Heat-shock-induced cross adaptation to heat, chilling, drought and salt stress in maize seedlings and involvement of H2O2

A heat-shock pretreatment at 42 °C for 4 h followed by a 4-h recovery significantly enhanced survival rates of seedlings from two varieties of maize that differ in stress resistance. The procedure mitigated electrolyte leakage of primary roots and alleviated vitality loss of coleoptiles under severe heat, chilling, drought and salt stress, indicating that heat-shock pretreatment can induce cross adaptation. The heat-shock pretreatment, that induced cross adaptation, also produced an endogenous H2O2 peak in maize seedlings. Exogenous H2O2 treatments simultaneously enhanced multi-resistance to heat, chilling, drought and salt stress, implying that H2O2 may play a signalling role in triggering cross adaptation of maize seedlings to various stresses.