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 respirati on (R(R)), photosynthesis (P(N)) and transpiration (T) of three differ ent citrus rootstocks were investigated. 30 mM NaCl or 30 mM KCl respe ctively 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 wer e significantly influenced by salinity. KCl application caused stronge r 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) induce d a significant decrease of R(R). In a short-term experiment R(R) of s alt intolerant 'Troyer' rootstocks decreased after a one hour supply o f 100 MM NaCl. After recovery in salt-free nutrient solution R(R) retu rned to the initial level prior to salt application. In contrast to th at R(R) of the more salt tolerant 'Volckameriana' and 'Rangpoor' roots tocks was not clearly affected by short-term salinisation.