The Effect of Dehydration on Leaf Photosynthesis Depends on Leaf Temperatures

Stomatal opening in wilted leaves at low temperatures has previously been reported for bean and soybean (1, 2). Photosynthetic net CO2 uptake by leaves of plants subjected to a mild drought decreases mainly because of the stomatal closure which occurs under these conditions (3). The resulting decrease in intercellular CO2 partial pressure favors photorespiration relative to photosynthetic carbon fixation and is expected to shift the optimal temperature for net photosynthesis downwards. This effect is further enhanced by the changes in the O2/CO2 solubility ratio with temperature. Here, we show results on pea leaves. We show some evidence that the temperature response of stomata can occur independently of photosynthetic fixation and reduction of carbon dioxide and root ABA signals.