Drought pretreatment increases the salinity resistance of tomato plants

Agricultural productivity is worldwide subjected to increasing salinity problems. Various strategies are applied to overcome the deleterious effects of salinity on plants. This study was conducted in order to determine whether drought pretreatment of seedlings or seed pretreatment with NaCl increases the long-term salinity resistance of tomato (Solanum lycopersicum L.) and whether the adaptive response to salinity is accompanied by physiological changes throughout the plant-growth cycle. When plants were pretreated at the five-leaf growth stage, the plant dry weight was significantly higher in drought-pretreated than in non-pretreated plants after 50 d of salt treatment. The positive effect of drought pretreatment applied at the five-leaf stage was maintained throughout the entire growth cycle, as fruit yield of drought-pretreated plants was 40% higher than that of non-pretreated plants at the end of the harvest period (150 d of 70 mM NaCl treatment). Moreover, the most productive plants maintained lower Na+ and Cl– accumulation in their leaves until the end of the growth cycle, which shows that adaptation is a long-term response during which the plants adjust their physiology to the environmental conditions. Salt resistance was also improved through seed pretreatment with NaCl. In conclusion, drought pretreatment applied at the five-leaf stage or seed pretreatment with NaCl provide an alternative way to enhance salt resistance in tomato, and the increase in yield is associated with physiological changes throughout the plant-growth cycle.