Edelstein, M., Department of Vegetable Crops, Agricultural Research Organization, Newe ya'Ar Research Center, PO Box 1021, Ramat Yishay 300-95, Israel
Plaut, Z., Institute of Soil, Water and Environmental Sciences, ARO, Volcani Center, PO Box. 6, Bet Dagan 50-250, Israel
Ben-Hur, M., Institute of Soil, Water and Environmental Sciences, ARO, Volcani Center, PO Box. 6, Bet Dagan 50-250, Israel

The effects of grafting on Na and Cl- uptake and distribution in plant tissues were quantified in a greenhouse experiment using six combinations of melon (Cucumis melo L. cv. Arava) and pumpkin (Cucurbita maxima Duchesne×Cucurbita moschata Duchesne cv. TZ-148): non-grafted, self-grafted, melons grafted on pumpkins, and pumpkins grafted on melons. Total Na concentration in shoots of plants with pumpkin or melon rootstocks was <60mmol kg-1 and >400mmol kg-1, respectively, regardless of the scion. In contrast, shoot Cl- concentrations were quite similar among the different scion-rootstock combinations. Na concentrations in exudates from cut stems of plants with a pumpkin rootstock were very low (<0.18mM), whereas those in the exudates of plants with melon rootstocks ranged from 4.7mM to 6.2mM, and were quite similar to the Na concentration in the irrigation water. Root Na concentrations averaged 11.7 times those in the shoots of plants with pumpkin rootstocks, while in plants with melon rootstocks, values were similar. Two mechanisms could explain the decrease in shoot Na concentrations in plants with pumpkin rootstocks: (i) Na exclusion by the pumpkin roots; and (ii) Na retention and accumulation within the pumpkin rootstock. Quantitative analysis indicated that the pumpkin roots excluded ∼74% of available Na, while there was nearly no Na exclusion by melon roots. Na retention by the pumpkin rootstocks decreased its amount in the shoot by an average 46.9% compared with uniform Na distribution throughout the plant. In contrast, no retention of Na could be found in plants grafted on melons. © 2010 The Author.