Effect of the Shank Length of Pyrus BetulaefoliaRootstock on the Photosynthesis and the Sodium and Chloride Distribution of Japanese Pear Saplings Under Saline Conditions

Abstract

In this study, ‘Kousui’ pear ( Pyrus pyrifoliaNakai) was grafted onto P. betulaefolia(Bunge), a salt-tolerant rootstock for the Japanese pear, using different shank lengths. Following this, the salt tolerance of the plants was compared. Potted one-year-old plants were subjected to 30 mM or 60 mM NaCl solutions for seven weeks. Shoot growth, photosynthesis, and Na and Cl concentrations and distributions were assessed. Plants with longer shanks had a higher photosynthetic rate than those with shorter shanks; however, comparisons of leaf Na and Cl contents showed only slight differences when exposed to the 30 mM NaCl solution. For plants exposed to the 60 mM NaCl solution, those with longer shanks showed lower Na and Cl concentrations in the leaves than plants with shorter shanks. Moreover, those with longer shank lengths maintained structural root growth. Thus, plants with longer shanks restricted the transport of Na and Cl to their leaves by maintaining structural root growth and accumulating Na and Cl in the structural root. Grafting the scion onto a long shank rootstock can improve the salt tolerance of a young pear tree. Consequently, this practice may be useful for Japanese pear cultivation in regions where the plants would otherwise suffer salt stress.