Effects Of Warming Soil Temperature On Root, Stem And Leaf Of An Invasive Species Alternanthera Philoxeroides

The alligator weed Alternanthera philoxeroides(Mart.) Griseb(Amaranthaceae),a species native to South America,has introduced into China in 1930s.It was listed as "the first group of invasive plants in China" by State Environmental Protection Administration of China in 2003.Most previous studies have focused on the effects of different habitats and different soil nutrients on growth and reproduction of A. philoxeroides,little attention was paid to the effects of soil temperature on its growth and reproduction.In this study,we carried out an outdoor experiment to evaluate the soil wanning effects on both root growth and stem and leaf traits of invasive plant A. philoxeroides.The results are mainly as follows:1.The temperature of soil greatly influenced phenotypic plasticity of roots of A. philoxeroides.Under different soil temperature(contrast,2℃,and 4℃treatments),the number of primary branched roots are 5.5,5.1 and 5.7,the longest length of branched roots are 20.36,17.96 and 15.56 cm,the diameter of taproots are 1.88,1.89 and 1.87 cm, the length of taproots are 8.01,8.54 and 8.41 cm,and the root biomass are 5.19,3.88 and 3.89 g,respectively.As soil temperature increased,the branching density of taproots of A. philoxeroides decreased at early stage and then increased later,and the intensity of taproots of A.philoxeroides increased.The result showed that effect of the soil temperature on the longest length of branched roots is significant,indicating that the longest length of branched roots decreased as soil temperature increased.2.Under different soil temperature(contrast,2℃,and 4℃treatments),the longest length of internodes are 4.38,4.94 and 5.47 cm,the length of petioles are 0.54,0.46 and 0.61 cm,and the leave number are 99,131 and 138,respectively.There is a pronounced influence of soil temperature on the longest length of internodes.The results showed that there is a significant relationship among the soil temperature,the longest length of internodes,and leave number,indicating that the longest length of internodes and leave number increased as soil temperature increased.3.In the range of soil temperature between 2℃and 4℃,the data gap of the number of first branched roots are -0.4 and 0.2,the data gap of longest length of branched roots are-2.4 and -4.8,the data gap of diameter of taproots are 0.01 and -0.01, the data gap of length of taproots are 0.53 and 0.4 respectively,the data gap of root biomass are both -1.3,the data gap of longest length of internodes are 0.56 and 1.09 respectively,the data gap of length of petioles are -0.08 and 0.07,and the data gap of leave number are 32 and 39 respectively.These revealed that A.philoxeroides has ability to survive and distribute in multi-climatic zones by changing the fractal model of root.It was of great scientific significance and the value of application to reveal the diffusion mechanisms of A. philoxeroides.