As in True Fruit, Ca Distribution in Strawberry (A False Fruit), is Determined by Progressive Xylem Dysfunction

The physiology of calcium (Ca) in strawberry (Fragaria x ananassa Duch.), a pseudocarp, is likely to be affected by the loss of xylem functionality during development. The objective of this study was to test this hypothesis by quantifying fruit Ca and affecting factors. The Ca content of fruit and calyx increased with time. However, the Ca/dry mass ratio of the fruit decreased, whereas that of the calyx increased. Fruit Ca content and the Ca/dry mass ratio followed a normal distribution. Fruit Ca content decreased from primary to secondary to tertiary fruit, but the Ca/dry mass ratio increased. The fruit Ca content and Ca/dry mass ratio were positively and negatively correlated with fruit mass, respectively. Comparison of unripe and ripe fruits showed that the Ca/dry mass ratio increased only in the calyx, but decreased for the skin, flesh, pith, and achenes. The Ca/dry mass ratios were highest in the proximal (close to calyx) region and decreased toward the distal region. The Ca content and Ca/dry mass ratios were lowest for fruit grown at high RH as compared to ambient or low RH. The physiology of Ca in strawberry is primarily affected by the loss of xylem function during development. Hence, agronomic practices must focus on increasing Ca through foliar applications.