Influence of water salinity on growth and water relations of loquat plants grafted on two rootstocks

Abstract

The experiment was performed on two-year-old loquat “Algerie” trees (Eriobotrya japonica Lindl.) grafted on Franco and Anger rootstocks, growing in a glasshouse under partially controlled conditions. Trees were submitted to five saline treatments for 5 months: 5 (control), 25, 35, 50 and 70 mM NaCl in nutrient solutions. At the end of the experiment, plant biomass, leaf Na and Cl concentrations, photosynthesis rate and various water relations parameters from both scion-rootstock combinations were measured and evaluated. The total dry weight of loquat plants on Anger rootstock was unaffected by salinity, whereas those grafted on Franco, a significant reduction in total dry weight was noted. Loquat trees grafted onto Franco treated with 50mM and 70mM NaCl caused a substantial degree of defoliation and foliar necrosis. Plants grafted onto Anger showed lower Na+ concentrations in leaves than those grafted onto Franco, demonstrating that it is an efficient Na+ excluder. Under low salinity levels the accumulation of Cl- in both rootstock-scion combinations was similar. Sodium had a more adverse effect than chloride on the dry weight. The reduction in photosynthesis level was more marked on plants grafted on Franco. Lower leaf water potential values were observed in plants grafted on Franco than those grafted on Anger at moderate salinity levels. Osmotic adjustment permitted the maintenance of leaf turgor in treated plants grafted on Anger, but did not prevent a decrease in leaf turgor in Franco.