Electrolyte leakages and LT50 values of
Muscat Hamburg’ plantlets under combined drought−cold systems. (a) and (b) represent the pattern diagrams of different cooling modes. (a) Gradient cooling (GC) combined PEG 6% and continuous temperature decreased at a rate of 1°C/h from −2°C; (b) non−acclimated freezing (NAF) combined PEG 6% and directly frozen to each given temperature for 2 h. The feint arrows indicate the points when the plantlets began to subject cold stress, while the solid arrows represent the sample time at the end of each defined temperatures. (c) and (d) show electrolyte leakages under GC and NAF modes, respectively. (e) LT50 values of GC and NAF modes in V. amurensis and ‘Muscat Hamburg’. The values represent the mean value±SE from three to five replicates, * and ** indicate significant differences between V. amurensis and ‘Muscat Hamburg’ at P<0.05 and P<0.01 level (t test), respectively.