干旱胁迫下常春藤净光合速率日变化及其影响因子分析

利用CIRAS-2型便携式光合仪对干早胁迫下3a生常春藤(Hedera nepalensis var.sinensis)叶片光合速率Pn的日动态及其主要生态生理因子进行测定分析,以阐明干早胁迫下pn的日变化特征及其午休原因,并探讨了影响常春藤Pn的主要影响因子.结果表明,常春藤Pn日动态与土壤水分及微环境因子密切相关.随着干早胁迫的加重,其pn,日均值及最大值下降显著,其中轻度、中度、重度干早胁迫下,其pn,日均值分别比对照下降15%,4700,70%;随着干早胁迫的加重,常春藤pn.日动态由"单峰"向"双峰"型变化,光合作用午休原因由气孔限制为主逐渐过渡到以非气孔限制为主.多元回归及主成分分析表明,适宜水分条件下,影响常春藤Pn的日动态因素可归纳为两类,一类以气温、相对湿度和大气CO2:浓度为主,其次是以光照强度为主;随着干早胁迫的增强,光照强度、大气CO2浓度、相对湿度等生态因子对常春藤Pn的影响越大,其中相对湿度对pn的影响最显著.

Diurnal Variation of Net Photosynthetic Rate and Influencing Environmental Factors of Hedera Nep alensis var. Sinensis Under Drought Stress

The relat io n between diurnal variation of leaf net photo synthetic rate ( P_n ) and ecophy siological factors for three years old leaf of Hedera nepalensisvar. sinensis under drought stress was analyzed using CIRAS??2 portable photo synthesis system. T he diurnal variation of H . nep al ensisvar. sinensis photosy nthesis and its midday depression phenomenon was explained clearly and its predominant environmental factors under drought stress were ascertained. Results showed that diurnal variation of H . nep alensis var. sinensis photo synthesis and its micro-environmental factors were connected with soil moisture nearly at the same time. With the agg ravation of drought stress, the daily average and maximum P_n was decreased significantly . Compared with check treatment, the means of P_n in the drought stress of mild treatment, moderate treatment,and severe treatment were reduced by 15%, 47%, and 70%, respectively. With the aggravation of drought stress, the diurnal variation of photo synthesis changed from a single peak curve to a double peak curve and the predominant cause of midday depression turned into non-stomatal limitation. By the methods of stepwise multi??regression and principal component analysis, there was an obvious difference in the environmental factors of impact Pn under different drought stresses. Under the condition of mild soil moisture, the causes of diurnal variation of P_n can be classified into two categories: one was air temperature, relative humidity and CO₂ concent ration and another was photosynthetic active radiation. The effects of photosynthetic active radiation, CO₂ concentration, and relative humidity on P_n became more and more conspicuous with increase in drought stress and relative humidity was the dominant factor.??