Organic and inorganic solutes accumulation in the leaves and roots of grafted and ungrafted cucumber plants in response to NaCl stress

To determine if salt tolerance of grafted cucumber can be associated with the accumulation of organic solutes and inorganic solutes in the leaves and roots, a salt-sensitive cucumber cultivar Jinchun No. 2 (Cucumis sativus L.) was grafted onto the commercial salt-tolerant bottle gourd cultivar Chaofeng 8848 (Lagenaria siceraria Standl.). Grafted and ungrafted plants were grown in hydroponic systems and exposed to 0 or 100 mM NaCl stress under greenhouse conditions. The effects of NaCl stress on the shoot and root growth, organic solutes (soluble sugar and proline), malondialdehyde (MDA) and inorganic solutes (Na, K and Cl) contents, as well as K/Na ratio in the leaves and roots were determined at 0, 1, 4, 7 and 10 days after salt treatment. The results showed that salt resistance of cucumber plants can be enhanced by grafting, which is reflected in better shoot biomass production. In the roots, the grafted plants had higher accumulation of soluble sugar and proline, almost the same Na and Cl, higher K content and higher K/Na ratio, but lower MDA content in comparison to the ungrafted plants during most of the stress period under salt stress. In the leaves, the grafted plants had higher accumulation of soluble sugar and proline, but lower contents of Na and Cl (especially Na), and higher K content as well as higher K/Na ratio but lower MDA content in comparison to the ungrafted plants under salt stress. Taken together, these results suggested that the improved salt tolerance of grafted cucumber induced by rootstock is related to the re-establishment of homeostasis between organic and inorganic saline solutes in the leaves.