The effect of temperature and water stress on the timing of leaf death in Vicia faba

SUMMARY The timing and pattern of leaf death was studied in three field experiments from observations of the area and dates of death of individual leaves. Two linear regression lines adequately described the pattern of leaf death on the plant in all experiments and treatments. These represented an initial phase with a slow rate of leaf death changing to a second phase with a more rapid rate of leaf death. The change from the first to second phase of leaf death occurred when the maximum seed dry weight was reached. The rates of both the first and second phases of leaf death increased with temperature. This was confirmed in an experiment in growth rooms. The rate of leaf death in both phases of plants grown at three constant temperatures increased linearly with temperature from 14 °C to 22 °C. The rate of leaf death in phase 2 increased with increasing solar irradiance and vapour pressure deficit. The rate of leaf death in both phases increased with increasing water stress in three irrigation treatments in the field.