Dynamic Stomatal Changes

Dordrecht

Springer

2014

S. 61-82

Artikel aus einer ZeitschriftUnselbständiges Werk

200191910

Trees in a changing environment : ecophysiology, adaptation, and future survival, S. 61-82

Stomatal pores regulate CO2 uptake and water loss from leaves. Stomatal responses are dynamic by nature and often lag behind the faster changing environmental conditions as is common in tree canopies. Even under constant conditions, gas exchange of angiosperms occasionally shows cycling fluctuations, called stomatal oscillations. They are interpreted as an effect of feedback control failing to achieve stable regulation and thus demonstrate that stomata not only respond to external factors, but also to the environment inside the leaf. The processes which translate transpiration into turgor are called the physiological gain. The physical processes and environmental conditions which control stomatal aperture, stomatal conductance and transpiration are called the physical gain. More research on the physiological gain is needed in order to understand these processes. In order to overcome the epidermal backpressure, guard cell turgor has to reach a certain threshold level, although guard cell swelling anticipates the opening. When the pore opens, the relation between pore area and stomatal conductance determines the physical gain. In contrast to the Fick s first law of diffusion, this relation is not
linear, but convex shaped, with a rapid increase of conductance just after opening and much less effect of aperture changes at large apertures. The high and abruptly
changing gain at smallest pore openings can promote overshooting oscillatory responses, as supported by microscopic observations of stomatal apertures.