Interactions among stomata in response to perturbations in humidity

The existence of patchy stomatal closure suggests interactions among neighbouring stomata that synchronize stomatal movements in small areas of a leaf, go test for such interactions, water vapour partial pressure (e(wv)) for a small group of stomata was controlled independently of that for the surrounding stomata using gas flow from a small needle, The e(wv) for the surrounding stomata was controlled with a larger gas flow, termed the primary flow, The spatial pattern of e(wv) isobars caused by the needle flow was assessed experimentally and theoretically. Stomatal apertures were monitored Following perturbations in e(wv) of the primary flow and the needle flow. When e(wv) of the primary flow was perturbed and that of the needle now held constant, stomata for which there was little or no perturbation in e(wv) responded similarly to stomata experiencing the perturbation, When the e(ew) of the needle flow was perturbed and that of the primary flow held constant, many stomata experiencing little or no perturbation responded similarly to those experiencing a large perturbation, The results are discussed in relation to a mechanism for stomatal interactions that has been proposed in a previous study. [Haefner, Buckley & Mott (1997) Plant, Cell and Environment 20. 1087-1097, this issue].