. It can be induced by applying auxins or gibberellins to the flowers.