Influence of drought, high temperature, and carbamide cytokinin 4-PU-30 on photosynthetic activity of bean plants. 1. changes in chlorophyll fluorescence quenching

摘要

Fifteen-day-old bean plants (Phaseolus vulgaris L.) grown in a climatic chamber were exposed to water deficit (WD) and high temperature (HT) stresses applied separately or in combination. Changes in chlorophyll fluorescence quenching were investigated. Bean plants that endured mild (42 deg C, 5 h for 2 d) WD separately or in combination with HT did not change their q_p and q_N quenching (measured at 25 deg C) compared with those of the control. After 5 min testing at 45 deg C, q_p in control and droughted plants strongly decreased, while q_p of plants that experienced combined WD+HT stress was insignificantly influenced, suggesting the acclimation effect of HT treatments. At more severe stresses (after 3 d-treatment), q_p measured at 25 deg C was the lowest in WD+HT plants and q_N values were the highest. But when measured at 45 deg C. q_p of WD-HT plants had practically the same values as at 25 deg C. Under these conditions q_p of WD plants also showed an adaptation to HT. Twenty-four hours after recovery, the unfavourable effects of the stresses were strongly reduced when measured at 25 deg C, but they were still present when measured at 45 deg C. Positive effect of the carbamide cytokinin 4-PU-30 was well expressed only in droughted plants.