Studies On The Models Of Hydraulic Architecture And Mechanism Of Drought Tolerance In Trees Species

The hydraulic architecture is the strategies of water transport and morphological structure of plants adapted to survival competition in the natural environment. Discussing water transport in plants by hydraulic architecture, and modeling the dynamics of water flow through plants have attracted continued interest for many years. This paper analyses hydraulic architecture characteristic and establishes dynamics hydraulic architecture models of Pinus tabulaeformis. At the same time, the daily changes, seasonal changes and day and night changes of several trees species were measured, discussing the change law of water transport and distribute, the xylem embolism vulnerability and refilling ability, the relationship of and anatomical structure, and comparing the mechanisms of drought tolerance in plants.The models dynamics of water flow through of Pinus tabulaeformis are established and respectively discussed the influences of coronal levels and branch class on water transport in Pinus tabulaeformis. As far as coronal levels are concerned, the hydraulic conductivity capability of the middle coronal levels is the strongest, water transport efficiency is the most highest, and water supply is the most sufficient in all over the coronal levels. The hydraulic conductivity capability of the lower coronal levels is more smaller than other coronal levels, because of aging branches. When came under water stress, the slender and times without number twigs in lower coronal levels would be firstly eliminated, so during young or younger trees foster, the twigs in lower coronal levels could be cut down for ensuring water transport and survive of main branches, which is beneficial to improve afforestation survival rate. According to branch class, the hydraulic conductivity capability of backbone twigs is the strongest, so water transport efficiency is the most highest. The water transport efficiency of twigs in first branch class growing in backbone is lower than that of backbone, but water transport efficiency of twigs in second branch class growing in first branch class is even lower. This shows that water transport efficiency of higher branch class is higher than that of lower branch class. Otherwise, the more trees have branches, the lower water transport capability is. This hydraulic architecture characteristic of Pinus tabulaeformis is the important ecological strategy formed in natural selection over the long term.ABSTRACTThe studies on hydraulic architecture characteristic of 1-year-old twigs in several trees species show that the daily change, seasonal changes and day and night changes of hydraulic architecture parameters all manifest convex, the seasonal variation of xylem embolism in conifers are not distinct, even in winter, higher hydraulic conductivity could be observed, but the seasonal variation of xylem embolism in broad-leaved species are higher than that in conifer.The studies on anatomical structure show that the xylem microstructure is closely related to both hydraulic architecture characteristic and transpiration in plants. The water transport efficiency in ring-porous species vessels is higher than that in diffuse-porous species and none- porous species, but ring-porous species vessels more easily occur embolism. Analysis showed that the xylem water transport efficiency and embolism of the species were ring-porous species>diffuse-porous species>none-porous species. It was clear that the plants hydraulic architecture effectiveness and security were not entirely available at the same time.