Study Of Temporal And Spatial Heterogeneity In Photochemical Efficiency Of Phyllostachys Pubescens

Phyllostachys pubescens is a crucial economic bamboos species which is widely used in manyfields such as construction and food industry. Besides its huge economic benefits, Phyllostachyspubescens also has a strong capability of carbon fixation which is attributed to its rapid growth. Due tothe above advantages, Phyllostachys pubescens was selected for my investigation. This research aimsto evaluate its photochemical efficiency and light energy utilization in different seasons and lay atheoretical foundation for the study of fertility and carbon fixation of Phyllostachys pubescens.The experiments were conducted in an observation tower built in the Ecological MonitoringResearch Center of Zhejiang Agriculture and Forest University which is located in Yanli village,Lin’an. All the Phyllostachys pubescens samples are obtained and sorted according to its differentages (1year-old,3year-old,5year-old)and various harvest seasons (spring, summer, autumn andwinter). Certain factors of the samples were measured by SPAD502and PAM-2100, including therelative content of chlorophyll, chlorophyll fluorescence parameter and the response to light irradiance.Diurnal variation of chlorophyll fluorescence parameter was also measured between7am to16pm ineach season. The statistics were analyzed with the tool of Excel2003and SPSS19.0. The resultshowed:1. The photochemical efficiency is highly relevant to forest canopy. With the decreasing height ofcanopy, actual photochemical efficiency (Yield), maximum photochemical efficiency (Fv/Fm) andpotential activity (Fv/Fo) gradually increased. In terms of the comparison between the upper andmiddle-down layers of canopy, the results of these three factors displayed an increasingly notabledifference. Meanwhile, the sample at5-year old was more photochemically efficient than those at theother two ages.2. The leaves in middle layer of canopy performed better in photoresponsive aspect, comparedwith the upper and down layers. As the height of canopy increased, the light saturation point wasreached at a higher light intensity. Comprehensively speaking, the photoresponsive ability of samplesat3-year old surpassed others.3. Under extreme weather in winter season, the upper layer of canopy would suffer a more severelow temperature stress compared with the middle and down layers, and the samples at5-year old were much more tolerant to the cold. Low temperature decelerated the maximum photosynthetic electrontransport rate and led light saturation point to be achieved at a lower light intensity.4. Through the comparison of relative chlorophyll content, chlorophyll fluorescence parameters,response to light irradiance and diurnal changes among leaves in upper layer of canopy at the sameage in different seasons, Phyllostachys pubescens achieved its peak of photochemical efficiency inautumn (October). This result indicated that in autumn (October) the ratio of energy consumed forphotosynthesis with total absorbed energy was high. Therefore, October is the peak season ofPhyllostachys pubescens’s carbon fixation, considering its energy utilization efficiencyBased on the above researchments, capability and technology for carbon fixation ofPhyllostachys pubescens could be increased and innovated by delaying hooking and cutting in autumnand winter.