Enhancement of frost tolerance of almond flowers using potassium

Abstract

Using mineral nutrients is recommended as a plan to alleviate or avoid spring frost damage to blossoms. The purpose of this study was to investigate the effects of potassium application on reducing or preventing spring frost damage of almond (Prunus dulcis Mill.) flowers. Treatments were four levels of K2SO4 (0, 1, 2, and 4%). The nutrition solutions were sprayed on trees in two times (bud swell stage and green tip stage) in 2018–2019. The spurs containing flower buds were collected during the full blooming phase. The spurs segments were exposed to three different freeze test temperatures (0, −2, and −4 °C), and some relevant physiochemical changes were evaluated. The application of K2SO4, especially 4% K2SO4, decreased freezing injury, electrolyte leakage percentage, hydrogen peroxide (H2O2), and malondialdehyde (MDA) concentrations of flowers after freezing tests compared with control. The nutrient treatments, especially 4% K2SO4, increased significantly the contents of soluble proteins, soluble carbohydrates, total phenolic compounds, and proline of flowers. The results of the present study could have implications for the use of potassium in freezing tolerance improvement of other temperate fruit trees grown in low temperatures regions.