Demarcating specific ion (NaC1, Cl-, Na+) and osmotic effects in the response of two citrus rootstocks to salinity

The present work differentiates the effects of NaCl, Cl-, Na+ and concentrated macronutrients on two citrus species, sour orange (Citrus aurantium L) and Macrophylla (Citrus macrophylla Wester), Plants were grown in a base nutrient solution (0.07 MPa osmotic pressure) for 4 months before applying the treatments that consisted of isotonic solutions of 0.23 MPa osmotic pressure of Na+ (40 mM, without Cl-), Cl- (40 mM, without Na+1), NaCl (40 mM) and 3.5 times the concentration of macronutrients of the base solution. Plants were grown in the different treatment for 2 months before being examined for symptoms of toxicity. The two genotypes showed major differences in the extent of C1- and Na+ accumulation in leaves and in their ability to maintain the internal concentrations of essential nutrients in response to the different ionic compositions of the medium. Differences in mineral nutrient accumulation were observed among treatments in both rootstocks. It was concluded that growth response to the different treatments was primarily affected by an osmotic effect, although in Macrophylla, the ionic effects also seem to be present. (C) 1999 Elsevier Science B.V. All rights reserved.