Compositional Factors Associated with the Growth Responses of Young Cotton Plants to Gibberellic Acid.

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Abstract
Characteristically gibberellic acid (GA3) increased the main-stem length of young cotton plants in proportion to the total amount applied over the range of 10-1000 [mu]g; l.0[mu]g was ineffective. Dry weights of the stems and petioles, but not of the leaves, were consistently increased by the 10-100-[mu]g doses. The 1000-[mu]g dose, which had little or no effect on the dry weight of stems and petioles, drastically reduced leaf dry weight and caused pronounced chlorosis resembling nitrogen deficiency. It also reduced main-stem diameter and produced a condition resembling lodging. Effects of GA3 on the individual carbohydrate fractions were somewhat variable but total carbohydrates, as well as lignin, were each consistently increased in the stems and petioles as the level of GA3 was increased; the leaves, except for increases at the inhibitory level, were essentially unaffected. In the stems and petioles, but not in the leaves, total ash and total nitrogen contents (g/plant) were each increased by the growth promoting levels of GA3, but suppressed in both tissue fractions by the inhibitory level (1000 [mu]g).