Write down plants hormones.

 Plant Hormones

Some of the special substances produced by the plants which influence the growth and plant responses to various stimuli are given below.

Plant Hormones

(a) Auxins:

• In stem, promote cell enlargement in region behind apex. Promote cell division in cambium.

• In roots, promote growth at very low concentration. Inhabit growth at higher concentration e.g. geotropism. Promote growth of roots from cuttings and calluses.

• Promote bud initiation in shoots but sometimes antagonistic to cytokinins and is inhibitory.

• Cause delay in leaf senescence in a few species.

(b) Gibberellins:

• Promote cell enlargement in the presence of auxins. Also promote cell division in apical meristem and cambium.

• Promote "bolting" of some rosette plants.

• Promote bud initiation in shoots of chrysanthemum callus.

• Cause delay in leaf senescence in few species.

• Break bud and seed dormancy.

• Promote leaf growth and fruit growth.

(c) Cytokinins:

• Promote stem growth by cell division in apical meristem and cambium.

• Promote stomatal opening.

• Cause delay in leaf senescence.

• Inhibitory primary root growth.

• Promote lateral root growth.

• Promote bud initiation and leaf growth.

(d) Abscisic:

• Promote bud and seed dormancy.

• Promote flowering in short day plants, and inhibits in long day plants.

• Sometimes promotes leaf senescence.

• Promote abscission.

• Promote closing of stomata under condition of  water stress.

(e) Ethene:

• Inhibits root growth.

• Break dormancy of bud.

• Promotes fruit ripening.

• Promotes flowering in pineapple.

• Inhibits stem growth.

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