Dynamics Of Moso Bamboos'gas Exchange And Water Potential During Bumper Year's Rapid Growth Period

Phyllostachys edulis is a kind of bamboo resource,which is of great importance in our country.It possesses not only a high economic value but also sound ecological functions.Moso bamboo has its own unique pattern of growth,which has been termed as“rapid growth”or“explosive growth”.This special pattern of growth grants moso bamboo a good manifestation on carbon sequestration and conservation of water and soil.The studying of the gas exchange and water potential of moso bamboo during its shooting year's rapid growth period can help us to understand the characteristics of photosynthesis and the direction of water transportation.As a result,this study will reveal us the mechanism of water and nutrients flow,and thus unveiling a theoretical evidence towards the management of moso bamboo forest.This study counts on the Physiological ecology monitoring station of moso bamboo of Zhejiang A&F University.Setting up measuring bench in the experimental forest,using the Li-6400 photosynthetic system,PSYPRO and its associate leaf probe L-51A,this study measured the diurnal variation of gas exchange and water potential of three-year and five-year bamboos during March to May in 2016.Analyzing the correlation of gas exchange parameter and water potential in different ages of bamboo leaves and different stages of rapid growth,this study reveals the relationship between water potential and gas exchange parameter of bamboos'leaves.And the results are as following:?1?combing the light response curve with photosynthetic rate,we discover no significant difference between three-year and five-year bamboo in photosynthetic capacity?P>0.05?at their early rapid growth period;after turning into the middle and later stages of rapid growth period,five-year bamboos'photosynthetic capacity are stronger than three-year bamboo.?2?Stomatal conductance showed the same changing direction as the intercellular CO2 concentration?P<0.01?,which illustrates that the decrease of photosynthetic rate in three and five year bamboo during the rapid growth period is caused by non stomatal factors.?3?With the transpiration rate and the water use efficiency,this research shows,the transpiration rate of moso bamboos in the middle stage of rapid growth period is significantly lower than early and later stage?P<0.05?;oppositely,water use efficiency in middle stage outpaces the other two stages significantly.In addition,five-year bamboos'water use efficiency is way higher than three-year bamboo during the middle stage.?4?The water potential of moso bamboos has the highest changing capacity in the middle stage,followed by its later stage,and the early stage shows the lowest capacity in this regard;the five-year bamboos'water potential are higher than three-year bamboo throughout their whole growth period.Moso bamboos'water potential shows a significantly positive correlation with its water use efficiency,a completely negative correlation with the transpiration rate,and no relation with parameters such as bamboo's age,photosynthetic rate,stomatal conductance and intercellular CO₂ concentration.In addition,the differences of growth period also demonstrate an influential impact upon its water potential.Combining with the process of rapid growth,we can safely deduce that five-year bamboo is the source of water and nutrients flow.These water and nutrients are transmitted to three-year bamboo from five-year bamboo,and finally reached to the newly growing bamboo.Considering the high water potential in middle stage and the conclusions we have reached in?3?,we can conclude that the transmission of water and nutrients are most intense in the middle stage of rapid growth period.