Effect Of Salt On Growth, Photosynthesis, Cationic Distribution And Transportation In Seedling Stage Of Melilotoides Ruthenica And Medicago Sativa

The pot experiment was conducted to determine the effects of the different NaCl concentration (0,50,100,150,200,250,300 mmol·L-1) on growth, photosynthesis, cationic distribution and transportation in different organs in seedling stage of melilotodes ruthenica and Medicago sativa concentration. The main research results are as follows:1. Plant height, leaf area, stem diameter of Melilotodes ruthenica and Medicago sativa decreased with increased NaCl concentration, but root/shoot was increased with increased NaCl concentration at the same stress time. On 14th day,21st day and 28th day after stress, plant height of Melilotodes ruthenica under 150～300 mmol·L-1 was significantly lower than that of CK (p<0.05). On 14th day,21st day and 28th day after stress, leaf area, stem diameter of Melilotodes ruthenica under 300 mmol·L-1 was significantly lower than that of CK (p<0.05), and root/shoot was significantly higher than that of CK and other treatments (p<0.05). On 14th day and 21st day after stress, plant height of Medicago sativa under 250～300 mmol·L-1 was significantly lower than CK (p<0.05), on 7th,14th,21st,28th days after stress stem diameter of Medicago sativa under 300 mmol·L-1 was significantly lower than that of CK (p<0.05). On 21st day and 28th day after stress, root/shoot of Medicago sativa under 50～300 mmol·L-1 was significantly higher than that of CK (p<0.05). The dry weight of root of Medicago sativa increased with increased NaCl concentration, but Melilotodes ruthenica decreased at the same stress time. On 7th,14th,21st,28th, days after stress, the dry weight of root of Melilotodes ruthenica under 300 mmol·L-1 was significantly lower than that of CK (p<0.05). But, on 21st day and 28th day after stress, the dry weight of root of Medicago sativa under 50～300 mmol·L-1 was significantly higher than that of CK(p<0.05). The dry weight of stem and leaves of Melilotodes ruthenica and Medicago sativa decreased with increased NaCl concentration. On 7th,14th,21st,28th days after stress, the dry weight of stem of Melilotodes ruthenica and Medicago sativa under 300 mmol·L-1 was significantly lower than that of CK(p<0.05), the dry weight of leaves of Melilotodes ruthenica and Medicago sativa under 250～300 mmol·L-1 was significantly lower than that of CK(p<0.05). Each part of Melilotoides ruthenica and Medicago sativa has different sensitivity to salt stress.2. Leaf relative water content, the relative conductivity, contents of malondialdehyde, SOD activities, POD activites, CAT activities of Melilotodes ruthenica and Medicago sativa varied along with different salt concentration and stress time. On 14th day after NaCl stress (250～300 mmol·L-1),21st day after NaCl stress (200～300 mmol·L-1) and 28th day after NaCl stress (150～300 mmol·L-1), the leaf relative water contents of Melilotodes ruthenica were significantly lower than CK and other treatments (p<0.05).On 14th day after stress, malondialdehyde content under 200～300 mmol·L-1 was significantly lower than CK (p<0.05). On 21st and 28th day after stress, malondialdehyde content under 100～300 mmol·L-1 was significantly lower than CK (p<0.05). On 14th day after stress, SOD activities under 150～300 mmol·L-1 was significantly higher than CK. On 21st day and 28th day after stress, SOD activities under 300 mmol·L-1 was significantly higher than CK (p<0.05). On 7th after stress, CAT activities under 300 mmol·L-1 was significantly higher than CK. But, on 21st day after NaCl stress (300 mmol·L-1) and 28th day after NaCl stress (200～300 mmol·L-1), the CAT activities was significantly lower than CK(p<0.05). On 14th day,21st day and 28th day after stress, leaf relative water content of Medicago sativa under 200～300 mmol·L-1 was significantly lower than CK (p<0,05).14th and 21st days after NaCl stress (150～300 mmol·L-1) and 28th day after NaCl stress (50～300 mmol·L-1), the contents of malondialdehyde was significantly higher than CK(p<0.05). On 14th and 28th day after stress, POD activities under 50～300 mmol·L-1 were significantly higher than CK (p<0.05). On 21st and 28th after stress, the CAT activities decreased with increased NaCl concentration. With increased NaCl concentration and stress time, the critical concentration of NaCl that restrained Melilotoides ruthenica and Medicago sativa seedlings’ growing was decreased.3. Different