Photosynthetic responses to slowly decreasing leaf water potentials in Encelia frutescens
Photosynthetic responses to slowly decreasing leaf water potentials in Encelia frutescens
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DOI：
10.1007/bf00396767
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发表时间：
1984-02
期刊：
影响因子：
2.7
通讯作者：
J. Comstock;J. Ehleringer
中科院分区：
文献类型：
--
作者：
J. Comstock;J. Ehleringer
在莫哈德和索诺兰沙漠的一种干旱落叶亚灌木Encelia rutescens中，研究了水分胁迫期间叶片导度(气孔层和边界层)降低在限制光合作用速率中的重要性。温室植物光饱和CO2同化速率由42.6±1.6molCO2m-2s-1(x±S.E.)μ当叶片水势从-1.5Mpa降至-4.0Mpa时，叶片水势下降到1.7molCO2m-2s-1.7±1.7mmolCO2m-2s-1.当叶片水势从-1.5Mpa降至-4.0Mpa时，μmolCO2m-2s-1s-1。在60~335μL·L-1浓度范围内，随着叶片水势的下降，光饱和度、CO2同化速率与叶片胞间CO2浓度的依赖关系也被测定。这使得我们能够比较叶片水势对由叶片电导率和内在光合作用能力施加的碳同化限制的影响。叶片电导率和内源光合作用能力均随叶片水势的降低而降低，但叶片电导率的下降幅度相对较大。相对气孔限制，定义为由于气相扩散障碍的存在而导致的光合作用速率的百分比限制，从(x±S.E.)随着水势变得更负，下降到41%±3%。然而，由于叶片电导率和内在光合作用能力在绝对意义上都严重降低，如果不同时提高这两个组分，就不可能在低叶水势下恢复较高的光合速率。
The importance of reduced leaf conductance (stomatal and boundary layer) in limiting photosynthetic rates during water stress was studied inEncelia frutescens, a drought-deciduous leaved subshrub of the Mohave and Sonoran Deserts. Light-saturated CO2assimilation rates of greenhouse grown plants decreased from 42.6±1.6μmol CO2m-2s-1(x±s.e.) to 1.7±1.7 μmol CO2m-2s-1as leaf water potential decreased from-1.5 MPa to-4.0 MPa. The dependence of light saturated, CO2assimilation rate on leaf intercellular CO2concentrations between 60 and 335 μl l-1was also determined as leaf water potential decline. This enabled us to compare the effects of leaf water potentials on limitations to carbon assimilation imposed by leaf conductance and by intrinsic photosynthetic capacity. Both leaf conductance and intrinsic photosynthetic capacity decreased with decreasing leaf water potential, but the decrease in leaf conductance was proportionately greater. The relative stomatal limitation, defined as the percent limitation in photosynthetic rate due to the presence of gas-phase diffusional barriers, increased from (x±s.e.) to 41±3% as water potentials became more negative. Since both leaf conductance and intrinsic photosynthetic capacity were severely reduced in an absolute sense, however, high photosynthetic rates could not have been restored at low leaf water potentials without simultaneous increases in both components.