Response of strawberry (Fragaria ananassa L.) to chilling and potassium supply from inorganic and amino acid-complexed sources

Abstract

There is growing evidence that plants need higher potassium (K) when subjected to environmental stresses i.e., chilling in order to tolerate oxidative damages provided by stress. In this work, influence of potassium (K) foliar spray from different fertilizer sources including K2SO4 and lysine (Lys)- and methionine (Met)-complexed K on physiological and antioxidative responses of strawberry (Fragaria ananassa ‘Gavieta’) to chilling (6 h d−1 at 4 °C for 3 consecutive days) was investigated. Chilling of control, Lys, and K-Lys-strawberry plants to 4 °C increased ion leakage and malondialdehyde (MDA) concentration. In contrast, chilling was ineffective on the amount of ion leakage and MDA in the plants supplied by K2SO4, K-Met, and only Met. The leaf chlorophyll concentration was found to reduce by chilling in both control (free of K and amino acid) and Lys-treatments, however, the chill-treatment leaf chlorophyll concentration remained unchanged in the plants supplied with K-Met, K2SO4, and only Met. The chilling at 4 °C resulted in between 0.58 % to 5.2-fold rise in strawberry leaf CAT, APX, and SOD activities, the largest increase was found at K-Met-treatment. Chilling substantially increased leaf proline concentration (on average 99.5 %), the largest increase was found at the K-Met-treatment. Chilling caused significant reduction in water potential (ΨL) and relative water content (RWC) of control and only Lys-and Met-strawberry plants but it had no effect on these water relations of K-fed plants. According to the results, foliar fertilization of K particularly from K-Met-complex was effective in alleviating the destructive effect of chilling on cell membrane of plant leaves. The protective effect of K and Met-fertilization against chilling-induced injuries was in part related to a substantial rise in leaf activity of CAT, APX, and SOD and leaf proline concentration.