| The Hetao area is the main producing area of high-quality melon in my country.The increasing trend of local soil salinization has become one of the important factors restricting the development of the melon industry.It is of great theoretical and practical significance to carry out research on the salinity and alkali tolerance of melon.In this study,the excellent local variety ’Hetao Honeydew’ melon in the Hetao area and the seedlings of the melon variety ’Yindiwang’ introduced in recent years with excellent performance were used as experimental materials.The three salts(NaCl,Na2SO4,NaHCO3)are mixed according to the substance ratio(1:2:1),and 4 salt-alkali concentration levels are set:T1(50 mmol/L),T2(100 mmol/L),T3(150 mmol/L),T4(200 mmol/L),with clear water as the control(CK),stress For 7 and 14 days of treatment,the growth and development of seedlings of the two melon varieties,the content of osmotic regulators in different organs(leaves,stems,roots),as well as the changes in ion absorption and distribution characteristics,were observed under saline-alkali stress.Salt tolerance physiological characteristics and response mechanism of seedlings,and provide a basis for rational selection and utilization of variety resources in production or establishment of reasonable cultivation management measures in production.The main findings are as follows:(1)The plant height,stem diameter,biomass accumulation,relative water content and other indicators of the two kinds of melon seedlings showed that they were promoted under low-concentration saline-alkali stress and inhibited under high-concentration saline-alkali stress.Among them,the growth of ’Hetao honeydew’ melon was inhibited.It was larger than that of ’Yindiwang’,and it was more obvious in the later stage of stress.At the same time,saline-alkali stress increased the root-shoot ratio of the two kinds of melon seedlings.(2)The contents of H2O2 and MDA in each organ of the two kinds of melon seedlings under the control treatment were lower,and the change range was small;under the T1 treatment,the contents of H2O2 and MDA in each organ increased slightly compared with the control,but remained at a low level;with the increase of the stress concentration The content of H2O2 and MDA in each organ increased significantly with the prolongation of high temperature and treatment time,among which the content of H2O2 and MDA in leaves was significantly higher than that in roots and stems;the changes of the above indicators of different varieties were the same,but ’Hetao honeydew’ melon had higher salt concentration than ’Yindiwang’.The content increased more under alkali stress.(3)Under the control treatment,the osmotic adjustment substances in each organ of the two kinds of melon seedlings maintained a low level;under the saline-alkali stress,the content of the osmotic adjustment substances in the various organs of the melon seedlings increased.There were differences in substance accumulation.Among them,under T1 and T2 treatments,the contents of soluble sugar(SS)and free amino acids(AA)in various organs of ’Hetao honeydew’ melon increased significantly;the contents of proline(Pro),SS and AA in various organs of ’Yindiwang’ increased significantly,and the substance content of each organ of the two kinds of melon seedlings in the later stage of treatment was higher than that in the early stage of treatment.Under the treatments of T3 and T4,the content of osmotic adjustment substances in ’Hetao honeydew’ melon decreased;the content of osmotic adjustment substances in ’Yindiwang’ still showed an increasing trend.The root increase of the two kinds of melon seedlings was significantly higher than that of leaves and stems,showing stronger osmotic regulation ability.At the same time,the changes in the accumulation of osmotic adjustment substances in the two kinds of melon seedlings under different saline-alkali stress were different.The osmotic adjustment substances can still maintain a higher content,showing that its adjustment ability to high-concentration saline-alkali stress is stronger than that of ’Hetao honeydew’ melon.(4)The Na+ content in each organ of the two kinds of melon seedlings under the control treatment was lower;with the increase of the stress concentration and the prolongation of the treatment time,the Na+ content in the roots,stems and leaves of the two kinds of melon seedlings increased gradually.The trend was leaf>stem>root;the increase of Na+ in leaves and stems of ’Hetao honeydew’ melon was higher than that of’Yindiwang’,and the increase of Na+ in roots was lower than that of ’Yindiwang’.The ratio of K+/Na+ in each organ of ’Hetao honeydew’ melon was higher than that of Yindiwang’,and the ratios of Ca2+/Na+ and Mg2+/Na+ in leaves were significantly smaller than those of’Yindiwang’.(5)The correlation analysis between various physiological and biochemical indicators showed that SP,AA accumulated in the leaves of ’Hetao honeydew’ melon,and Pro,SS,AA and MDA accumulated in stems and roots were closely related;AA,GB are closely related to MDA.At the same time,the Na+ content in each organ of the two kinds of melon seedlings was positively correlated with the MDA content.By increasing the content of osmotic regulating substances,melon seedlings can effectively block the transport of Na+to the shoot,there by maintaining the effective water content of the plant,maintaining normal ion balance,and reducing the peroxidative damage of membrane lipids.It is an important physiological response of melon to resist saline-alkali stress.All kinds of melon seedlings have a certain tolerance to saline-alkali stress,and the saline-alkali tolerance of’Yindiwang’ is better than that of ’Hetao honeydew’ melon. |
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