EFFECTS OF SALINITY ON GROWTH AND CONCENTRATIONS OF SODIUM, POTASSIUM, AND CALCIUM IN GRAFTED CUCUMBER SEEDLINGS

Cucurbita ficifolia (referred as C/CF) and Cucurbita moschata (referred as C/CM) are usually used as rootstocks for cucumber. Plants were supplied with Hoagland solution before the salt stress started. The seedlings were supplied with the nutrient solution to which either 0 (control) or 200 mM NaCl (salt treatment) was added. Dry weight, leaf area, root activity, the contents of soluble sugar, the contents of K⁺ and Ca²⁺ were higher in grafted seedlings than own-rooted seedlings indicating that grafting did improve the growth and nutritional status of plants. After 200 mM NaCl treatment for 4 and 8 d, the content of free proline was distinctively higher, the Na⁺ content in aerial part and root, MDA content and cell membrane permeability in leaves were dramatically lower in grafted seedlings than own-rooted seedlings. Under the normal conditions, however, there were no significant differences in these indexes mentioned above between grafted and own-rooted seedlings. Compared with salt-treated C/CM, shoot dry weight and the contents of free proline and soluble sugar were higher whereas MDA contents and Na/cations of aerial part were lower in salt-treated C/CM. We therefore propose that higher Na⁺ exclusion capability of roots of grafted seedlings would lead to the low Na⁺ content in the whole plant of grafted seedlings. This might be one of the main reasons why grafted seedlings were more salt-tolerant than own-rooted seedlings. The two rootstock genotypes had little difference on the salt-tolerance of grafted cucumber seedlings; grafted plants were more salt-tolerant than own-rooted plants.