Estimating photosynthetic electron transport via chlorophyll. uorometry without Photosystem II light saturation
Estimating photosynthetic electron transport via chlorophyll. uorometry without Photosystem II light saturation
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DOI：
10.1007/s11120-004-1454-3
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发表时间：
2004-01-01
影响因子：
3.7
通讯作者：
Ennahli, S
中科院分区：
文献类型：
--
作者：
Earl, HJ;Ennahli, S
叶绿素荧光测定法的类囊体电子传递速率（J（e））的估计通常与叶片气体交换测量结合使用，以提供有关叶片原位光合活性的详细信息。估算J（e）需要精确测定光系统II的量子效率（Phi（P）），这又需要光系统II捕光复合物的瞬时光饱和以诱导最大荧光信号（F-M ′）。在实践中，通常难以实现完全饱和，特别是当入射光合光子通量密度（Q）高并且能量通过非光化学猝灭有效地耗散时。本文提出了一种利用多个不同强度（Q '）的光脉冲来估算高Q下真实F-M'的方法。表观F-M'和Q'之间的预期关系的形式是从理论上推导出来的。这允许在无限Q'下的真实F-M'从线性回归估计。使用市售的叶气体交换/叶绿素荧光测量系统，在J（e）和A（G）之间的关系预期为线性的条件下，将J（e）与总光合CO2同化（A（G））进行比较。在环境空气中的C-4叶（Zea mays）和在非光呼吸条件下的C-3叶（Gossypium hirsutum）中，J（e）和A（G）之间的表观比率在高Q下下降，当Phi（P）由简单地使用最高可用饱和脉冲强度测量的F-M'计算时。当使用多脉冲/线性回归技术确定F-M'时，恢复了高Q时J（e）和A（G）之间的预期关系，表明Phi（P）估计得到改善。这种确定F-M'的方法应该证明对于验证饱和脉冲强度何时是足够的，以及对于精确地确定Phi（P）何时不是足够的是有用的。
Estimates of thylakoid electron transport rates (J(e)) from chlorophyll fluorometry are often used in combination with leaf gas exchange measurements to provide detailed information about photosynthetic activity of leaves in situ. Estimating J(e) requires accurate determination of the quantum efficiency of Photosystem II (Phi(P)), which in turn requires momentary light saturation of the Photosystem II light harvesting complex to induce the maximum fluorescence signal (F-M'). In practice, full saturation is often difficult to achieve, especially when incident photosynthetic photon flux density (Q) is high and energy is effectively dissipated by non-photochemical quenching. In the present work, a method for estimating the true F-M' under high Q was developed, using multiple light pulses of varying intensity (Q'). The form of the expected relationship between the apparent F-M' and Q' was derived from theoretical considerations. This allowed the true F-M' at infinite Q' to be estimated from linear regression. Using a commercially available leaf gas exchange/chlorophyll fluorescence measurement system, J(e) was compared to gross photosynthetic CO2 assimilation (A(G)) under conditions where the relationship between J(e) and A(G) was expected to be linear. Both in C-4 leaves (Zea mays) in ambient air and also in C-3 leaves (Gossypium hirsutum) under non-photorespiratory conditions the apparent ratio between J(e) and A(G) declined at high Q when Phi(P) was calculated from F-M' measured simply using the highest available saturating pulse intensity. When F-M' was determined using the multiple pulse/linear regression technique, the expected relationship between J(e) and A(G) at high Q was restored, indicating that the Phi(P) estimate was improved. This method of determining F-M' should prove useful for verifying when saturating pulse intensities are sufficient, and for accurately determining Phi(P) when they are not.