Weber J A, Jurik T W, Tenhunen J D, Gates D M
Biological Station and Botanical Gardens, University of Michigan, 48109-1048, Ann Arbor, MI, USA.
Oecologia. 1985 Feb;65(3):338-347. doi: 10.1007/BF00378907.
In the field, photosynthesis of Acer saccharum seedlings was rarely light saturated, even though light saturation occurs at about 100 μmol quanta m s photosynthetic photon flux density (PPFD). PPFD during more than 75% of the daylight period was 50 μmol m s or less. At these low PPFD's there is a marked interaction of PPFD with the initial slope (CE) of the CO response. At PPFD-saturation CE was 0.018 μmol m s/(μl/l). The apparent quantum efficiency (incident PPFD) at saturating CO was 0.05-0.08 mol/mol. [Formula: see text] and PPFD-saturated CO exchange was 6-8 μmol m s. The ratio of internal CO concentration to external (C /C ) was 0.7 to 0.8 except during sunflecks when it decreased to 0.5. The decrease in C /C during sunflecks was the result of the slow response of stomates to increased PPFD compared to the response of net photosynthesis. An empirical model, which included the above parameters was used to simulate the measured CO exchange rate for portions of two days. Parameter values for the model were determined in experiments separate from the daily time courses being sumulated. Analysis of the field data, partly through the use of simulations, indicate that the elimination of sunflecks would reduce net carbon gain by 5-10%.
在野外，糖槭幼苗的光合作用很少达到光饱和，尽管在光合光子通量密度（PPFD）约为100 μmol 量子·m⁻²·s⁻¹时会出现光饱和。超过75%的白天时段内PPFD为50 μmol·m⁻²·s⁻¹或更低。在这些低PPFD条件下，PPFD与CO₂响应的初始斜率（CE）存在显著相互作用。在PPFD饱和时，CE为0.018 μmol·m⁻²·s⁻¹/(μl/l)。在CO₂饱和时的表观量子效率（入射PPFD）为0.05 - 0.08 mol/mol。[公式：见原文]且PPFD饱和时的CO₂交换量为6 - 8 μmol·m⁻²·s⁻¹。内部CO₂浓度与外部CO₂浓度之比（Ci/Ca）为0.7至0.8，但在光斑期间会降至0.5。光斑期间Ci/Ca的降低是由于气孔对PPFD增加的响应比对净光合作用的响应慢。一个包含上述参数的经验模型被用于模拟两天内部分时段测量的CO₂交换率。该模型的参数值是在与所模拟的每日时间进程分开的实验中确定的。对野外数据的分析，部分通过模拟表明，消除光斑会使净碳增益减少5 - 10%。
