Physiological Characteristics And Glyphosate Tolerance Biochemical Mechanisms Of Alligator Weed (Alternanthera Philoxeroides) Under Manganese Stress

Alligator weed, Alternanthera philoxeroides (Mart.) Griseb., was one of the most invasive alien weeds in China. This plant can tolerate high concentration manganese and reduce the sensitivity of glyphosate in high concentration manganese-stressed. In this study, the plant morphology, biomass, ultrastructure and the biochemical response mechanism of glyphosate resistant was expounded in high concentration manganese-stressed.The plant culture in median concentration Mn (0.31m mol/L) can promote the growth of plant, the lush foliage, and well-developed root system and can increase biomass , enhances the adaptability to Manganese. There is no significant difference between high concentration Mn (2.45m mol/L) -treatment group with control group in growth conditions. After 120 days cultured in median concentration Mn, several microscopic characters have been changed at cell interior: mitochondria increased, chloroplast swelling, lamellar structure come to disorder slightly, however,starch granules fill out and significantly increased, this change can raise photosynthetic rate and respiration. After 120 days cultured in high concentration Mn ,the plant cells demonstrate injury on some degree: Chloroplast swelling and deformation, Lamellar structure in wild disorder, osmiophilic granules manifold and cell distortion. However, both the two treatment do not damage the nucleus and nucleolus, and show some antidotal features: the vacuole increased, cell wall thickening, sediment aggrading in the cell wall cavity, high-density electron donor adhered to cell wall.The Alligator weed could start-up antioxidant enzyme system scavenging free radical to protect the membrane system in median concentration Mn environment, but in high concentration Mn environment the plant can not start-up antioxidant enzyme system effectively, and instead, the plant may show some membrane lipid peroxidation injury. After Glyphosate treatment, the antioxidant enzyme activity of Alligator weed under medium and high manganese treatment is higher than that under conventional manganese treatment, the free radical scavenging effect become stronger, in Alligator weed this might be one of the biochemical mechanisms of increasing tolerance for glyphosate under high Mn. In Alligator weed the shikimate content don't change after median and high manganese treated. Glyphosate treated early, the shikimic acid content in Alligator weed under median and high manganese treatment was significantly lower than that under conventional manganese treatment, that means the Shikimate way blocked slightly, that may be the one of reasons why Alligator weed reduced susceptibility to glyphosate under manganese -stressed.