Physiological effects of Ethylene

Physiological effects of Ethylene:- 

i. Fruit Ripening:- Its main function is to ripen fruits. The most commonly used chemical is called ethephon (2-chloro ethylphosphonic acid). It penetrates into the fruit and decomposes ethylene.

ii. Triple Response:- Ethylene  causes plants to have – 

    i. Short shoots:- Inhibition of stem elongation.

    ii. Fat shoots:- Stimulation of radial swelling of stems.

    iii. Diageotropism:- Increased lateral root growth and horizon­tal growth of stems with respect to gravity.

iii. Formation of Adventitious Roots and Root Hairs:- Ethylene induces formation of adventitious roots in plants from different plant parts such as leaf, stem, peduncle and even other roots. In many plants especially Arabidopsis, ethylene treatment promotes initiation of root hairs.

iv. Inhibition of Root Growth:- Ethylene is known to inhibit linear growth of roots of dicotyledonous plants.

v. Leaf Epinasty:- When upper side (adaxial side) of the petiole of the leaf grows faster than the lower side (abaxial side), the leaf curves downward. This is called as epinasty. Ethylene causes leaf epinasty in tomato and other dicot plants such as potato, pea and sunflower. Young leaves are more sensitive than the older leaves. However, monocots do not exhibit this response.

vi. Flowering:- Ethylene is known to inhibit flowering in plants.

vii. Sex Expression:- In monoecious species especially some cucurbits like cucumber, pumpkin, squash and melon; ethylene strongly promotes formation of female flowers thereby suppressing the number of male flowers considerably.

viii. Senescence:- Ethylene enhances senescence of leaves and flowers in plants. In senescence, concentra­tion of endogenous ethylene increases with decrease in conc. of cytokinins and it is now generally held that a balance between these two phytohormones controls senescence.

ix. Abscission of Leaves:- Ethylene promotes abscission of leaves in plants. Older leaves are more sensitive than the younger ones.

x. Breaking Dormancy of Seeds and Buds:- Ethylene is known to break dormancy and initiate germination of seeds in barley and other cereals. Seed dormancy is also overcome in strawberry, apple and other plants by treatment with ethylene. Non-dormant varieties of seeds produce more ethylene than those of dormant varieties.