What are the physiological roles of auxins?


1. Cell Division and cell elongation:

Auxins stimulate cell division in cambium and also in the primary meristems. Cell elongation brought about by additional production of wall materials (see mechanism of auxin action) is an important physiological role played by auxins. Another important characteristic of auxin is its differential action on shoot tip and root tip. While a higher auxin concentration promotes cell division at shoot tip, it actually inhibits cell division at root tip.

2. Root Formation:


Auxins induce root formation at low concentrations. This is made use of by horticulturists to induce root formations in stem cuttings. The concentration is very critical because a higher concentration inhibits root growth.


1. Prevention of abscission layer:

Auxin prevents leaf fall by suppressing the formation of abscission layer.


2. Parthenocarpy:

Parthenocarpy or seedless formation of fruit is induced by auxins. Spraying of auxins on flowers induces parthenocarpic developĀ­ment of fruits in tomato, apples, cucumbers etc.


1. Xylem differentiation:


Auxins can induce the differentiation of xylem vascular differentiation in callus, produced during grafting.

2. Miscellaneous activities:

Enzymes concerned with aspartic acid meĀ­tabolism are activated by auxins, while the activity of the peroxidases is lowered. Floral inhibition is another auxin activity, but in pineapple auxin promotes flowering.

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