Improvement of Tolerance to Chilling in Watermelon Seedlings with Methyl Jasmonate and Methyl Salicylate

Abstract

Tropical plants usually are sensitive to chilling and easily damaged. Tolerance of watermelon (Citrullus lanatus L.), cv. Charleston gray, seedlings to chilling was investigated through exogenous application of methyl jasmonate (MeJA; 15 and 30 μM) and methyl salicylate (MeSA; 50 and 100 μM). Four days after receiving MeJA and MeSA seedlings at the 2–true leaf stage were subjected to chilling at 3°C for 6 h daily for 6 days. The MeJA and MeSA treatments enhanced seedling chilling tolerance and improved plant height and shoot and root fresh and dry weights. The MeJA and MeSA increased leaf chlorophyll and relative water contents (RWC) and reduced rate of malondialdehyde (MDA) buildup and electrolyte leakage (EL), alleviating chilling injury to seedlings. Under greenhouse conditions use of MeJA and MeSA appears to be able to protect watermelon seedlings against chilling at the early stage of their growth.