Uptake and distribution of chloride, sodium and potassium ions in salt-treated citrus plants

Abstract

Seedlings of a range of citrus rootstocks were grown under glasshouse conditions and supplied with dilute nutrient solution containing either 0 or 50 mM NaCl. The partitioning of accumulated chloride and sodium into and within the major organs was compared between plants of Rangpur lime (Citrus reticulata var. austera hybrid?), Trifoliata (Poncirus trifoliata) and sweet orange (C. sinensis). Rootstocks differed in their leaf and stem chloride and sodium concentrations, but there was little or no difference between the rootstocks in root chloride and sodium concentrations. The lowest leaf chloride and sodium concentrations were found in the top region of shoots of all rootstocks. The different patterns of accumulation of chloride and sodium found in the three rootstocks were consistent with the existence of apparently separate mechanisms which operate to limit the transport of these two ions from the roots into the young leaves of citrus plants. The chloride excluding ability of 10 rootstocks and two hybrids was also compared and assessed in relation to rootstock vigour. Sampling from the middle leaves on salt-treated plants enabled a distinction to be made between rootstocks in their chloride accumulation properties. Cleopatra mandarin (C. reticulata), Rangpur lime, Macrophylla (C. macrophylla) and Appleby smooth Seville (C. paradisi x C. sinensis) accumulated significantly less chloride than did Trifoliata and rough lemon (C. jambhiri). Differences in chloride accumulation properties between rootstocks were unrelated to rootstock vigour.