Influence Of Water And Nutrients On Morphological Characteristics And Root Turnover Of Gaura Parviflora

Gaura parviflora Douglas ex Lehmann is a herbaceous plant of Onagraceae Gaura L. and it is an alien invasive plant which has a serious damage. Current research focuses on the biomass dynamic of the ground of G. parviflora, biological characteristics, anatomical structure, allelopathy and karyotype(analysis), salt resistance, drought resistance and so on. There is no research report about its morphological characteristics and root turnover under different conditions of water and nutrients. In order to provide theory basis for the invasion mechanism of G. parviflora and know about the morphological characteristics of it, which response to the water and nutrient, we set up the plot experiment consists of four water treatment and three nutrient treatment. we statistic the root and stomatal number directly by observation; The dry weight of every organ are weighted by balance after dry treatment; grow bags method are applied to the root turnover and decomposition experiment. Five root sequence classification method to determinate the foot order. Leaf slice is made by paraffin sectioning. Nitric acid-chromate segregation law for vessel materials of segregation. Nail polish imprinting legal system for temporary with porosity. The main research results are as follows:1. Leaf anatomical structure characteristicsUnder the drought resistance, the palisade tissue thickness and stomatal density of G. parviflora become smaller with the drought stress increasing gradually; the average value of leaf thickness and stomatal length in the order from large to small is: high moisture, the highest moisture, low moisture, minimum moisture; the value of stomatal length and density are the smallest under the minimum moisture treatment. The ratio of spongy to palisade and cell tense ratio has a significant difference between the highest moisture and low moisture.Under the nutrition treatment, the down skin thickness, skin thickness, sponge tissue and blade thickness from thick to thin in the order is: nutrition, high nutrition and low nutrient. The down skin thickness, skin thickness, leaf thickness, cell tense ratio and spongy ratio under nutrition treatment are significant different with the other treatment; the stomatal density is the smallest and the stomatal length is the biggest.2. Vessel structure characteristicsThe vessel types of G. Parviflora are spiral vessel, reticulate vessel, and its perforated plate type is simple perforation plate; vessel with primitive type and evolutionary type, and the later is more. The percentage of vessels with one tali or no tail in the end is more than the value of vessel with two tails in the end.Compared with the vessels in the stem, the vessels in the root have a stronger water-carrying capacity under drought stress and nutrition treatment. vessel has a good adaptability to soil nutrient.3. BiomassThe dry weight of various organs of G. parviflora, the number of seeds, the dry weight of plant decreased with the drought stress increased;The dry weight of various organs is biggest and the number of seeds is largest in the nutrition treatment. On the contrary, these are smallest in the low nutrition treatment.4. Architecture characteristics of root systemsThe maximum number of every order roots is in the the highest moisture, the minimum value is in high moisture; the number of every order roots in the order from large to small is: the highest moisture, minimum moisture, low moisture, high moisture. The root biomass ratio of every order from large to small is:first-order roots, secondorder roots, third-order roots, fourth-order roots. There is no fifth-order root in the drought resistance treatment. Root branch ratio has no significant difference and root branches tend to fork.Under the nutritional treatment, the root biomass ratio of every order roots from large to small is: first-order roots, second-order roots, third-order roots, fourth-order roots. The ROLP value of every order has no significant difference. With the deterioration of the nutrition, root branch tend to fishtail shape from fork shape.The cross-sectional areas of G. parviflora before and after the root branches conform to the piping model.5. Root turnover and decompositionThe total fine root biomass, the living and die root biomass of G. parviflora is largest in nutrition group. Fine root biomass and decomposition biomass from large to small is: nutrition, high nutrition and low in nutrition.In conclusion, G. parviflora has typical xerophytic plant anatomical structure characteristics; its vessel has a strong adaptability to water and nutrient and has a strong water-carrying capacity; its root architecture has a good adaptability to different water and nutrient; it has a good coordination between components. All these features is of great significance to its successful invasion.