不同土壤水分条件下文冠果的光合作用日变化

摘要

在黄土丘陵区，以3年生文冠果苗木为材料，测定其在不同土壤水分条件下的气体交换和荧光参数日变化，分析其光合作用与不同土壤水分的定量关系，以指导文冠果这一能源树种在半干旱地区的推广种植。结果表明：（1）文冠果叶片的净光合速率（Pn ）、水分利用效率（WUE）、光下最大荧光（Fm ）、PSⅡ最大光量子产量（Fv／Fm ）、PSⅡ实际量子效率（ΦPSⅡ）、光化学猝灭系数（qP）均随土壤相对含水量（W r ）降低呈先升高后降低趋势，其最小荧光（ Fo ）先降后升，而其 N PQ持续升高，当W r 为44．7％～81．2％时各参数都维持在较高水平。（2）文冠果叶片日净光合累计量（PD ）和WUE在Wr 为58．6％～81．2％时都处于较高水平，当Wr 为66．6％时WUE达到最大值，过高或过低的土壤水分含量均不利于文冠果叶片光合作用的进行和水分的利用。（3）气体交换参数分析表明，文冠果中午光合作用的下降在W r 为38．1％～81．2％时是由气孔因素导致，而在W r 低于31．8％时转为非气孔限制；当W r 低于73．9％时，文冠果中午会出现光抑制，光合机构受到破坏。研究认为，在黄土丘陵区，适宜文冠果栽培的土壤相对含水量在58．6％～81．2％之间，低于38．1％时则无法正常生长。%In order to promote the planting of X anthoceras sorbi f olia Bunge in Semi‐arid area ,this study took 3‐year‐old seedlings of X . sorbi f olia Bunge as materials in Loess Hilly Region in w hich its gas exchange and diurnal variation of chlorophyll fluorescence parameters under different moisture conditions were measured and the quantitative relationship between photosynthesis and different soil moisture was analyzed .The results indicated that :(1) with the decrease of relative soil water content ,the net photosyn‐thetic(Pn),wateruseefficiency(WUE),maximalfluorescenceunderlight(Fm),PSⅡ maximumlightquan‐tum yield (Fv/Fm ) ,PSⅡ practical quantum efficiency (ΦPSⅡ )and photochemical quenching (qP) increased at first and then decreased , minimum fluorescence ( Fo ) decreased first and then increased , and N PQ continued to rise .All parameters were maintained at a higher level when Wr was 44 .7% -81 .2% .(2) The daily net photosynthetic accumulation and water use efficiency (WUE) were at a higher level while Wr was at 58 .6% -81 .2% .WUE reached the maximum value when Wr was 66 .6% .It is not favorable to the photosynthesis and water utilization of X .sorbifolia Bunge when the soil water content was too high or too low .(3) Gas exchange data showed that the decline of photosynthesis at noon was caused by stomatal factor when Wr was at 38 .1% -81 .2% ,but it was restricted to non‐stomatal factor when Wr was less than 31 .8% .There would be photo inhibition at noon and it would damage the photosynthetic mechanism while Wr was less than 73 .9% .In short ,it is suitable for the cultivation of X .sorbifoliaBunge in Loess Hilly Region while Wr was at 58 .6% -81 .2% and it cannot grow normally while Wr was less than 38 .1% .