| Plants through photosynthesis to absorb and fix energy,the photosynthetic carbon sequestration is closely related to plant water use,and the distribution of organic matter is transported by water.Bamboo is a typical clonal plant and physiological integration is one of the most important characteristics of clonal plants.Organic matter resources,mineral nutrients and water can be transferred through the connected rhizome in different plants.Photosynthetic characteristics,water use efficiency and internal physiological integration are directly affected the survival,growth,reproduction,expansion and resource utilization of clonal plants.As an excellent used bamboo species with early shooting and high output,Phyllostachys violascens was widely cultivated in Jiangsu and Zhejiang.In order to demenstrate the photosynthetic characteristics and response of water use efficiency to environment factors and the distribution and transfer mechanism of carbon,and provided theoretical guidance for structure regulation and rational management.The individual plant biomass model was constructed,photosynthetic characteristics of different ages,water use efficiency and organic carbon content in the shooting period with different ramets was investigated.Main results as follows:?1?The biomass overground part of P.violascens accounted for 92.76% and the underground biomass accounted for 7.24%.Individual plant biomass decreased in the order of: stem?60.31%?>leaf?18.28%?>branch?14.16%?>root?7.24%?.The biomass of various organs and whole plant biomass were significantly and positively correlated with diameter at breast height.?2?The results showed that the daily dynamics of net photosynthetic rate?Pn?of leaves was a one-peak curve,and the peak value at about 12:00.The One-year-old(3.9466?mol·m-2·s-1)>two-year-old(2.7054 ? mol · m-2·s-1)>three-year-old(2.4648 ? mol · m-2·s-1).The daily dynamics of water use efficiency?WUE?of leaves was a bimodal and the daily average of WUE of different age was one-year-old?3.99 ?mol·mmol-1?> three-year-old?3.68 ?mol·mmol-1?> two-year-old?3.07?mol·mmol-1?.There were significant correlation between Pn and photosynthetic active radiation?PAR?,air temperature?Ta?.Air relative humidity?RH?declined with PAR and Ta increased.PAR was the main environmental factor affecting Pn of different age and Ta was the secondary factor.RH was the main environmental factor affecting WUE of one-year-old P.violascens and PAR was the main environmental factor affecting WUE of two-year-old,three-year-old P.violascens.In conclusion,the photosynthetic capacity and transpiration capacity were significantly higher than two-year-old,three-year-old P.violascens.The drought resistance capacity of three-year-old P.violascens was higher.Making an appropriate proportion of different age P.violascens to adjusted the age structure is very important to improved productivity.?3?Net photosynthetic rate?Pn?,transpiration rate?Tr?and stomatic conductance were higher in the summer than that in the winter and lessening with age increasing.Water use efficiency?WUE?was lessening with age increasing in winter and the trend contrary in the summer.The variation trend of ?13C contrary to WUE.Overall,Pn?WUE?Tr??13C were significant correlation with environment factors which has a negative correlation with soil water content?W?.The average daily sap flow rate in cloudy or rainy days were lower than that in sunny days.Magnitude of sap flow changed considerably between sunny and rainy days.Correlation analysis showed that sap flow rate had significant positive correlations with solar radiation,air temperature and soil temperature,but negative correlation with air relative humidity and soil water content.?4?The organic carbon content was significantly different in various organs of P.violascens and it changed signficanly during the shooting period.Before the shooting period started organic carbon content decreased in the order of branch>rhizome>leaf>stem>root;after the shooting is completed,it decreased in the order of stem>rhizome>leaf>branch>root in the mulching P.violascens clone system stands.The carbon content has significant changes in different organs of P.violascens in shooting period,in which the carbonaceous rate of branches,leaves,stems and rhizome has upward trend after the first fall and the carbonaceous rate of root showed "N" type variation.Before the shooting period started organic carbon content decreased in the order of branch>leaf>stem>rhizome>root;after the shooting is completed,it decreased in the order of branch>stem>leaf>rhizome>root in the nature P.violascens clone system stands.Organic carbon content decreased with a following increase in branch and leaf and there was a "N" –like type variation of organic carbon content in root,stem and rhizome.The decrease of organic carbon content was negatively related to the shoots yield in the one-ramet plants and multi-ramet plants.The reduction of organic carbon of various organs in the one-ramet plants higher than multi-ramet plants,but in the three-ramet plants higher than in the two-ramet plants.The reduction of organic carbon of stem more than other organs.Varation of organic carbon was also found between plants with different ramet age.In the two-ramet plants,the reduction of organic carbon was larger in 1-year-old plants than 2-years-old plants and in three-ramet plants,the reduction of organic carbon was larger in 3-years-old plants than in 2-years-old plants and 1-year-old plants.These findings indicate that bamboo shooting affects organic carbon allocation,with decrease content in branch and leaf increase content in root,stem and rhizome.The potential source sink relationship of different organs changed to provide organic carbon for bamboo shoots.Physiological integration of photosynthesis product exsited within P.violascens cloned segment.The loss in the one-ramet plants higher than multi-ramet plants.The organic carbon content also vary with the P.violascens plants age in shooting period.Therefore,it has important realistic significance to improve the shoots output and economic benefit by improve connectivity among ramets and adjust the natural structure of P.violascens by ground. |
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