Response of tomato plants to a step-change in root zone salinity, under two different transpiration regimes

The response of a tomato crop to a step-change in salinity was investigated under different potential transpiration conditions. A crop growing for 5 months under saline irrigation water (EC 9 dS m−1) was given thereafter a standard nutrient solution with an EC of 2 dS m−1. The previous effects of salinity were largely reversed, especially for fruits and leaves that had not yet reached the rapid growth phase. After a period of 8 weeks, the final weight of fruits reached that of “normal” (EC 2 dS m−1) fruits. There was a high incidence of fruit cracking, even greater in the low transpiration treatment than the high one. The peak incidence of cracking was in fruits that were harvested some 25 days after lowering the EC. The chance of cracking was positively affected by the increase in skin expansion rate due to a change in EC and further enhanced by reduced potential transpiration (high ambient humidity). New leaves formed after the EC was lowered were comparable with those grown in low EC, but leaves that were fully expanded at that moment did not respond to the change in EC