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胡杨不同叶形光合特性、水分利用效率及其对加富CO2的响应
引用本文:苏培玺,张立新,杜明武,毕玉蓉,赵爱芬,刘新民.胡杨不同叶形光合特性、水分利用效率及其对加富CO2的响应[J].植物生态学报,2003,27(1):34-40.
作者姓名:苏培玺  张立新  杜明武  毕玉蓉  赵爱芬  刘新民
作者单位:中国科学院寒区旱区环境与工程研究所,沙坡头站,兰州,730000
基金项目:中国科学院“百人计划”,国家重点基础研究发展规划项目 (G2 0 0 0 0 4870 4),中国科学院重大项目 (KZCX1-0 9-0 2 )
摘    要: 胡杨(Populus euphratica Oliv.)叶形多变化,大致归纳为杨树叶(卵圆形叶)和柳树叶(披针形叶)两大类。在内蒙古额济纳旗胡杨林自然保护区,选择成年树同时具有卵圆形叶和披针形叶的标准株,将枝条拉至同一高度,通过活体测定,比较了其光合特征、水分利用效率及对CO2加富的响应。结果表明:在目前大气CO2浓度下,当光强为1 000 μmol·m-2·s-1时,卵圆形叶(成年树主要叶片)(A)和披针形叶(成年树下部萌条叶片)(B)的净光合速率(Pn)分别为16.40 μmol CO2·m-2·s-1和9.38 μmol CO2·m-2·s-1;水分利用效率(WUE)分别为1.52 mmol CO2·mol-1 H2O和1.18 mmol CO2·mol-1 H2O;A的光饱和点和补偿点分别为1 600 μmol·m-2·s-1和79 μmol·m-2·s-1,B的相对应值则为1 500 μmol·m m-2·s-1和168 μmol·m-2·s-1。当CO2浓度加富到450 μmol·mol-1时,A的光饱和点升高了150 μmol·m-2·s-1,光补偿点降低了36 μmol·m-2·s-1;而B的光饱和点降低了272 μmol·m-2·s-1,光补偿点则升高了32 μmol·m-2·s-1。这表明,柳树叶的光合效率较低,以维持生长为主;随着树体长大,柳树叶难以维系其生长,出现杨树叶,杨树叶更能耐大气干旱,光合效率高,通过积累光合产物,使胡杨在极端逆境下得以生存并能达到较高的生长量,这就是胡杨从幼苗到成年树叶形变化的原因。随着CO2加富,两种叶片表现出截然相反的响应,柳树叶的光合时间缩短,光能利用率减小;而杨树叶的光合时间延长,光能利用率提高。如果地下水位下降,近地层空气变干燥,或随着大气CO2浓度升高,气候变暖,柳树叶可能会逐渐减少以至消失。

关 键 词:光合作用  蒸腾作用  水分利用效率  CO2加富
修稿时间:2002年2月25日

PHOTOSYNTHETIC CHARACTER AND WATER USE EFFICIENCY OF DIFFERENT LEAF SHAPES OF POPULUS EUPHRATICA AND THEIR RESPONSE TO CO2 ENRICHMENT
SU Pei_Xi,ZHANG Li_Xin,DU Ming_Wu,BI Yu_Rong,ZHAO Ai_Fen and LIU Xin_Min.PHOTOSYNTHETIC CHARACTER AND WATER USE EFFICIENCY OF DIFFERENT LEAF SHAPES OF POPULUS EUPHRATICA AND THEIR RESPONSE TO CO2 ENRICHMENT[J].Acta Phytoecologica Sinica,2003,27(1):34-40.
