Does calcium determine water uptake under saline conditions in pepper plants, or is it water flux which determines calcium uptake?

Under saline conditions, we investigated the effects of root-zone temperature on pepper plants (Capsicum annumm L.) treated with extra calcium, in order to study the influence of this parameter on water and calcium uptake. The treatments, for plants cultivated hydroponically in a controlled environment chamber, were control, NaCl (50 mM), Ca2+ (10 mM) and Ca2+ (10 mM) + NaCl (50 mM), all at 25 and 35degreesC root temperature. After these treatments, it could be seen that salinity reduced the concentration of calcium in roots and leaves, which were restored when calcium was added to saline-stressed plants. This effect of calcium was increased when plants were grown at 35degreesC root-zone temperature. The effect of both high temperature and extra supply of calcium influenced plant water relations, involving functionality of aquaporins. Therefore, the negative effect of salinity, with respect to tissue calcium concentration and water relations, was mitigated if there was a supply of Ca2+, this effect being greater when the root-zone temperature was increased. (C) 2003 Elsevier Ireland Ltd. All rights reserved.