红砂3个地理种群的光合特性及其影响因素

Photosynthetic characteristics and their effect factors of Reaumuria soongorica on three geographical populations

在自然条件下对分布于兰州九州台(LZJ)、张掖临泽(ZYL)和武威民勤(WWM)3个地理种群的红砂(Reaumuria soongorica)的光合特性进行了研究,并对其影响因素进行了分析。结果表明,红砂3个地理种群叶片的光合速率和蒸腾速率日变化规律相似,均为双峰型,光合有明显的"午休"现象。影响红砂光合的因素既有环境因子又有自身因素。在环境因子中,无论是对光合速率还是蒸腾速率,光照强度都是最重要的主导因子,其次是气温,大气湿度则与植物的蒸腾速率成负相关。各因素的影响程度因不同地理种群所处土壤含水量不同而有所不同。内在因素中气孔导度下降是光合速率下降的主要原因,外界因素又通过气孔调节来影响蒸腾速率。光抑制是影响红砂光合午休的非气孔因素之一,且干旱加重了光抑制。在干旱胁迫下,叶绿素含量也是影响光合速率的主要原因。所有这些因素协同作用于红砂的光合作用,处于极端干旱环境中的红砂则通过降低蒸腾,提高水分利用率和稳定性碳同位素等途径来响应环境胁迫,从而提高对环境的适应性。

The photosynthetic characteristics and their control factors of Reaumuria soongorica from three geographical populations（LZJ,WWM,and ZYL） were studied under natural environment.The results showed that diurnal variations in net photosynthetic（Pn） rate and transpiration rate（Tr） of R.soongorica from different populations displayed a similar pattern-a bimodal curve but with an obvious depression in Pn,occurring in midday.Both environmental factors and internal biological causes of the plants played roles in controlling Pn and Tr.Among the environmental factors,photosynthetically active radiation（PAR） had a leading effect on both Pr and Tr while air temperature（Ta） affected less.Relative humidity（RH） affected more onTr than on Pn.It was also noted that the effects on Pn and Tr varied with the water contents in the soil where the plants grew.Among internal factors,stomatal conductance（Gs） was the major determinant of Pn which was concurrently determined by Tr that was affected by environmental factors via Gs.Photoinhibition which could be aggravated by water stress was also responsible for the midday depression in Pn.Chlorophyll was an additional factor affecting Pn under water stress condition.Although the mentioned factors may interactively influence on the photosynthesis,R.soongorica growing in different environments,in particular with super water stress,may adapt the adverse environments through adjusting their transpiration rates,increasing water use efficiency（WUE） and δ^13C.