Effect of salt and water stress on fruit quality, physiological responses, macro- and micro-element contents in leaves of Satsuma mandarin trees under greenhouse conditions

Experiments were conducted using Satsuma mandarin trees grown in small containers to investigate the effects of mild salt (5 and 10 mM NaCl in irrigation water) and water stress on growth, photosynthesis, transpiration, fruit quality as well as macro- and micro-element contents in leaves of Silverhill Satsuma mandarin (Citrus unshiu Marc.) grafted on trifoliate orange (Poncirus trifoliata (L) Raf.) rootstocks. Salt and, to a greater extent, water stress treatments resulted in reduced photosynthetic rates, although there were no significant effects on tree growth estimated by recording the increase in stem diameter. Water stress decreased the leaf water potential and increased the stomatal resistance compared to control and salt-stressed trees which showed similar values, while the concentrations of sodium and chloride of the spring-flush leaves were not affected by the salt or water stress treatments. Potassium concentration of these leaves, however, was reduced significantly by 10 mM NaCl and water stress. Fruit maturity was advanced by water stress although the fruit size (diameter) and fresh weight were reduced. Internal fruit quality in terms of Brix:citricalue and Brix:citric acid ratio was improved for the trees irrigated with 10 mM NaCl solutions or subjected to water stress.