Photosynthesis and transpiration in the heads of droughted grain sorghum

Abstract

The effect of water deficits on the relative photosynthetic rates in heads and leaves of sorghum was measured. When water was withheld, photosynthesis virtually ceased in the leaves but continued in the heads at the same rate. The photosynthetic activity of heads increased from about 12 per cent of the total in a well watered plant to about 88 per cent for a plant at high moisture deficit. Relative transpiration of heads also increased as water status declined. In watered plants, loss from heads was, like photosynthesis, about 12 per cent of the total but increased with water shortage to about 35 per cent.