Composition of xylem and phloem exudates in relation to the salt-tolerance of domestic and wild tomato species

Plants of Lycopersicon esculentum cv. Volgogradskij (Le) and L. pennellii accession PE-47 (Lp) were cultivated for 22 days under control and saline (100 mmol/L NaCl) conditions. Besides growth parameters and leaf water content, toxic ions (Na+, Cl-), major nutrients (K+, Ca2+, Mg2+ and PO43-) and assimilates (carbohydrates and amino acids) were determined weekly in xylem and phloem exudates. Salinity reduced plant dry weight by 55% and 29% in Le and Lp, respectively while a 46% increase in the root biomass was found in the latter. An earlier and higher Na+ and Cl- accumulation in the xylem and a greater Na+ retranslocation through phloem was found in Lp. The better nutritional status found in the xylem of the salinized plants of the wild species at the end of the salinization period seems also to be linked to phloemxylem retranslocation. Thereafter, a more rapid and higher transport of carbohydrates and amino acids from roots to shoot through xylem was found in Lp than in Le under salinity. The implication of these parameters in the salt-tolerance of tomato has been discussed.