Potassium Phosphite Induces Tolerance to Water Deficit Combined with High Irradiance in Soybean Plants

Changes in plant metabolism due to water deficit combined with other stresses, such as high irradiance and high temperatures, cause damage to the physiology and development of crops, which can lead to significant yield losses. The aim of this study was to determine the potential of potassium phosphite (PP) to induce tolerance to water deficit combined with high irradiance in soybean plants. The experiment was carried out in an acclimatized growth chamber. Soybean plants, upon reaching the R1 developmental stage, received the following treatments: PP application (0 L ha(-1)-control; 0.6 L ha(-1) PP; and 1.2 L ha(-1) PP), two levels of PAR irradiance (650 mu mol m(-2) s(-1)-control; and 1500 mu mol m(-2) s(-1)-high irradiance (HI)), and three water availability levels (90% of field capacity (FC), and water deficit at 40% FC and 50% FC). The treatments were maintained for 12 days. The PP increased the photosynthetic rate of plants submitted to a dosage of 1.2 L ha(-1) and stresses of 50% FC + HI. PP also decreased the intensity of lipid peroxidation, and rate of electrolyte leakage, which suggests stability of cell membranes. These responses may have occurred due to the activation of the antioxidant enzymes superoxide dismutase and peroxidase. Furthermore, the application of PP increased the proline concentrations, suggesting osmotic adjustment in response to stress. These results provide the first record of PP-induced tolerance in plants under combined water and HI stresses. PP proves to be a potential alternative method to reduce the harmful effects caused by the combined stresses of water deficit and high irradiance in soybean.

Automated summary

Changes in plant metabolism due to combined water deficit, high irradiance, and high temperatures can cause damage to crops, leading to yield losses. This study aimed to investigate the potential of potassium phosphite (PP) to induce tolerance in soybean plants under water deficit and high irradiance conditions. The experiment was conducted in a controlled growth chamber, and the results showed that PP application increased photosynthetic rate and decreased lipid peroxidation and electrolyte leakage, indicating enhanced stability of cell membranes. These positive effects may be attributed to the activation of antioxidant enzymes and osmotic adjustment. Overall, PP is a promising method to alleviate the negative effects of combined water deficit and high irradiance stresses on soybean plants.