What are the two effects of ethylene in plant metabolism?

1. Abscission:

Ethylene promotes the changes that occur before the abscis­sion of leaves, flowers and fruits. It promotes cellulase activity.

2. Ripening and climateric rise:

Climateric rise is a term employed to denote the increased rate of respiration in mature and senescing tissues such as ripe fruits. Originally it was believed that ethylene is a product and not cause of senescence. Recent studies however have shown that ethylene production begins even before the climacteric rise.

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1. Activation of enzymes:

Ethylene activates the action of certain enzymes like malic enzyme and pyruvate decarboxylase. Chlorophyllase, an enzyme that degrades chlorophyll is also activated by enthlene.

2. Elongation of roots and stems:

Ethylene inhibits root and stem elongation in dicots.

3. Effects of flowering:

Although, ethylene generally inhibits flowering in most plants, in some of the bromeliads like-pineapple, ethylene is known to initiate the flowering. An ethylene releasing substance has been commer­cially produced (ethrel) to promote flowering in pineapple. Ethylene also produces the degreening effect in cirtus and banana fruits.