The Effect of Mycorrhiza and Potassium Silicate Application on Photosynthetic and Fluorescence Parameters of ‎Strawberry under Heat Stress

The present research tries to investigate the effect of potassium silicate and mycorrhizal fungus on heat stress tolerance of strawberries and evaluate the possibility of increasing plant tolerance to heat at research greenhouse in Sari Agriculture and Natural Resources University at 2019. It is in a completely randomized factorial design with three factors including two levels of mycorrhizal fungi (presence and absence of mycorrhizal fungi), three levels of potassium silicate (0, 50 and 100 mg.l-1) spray in heat stress (25 and 41 °C) with three replications. The results show that application of potassium silicate reduces the Photosynthtic active radiation (PAR) damage in strawberry leaves, which PAR of leaves bottom reduce three folds in comparison to the control, when the PARtop is 1133 umol.m2.s-1. In contrast, treatment of the plant with potassium silicate in the presence of mycorrhiza prevented increases transpiration and stomatal conductivity for water cooling the leaves during heat stress. Inoculation of the roots with mycorrhiza fungi leads to a wide network of hyphae in root uptake, improving water use efficiency by up to 72%, which in turn results in increaseed net photosynthesis. However, heat stress increases minimum fluorescence and reduces maximal quantum efficiency of photosystem II. But the simultaneous application of mycorrhiza and potassium silicate is able to improve this index to a good level (0.76). Finally, it has been found that high temperature stress affects many photosynthetic factors of strawberry plant that the use of potassium silicate in combination with mycorrhizal fungus, despite their separate use, to a large extent prevents heat damage to different parts of the plant.