Physiological Response of Cold Stress on 2 Cultivars of Phalaenopsis amabilis

Two-year-old Phalaenopsis amabilis 'Green bear' and P. amabilis 'Anna' were used as experimental materials to determine the net photosynthetic rate(Pn), stomatal conductance(Gs), relative electrical conductivity(REC), proline, soluble protein and malondialdehyde(MDA) contents and superoxide dismutase(SOD), catalase(CAT) and peroxidase(POD) activities at 5 ℃ for 12, 24 and 48 hours. The effects of cold stress on leaf morphology, photosynthetic parameters, antioxidant enzyme activity and content of osmotic adjustment substance in different cultivars of P. amabilis were analyzed. The results showed that 5 ℃ stress significantly reduced the Pn and Gs of P. amabilis 'Green bear' and P. amabilis 'Anna', and increased the contents of MDA, proline and soluble sugar, as well as SOD, CAT, POD enzyme activities and REC. And with the increase of the treatment time, the change degree deepens gradually. However, the decrease in Pn of P. amabilis 'Green bear' was lower than that of P. amabilis 'Anna', and its leaf morphology, soluble sugar and soluble protein content were significantly higher than that of P. amabilis 'Anna'. Under 5 ℃ cold stress, the leaf morphology of P. amabilis 'Green bear' was better, Pn, Gs, CAT activity, content of soluble protein and soluble sugar were significantly higher than that of P. amabilis 'Anna'. This research proves the cold resistance of P. amabilis 'Green bear' better than that of P. amabilis 'Anna'.