The physiological basis for high fruit yield and susceptibility to calcium deficiency in tomato and cucumber

SummaryThe accumulation and distribution of both dry matter and Ca were studied in tomato and cucumber grown hydroponically. During vegetative growth, total dry-matter accumulation was similar for both crops. However, plant dry-matter increments were higher in cucumber than tomato once fruit began to grow. Increasing salinity over the range 3 to 8 mS cm−1 markedly reduced total dry-matter accumulation and partitioning to the upper shoot in cucumber. In contrast, increasing the salinity up to 15 mS cm−1reduced the plant dry weight of tomato significantly, but still had no effect on partitioning. Ca uptake was twice as high in cucumber as in tomato, resulting in higher Ca concentrations in the dry matter. The rate of root exudation and the amount of Ca in the xylem exudate (shoot removed) was higher in cucumber than in tomato. Ca absorbed by the root alone accounted for half of the observed uptake by the intact plants. High salinity reduced Ca uptake in cucumber more than in tomato. Distribution of Ca to th...