Effects of Potassium and Nanocapsule of Potassium on Pepper Growth and Physiological Changes in High-Temperature Stress

Abstract Abiotic stresses have been observed to cause alterations in the morphology, physiology, and biochemistry of plants. However, in recent years, the utilization of nanocompounds has emerged as a strategy to induce modifications in multiple facets of plant biology. These modifications include plant growth, nutrient absorption, the production of significant secondary metabolites, and the improvement of plants’ resistance against both abiotic and biotic stress factors. A completely randomized factorial experiment with 12 replications was created. Potassium sources including control, potassium (K), and nanocapsule-potassium (N-K) with concentration 1 µM and temperature treatments including control temperature (25 °C) and high-temperature stress (35 °C) were applied as treatments. In the control treatment, proline was increased at the high temperature, whereas proline was reduced at both treated temperatures by K and N-K. High temperature raised electrolyte leakage (EL), which peaked in the control treatment but was lowered by K and N-K. Temperature-dependent increase in glucose and fructose was observed in control and K treatments when the temperature was 35 °C, but no significant difference was observed between different levels of K at 35 °C. When K was not applied at high temperatures, the main stress indicators such as antioxidant activity (DPPH) and malondialdehyde (MDA) rose significantly, as did the water potential and linoleic acid. When high temperatures were applied, nanocapsule-potassium applied in high temperatures had the lowest stress indices. In conclusion, stress indices diminish when nanocapsule-potassium is applied under high temperatures. Additionally, nanocapsule-potassium applied at high temperatures was preferable to K applied at high temperatures in terms of pepper growth and resistance measures. Likewise, the application of nanocapsule-potassium at high temperatures alters the fatty acid composition of membranes and antioxidant enzymes.