Abstract
Soil salinity is a major constraint to the cultivation of horticultural crops. In the present study, potted trees of the pear variety Abbé Fetel, either with their own roots or grafted on different rootstocks, received irrigation water at two levels of salinity to: (i) evaluate the effect of the rootstock genotype on the vegetative growth; (ii) assess their differential ability to take up and partition sodium (Na+) and chloride (Cl−); (iii) verify the effect of salinity on the uptake of major cations (potassium, calcium and magnesium). Irrigation water at 5.0 dS m−1 only slightly reduced vegetative growth regardless the genotype used as rootstock, suggesting a relative degree tolerance of pear (Pyrus communis) to soil salinity, at least in the short term. Quince (Cydonia oblonga) and pear rootstock genotypes had a contrasting effect on the uptake of chloride and sodium and differed regarding their ability to exclude these ions from the foliage. Quinces significantly increased their uptake of sodium and chloride when irrigated with saline water, while pear roots adopted an ion exclusion strategy to avoid accumulation of Na+ and Cl−. Trees grafted on quinces accumulated a significant amount of Cl− in the leaves, but were able to store most absorbed Na+ in their roots, a mechanism that prevented xylem loading and transport to the leaves. No effect of salinity on the uptake of potassium (K+), calcium (Ca2+) and magnesium (Mg2+) was recorded; however, leaf potassium concentration was markedly lower when roots belonged to quince than to pear. The ability of pear genotypes to take up K+ occurred in control trees and was unaffected by saline treatment and might be related to the strategy adopted by pears to exclude Na+ due to a high selectivity K+/Na+.