Effects of fulvic acid on the photosynthetic and physiological characteristics of under drought stress.

has become an economically important oil crop in recent years, but its growth is seriously affected by drought stress in dry areas. In this study, the alleviating effect of fulvic acid (FA) on potted under natural drought stress was investigated. The natural drought stress adopted in this experiment was mainly characterized by the low soil water content, and the roots of plants cannot absorb enough water to compensate for the consumption of transpiration, which affects the normal physiological activities and causes damage. The results showed that FA treatment significantly increased the leaf water content and antioxidant enzyme activities and decreased reactive oxygen species (ROS) accumulation, the proline (Pro) content, and the relative electrical conductivity (REC). Moreover, FA treatment improved photosynthetic parameters and chlorophyll (Chl) fluorescence parameters, maintained the integrity of chloroplasts and mesophyll cells, and increased the expression level of drought-tolerant genes. These results indicated that FA treatment could induce antioxidant enzymes to eliminate ROS, reduce membrane lipid peroxidation and decrease damage to photosynthesis in under drought stress, which would provide a measure for alleviating the damage of caused by drought stress.