Impact of Salinity Stress on Photochemical Efficiency of Photosystem II, Chlorophyll Content and Nutrient Elements of Nitere Bush (Nitraria schoberi L.) Plants

Abstract

Salinity is one of major stresses which can severely limit plant production, especially in the arid and semi-arid regions. The present study was carried out to evaluate the impact of salinity stress on some physio-biochemical parameters in nitre bush plants (Nitraria schoberi). Thus, an experiment was carried out under natural conditions and salinity stress was induced by a combination of different salts (NaCl, MgCl2 and CaCl2) at four levels. The salinity treatments were: Control (Ctrl), Low Salinity (LS), Medium Salinity (MS) and High Salinity (HS) of the combined salts. In this study, photosynthetic apparatus of N. schoberi was damaged to a certain extent as it has been observed from leaf chlorophyll fluorescence parameters (Chl. FPs) such as minimal fluorescence (F0), maximal fluorescence (Fm) and maximal photochemical efficiency (Fv / Fm). A significant alteration in chlorophyll content of leaf was not noticed with the increased soil salt content up MS and thereafter, it significantly declined at HS. The reduced level of total chlorophyll content under salt stress conditions can be attributed to chloroplastid membrane deterioration leading to lesser accumulation of chlorophyll. The amount of inorganic ions in nitre bush plant leaves altered with an increase in salinity stress. The concentration of Na+ and Cl- steadily increased and on the contrary, the concentrations of K+, Ca2+ and Mg+ showed significant decreases only at HS. This phenomenon is explainable by the inhibition of K+ uptake by high Na+ levels because these cations are transported by the same proteins. In our experiments, we did not observe significant differences between control plants and those grown in presence of 300 mMol salt kg-1 dry soil (DS). Thus, nitre bush is considered to be a salt tolerant species.