| Alfalfa(Medicago sativa)is a High quality of perennial legume forage,has a good fame of "king of the pasturage",also paly a role in water and soil conservation,therefore,alfalfa is widely grown in our country.Alfalfa can not grow well in in southern China where extensive soils are acid in general,due to low pH induced cytotoxicity aluminum restricting the growth of plants.Normal growth of alfalfa plants,not only requies a lot of elements,such as nitrogen,phosphorus,sulfur,et al,also need boron,manganese,zinc,molybdenum and other micronutrients,if only rely on soil privides is not enough,but also need outside input.In order to clarity the mechanism of acid-aluminum tolerance,learn effects serveral nutrients under acid-aluninum stress on seed germination and seeding growth of alfalfa.In this paper,‘Golden empress' alfalfa were treated with acid(pH 3.0,4.5,6.0,7.5)and aluminum(0,50,100,200 mg/L Al3+)solution to study the effect of pH and Al3+stresses on seed germination and seedling growth,Established the evaluation method,the level of acidity and aluminum ion treatment.An orthogonal quadratic regression rotation combinatorial design with 4 factors,i.e.molybdenum(Mo),magnesium(Mg),calcium(Ca),boron(B),was adopted in field experiments to study their effects on seedling growth of alfalfa under acid-aluminum stress(pH = 4.5 and aluminum concentration is 81mg/L).Analysis index of seed germination rates,germination indexes,stem lengths,root lengths,vigor index,POD activity,Chlorophyll content and MDA content,there sults are as follows:The growth conditions under a single acid stress,the germinations of alfalfa seed and seedling growths were increasingly inhibited significantly as acidity increase;When pH value at 4.5,6.0,7.5,the vigor indexa and root length of alfalfa seeds were 1.24,1.54,1.51,1.63 cm,2.06 cm,1.95 cm,meanwhile the alfalfa growth were even encouraged with slightly acidic(pH 6.0)treatments.The germination rates,germinative forces,germination indexes,stem lengths and root lengths of 0 mg/L and 50 mg/L Al3+ treatments were significantly higher(P<0.05)than other treatments.While the germination of alfalfa seed and seedling growth was restricted seriously with higher Al3+ concentrations(100 or 200 mg/L solution),and resulted in a significant decreased growth index(P<0.05).The interaction effect of acid stress and aluminum stress on germination of alfalfa seeds and seedling growth was more intensive than those of single stress.The seed germination rate,seedling root length at pH 4.5,100 mg/L Al3+ treatments and pH 6.0,50 mg/L Al3+ treatments were 53%,95%,0.107,0.85,when pH<4.5 and Al3+ >50 mg/L,the inhibition effects on alfalfa germination and growth were already presented.All four micro-nutrients have improved germination index of alfalfa seeds significantly(P<0.05).In order to counteract the combination effects of acid & Al on germination rate,the optimum micro-nutrient combination should be: calcium 160 mg/L,molybdenum 0.5 mg/L,magnesium 800 mg/L,boron 3 mg/L;In order to counteract the combination effects of acid & Al on vigor index,the optimum micro-nutrient combination should be: calcium 160 mg/L,molybdenum 0.5 mg/L,magnesium 800mg/L,boron 3 mg/L;For germination index of alfalfa seeds,the optimum micro-nutrient combination should be: calcium 160 mg/L,molybdenum 0.5 mg/L,magnesium 800 mg/L,boron 3 mg/L;for alfalfa seeding root length,the optimum micro-nutrient combination should be: calcium 280 mg/L,molybdenum 0.5 mg/L,magnesium 800 mg/L,boron 3 mg/L.Boron(B),molybdenum(Mo)have improved chlorophyll content of alfalfa seedling significantly(P<0.05),four micro-nutrients have improved MDA content of alfalfa seedlings significantly(P<0.05).For chlorophyll content of alfalfa seedlings,the optimum micro-nutrient combination should be: calcium 160 mg/L,molybdenum 0.5mg/L,magnesium 600 mg/L,boron 3 mg/L;for MDA content of alfalfa seeding,the optimum micro-nutrient combination should be: calcium 640 mg/L,molybdenum 0.4mg/L,magnesium 800 mg/L,boron 1 mg/L. |
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