崇明东滩围垦湿地芦苇光合作用对模拟升温的响应初探

采用开顶式气室法(Open top Chamber, OTC)模拟升温，分别于升温1 a和升温2 a后，测定崇明东滩围垦湿地代表植物--芦苇快速生长期叶片的光响应进程，分析最大净光合速率(Pmax)、暗呼吸速率〖WTBX〗(Rd)、表观量子效率(AQY)、光补偿点(LCP)、光饱和点(LSP)等光合参数对升温时间的累积响应。结果表明：与对照样地相比，升温1 a后Pmax、〖WTBX〗LSP显著增加，Rd、LCP显著降低，表现出正效应，而升温2 a后结果相反；升温条件下〖WTBX〗AQY的年际差异不显著；非线性拟合芦苇叶片光合 光响应(Pn PAR)曲线，结果显示其在升温第一年和第二年分别发生上调和下移现象；蒸腾速率(Tr)对升温表现增加趋势；气孔导度(Gs)、胞间CO2浓度(Ci)对升温的响应与光合有效辐射(PAR〖WTBZ〗)强度有关。这可能意味着长时间升温条件下芦苇叶片因非气孔因素限制发生光合适应现象

RESPONSES OF THE PHOTO-SYNTHESIS OF RECLAMATION PHRAGMITES AUSTRALISIN EASTERN CHONGMING ISLAND ON ELEVATED TEMPERATURE

An open-top chamber(OTC) system was used on the dominant species Phragmites australis in reclaimed marsh in Eastern Chongming island to study the effects of elevated temperature(ET) on the photosynthesis of leaves in rapid growth season.Photosynthetic parameters containing maximum net photosynthetic rate(Pmax),dark respiration rate(Rd),apparent quantum yield(AQY),light compensation point(LCP),light saturation point(LSP) and light response processes of leaves of Phragmites australis were measured after one-and two-year treatment.The results showed that these physical characteristics were diverse under different ET time.Comparing with the control(CK),the OTC manipulation showed positive effects,Pmax and LSP increased significantly,Rd and LCP decreased significantly after one-year treatment(1aET).The opposite results happened to two-year treatment(2aET).No significant differences happened to AQY between years.The net photosynthetic rate-light intensity(Pn-PAR) curves which were nonlinear(R2>0.98) fitted moved up and jumped down after 1aET and 2aET respectively.Furthermore,the effect of ET on transpiration rate(Tr) was enhanced significantly,which served as a self-protection response for dissipating heat.The responses of stomatal conductance(Gs) and intercellular CO2 concentration(Ci) were correlated with photosynthetic active radiation(PAR).All results implied that photosynthetic acclimatization occurred due to non-stomatal factors limited under longer time scale.