Influence of salinity on phosphorus and potassium uptake of tomato plants grown in hydroponic conditions

Salt stress is considered as one of the major abiotic stress to plant health and soil quality in the Mediterranean region that affects the productivity of most crops. The literature data concerning the P- or K- Salinity interaction showed contradictory results depending upon selected plants and experiment conditions. Therefore, understanding the physiological and biochemical mechanisms occurring in salt-stressed plants is an important way to counter the negative effects of salinity, detect sensitive and tolerant traits and optimize fertilization management in order to improve P and K use efficiency in crop production. In this work, we emphasized the change in chlorophyll a fluorescence, chlorophyll content index, root morphology parameters and phosphorus (P) and potassium (K) uptake. Tomato plants were grown in hydroponic culture with two salt sodium chloride concentrations (S1 = 2.8 dS m-1 and S2 = 4.8 dS m-1). A significant decrease in the chlorophyll content index and shoot and root dry weight were observed. Furthermore, salt treatment induced a significant nutrient imbalance indicated by a decrease in P and K uptake. Under salt treatment, a decrease in J-I-P fluorescence yield was observed and this result indicated an inhibition at PSI acceptor sites. It seems that inhibition of the intersystem electron transport between photosystem II and photosystem I and then in chlorophyll a fluorescence transient under salt stress could be due to an imbalance in nutrient uptake and then an electron transport downregulation. In conclusion, the observed reduction in studied physiological parameters could be due to a negative change in nutrient uptake which creates a disequilibrium in ion homeostasis and then a cascade of changes in physiological and biochemical processes.