Ncert Exercises & Solutions

29. Auxins are growth hormones capable of promoting cell elongation. They have been used in horticulture to promote growth, flowering and rooting. Write a line to explain the meaning of the following terms related to auxins.

(a) Auxins precursors

(b) Anti-auxins

Auxin is an important plant phytohormone required for the growth and development of every plant in its life cycle.

(a) Auxin Precursors are raw materials required to initials synthesis of auxins. IAA is synthesised from tryptophan, adenine compoundsand derivatives of carotenoids.

(b) Anti-Auxins are compounds that inhibit action of auxins, e.g., p-chlorophenoxy isobutyric acid (PCIB), TIBA.

(c) Synthetic Auxin These are synthesised not by plants but artificially by man, e.g., 2-4 D (weedicide), NAA, dicamba and IBA, (Indole Butyric Acid) which are natural as well as synthetic auxin.

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