Effects of paclobutrazol on the physiological characteristics of Malus halliana Koehne Seedlings under drought stress via principal component analysis and membership function analysis

AbstractTo study the effect of paclobutrazol (PBZ) on Malus halliana seedlings under water stress, principal component analysis (PCA) and membership function analysis (MFV) were employed to evaluate the effects of PBZ on gas exchange, fluorescence, and physiological characteristics. M. halliana seedlings, each with approximately ten leaves, were subjected to drought conditions and different concentrations of exogenous PBZ (CK, C0, C1, C2, C3, and C4) were then applied in pot experiments. The results showed that the effects of PBZ were concentration dependent. Compared to the CK treatment, the use of PBZ increased the intercellular CO2 concentration (Ci), nonphotochemical quenching coefficient (NPQ), peroxidase activity (POD), relative electrical conductivity (REC), and proline (Pro) and malondialdehyde (MDA) contents. The POD activity was higher by 124.24, 132.26, 93.75, 77.42, 85.29, and 90.63% in the CK, C0, C1, C2, C3, and C4 groups, respectively, at 15 days than at 0 day. The decrease in the net photo...