Towards a causal analysis of stomatal patchiness: the role of stomatal size variability and hydrological heterogeneity

The induction of the well known and widespread phenomenon 'stomatal patchin ess' has been attributed to a variety of potential causes: from low PPFD le vels, all kinds of stress conditions to CO2-changes and even fungal infecti ons. A mechanism which explains the occurrence of reproducible patterns of static (i.e. stable) stomatal patchiness at low PPFD levels is proposed. Fu rther, experimental evidence is presented for the hypothesis that dynamic ( i.e. not stable) stomatal patchiness is a consequence of heterogeneous wate r status in different parts of the leaf and can be induced by all ambient f actors which cause such heterogeneities. (C) 2001 Editions scientifiques et medicales Elsevier SAS.