Phosphorus and cold stress: physiological and biochemical assessment in two grape (Vitis vinifera L.) cultivars.

Low temperature is one of the most damaging factors in the production of horticultural crops. This study was conducted to investigate the mechanisms of frost tolerance resulting from the use of different concentrations of phosphorus (P) fertilizer in two grape (Vitis vinifera L.) cultivars, ‘Khalili’ and ‘Perlette’, factorially based on a completely randomized design on potted vines. The cultivars were treated with a Hoagland nutrient solution containing three different P concentrations (0, 0.5, and 1 mM), and were examined at two temperatures, 24 °C and 2 °C. The results showed that cold tolerance was higher in the ‘Khalili’ cultivar compared with the ‘Perlette’ cultivar. In both cultivars, the samples treated with 1 mM P concentration exhibited the lowest values for cold tolerance-related indices. The highest cold tolerance, measured using the electrolyte leakage method, was observed in the ‘Khalili’ cultivar at 0.5 mM P concentration. The highest amounts of hydrogen peroxide and malondialdehyde were observed at 0 and 1 mM P concentrations under the + 2 °C temperature treatment. The lowest activity of antioxidant enzymes, soluble sugars, soluble proteins, and polyamines was observed at a 1 mM P concentration in both ‘Khalili’ and ‘Perlette’ cultivars. In this treatment, the lowest amounts of chlorophyll, anthocyanins, and leaf calcium, magnesium, zinc, copper, and active iron were observed. The ratio of active iron to total iron significantly decreased at the 1 mM P concentration, and leaf chlorosis was visible in this treatment. These results indicate that optimum concentrations of P (0.5 mM) can physiologically and biochemically lead to improved cold tolerance of grapevine plants.