Stomatal patchiness of grapevine leaves. 2. Uncoordinated and coordinated stomatal movements

Abstract

The dynamics of stomatal patchiness of grapevine leaves (var. Richter 110) were studied by in situ infiltration of water into the intercellular spaces (see: DÜRING and LOVEYS 1996). As infiltrations were shown not to affect stomatal conductance (g) a series of experiments was performed in which a leaf segment was infiltrated and photographed repeatedly. While stomata of some patches did not alter their apertures within a 90-minute experiment, others opened and closed their stomata more or less frequently leading to irregular fluctuations of patches with open, partly open and closed stomata. In contrast to this uncoordinated behavior coordinated, synchronous stomatal movements were recorded by gas exchange. Sinus wave-like stomatal oscillations with periods of 32-70 min and amplitudes of 38-95 mmol CO₂ m^-2 s^-1 at constant ambient conditions were observed in a 12 h experiment. The stomatal oscillations were closely related to rhythmic alterations of the intercellular CO₂ concentration (c_i) and to the rate of CO₂ assimilation (A). An increase of amplitudes of g was associated with a decrease of the carboxylation efficiency (A/c_i) and the water use efficiency (A/g). It is concluded that uncoordinated, patchy fluctuations of stomatal apertures enable effective adaptation of single patches to changes of ambient stress factors.