Effects of salt-tolerant rootstock grafting on ultrastructure, photosynthetic capacity, and H2O 2-scavenging system in chloroplasts of cucumber seedlings under NaCl stress
2011
Zhen, Ai | Bie, Zhilong | Huang, Yuan | Liu, Zhixiong | Lei, Bo
Plant growth, photosynthetic parameters, chloroplast ultrastructure, and the ascorbate-glutathione cycle system in chloroplasts of self-grafted and rootstock-grafted cucumber leaves were investigated. Grafted plants were grown hydroponically and were exposed to 0, 50, and 100Â mM NaCl concentrations for 10Â days. Under NaCl stress, the hydrogen peroxide (H2O2) content in cucumber chloroplasts increased, the chloroplast ultrastructure was damaged, and the gas stomatal conductance, intercellular CO2 concentration, as well as shoot dry weight, plant height, stem diameter, leaf area, and leaf relative water content were inhibited, whereas these changes were less severe in rootstock-grafted plants. The activities of ascorbate peroxidase (APX; EC 1.11.1.11), glutathione reductase (GR; EC 1.6.4.2), and dehydroascorbate reductase (DHAR EC 1.8.5.1) were higher in the chloroplasts of rootstock-grafted plants compared with those of self-grafted plants under 50 and 100Â mM NaCl. Similar trends were shown in leaf net CO2 assimilation rate and transpiration rate, as well as reduced glutathione content under 100Â mM NaCl. Results suggest that rootstock grafting enhances the H2O2-scavenging capacity of the ascorbate–glutathione cycle in cucumber chloroplasts under NaCl stress, thereby protecting the chloroplast structure and improving the photosynthetic performance of cucumber leaves. As a result, cucumber growth is promoted.
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