| Polygonatum odoratum（Mill.）Druce is a Polygonatum perennial herb of the family Liliaceae.It grows in temperate regions of China and Eurasia,originating in southwestern China.More cold-resistant,shade-tolerant,moisture-resistant,suitable for growth in humus-rich loose soil.Polygonatum as a Chinese herbal medicine,the whole plant can be used as medicine,in which extracts of flavonoids can lower blood pressure and blood lipids.Not only that,Yuzhu is still a good garden ornamental plant,its green leaves,its flowers are noble,green shade,green,vibrant,and considerable ecological value.In order to explore its ability to plant and resist stress on saline soil,the leaves of Polygonatum odoratum were used as experimental materials,spermidine（Spd）and NO donor SNP were used as exogenous substances to investigate the effects of different concentrations on salt stress.Effects of chlorophyll,osmotic adjustment substances,and proline metabolism of Polygonatum odoratum have explored the regulatory mechanisms of resistance to abiotic stress of Polygonatum odoratum under salt stress.Get the following conclusions:（1）Under the stress of 150 mmol·L-1NaCl,the degree of succulence of Polygonatum odoratum leaves was significantly reduced,and the degree of succinization increased with the increase of exogenous Spd concentration,and peaked when the concentration of Spd reached1000μmol·L-1,when Spd and NO were co-treated.Under salt stress,the degree of succulence increased first and then decreased.The degree of succulence decreased with Spd concentration>10μmol·L-1.（2）Salt stress promoted the process of membranous peroxidation of eucalyptus leaves,and the MDA content increased significantly.As the concentration of exogenous Spd increased,it first decreased and then rose,but it was always lower than the original injury MDA content,indicating that a certain concentration of Spd(<1000μmol·L-1)can reduce damage to plants by osmotic stress.Plant damage was best achieved with an Spd concentration of 100μmol·L-1.When exogenous Spd and NO were co-treated,the content of malondialdehyde in leaves of Polygonatum odoratum could be reduced when Spd concentration was less than 100μmol·L-1.Above this concentration,it not only did not alleviate,but also inhibited the leaves of Polygonatum odoratum.（3）Under salt stress,the content of organic osmotic regulating substances in the leaves of Polygonatum odoratum increased,and the application of NO donor SNP at a concentration of 100μmol·L-1could promote the accumulation of organic osmoregulation substances.When different concentrations of Spd were applied,the content of osmoregulatory substances increased first and then stabilized,and the high concentration of Spd(Spd>100μmol·L-1)had no significant effect on the osmotic adjustment substances.When Spd and NO are processed together,the additive effect of the two is not obvious.Proline is an important osmotic regulator.Under the stress,the reaction is most obvious and rapid.The proline content of eucalyptus seedlings increases rapidly under salt stress.Proline is one of the key enzymes in the ornithine pathway,arginine synthesis.The activities of Arginase and Ornithine Transferase（OAT）are enhanced;the other pathway,the glutamate pathway,has no significant change in the activity of the key enzymeΔ1-pyrroline-5-carboxylic acid synthase（P5CS）.The rate-limiting enzyme,proline dehydrogenase（ProDH）activity is inhibited.Exogenous Spd and NO treatment increased the content of proline under salt stress,activated the activity of OAT and Arginase,and decreased the activity of ProDH,a degradative pathway-related enzyme.The effect of exogenous Spd and NO treatment was the most obvious at 100μmol·L-1Spd,but the activity of P5CS no effect.The above results indicate that the ornithine-proline synthesis pathway and degradation pathway both contribute to the accumulation of proline during salt stress and the treatment with exogenous Spd and SNP. |
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