Effects of Low Temperature Stress on Antioxidant System and Fatty Acid Composition in Pitaya Plants
[Objective]The objective of this study was to explore the mechanisms of cold tolerance in two varieties of pitaya under low-temperature stress.[Method]′Baishuijing′ and ′Taiwan No.6′ pitayas were used as materials to analyze changes in the chilling injury index(CI),antioxidant systems,and fatty acid composition across three temperature gradients:optimal(30°C/24°C),chilling(15°C/8°C),and freezing(4°C/-2°C).[Result]The CI of both pitaya varieties increased under low-temperature stress,with higher levels observed under freezing conditions.Under chilling and freezing conditions,the CI of ′Baishuijing′ was consistently lower than that of ′Taiwan No.6′.The activity of anti-oxidant enzymes in both pitaya plants significantly increased in response to low temperatures,with ′Bai-shuijing′ consistently showing higher activity than ′Taiwan No.6′.Additionally,′Baishuijing′ exhibited lower accumulation of reactive oxygen species(ROS),lower increases in malondialdehyde(MDA)con-tent,and reduced electrolyte leakage(REC).The relative content of unsaturated fatty acids and the ratio of unsaturated to saturated fatty acids(UFA/SFA)in both pitaya plants decreased with temperature re-duction,but this decline was less pronounced in ′Baishuijing′.[Conclusion]Both pitaya varieties were susceptible to freezing under low-temperature stress,but'Baishuijing'demonstrated stronger cold toler-ance than ′Taiwan No.6′.′Baishuijing′ maintained higher antioxidant enzyme activity and ROS scaveng-ing capacity,reduced membrane lipid peroxidation damage,and enhanced fatty acid unsaturation under chilling and freezing conditions,which are the main reasons for its enhanced cold tolerance.These find-ings provide a theoretical basis for the cold-resistant cultivation of pitaya in subtropical regions.
low temperature stresspitaya plantscold resistanceantioxidant systemfatty acid
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