| With the increasing of salinization, agriculture production is seriously affected. Sugar be et, which is one of major sugar crops, is naturally salt tolerance. Hence, it is worth to studyin g tolerance of sugar beet for agriculture development. In this study, hydroponic culture was e mployed to identify the degree of salt tolerance in 146 sugar beets. Both salt tolerance and sen sitive cultivars were used for further analysis. The difference of photosynthesis, osmoregulati on substance, anti-oxidization system, ionic distribution and nutrient uptake between salt toler ance and sensitive cultivars were determined. Additionally, the effects of Na-K replacement a nd exogenous betaine on the sugar beet seedlings were also studied to understand salt toleranc e mechanism. Those results are significant for salt tolerance breeding and development of sali ne land. The details of the study were showed as follow:1.15 high levels of salt tolerance varieties and 5 low levels of salt tolerance var ieties were screened by the first test. And then 6 high levels of salt tolerance varietie s such as 265 and 3 low levels of salt tolerance varieties such as 210 were validated after the second screening. Meanwhile, the commercial varieties were screened and fo und out 2 high levels of salt tolerance varieties and 2 low levels of salt tolerance var ieties.2.The effect of salt stress on morphogenesis of sugarbeet seedling was obvious.T510 was of evident adaptive on the contour compared with 210; The effects on the plant height, leaf area,dry matter accumulation of the seedlings of the two sugarbeet varieties were enhanced with the increase of salt concentration under salt stress. In addition, T510 had stronger ability in water regulation than 210 under the same salt stress conditions.Chlorophyll content, stomatal conductance, transpiration rate, intercellular CO2 concentration and net photosynthetic rate of the two sugarbeet varieties decreased significantly under salt stress conditions. The photosynthetic parameters and the activity of RuBPcase of T510 was higher than those of 210 under the same salt stress conditions, which showed that the regulation ability of the photosynthetic organs of the salt-tolerance varieties was stronger under salt stress conditions.The content of quaternary ammonium compound, sucrose, soluble protein, free amino acids and organic acid increased obviously under salt stress conditions, but the content of reducing sugar declined; The those content of T510 was higher than 210 in the same treatment type, which showed that T510 had better performance on osmotic adjustment. The content of malic acid and citric acid in T510 was both higher than that in 210, which showed that malic acid and citric acid obviously improved the osmotic adjustment ability of sugarbeet. The content of the other 15 kinds of amino-acid was increasing under salt stress conditions except the Asp and Glu; with the increase of salt concentration, the kinds of amino-acid in T510 were increasing, which were involved in regulation compared with 210.With the increase of salt concentration, the activities of SOD,POD,CAT and APX in antioxidant enzyme system of beet leaf also increased significantly under salt stress conditions; APX activities increased most obviously, followed by SOD and CAT, and POD activity showed a little change. The higher activities of 4 kinds of antioxidant enzymes in T510 than 210 showed that T510 had better antioxidant ability, which could reduce the injury of oxygen anion. The amounts of conductivity and MDA were increasing with the increase of salt concentration. But those of the seedling leaf of T510 increased indistinctively, which showed that the effect of salt injury on leaf cell membrane system of T510 was little compared with 210.The content of ABA in leaf increased obviously under salt stress conditions, and that in the leaf of 210 was higher than T510; the content of IAA and GA3 in leaf declined significantly, and that in 210 were lower than T510. With the increase of salt concentration, the content of N and K in sugarbeet decreased, while the content of P increased; the content of N and K in 210 was lower than that in T510, while the content of P in 210 was higher than that in T510.3. The order about Na+ and Cl- content in beet under salt stress was petiole>leaf>root from high to low; with the increase of salt concentration, the Na+ and Cl- content increased obviously. However, the Na+ content in 210 was higher than that in T510, while the Cl" content had little difference in the two seedlings compared with the Na+.The Na+ and Cl- content in leaf decreased with increasing height of leaf position. The Na+ prior accumulation in the lower leaf protected the upper leaf from salt injury. There was still a high Cl" accumulation in upper leaf. The Na+ and Cl" content in 210 both was higher than that in T510.The ability of Na+ and Cl- accumulation in the lower part in T510 leaf was stronger under the high-concentration salt treatment, which decreased the Na+ and Cl- content in the upper part and reduced the effect of more salt on the plant.The Na+ content in apoplast and protoplasts of beet leaf increased with the increase of salt concentration. Meanwhile, the Na+ content in apoplast was significantly higher than that in protoplasts. The Na+ content in apoplast and protoplasts of beet leaf in 210 was significantly higher than that in T510.4. Compared with CK, after 50% of potassium replaced by sodium, there was also no obvious difference in accumulation of dry material in different parts. The replacement efficient of root and petiole was up to nearly 99%, and the replacement efficient of the whole plant was 95%. With the increase of the proportion of potassium replaced by sodium, the content and accumulation of K+ obviously decreased, and the content and accumulation of Na+ obviously increased in sugar beet. That showed the content of nitrogen in sugar beet roots and leaves had the same co-relationship with Na+ in the environment, and had little influence on the phosphorus content.5. With spraying betaine on salt treatment, the biomass and relative water content of the salt resistant variety ST13092 increased obviously; the endogenous betaine content of two seedlings both increased obviously, and the salt resistant variety ST13092 increased more obviously; the net photosynthetic rate, the transpiration rate, the stomatal conductance, the intercellular CO2 concentrations and the chlorophyll content of the salt resistant variety ST13092 increased significantly by spraying betine under salt stress; but except for the stomatal conductance, the other indexes of the salt sensitive variety 25 had no obvious influence; the activities of SOD,POD,CAT of ST13092 was increased significantly by spraying betine, but the activities of POD was only increased significantly in 25. |
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