The Response of Photosynthetic Functions of F Cutting Seedlings From Maxim (♀) × "Diabolo" (♂) and the Parental Seedlings to Salt Stress.

This paper selected clonal cutting seedlings from the F hybrid varieties of Maxim (♀) × "Diabolo" (♂) as research material to study the response of the photosynthetic gas exchange parameters and chlorophyll fluorescence parameters of hybrids and their parental leaves to NaCl stress (with concentrations of 0, 50, 100, and 200 mmol⋅L). The results showed that under salt stress, the stomatal conductance (), transpiration rate (), and net photosynthetic rate () of the three kinds of all significantly decreased. When the NaCl concentration was below 100 mmol⋅L, the intercellular CO concentration () of leaves of the three samples declined with the increase of salt concentration; however, when the concentration increased to 200 mmol⋅L, did not decrease significantly, especially when the of "Diabolo" presented a slight increase. This indicated that the decline of photosynthetic carbon assimilation capacity induced by salt stress was the consequence of interaction between stomatal factors and non-stomatal factors, and the stomatal factors played an important role when the salt concentration was below 200 mmol⋅L. Compared with , the photosynthetic gas exchange capability of "Diabolo" leaves was more sensitive to salt stress, and the limitation of non-stomatal factors was relatively evident. However, the photosynthetic capacity of hybrid leaves with the desired purple color was improved compared with . Under salt stress, the PSII activity of the three kinds of leaves declined, the electron transfer was inhibited, and obvious signs of photoinhibition were present. The PSII activity of "Diabolo" leaves was more sensitive to salt stress than that in . Under salt stress, the NPQ of "Diabolo" leaves decreased greatly, while under high salt concentrations the degree of photoinhibition in and hybrid were reduced due to a relatively high NPQ. With the increase of salt concentration, the of and hybrid leaves presented a decreasing trend. However, the of "Diabolo" leaves increased slightly. This suggested that the effects of salt stress on the oxygen-evolving complex (OEC) of the three sample types were relatively limited and only the OEC of "Diabolo" leaves were slightly sensitive to salt stress. The of all leaves from the three types increased under salt stress, and the increased significantly when the salt concentration increased to 200 mmol⋅L, indicating that salt stress obviously impeded the electron transfer chain from to on the PSII receptor side. Moreover, high salt concentrations caused thylakoid membrane dissociation. The electron transfer and degree of damage to the thylakoid membrane of "Diabolo" leaves were obviously higher than that of . However, the electron transfer capacity on the PSII receptor side as well as the degree of damage of the thylakoid membrane of hybrid leaves was obviously lower than those of "Diabolo." The salt tolerance of photosynthetic functions of hybrid (♀) × "Diabolo" (♂) leaves was improved compared with that of parental "Diabolo," and the hybrid shows obvious hybrid vigor for photosynthesis.