Effects of salt stress on photosynthetic characteristics and antioxidant capacity of cutting seedlings of two grape varieties

【Objective】To study the effect of salt stress on the photosynthetic characteristics and antioxidant capacity of cutting seedlings of two grape varieties,in order to provide theoretical basis for investigating the mechanism of salt resistance of grapes and the improvement and utilization of saline soils.【Method】Set 100 mmol/L NaCl irrigation of Kyoho and Shine Muscat grape pot cuttings as salt stress treatment and water irrigation as control (CK),and investigated the salt damage symptoms of the two varieties of grape plants at 0,7,14,21 and 28 d of stress respectively,calculated salt damage index;and measured the photosynthetic indexes and the activities of peroxidase (POD),superoxide dismutase(SOD),and ascorbic acid catalase (APX),as well as malondialdehyde (MDA),proline (Pro) and soluble protein contents;and the growth and physiological indexes of the two grape varieties under salt stress treatment were analyzed by principal component analysis and affiliation function analysis.【Result】The salt damage symptoms of both Kyoho and Shine Muscat varieties showed that the old leaves first appeared scorched with brown spots at the beginning of the salt stress period,and the leaves of the plants lost their green color and wilted to yellow at the end of the stress period.Shine Muscat showed salt stress symptoms earlier than Kyoho;the plant height,stem diameter and number of leaves of the two grape varieties showed a trend of increasing and then decreasing with the increase in the number of days of salt stress;after 28 d of stress treatment,the salt damage index of Shine Muscat (87.29%) was higher than that of Kyoho (31.67%).The chlorophyll content of the leaves of two grape varieties,the maximum photochemical yield of PSⅡ(F_v/F_m) the actual photochemical efficiency Y(PSⅡ)and the coefficient of photochemical quenching (qP) showed an overall decreasing trend;and the value of the non-photochemical quenching coefficient (NPQ),POD and SOD activities showed an increasing and then decreasing trend,while quantum yield of non-regulated energy dissipationY (NO),APX activity and MDA,Pro and soluble protein contents showed an increasing trend;and the average affiliation function values for Kyoho and Shine Muscat under salt stress were 0.52 and 0.51 respectively,and the salt stress tolerance of Kyoho was slightly higher than that of Shine Muscat.【Conclusion】Under salt stress,the two grape varieties,Kyoho and Shine Muscat,show the same trend of response to salt stress but with differences in the degree of response,and Kyoho is more tolerant to salt than Shine Muscat;the chlorophyll content,F_v/F_m,NPQ,qP,Y(Ⅱ),Y(NO),POD activity and Pro content can be used as evaluation criteria for salt tolerance in grapes.