Rape is one of the main oil crops in the world and the most important dietary lipid source in China. In recent years, the planting area of rapeseed in China has been increasing rapidly, but the photosynthetic rate has been significantly hindered under drought stress

　　Dan Liu et al., Institute of Plant Physiology, Polish Academy of Sciences, published the article "5-ALA enhances photosynthetic gas exchange, chlorophyll sunlight and antioxidant system in rapeseed under drought stress". The effects of water relationship, gas exchange, chlorophyll fluorescence, antioxidant enzyme activity and gene expression pattern on rapeseed leaves under drought stress were studied.

　　1. Effects of exogenous 5-ALA on rapeseed growth under drought stress

　　As can be seen from the table, drought stress has a significant inhibitory effect on plant growth, and the growth of above-ground parts and roots of plants is significantly inhibited under drought stress. The application of ALA treatment on drought-treated plants can increase above-ground parts by 17% and root dry weight by 19.2%, among which RWC and WP are significantly increased, and the effect on rape seedlings is significant.

　　2. Effects of exogenous 5-ALA on gas exchange and chlorophyll content under drought stress

　　As can be seen from the table, drought stress has significant effects on Pn, gs and chlorophyll content, and drought inhibits the accumulation of total chlorophyll. The total chlorophyll content of drought-treated plants increased by 14% compared with those without ALA treatment.

　　3. Influence of exogenous 5-ALA on antioxidase activity

　　To investigate how ALA affects ROS elimination in rapeseed leaves, we measured the activities of CAT, POD, APX, GR and SOD. It can be seen from the table that ALA, drought and their interactions have significant effects on the activities of these enzymes. These results indicated that exogenous ALA could also reduce the accumulation of MDA and hydrogen peroxide, increase the activity of antioxidant enzymes, and enhance the expression of CAT and POD in drought-treated plants. It can obviously resist drought stress and promote rape growth.

　　Drought stress inhibits plant growth and physiological processes. Leaf surface application of ALA can maintain leaf water status, increase chlorophyll content, photosynthetic rate and electron transfer rate, and improve the tolerance to drought stress by improving photosynthetic efficiency, protecting leaves from light damage and manipulating the antioxidant enzyme system under drought stress.