Authors:SU Pei_Xi  ZHANG Li_Xin  DU Ming_Wu  BI Yu_Rong  ZHAO Ai_Fen and LIU Xin_Min
Abstract:Populus euphratica Oliv. is an important tree species of desert riparian forest. Leaf shape of P. euphratica is variable but can be roughly classified into two types, namely poplar leaf and willow leaf. Representative leaves of these types were ovate and lanceolate respectively. In this study some standard adult plants with both ovate leaves and lanceolate leaves were selected from the Nature Reserve of Populus euphratica in Ejin Qi, Inner Mongolia (41°58′ N, 101°05′ E, 930 m a.s.l.). In this measurement, the branches were put at the same height, then live leaves were measured and their photosynthesis, transpiration and water use efficiency were compared using the LI-6400 Portable Photosynthesis System of LI-cor; the response to CO2 enrichment was also ompared. The purpose of the study was to explore the cause responsible for the changes of leaf shape of P. euphratica, so as to provide a scientific basis for the protection of P. euphratica forest. In addition, the response of the different leaf shapes to increased CO2 concentration was analyzed and the possible effects of climatic changes on the growth of P. euphratica were predicted. The results showed that under present atmospheric CO2 concentration (350 μmol·mol-1) and 1 000 μmol·m-2·s-1 of light intensity, the net photosynthetic rates (Pn) of ovate leaves (leaf blades of adult tree) (A) and lanceolate leaves (lower coppica shoot leaves of adult tree) (B) are 16.40 μmol CO2·m-2·s-1 and 9.38 μmol CO2·m-2·s-1 respectively; transpiration rates (E) are 10.8 mmol H2O·m-2·s-1 and 7.98 mmol H2O·m-2·s-1 respectively; water use efficiency (WUE) is 1.52 mmol CO2·mol-1H2O and 1.18 mmol CO2·mol-1H2O respectively. Under these conditions, the light saturation and compensation points of A are 1 600 μmol·m-2·s-1 and 79 μmol·m-2·s-1 respectively, while the corresponding values of B are 1 500 μmol·m-2·s-1 and 168 μmol·m-2·s-1. When CO2 concentration reaches 450 μmol·mol-1 and 1 000 μmol·m-2·s-1 of light intensity, the photosynthetic characteristics of A and B exhibited quite different responses. The Pn of A increased by 25.6%, to 20.60 μmol CO2·m-2·s-1, whereas the Pn of B decreased by 10.0%, to 8.44 μmol CO2·m-2·s-1. The E of both A and B decreased; values were 9.11 mmol H2O·m-2·s-1 and 6.26 mmol H2O· m-2·s-1 respectively. The WUE of A and B was 2.26 mmol CO2·mol-1H2O and 1.35 mmol CO2·mol-1H2O respectively, i.e. WUE of A increased by 48.7% and WUE of B increased by 14.4%. The light saturation of A rises by 150 μmol·m-2·s-1 but light compensation point falls by 36 μmol·m-2·s-1, while the light saturation point of B falls by 272 μmol·m-2·s-1 and light compensation point rises by 32 μmol·m-2·s-1. The two types of leaf blade exhibit completely contrary responses to CO2 concentration elevation; the poplar leaves are more adapted to atmospheric CO2 concentration elevation. This study shows that the willow leaves have a lower photosynthetic efficiency and so are likely mainly used to maintain normal growth. With the growth of the tree the willow leaves can no longer support normal growth and hence poplar leaves occur. Poplar leaves have higher resistance to atmospheric drought and higher photosynthetic efficiency. They can accumulate photosynthetic products to maintain the growth of P. euphratica in extremely adverse environments and reach a higher increment. This seems to be the real cause responsible for leaf shape changes of P. euphratica from seedlings to adult trees. With the increase in CO2 concentration the photosynthetic time of willow leaves shortens and light use efficiency decreases, but poplar leaves show the opposite tendency in these two respects. When the ground water level decreases and near-surface air becomes dry, or with climate warming due to increasing atmospheric CO2 concentration, the numberof willow leaves are predicted to decrease, even disappear.
Keywords:Photosynthesis  Transpiration  Water use efficiency  CO2 enrichment  Diversiform-leaved poplar(Populus euphratica)  Desert  
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