Fig. 4

Effect of spraying SL on the activities of key enzymes in the photosynthesis of P. purpureum under drought stress. Effects of SL on NADP-ME (a), PEPC (b), and PPDK (c) activities of P. purpureum. Different lowercase letters at the same time indicate significant differences (P < 0.05). N: normal watering treatment; D: drought stress treatment only; T1, T2, T3, and T4 represent the different treatment concentrations of SL under drought stress (1, 3, 5, and 7 μmol·L^− 1 respectively)