摘要
胡杨 (PopuluseuphraticaOliv .)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 10 0 0 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 μmolCO2 ·m-2 ·s-1和 9.38μmolCO2 ·m-2 ·s-1;水分利用效率 (WUE)分别为 1.5 2mmolCO2 ·mol-1H2 O和 1.18mmolCO2 ·mol-1H2 O ;A的光饱和点和补偿点分别为 16 0 0 μmol·m-2 ·s-1和 79μmol·m-2 ·s-1,B的相对应值则为 15 0 0 μmol·m-2 ·s-1和 16 8μmol·m-2 ·s-1。当CO2 浓度加富到 45 0 μmol·mol-1时 ,A的光饱和点升高了 15 0μmol·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 2 72 μmol·m-2 ·s-1,光补偿点则升高了 32μmol·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 ,
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 CO 2 enrichment was also compared. 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 CO 2 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 CO 2 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 CO 2·m -2 ·s -1 and 9.38 μmol CO 2·m -2 ·s -1 respectively; transpiration rates ( E ) are 10.8 mmol H 2O·m -2 ·s -1 and 7.98 mmol H 2O·m -2 ·s -1 respectively; water use efficiency ( WUE ) is 1.52 mmol CO 2·mol -1 H 2O and 1.18 mmol CO 2·mol -1 H 2O 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 CO 2 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 CO 2·m -2 ·s -1 , whereas the Pn of B decreased by 10.0%, to 8.44 μmol CO 2·m -2 ·s -1 . The E of both A and B decreased; values were 9.11 mmol H 2O·m -2 ·s -1 and 6.26 mmol H 2O·m -2 ·s -1 respectively. The WUE of A and B was 2.26 mmol CO 2·mol -1 H 2O and 1.35 mmol CO 2·mol -1 H 2O 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 CO 2 concentration elevation; the poplar leaves are more adapted to atmospheric CO 2 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 CO 2 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
出处
《植物生态学报》
CAS
CSCD
北大核心
2003年第1期34-40,共7页
Chinese Journal of Plant Ecology
基金
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 )
关键词
胡杨
叶形
光合特性
水分利用效率
蒸腾作用
CO2加富
荒漠
响应
Photosynthesis,Transpiration,Water use efficiency,CO2 enrichment,Diversiform-leaved poplar(Populus euphratica),Desert
