Melatonin improves plant water status, photosynthetic performance, and antioxidant defense system in highbush blueberry (Vaccinium corymbosum L.) plants subjected to drought stress

Drought stress causes a decrease in agricultural yields. Recently, it has been reported that the phytohormone melatonin (MT), participates in different plant growth and developmental processes. Highbush blueberry (Vaccinium corymbosum L.) is quickly affected by drought, decreasing plant growth, yield, and quality. Thus, the aim of this study was to evaluate the role of melatonin on physiological performance, water status, chlorophyll concentration, and antioxidant metabolism in V. corymbosum plants exposed to drought stress. One-year-old V. corymbosum plants were subjected to four treatments: 1) 100% field capacity (FC) without melatonin; 2) 100% FC with 0.1 mM MT; 3) 50% FC without MT; and 4) 50% FC with MT. Plant water content, leaf area, photosynthetic performance, antioxidants compounds, and chlorophyll concentration were determined at different times post MT application (0, 3, 7, and 10 days). In our study, leaf area, plant water status, the photosynthetic performance and photosynthetic pigments decreased in the treatments with irrigation at 50% FC compared to the treatment whit irrigation at 100% FC. Interestingly, MT application improved plant water potential, CO2 assimilation, chlorophyll a, and total phenols by 35, 65, 22, and 27% respectively, at 50% FC treated with MT compared to plants without MT at 10 days of the experiment. Our results demonstrate that MT enhanced physiological and biochemical responses of V. corymbosum plants to cope with drought stress.