Drawback of Ethylene:

• It is not possible to totally remove ethylene within the tissue. It’s continuously produced as a metabolic product and is dissolved in the cytoplasm or absorbed in organelles.
• Ethylene enhances respiration, its formation enhanced only by active respiration.
• The ratio of respiration to C2H4 is not constants, as fruit ripen C2H4 are evolution drops off.
• It is not known whether C2H4 is required throughout the ripening process.

Occurrence:

Widely distributed bacteria, fungi, algae, animals and in higher plants. Higher concentration of ethylene are produced by senescing organ, organ subjected to stress, mechanically damaged organ or diseased organ. Any mechanical damage even touching the plants significantly effects ethylene production.

Mode of action:

1.Effect on ripening

2.Effect on epinastic response

3.Effect on abscission

4.Promotes flowering particularly NAA induce flowering in pineapple. Now it is believed that NAA effect on ethylene production.

5.It has a practical importance I,e degradation of fruits,lemon, orange. Ethylene has direct effect on chlorophyll breakdown and carotene synthesis.

Mechanism of action in ripening:

There is no evidence at present to show that C2H4 is itself a part of any known biochemical reaction, or co-enzyme. On the cellular level C2H4 is believed to increases the permeability of the cell membranes as well as the membranes of subsellular particles, thus making the substrate more accessible to the corresponding enzymes.

It has been started that inhibitor of ripening was isolated in mangoes. Matto and Modi (1969) shown that C2H4 promoted the activity of enzyme catalase, peroxidase and amylase in mango, concurrently with the disappearance of ripening inhibitors.