Stomatal and mesophyll limitations of photosynthesis in black spruce seedlings during multiple cycles of drought.
Stomatal and mesophyll limitations of photosynthesis in black spruce seedlings during multiple cycles of drought.
复制标题
多个干旱周期期间黑云杉幼苗光合作用的气孔和叶肉限制。
作者：
J. D. Stewart;A. Zine El Abidine;P. Bernier
集装箱栽培的黑云杉（Picea mariana（Mill.）B.S.P.）将幼苗种植在含有沙子和泥炭混合物的托盘中，并置于气候受控的温室中。一组幼苗保持充足的水分，另一组经受三个周期的干旱。气体交换分析表明，叶肉光合功能在很大程度上不受干旱的影响。相反，气孔导度对干旱敏感，但随着干旱周期的增加，气孔导度的敏感性降低。在对照和干旱胁迫下，气孔和叶肉导度均随时间增加，但叶肉导度随时间的增加比气孔导度更快。叶肉对光合速率的限制作用占主导地位。在对照幼苗中，相对气孔限制从6%增加到16%的实验结束。在干旱胁迫下，幼苗光合作用的相对气孔限制在第一次干旱时达到40%，但复水后立即下降到接近对照值。由于第三，最严重的干旱对气孔导度只有轻微的影响，光合作用的相对气孔限制是相似的，在控制幼苗的实验结束。在干旱胁迫过程中抑制个体发育变化可能是叶肉光合过程明显驯化的原因。我们的结论是，这将是更有效的选择高光合能力比降低气孔敏感性时，育种提高黑云杉幼苗的抗旱性。
Container-grown black spruce (Picea mariana (Mill.) B.S.P.) seedlings were planted in trays containing a sand and peat mixture, and placed in a climate-controlled greenhouse. One group of seedlings was kept well-watered, and another group was subjected to three cycles of drought. Gas exchange analysis showed that mesophyll photosynthetic function was largely unimpaired by drought. In contrast, stomatal conductance was sensitive to drought, although it became less sensitive with each drought cycle. Both stomatal and mesophyll conductances increased with time in control and drought-stressed seedlings, but mesophyll conductance increased with time more rapidly than did stomatal conductance. Limitation of photosynthetic rate was dominated by the mesophyll. In control seedlings, relative stomatal limitation increased from 6 to 16% by the end of the experiment. In drought-stressed seedlings, relative stomatal limitation of photosynthesis reached 40% during the first drought, but decreased to near control values immediately after rewatering. Because the third, most severe drought had only a minor effect on stomatal conductance, relative stomatal limitation of photosynthesis was similar to that in control seedlings by the end of the experiment. Inhibition of ontogenetic change during drought stress may be responsible for the apparent acclimation of mesophyll photosynthetic processes. We conclude that it would be more effective to select for high photosynthetic capacity than for reduced stomatal sensitivity when breeding for increased drought resistance in black spruce seedlings.