BOTANY Higher Secondary Second Year - Textbooks Online

endosperm of coconut. Cytokinin occurs in various seed plants. They are
found particularly in embryos, developing fruits and roots. Varying
mixtures of auxin and cytokinin influence plant growth and differentiation.
Physiological effects of cytokinin
The most important function of cytokinin is the promotion of cell
division.
In association with IAA, cytokinin initiates bud and root formation in
callus tissue.
External application of cytokinin promotes the growth of lateral buds
even if the apical bud is intact.
Cytokinin breaks the dormancy of many seeds and also promotes
germination.
Application of cytokinin delays the process of ageing in plants. This
is also known as Richmond Lang effect.
Ethylene
Ethylene is a simple gaseous hormone. It is usually present in a
minute quantity. It is synthesised in large amounts by tissues undergoing
ageing and acts as a natural plant growth hormone.
Physiological effects of ethylene
Ethylene prevents elongation of stem and root in longitudinal direction.
Simultaneously, the tissue enlarges radially resulting in thickening of
plant parts.
Ethylene promotes positive geotropic growth of roots.
Ethylene inhibits the growth of lateral buds in pea seedlings.
Ethylene is involved in the ripening of fruits.
Ethylene stimulates the formation of abscission zone in leaves, flowers
and fruits. This causes leaves, flowers and fruits to shed prematurely.
Flowering can be induced by application of ethylene in plants like
pineapple and mango.
Ethylene stimulates rooting of cuttings, initiation of lateral roots and
growth of root hair.
Ethylene is responsible for breaking the dormancy of buds and seeds.
223