The Xylme Structure And Relationship Between Water Relations And Photosynthesis In Three Phyllostachys Bamboo

Bamboo is one of typical perennial evergreen plants as extremely important renewable non-timber forestry resources and landscape garden plants. The main purpose of this study is to explore the internal relationships among stem xylem structure, xylem resist embolism capability and photosynthesis capacity in bamboo species, and reveal their adaptive strategies to the environment. The hydraulic conductivity of stem and branch segments, leaf photosynthesis rate diurnal dynamic, and anatomical parameters on xylem vessels were measured on one or two-year old three bamboo species in Northwest A & F University campus. In addition, seasonal dynamic of percentage loss water conductivity and root pressure were also investigated. The results are shown in the following:1. Xylem anatomy of bamboo:bamboo maximum vessel length is greater than 120 cm, and vessel length distributed mainly between 10-100 cm. The average vessel diameters are ranged between 50-60 μm, and the average vessel size of bamboo stems greater than that in the branches.2. Vessel structure and the relationship with water transport efficiency:The stem mean vessel diameter was significantly correlated with the maximum conductance (P<0.001) in all three species. The species with the larger diameter, the greater the water conductivity.3. Vessel structure and relationship with resist embolism capability:Embolism vulnerability of branch was greater than the stem, with stem P50> branch P50. This might be the strategy of bamboo species respond to the environmental stress. They could choose abandon branches or leaves to maintain normal physiological activity of the stem.4. Bamboo stems and leaf water potential diurnal dynamic under different light environment:Under the sunlight environment, embolization degree of the bamboo stem showed increased firstly and then decreased within a day, with the inverse trend of leaf water potential. The most serious embolization happened at 14 PM then slowly reducing, however, the leaf water potential showed decreased firstly and then rising, at 17 PM got the minimum and then gradually increased. Embolization of stem kept nearly constant within one day in a shad environment, similar result happened in leaf water potential dynamics.5. Bamboo daily dynamic of photosynthesis:Net photosynthetic rate were significantly correlated with stomatal conductance, leaf and stem water potential and intercellular carbon dioxide concentration. The results indicated that stems, leaf water conditions are important factors in limiting the photosynthesis capacity of bamboo species. In addition, positive correlation between plant water use efficiency and net photosynthetic rate further showed that improving water use efficiency will help advance the photosynthetic rate of bamboo species.6. Relationship between root pressure and the xylem embolism repair: Bamboo stem percentage loss of hydraulic conductivity did not significantly change with seasons. There was significant correlation between root pressure and embolism of stem in some month, which means that root pressure is not the only recovery mechanism of embolism in bamboo species.