Shading net and foliar applications of Si and K alleviates heat stress and improves pomegranate fruit quality

High temperature and light intensity are limiting factors for reducing quality during pomegranate fruit growth and development. In this research, mitigation of the heat stress detrimental effects was investigated on pomegranate through the use of a shading net and foliar application of silicon and potassium nutrient elements. Treatments included net shading (0 and 50%) and foliar spraying of trees during the growing season with K (1% and 2%) and Si (0.05%, 0.1%, and 0.15%). The foliar sprays were applied three times, first after fruit set and then twice after with one-month intervals. Shading net increased leaf chlorophyll content, net photosynthetic rate, transpiration, substomatal CO₂, relative water content, and antioxidant enzymes activity. Shading net guards membrane integrity, being obvious through the reduction of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) contents in pomegranate leaves. Shading net significantly reduced the percentage of fruit sunburn to 12% and cracking to 11% on compared to the control (41% and 27%). Si and K applications were also effective on the physiology of pomegranate trees in response to heat stress. Si applications increased superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX), chlorophyll content, and relative water content, while reduced MDA and H₂O₂ contents. Shading net and Si spraying positively affected the uptake of macronutrients while having no significant effect on leaf micronutrients. High temperatures adversely affected the recorded responses of the pomegranate trees and, the shading net effectively reduced heat-induced disorders. In addition, application of Si and K ameliorated the negative effects of heat stress.