Zhen Shuyang, van Iersel Marc W
Department of Horticulture, University of Georgia, 1111 Miller Plant Science Building, Athens, GA 30602, USA.
J Plant Physiol. 2017 Feb;209:115-122. doi: 10.1016/j.jplph.2016.12.004. Epub 2016 Dec 15.
The efficiency of monochromatic light to drive photosynthesis drops rapidly at wavelengths longer than 685nm. The photosynthetic efficiency of these longer wavelengths can be improved by adding shorter wavelength light, a phenomenon known as the Emerson enhancement effect. The reverse effect, the enhancement of photosynthesis under shorter wavelength light by longer wavelengths, however, has not been well studied and is often thought to be insignificant. We quantified the effect of adding far-red light (peak at 735nm) to red/blue or warm-white light on the photosynthetic efficiency of lettuce (Lactuca sativa). Adding far-red light immediately increased quantum yield of photosystem II (Φ) of lettuce by an average of 6.5 and 3.6% under red/blue and warm-white light, respectively. Similar or greater increases in Φ were observed after 20min of exposure to far-red light. This longer-term effect of far-red light on Φ was accompanied by a reduction in non-photochemical quenching of fluorescence (NPQ), indicating that far-red light reduced the dissipation of absorbed light as heat. The increase in Φ and complementary decrease in NPQ is presumably due to preferential excitation of photosystem I (PSI) by far-red light, which leads to faster re-oxidization of the plastoquinone pool. This facilitates reopening of PSII reaction centers, enabling them to use absorbed photons more efficiently. The increase in Φ by far-red light was associated with an increase in net photosynthesis (P). The stimulatory effect of far-red light increased asymptotically with increasing amounts of far-red. Overall, our results show that far-red light can increase the photosynthetic efficiency of shorter wavelength light that over-excites PSII.
波长超过685nm时，单色光驱动光合作用的效率会迅速下降。通过添加较短波长的光，可以提高这些较长波长的光合效率，这种现象被称为爱默生增强效应。然而，相反的效应，即较长波长的光对较短波长光下光合作用的增强作用，尚未得到充分研究，并且通常被认为是微不足道的。我们量化了在红/蓝光或暖白光中添加远红光（峰值在735nm）对生菜（Lactuca sativa）光合效率的影响。添加远红光后，生菜光系统II的量子产率（Φ）在红/蓝光和暖白光条件下分别平均立即提高了6.5%和3.6%。在暴露于远红光20分钟后，观察到Φ有相似或更大的增加。远红光对Φ的这种长期影响伴随着荧光非光化学猝灭（NPQ）的降低，这表明远红光减少了吸收光以热的形式耗散。Φ的增加和NPQ的互补性降低可能是由于远红光优先激发光系统I（PSI），这导致质体醌库更快地再氧化。这有助于光系统II反应中心重新开放，使其能够更有效地利用吸收的光子。远红光使Φ增加与净光合作用（P）的增加相关。远红光的刺激作用随着远红光量的增加而渐近增加。总体而言，我们的结果表明，远红光可以提高过度激发光系统II的较短波长光的光合效率。
