Ritchie Raymond J
School of Biological Sciences A-08, The University of Sydney, Sydney, NSW 2006, Australia.
Photosynth Res. 2008 Jun;96(3):201-15. doi: 10.1007/s11120-008-9300-7. Epub 2008 Apr 16.
A blue diode PAM (Pulse Amplitude Modulation) fluorometer was used to measure rapid Photosynthesis (P) versus Irradiance (E) curves (P vs. E curves) in Synechococcus (classical cyanobacteria), Prochlorothrix (prochlorophyta), Chlorella (chlorophyta), Rhodomonas (cryptophyta), Phaeodactylum (bacillariophyta) Acaryochloris (Chl d/a cyanobacteria) and Subterranean Clover (Trifolium subterraneum, Papilionaceae, Angiospermae). Effective quantum yield (Phi(PSII)) versus irradiance curves could be described by a simple exponential decay function (Phi(PSII) = Phi(PSII, maxe(-kE)) although Log/Log transformation was sometimes found to be necessary to obtain the best fits. Photosynthesis was measured as relative Electron Transport Rate (rETR) standardised on a chlorophyll basis. P versus E curves were fitted to the waiting-in-line function (an equation of the form P = P(max) x k x E x e(-kE)) allowing half-saturating and optimal irradiances (E(optimum)) to be estimated. The second differential of the equation shows that at twice optimal light intensities, there is a point of inflection in the P versus E curve. Photosynthesis is inhibited 26.4% at this point of inflection. The waiting-in-line model was found to be a very good descriptor of photosynthetic light saturation curves and superior to hyperbolic functions with an asymptotic saturation point (Michaelis-Menten, exponential saturation and hyperbolic tangent). The exponential constants (k) of the Phi(PSII) versus E and P versus E curves should be equal because rETR is directly proportional to Phi(PSII) x E. The conventionally calculated Non-Photochemical Quenching (NPQ) in Synechococcus was not significantly different to zero but NPQ versus E curves for the other algae could be fitted to an exponential saturation model. The kinetics of NPQ does not appear to be related to the kinetics of Phi(PSII) or rETR.
使用蓝色二极管脉冲幅度调制（PAM）荧光计来测量聚球藻属（经典蓝细菌）、原绿丝藻属（原绿藻）、小球藻属（绿藻）、红胞藻属（隐藻）、三角褐指藻属（硅藻）、蓝藻纲（叶绿素d/a蓝细菌）和地下三叶草（三叶草属，豆科，被子植物）中快速光合速率（P）与辐照度（E）的关系曲线（P-E曲线）。有效量子产率（Phi(PSII)）与辐照度的关系曲线可以用一个简单的指数衰减函数来描述（Phi(PSII)=Phi(PSII, max)e^(-kE)），不过有时发现进行对数/对数变换才能得到最佳拟合。光合速率以基于叶绿素标准化的相对电子传递速率（rETR）来衡量。P-E曲线拟合排队函数（形式为P = P(max)×k×E×e^(-kE)的方程），从而可以估算半饱和辐照度和最佳辐照度（E(optimum)）。该方程的二阶导数表明，在两倍最佳光强时，P-E曲线存在一个拐点。在这个拐点处，光合作用受到26.4%的抑制。排队模型被发现是光合光饱和曲线的一个非常好的描述方式，优于具有渐近饱和点的双曲线函数（米氏方程、指数饱和和双曲线正切）。Phi(PSII)与E以及P与E曲线的指数常数（k）应该相等，因为rETR与Phi(PSII)×E成正比。聚球藻属中按常规计算的非光化学猝灭（NPQ）与零没有显著差异，但其他藻类的NPQ与E曲线可以拟合到指数饱和模型。NPQ的动力学似乎与Phi(PSII)或rETR的动力学无关。
