The response of photosynthetic functions of F 1 cutting seedlings from Physocarpus amurensis Maxim × Physocarpus opulifolius “Diabolo” and the parental leaves to saline stress

This paper selected clonal cutting seedlings from the F 1 hybrid varieties of Physocarpus amurensis Maxim (♀) × Physocarpus opulifolius “Diabolo” (♂) as research material to study the response of the photosynthetic gas exchange parameters and chlorophyll fluorescence parameters of Physocarpus amurensis hybrids and their parental leaves to NaCl stress (with concentrations of 0, 50, 100 and 200 mmol·L -1 ). The results showed that under saline stress, the stomatal conductance ( G s ), transpiration rate ( T r ), and net photosynthetic rate ( P n ) of the three kinds of P. amurensis all significantly decreased. When the NaCl concentration was below 100 mmol·L -1 , the intercellular CO 2 concentration ( C i ) of leaves of the three samples declined with the increase of salt concentration; however, when the concentration increased to 200 mmol·L -1 , C i did not decrease significantly, especially when the C i of P. opulifolius “Diabolo” presented a slight increase. This indicated that the decline of photosynthetic carbon assimilation capacity induced by saline stress was the consequence of interaction between stomatal factors and non-stomatal factors, and the non-stomatal factors played an important role when the saline concentration was below 200 mmol·L -1 . Compared with P. amurensis , the photosynthetic gas exchange capability of P. opulifolius “Diabolo” leaves was more sensitive to saline stress, and the limitation of non-stomatal factors was relatively evident, but the photosynthetic capacity of hybrid Physocarpus amurensis Maxim leaves with the desired purple color was improved compared with Physocarpus amurensis . Under saline stress, the PSII activity of the three kinds of P. amurensis leaves declined, the electron transfer was inhibited, and obvious signs of photoinhibition were present. With the increase of saline concentration, the V k of P. amurensis and hybrid P. amurensis leaves presented a decreasing trend, but the V k of P. opulifolius “Diabolo” leaves increased slightly. This suggested that the effects of saline stress on the oxygen-evolving complex (OEC) of the three P. amurensis sample types were relatively limited and only the OEC of P.s opulifolius “Diabolo” leaves were slightly sensitive to saline stress. The V J of all the leaves of the three Physocarpus amurensis types increased under saline stress, and increased significantly when the saline concentration increased to 200 mmol·L -1 , indicating that saline stress obviously impeded the electron transfer chain from Q A to Q B on the PSII receptor side of the leaves. Moreover, high saline concentrations would cause thylakoid membrane dissociation.The salt tolerance of photosynthetic functions of hybrid Physocarpus amurensis (♀) × Physocarpus opulifolius “Diabolo” (♂) leaves was improved compared with that of parental Physocarpus opulifolius “Diabolo,” and the hybrid shows obvious hybrid vigor in the aspect of photosynthesis.