SIMULATION OF THE EFFECT OF DROUGHT STRESS ON THE RATE OF PHOTOSYNTHESIS IN COTTON

The purpose of this study was to use field experimental data to evalua te the quantitative effects of drought stress on the rate of photosynt hesis of cotton plants. Measurements were made on plants growing at va rious distances from a single line source. Relationships between daily sums of photosynthetic rates and noon values of leaf water potential (LWP), and between LWP and a drought stress factor computed in the mod el have been evaluated. The derived equation for the effect of drought stress on the rate of photosynthesis was used in a modified model, an d it significantly improved the simulation results. The modified model was tested with data from four treatments of a drip irrigation experi ment, which represent extreme soil moisture conditions during two irri gation periods. The simulation results also agreed closely with the ex perimental data.