Abstract: Cold resistance of individual plants of three Acacia species \[Acacia mangium ×A. auriculiformis (Chiyun) (CY), A. mangium× A. auriculiformis (ZJ) and A. mangium (MZ)\] was evaluated by subjecting the cutting seedlings of eight individuals to different low temperatures (12, 9, 6, 3, 0 ℃, and 25 ℃ as the control). Six physiological indices (relative conductivity, malondialdehyde, soluble sugar, free proline, soluble protein, and superoxide dismutase content) were analyzed. Cold resistance ability of individual plants was evaluated by the membership function method. The results showed that relative conductivity, free proline, soluble protein and soluble sugar contents in the leaves increased under low temperature, which could be used as the reference indices for evaluating cold resistance of Acacia. Temperature threshold for cold injury of Acacia was 0-6 ℃ after low temperature stress. Results from the membership function analyses showed that ZJ1, ZJ4 and CY1 had the highest cold resistance, while MZ11 had the lowest cold resistance.

Key words: Fuji apple, altitude, leaf characteristic, fruit quality, environmental factors.