Recovery of Different CitrusRootstock Seedlings Previously Irrigated with Saline Waters

Abstract

Potted plants of three citrus rootstocks, sour orange ( Citrus aurantium(L.)), Cleopatra mandarin ( Citrus reshmHort. ex Tan.) and Citrus macrophylla( Citrus macrophyllaWester) were irrigated with 5 (control), 25 and 50 mM of NaCl during a salinization period. Plants were then irrigated with fresh water (5 mM NaCl) during a desalinization period, and the levels of Cl ^-, Na ⁺and K ⁺were determined in leaves and roots. Rootstocks differences were evident at moderate and high levels of exogenous NaCl. Cleopatra mandarin seemed to be the most effective at excluding Cl ^-. During the desalinization period, Cleopatra mandarin irrigated at moderate salinity levels quickly recovered its foliar Cl ^-concentration, whereas sour orange and C. macrophyllaneeded two and three months, respectively; even after this time, C. macrophylladid not achieve the Cl ^-concentrations of the control plants. After three months of desalinization, Cl ^-levels in Cleopatra mandarin plants recovered but not Na ⁺concentrations, whereas in sour orange basal Na ⁺levels were quickly reached but not Cl ^-. In the case of C. macrophylla,Na ⁺and Cl ^-concentrations remained high even after three months of desalinization. Root Cl ^-values increased in saline conditions in sour orange and C. macrophyllaand during the desalinization period the Cl ^-concentration of sour orange reached those of the control roots. Root Na ⁺concentration increased with salinity in all rootstocks and after desalinization all roots had similar Na ⁺concentrations to control plants. The highest saline treatment reduced the dry weight of sour orange plants whereas plant dry weight in Cleopatra mandarin and C. macrophyllawas not altered. The higher salt tolerance of Cleopatra mandarin with salinity could be related to its lower leaf Na ⁺and Cl ^-levels compared with the other rootstocks.