Hydropassive evidence and effective factors in stomatal oscillations of Glycyrrhiza inflata under desert conditions

Whether stomata oscillations induced by atmospheric drought stress are hydropassive or metabolic energy-dependent and the thresholds of some effective factors were studied in Glycyrrhiza inflata. The metabolic inhibitors NaN3 and carbonyl cyanide-m-phenyl-hydrazone inhibited the respiration. However they could not significantly change the intensity (amplitude/average) of the stomata oscillation. The leaf turgor-pressure was fluctuated simultaneously with the stomata oscillations, whereas the K+ content of the guard cells did not show oscillations. The oscillation intensity was found to be regulated by vapour pressure deficit (VPD): the proportion of the retained root and the stem flux lag. The minimum threshold of VPD, roots and the stem Aux lag may be required to induce the stomata oscillations. The fluctuations of the leaf turgor-pressure induced by the non-synchronization between the transpiration demand and provide of water by the stem flux may be the direct cause of the stomata oscillations in G. inflata under the conditions of high transpiration demand. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.