LONG-TERM AND SHORT-TERM EFFECTS OF SALINITY ON ROOT RESPIRATION, PHOTOSYNTHESIS AND TRANSPIRATION OF CITRUS ROOTSTOCKS

Long-term and short-term effects of salt application on root respiration (R(R)), photosynthesis (P(N)) and transpiration (T) of three different citrus rootstocks were investigated. 30 mM NaCl or 30 mM KCl respectively were added to a standard nutrient solution for a period of six weeks (long-term experiment A). P(N) and T of salt-treated plants were significantly influenced by salinity. KCl application caused stronger effects than NaCl. The diurnal variation of RR as found for control plants was suppressed by the salt treatment. Application of high NaCl concentrations (50, 75 and 100 mM NaCl, long-term experiment B) induced a significant decrease of R(R). In a short-term experiment R(R) of salt intolerant 'Troyer' rootstocks decreased after a one hour supply of 100 MM NaCl. After recovery in salt-free nutrient solution R(R) returned to the initial level prior to salt application. In contrast to that R(R) of the more salt tolerant 'Volckameriana' and 'Rangpoor' rootstocks was not clearly affected by short-term salinisation.