Effects of Grafting and Salinity on Agronomic Characteristics and Ion Uptake by Cucumber Plants Grown in a Closed Hydroponic System

Recently grafting is being applied as a means of alleviating the negative effects of high salinity. In the present study we examined the effect of three salinity levels (1.9, 3.5 and 5.5 dS m(-1)) on cucumber plants (Cucumis sativus L. hybrid '722 Virginia RZ.') grafted onto three commercial rootstocks ('Power F-1', 'Leon F-1' and 'Mammoth F-1') and cultivated in recirculating nutrient solution. The results showed a significant effect of high salinity levels on plant growth parameters (shoot length, FM and DM of shoots and leaf area), which was more profound when '722 Virginia' was grafted onto 'Power F-1'. Total fruit weight and fruit number per plant were reduced by high salinity, except for the 'Mammoth' x '722 Virginia RZ.' combination, where no significant effect was observed. The presence of NaCl in the nutrient solution had a significant effect on the concentration of Na+, Cl- and K+ in plant tissues, whereas Ca2+ and Mg2+ were not significantly influenced. Plants grafted onto 'Mammoth' had lower Na+ content in root tissues than Leon and Power rootstocks, whereas Na+ content in the shoots was higher in plants grafted onto 'Mammoth' than in the other rootstock-scion combinations. Similar results were observed also in the case of K+ content in roots, especially at the highest salinity level. The gradual increase of the NaCl concentration in the nutrient solution increased the Cl- concentration in both shoots and roots, whereas the rootstock-scion combination had no significant impact on the tissue Cl- levels. These results indicate that the use of 'Mammoth' as a rootstock may enhance the salt tolerance of grafted cucumber plants but this effect is not due to a restriction in Na+ or Cl- translocation to the photosynthetically active leaves.