PJB-2017-837
MECHANISMS OF SALINITY TOLERANCE OF CUCUMBER SEEDLINGS GRAFTED ONTO CUCURBITA ROOTSTOCKS
Yan Li
Abstract
Salt stress inhibits plant growth and has caused severe agricultural problems worldwide. Under salt stress, oxidative damage by excessive reactive oxygen species (ROS) leads to plant growth depression and physiological disorders. Grafting is believed to be a promising approach to enhance salt tolerance of cucumber. In this study, we investigated the physiology and molecular responses to 100 mM NaCl in cucumber (Cucumis sativus L. cv. ‘Xintaimici’) seedlings that were grafted onto three rootstock cultivars (‘Shielba’, ‘Tielizhen’ and ‘Figleaf gourd’). The results revealed that seedlings grafted onto ‘Figleaf gourd’ showed the highest proline content as well as enzyme activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) followed by those grafted onto ‘Tielizhen’, ‘Shielba’ and ungrafted ones. Relative expressions of Cu / Zn-SOD, Mn-SOD, CAT and APX genes were positively correlated with their enzyme activities in ‘Figleaf gourd’ and ‘Tielizhen’. Cucumbers grafted onto ‘Figleaf gourd’ have the highest gene expression, which were followed by seedlings grafted onto ‘Tielizhen’ and ‘Shielba’, respectively. Cu / Zn-SOD and CAT expression were also stimulated in grafted cucumbers of ‘Shielba’ at the initial stage of the experiment, while decreased during the remainder period, although the activities of corresponding enzymes were continuously increasing. In conclusion, the results indicated that the alleviation of oxidative damage on rootstock-grafted cucumbers is due to enhancement of the antioxidant defense system, and the tolerance difference of cucumber seedlings grafted onto different rootstocks is reflected on the variation of transcription levels and activities of antioxidant enzymes.
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