An increase in the "inhibitor-β" content of detached wheat leaves following a period of wilting.

Wheat seedlings were grown under a 14-hour photoperiod and the first leaves excised at the end of the eighth dark period. The effect of treatments causing wilting on the "inhibitor-β" content of such leaves was studied.When leaves were rapidly wilted (i.e. to a 6% fresh weight loss) and extracted immediately, the amount of "inhibitor-β" per leaf was found to be the same as in fresh turgid leaves. However, when the leaves were maintained in a wilted condition in darkness for a period of 110 minutes, there was a marked increase in "inhibitor-β" content.The greater the degree of wilting (i.e. up to about a 9% loss in fresh weight) the greater the eventual "inhibitor-β" content. Moreover, the increment in "inhibitor-β" was shown to be temperature dependent.The time lapse requirement and the temperature dependency of the "inhibitor-β" formation suggest an enzymic conversion from a precursor.If a similar phenomenon occurs during the wilting of intact plants then the increase in this growth inhibitor might play a role in some of the physiological changes which accompany water stress.