Study On The Effects Of NaCl And Seawater On Physiological And Biochemical Indexes And Quality Characteristics Of Vegetable Crops Of Brassica Rapa

Three vegetable crops of Brassica rapa, Chinese cabbage (cv.‘Zaoshu No.5’), pakchoi(‘Suzhouqing’ and ‘Guilin’) were used to study the effects of different salt treatments on theirphysiological, biochemical and quality characteristics. The treatments were set as differentconcentrations of NaCl (12.5mmol L-1、25mmol L-1、50mmol L-1and100mmol L-1) and differentdiluted seawater (32,16,8and4times dilution). By studying the effects of different salt treatments onthe contents of MDA, proline, organic acid, soluble sugar, soluble protein, ion, glucosinolates andactivity of antioxidant enzymes, we may establish a basic system of improving the quality of leafyvegetables or selection of salt tolerant cultivars. The results were as follows:1. NaCl and seawater treatments reduced the fructose, glucose and sucrose content of‘Suzhouqing’ leaves, and the effect of NaCl is stronger than that of seawater. NaCl treatment reducedthe fructose and glucose content of ‘Guilin’ leaves, but increased its sucrose content. Seawatertreatment increased these three kinds of soluble sugar contents of ‘Guilin’ leaves, and the increasedrate on sucrose is higher than that of NaCl treatment. Seawater treatment significantly increased thecontents of fructose and glucose in ‘Guilin’ flower stalk, but reduced the contents of fructose, glucoseand sucrose in leaves of Chinese cabbage ‘Zaoshu No.5’.2. The soluble protein content was increased in ‘Suzhouqing’, and decreased in ‘Zaoshu No.5’with seawater treatment. The soluble protein content of ‘Guilin’ leaves was significantly increasedwith12.5mmol L-1NaCl treatment.3. NaCl treatment significantly reduced the shoot fresh weight and dry matter proportion of‘Suzhouqing’. NaCl and seawater treatments increased the above-ground and underground freshweight of ‘Guilin’, reduced the proportion of dry matter, and the effect of seawater was higher thanthat of NaCl treatment. Seawater treatments reduced the aboveground and underground fresh weightof ‘Zaoshu No.5’. Low concentrations of seawater (diluted16times) increased the proportion of drymatter, but high concentrations of seawater (diluted8or4times) reduced it. NaCl treatmentsignificantly reduced the fresh weight of ‘Suzhouqing’ whole plant, increased that of ‘Guilin’.Seawater treatment reduced the fresh weight of ‘Zaoshu No.5’ whole plant, increased that of ‘Guilin’.4. NaCl treatment reduced the shoot aliphatic glucosinolate content of ‘Suzhouqing’, increasedthe indole glucosinolate content. Seawater treatment reduced the aliphatic glucosinolate, indole glucosinolate and aromatic glucosinolate contents of ‘Suzhouqing’ shoot after an initial increase. Thealiphatic and aromatic glucosinolate contents of underground parts decreased after an initial increase,but indole glucosinolate content decreased gradually.NaCl treatment significantly increased the glucosinolate content of ‘Guilin’ flower stalk. Withthe increase of NaCl concentration, aliphatic glucosinolate content of ‘Guilin’ underground partdecreased gradually. Aromatic glucosinolate content was significantly increased only under the100mmol L-1NaCl treatment. Seawater treatment significantly increased the content of aliphaticglucosinolates in ‘Guilin’ flower stalk, the indole and aromatic glucosinolate content of its flowerstalk and underground parts.After seawater treatment, aliphatic glucosinolate content of ‘Zaoshu No.5’ leaves weresignificantly reduced, but indole and aromatic glucosinolate contents were significantly increased.With the increase of seawater concentrations, indole and aromatic glucosinolate contents ofunderground parts decreased gradually, while the aliphatic glucosinolate content was reduced at firstand then increased.5. NaCl and seawater treatments increased MDA content of ‘Suzhouqing’ leaves, which washigher under NaCl treatment than that of seawater treatment when NaCl concentration was less than100mmol L-1. With the increased concentrations of NaCl and seawater, MDA content of ‘Guilin’leaves increased gradually.12.5mmol L-1NaCl treatment significantly increased MDA content of‘Guilin’ flower stalk. Seawater treatment slightly decreased MDA content of ‘Zaoshu Wu’ leaves.High concentrations of NaCl (50mmol L-1and100mmol L-1) significantly increased the prolinecontent of ‘Suzhouqing’ leaves and ‘Guilin’ flower stalk, but reduced that of ‘Guilin’ leaves. Seawatertreatments have no effect on proline content of ‘Suzhouqing’ and ‘Zaoshu No.5’ leaves.6. NaCl treatment increased the activity of CAT, POD in ‘Suzhouqing’ leaves and its effect washigher than that of seawater treatments. Seawater treatment increased the CAT, POD activities of‘Guilin’ leaves and the effect was higher than that of NaCl treatment.16times dilution of seawatertreatment significantly increased CAT activity of ‘Guilin’ flower stalk.25mmol L-1NaCl treatmentsignificantly increased POD and APX activities of ‘Guilin’ flower stalk. Diluted32times of seawatertreatment significantly increased POD and SOD activities of ‘Zaoshu No.5’.7. NaCl and seawater treatments significantly increased the contents of oxalic acid, malic acid, lactic acid and fumaric acid of ‘Suzhouqing’ leaves. The effect of NaCl was stronger than that ofseawater treatments.8. NaCl and seawater treatments had little effect on Na+content of ‘Suzhouqing’ shoot,‘Guilin’underground part, aboveground and underground parts of ‘Zaoshu No.5’. Seawater treatment couldincrease the Na+content of the ‘Suzhouqing’ underground part. Na+content of ‘Guilin’ shootdecreased gradually under NaCl treatment, and was maintained the same level under seawatertreatment. NaCl treatment significantly increased K+content of ‘Guilin’ shoot, not the undergroundpart. With the increased seawater concentration, K+content of ‘Guilin’and ‘Zaoshu No.5’ shootincreased gradually, while the underground portion is essentially the same. NaCl and seawatertreatments significantly increased the content of Ca2+in shoot and underground portion of ‘Guilin’.Seawater treatment slightly reduced the content of Ca2+in aboveground and underground parts of‘Zaoshu No.5’. Phosphorus content was not affected by all salt treatments. NaCl and seawatertreatments did not affect the content of sodium, potassium, calcium and phosphorus in the soil.