Effects of four types of sodium salt stress on plant growth and photosynthetic apparatus in sorghum leaves

Sorghum variety Longza 17 was used as the experimental organism in a study of the effects of different types of sodium salt (two neutral salts, NaCl and Na2SO4; and two alkaline salts, NaHCO3 and Na2CO3), at an equivalent Na+ concentration (100mmolL(-1)) on leaf growth parameters and PSII and PSI function by using the Fast Chlorophyll Fluorescence Induction Dynamics technique and 820nm light reflectance curves. The results showed that at Na+ concentration of 100mmolL(-1), different types of sodium salt stress significantly inhibited the growth of sorghum plants. Different types of sodium salt stress showed significant inhibition on the activities of PSII and PSI in sorghum leaves, the impact of different types of sodium salt on the activities of PSII and PSI in sorghum leaves was consistent, listed from greatest to least impact as Na2CO3 > NaHCO3 Na2SO4 > NaCl. The effects of alkaline salt stress on the growth and photosynthetic properties of sorghum were greater than those under the neutral salt stress, therefore, in addition to considering the impact of Na+ concentration in the sorghum planting area, emphasis should also be given to the influence of the degree of alkalization, especially the higher alkalinity of Na2CO3.Abbreviations:F-v/F-m: PSII maximum photochemical efficiency; PItotal: the total performance index; PIABS: the photosynthesis indices based on the absorption of light energy; oI/I-o: the initial slope of the curve of 820nm light reflection; RC/CSm: the number of the reactive centers per unit area.