Influence On Growth And Physiological Indexs Of Seedling Of Medicago Sativa By Using PGPR

Alfalfa (Medicago sativa) is perennial leguminous herbage. Its nutritional value is high, and the palatability is good. Its output is high and stable. This experiment was carried out under manual contral in the laboratory, which studied the six kinds of plant growth promoting bacteria on alfalfa seedlings'growth. The result showed:(1) The treatment of six kinds of plant growth promoting bacteria all had certain impacts on the germination percentage of alfalfa seeds. Compared with the contrast group (CK), the CS2's germination percentage in the experiment was the highest, which being 1.26 times of CK (p < 0.05). There was no obvious difference between CS4's and CK on germination percentage. The germination gercentage of other groups increased evidently.(2) After being treated by six kinds of plant growth promoting bacteria, all morphological parameters of alfalfa seedlings changed in some extent. All plant growth promoting bacteria could increase the root length, plant height , shoot biomass and underground biomass significantly.(3) All plant growth promoting bacterias could obviously increase the content of chlorophylls in alfalfa seedlings'leaves. After being treated by different bacterias, the content of chlorophyll b was slightly higher than that of the contrast group in alfalfa seedlings. The increment of the content of chlorophyll a was higher than that of chlorophyll b, and the content of chlorophylls in CS6 is the highest (p < 0.05).(4) The influences of different plant growth-promoting bacterias on the content of MDA in alfalfa seedlings were different. The contents of MDA in group CS2, CS4 and CS5 were higher than that of CK ( p > 0.05), while the contents of MDA in CS1,and CS6 were lower than that of CK. The results indicated that CS2, CS4 and CS5 increased the accumulation of MDA, but CS1 and CS6 declined the accumulation of MDA in different extents.(5) The influences of different plant growth-promoting bacterias on the activity of SOD in alfalfa seedlings were different. After being treated by bacterias, the activity of SOD in CS3 increased significantly, then followed by CS1 group (p < 0.05). There was no obvious difference between other groups and CK (p > 0.05).(6) The activities of POD were different under different treatments in alfalfa seedlings. Compared with CK, the activity of POD in CS5 significantly increasesd (p < 0.05), while that in CS6 was lower, and there was no obvious difference in CS2, CS3 and CS4 (p < 0.05), which indicated that CS5 strains played a significant role in promoting the activity of POD in alfalfa seedlings.(7) Different bacterias had different impacts on alfalfa seedlings. Compared with CK, the activities of CAT in alfalfa seedlings treated with plant growth-promoting bacterias were higher. The activities of CAT in CS3, CS4 and CS5 were significantly higher than that in CK, which showed that the three growth-promoting bacterias of CS3, CS4 and CS5 played a promoting role on alfalfa seedlings.