Impact of grafting and rootstock genotype on cation uptake by cucumber (Cucumis sativus L.) exposed to Cd or Ni stress

Abstract

Previous research has indicated that grafting fruit vegetables onto some rootstocks may restrict heavy metal uptake while improving the uptake of some nutrients. In the present study, the ability of four commercial C. maxima×C. moschata rootstocks to restrict Cd and Ni uptake and enhance nutrient uptake by cucumber (Cucumis sativus L. cv. ‘Creta’) under Cd or Ni stress was tested. In an experiment conducted at the Agricultural University of Athens from 04/11/2009 to 06/06/2009, non-grafted and grafted cucumber plants were exposed to excessively high external Cd and Ni concentrations (10 and 50μmolL−1, respectively). The rootstocks used for grafting were ‘Creta’ (self-grafting treatment), ‘Power’, ‘TZ-148’, ‘Ferro’, and ‘Strong Tosa’. Of the tested rootstocks, ‘Power’ could efficiently restrict the Cd levels in all of the tested plant parts by 12–50% in comparison with all other grafting treatments. The levels of Ni in old leaves and fruit were significantly reduced in all grafted plants including the self-grafted ones by 22–32%, in comparison with non-grafted plants, with the exception of ‘Power’ in fruit. With respect to the root, the plants grafted onto‘TZ-148’, ‘Ferro’, and ‘Strong Tosa’ exhibited significantly lower Ni levels than both self-grafted and non-grafted ‘Creta’ plants, as well as plants grafted onto ‘Power’. Grafting onto the tested rootstocks did not improve nutrient uptake by cucumber, with the exception of ‘Power’ which enhanced the levels of K, Zn, and Mn in fruit, but this difference disappeared under Cd stress. Cadmium had little effect on Ca, Mg and K uptake by cucumber. Nickel enhanced Mg levels in stem, old leaves and fruit, Ca in fruit, and K in root and young leaves, while reducing the levels of Ca in stem and old leaves, and K in fruit. Both Cd and Ni imposed a deposition of Fe and Cu to the roots while restricting the Fe and Cu translocation to the aerial plant parts. The levels of Mn were reduced by both Cd and Ni in some plant parts, while those of Zn were reduced only by Ni stress in stem, fruit and young leaves. In conclusion, Cd and nutrient uptake by grafted cucumber depends on the rootstock genotype, while Ni uptake and translocation to different plant tissues depends on both, root genotype and grafting incision. Furthermore, Cd affects mainly the uptake of micronutrient cations by cucumber, while Ni results in a redistribution of all nutrient cations between some plant parts.