Effects of humidity, Ca and salinity on the accumulation of dry matter and Ca by the leaves and fruit of tomato(Lycopersicon esculentum)

Abstract

Tomato plants were grown at four humidities in factorial combination with two levels each of Ca (150 and 300 mg 1-1) and salinity (5 and 7 mS cm-1) in the nutrient solution applied to the rockwool substrate. The humidity treatments, defined as vapour pressure deficits, were 0.15, 0.25, 0.43 and 0.65 kPa (held constant day and night) in Experiment A, and high (0.21 kPa) or low (0.47-0.55 kPa) humidity during the day in combination with high (0.16 kPa) or low (0.45-0.50 kPa) humidity at night in Experiment B. High humidity reduced the dry weight of the leaves, as did the higher salinity. The Ca content (%) and the total amount of Ca (mg) accumulated by the leaves always decreased at high humidity, this response being greater at night than during the day, and always increased with the higher level of Ca. Accumulation of Ca by the fruit was markedly reduced by low humidity during the day, increased by the higher Ca level, and was decreased by high salinity at the lower Ca level. High humidity during the day appears to promote Ca movement into the young fruit, irrespective of the humidity at night.