In situObservations of Stomatal Movements

Abstract

Kappen, L., Andresen, G. and Lösch, R. 1987. In situ observations of stomatal movements.—J. exp. Bot. 38: 126–141. A device is described by which stomatal movements in situ can be observed and recorded continuously in light and in darkness. It is mounted in a conditioned CO₂ exchange measuring chamber so that stomatal movements can be observed whilst CO₂ exchange (photosynthesis and respiration) of the same leaf is measured. Advantages and limitations are discussed. By this method it was shown that stomata of Vicia faba although responding in the same direction to environmental stimuli exhibited a wide range of pore widths. Responses to changes of air humidity and of CO₂ content were clearly evident when the leaves were exposed to light. Before stomata closed due to decreasing water vapour pressure differences between leaf and air they showed a marked widening of the pore. An inverse response occurred when water vapour pressure deficit decreased. In darkness stomata did not respond to such changes.