stress time and stress concentration, the change rulers of Photosynthetic parameter of three observation periods are not same. On 14th day after stress, along with increased salt concentration, Pn, Tr, Gs and Ci of Melilotodes ruthenica increased at first and then decresed with increased NaCl concentration. Pn, Tr, Gs under 50～100 mmol·L-1 was significantly higher than CK, while Pn, Tr under 300 mmol·L-1 lower than CK and other treatments (p<0.05). And along with increased salt concentration, Pn, Tr and Gs of Medicago sativa increased at first and then decresed. Under 200～300 mmol·L-1, Pn was significantly lower than CK(p<0.05). Under 150 mmol·L-1, Gs was significantly higher than CK, while under 300 mmol·L-1 lower than CK (p<0.05). With increased NaCl concentration, Ci was significantly lower than CK(p<0.05) at the same stress time. On 28th day after stress, Pn, Tr, Gs and Ci was decreased with increased salt concentration. On 14th and 28th, Ls, WUE of Melilotodes ruthenica and Medicago sativa was increased with incresed NaCl concentration. The change rulers of Ls of Medicago sativa were same with Melilotodes ruthenica, while the WUE is not same.4. Soluble protein content, soluble sugar content decreased with increased NaCl concentration at the same stress time. But proline content was increased with increased NaCl concentration at the same stress time. On 7th day and 14th day after stress, soluble protein content under 300 mmol·L-1 was significantly lower than CK (p<0.05). On 7th day,14th day and 21st day after stress, soluble sugar content under 50～100 mmol·L-1 was higher than CK, while on 28th day after stress, soluble sugar content under 250～300 mmol·L-1 was significantly lower than CK (p<0.05). On 7th day after NaCl stress (150～300 mmol·L-1),14th day after NaCl stress (200～300 mmol·L-1) and 21st day after NaCl stress (250～300 mmol·L-1), the proline contents were significantly higher than CK and other treatments (p<0.05). Soluble protein content of Medicago sativa increased at first and then decresed, soluble sugar content decreased and proline content was increased with increased NaCl concentration. On 7th day and 28th day after stress, Soluble protein content under 50～100 mmol·L-1 was higher than CK (p<0.05). On 7th days after NaCl stress (150～300 mmol·L-1),21st day after NaCl stress (200～300 mmol·L-1) and 28th day after NaCl stress (300 mmol·L-1), the proline contents were significantly higher than CK (p<0.05). Three kinds of osmosis adjustment matters have different adjust ways and with increased NaCl concentration and stress time, the damages of seedlings were increased.5. The change rulers of K+ content in roots, stems, leaves of Melilotoides ruthenica and Medicago sativa seedlings are not same at the same stress time. K+ content in roots of Melilotoides ruthenica and Medicago sativa decreased, while in stems, leaves of Melilotoides ruthenica and Medicago sativa are not same with the increased NaCl concentration. K+ content in stems of Melilotoides ruthenica increased at early stage and decreased at later stage, while Medicago sativa decresed in four observation periods. On 7th and 14th day after NaCl stress (150 mmol·L-1),21st day after NaCl stress (50～300 mmol·L-1) and 28th day after NaCl stress (200～300 mmol·L-1), the K+ contents in roots of Melilotoides ruthenica were significantly lower than CK (p<0.05); On 7th day,14th day,21st and 28th day after stress, K+ content in roots of Medicago sativa under 150～300 mmol·L-1 was lower than CK (p<0.05). K+ content in leaves of Melilotoides ruthenica was higher than Medicago sativa. The Na+ content in roots, stems, leaves of Melilotoides ruthenica and Medicago sativa seedlings increased with the increased NaCl concentration, while increased extents are not same at the same stress time. The Na+ content in roots, stems, leaves of Melilotoides ruthenica under 100～300 mmol·L-1 was higer than CK (p<0.05) in four observation periods. The Na+ content in roots, leaves of Medicago sativa under 100～300 mmol·L-1 was higer than CK (p<0.05) in four observation periods, while the change of Na+ content in stem is different with increased stress time. On 7th day after NaCl stress (200～300 mmol·L-1),14th day and 21st day after NaCl stress (150～300 mmol·L-1) and 28th day after NaCl stress (100～300 mmol·L-1), the Na+ contents in stem of Medicago sativa were significantly higer than CK (p<0.05). So, the Na+ in roots of Medicago sativa was transport to steam with increased stress time.