The Effect of Relative Air Humidity on the Development of Water Saturation Deficit in the Cut Leaves of two Varieties of Barley

Abstract

The study of the water relations is carried out at our Institute with a view to its application in plant production management. From the point of view of plant physiology, the whole of plant production is conceived as essentially an accumulation of the products of photosynthesis by the plant. It is known that among numerous factors influencing photosynthesis, the water relations have a particularly important significance. The indirect effect of water deficit on the photosynthetic rate is especially striking. This indirect effect acts by the hydroactive closing of the stomata with increasing water deficit, causing restricted up to complete halting of CO₂ uptake (Pisek 1956 and Winkler 1956). The fact is even more important since the highest water deficit occurs most often on warm sunny days when all other factors, such as light, temperature and CO₂, are very favourable for high net photosynthesis. Under these conditions — relatively small change in water deficit can lead to relatively big changes in photosynthetic rate.