The Comparative Study Of Leaf Water Characteristics And Characteristics Of Stem Hydraulic Conductivity In Eight Species

The purposes of the thesis were to study the leaf water traits, stomatal characteristics,xylem anatomy and hydraulic conductivity and compare differences in water transportation of eight species combination of these parameters using PV curve, hydraulic conductivity and anatomy.The species, Metasequoia glyptostroboides,Ginkgo biloba,Cedrus deodara,Populus tomentosa,Ulmus pumila,Ulums macrocarpa,Salix babylonica and Wisteria sinensis were chosen as materials. These plants were introduced into Beijing Botanical Garden from their original habitats of China in 1960s'and have cultivated for almost 50 years. So the variance in water transportation mainly depend on their genetically differences, rather than the environment factors. The main results were as follows:1. Water parameters from the PV curve showed the variations during growth stage in the same species, and the inconsistent changes in different species. The trends related to adaptability and hysteresis of different species on the environmental conditions (light, moisture, temperature, etc.) Gymnosperms have shown a high saturation osmotic potential (ψs) and water potential at turgor loss point (ψw) in the fast-growing period (July-september). In contrast, the lower values ofψs andψw were recorded in Populus. No significant variation of other species.2. Eight kinds of plants will be divided into four different ecological types based on the analysis of leaf water parameters and stomatal characteristics of each species: (1)Metasequoia glyptostroboides,Ginkgo biloba and Cedrus deodara of gymnosperms showed higher values inψs andψw, lower stomatal density and smaller stoma;(2)Populus of xerophytic trees was lowerψs andψw, larger cell elastic modulus, lower stomatal density and smaller stoma;(3)Ulmus pumila,Ulums macrocarpa and Salix babylonica had higherψs andψw, greater stomatal density and larger stoma;(4)Wisteria sinensis of liana displayed lowerψs andψw, higher stomatal density and smaller stoma.3. Hydraulic conductivity of stem showed significant differences in eight species. Wisteria sinensis of liana had the largest conduit diameter and the strongest hydraulic conductivity, while the gymnosperms have the largest tracheid density, but the worst hydraulic conductivity among eight species. Hydraulic conductivity of other species fluctuated between the types.4. Huber value and hydraulic architecture parameters of the other three was found to be negative correlation, which indicated that maintaining coordination and coherence of structure and function in water transportation and disperse of plants. Diameter of conduit or tracheid was positively correlated with maximum hydraulic conductivity, specific conductivity and leaf specific conductivity. It suggested that the larger diameter of conduit was helpful of water transportation.