Kirschbaum Miko U F, Ohlemacher Christian, Küppers Manfred
CSIRO Forestry and Forest Products, PO Box E4008, ACT 2604 Kingston, Australia.
Planta. 2004 Apr;218(6):1046-53. doi: 10.1007/s00425-003-1186-1. Epub 2004 Jan 13.
It has generally been assumed that the photosynthetic quantum yield of all C3 plants is essentially the same for all unstressed leaves at the same temperature and CO2 and O2 concentrations. However, some recent work by H.C. Timm et al. (2002, Trees 16:47-62) has shown that quantum yield can be reduced for some time after leaves have been exposed to darkness. To investigate under what light conditions quantum yield can be reduced, we carried out a number of experiments on leaves of a partial-shade (unlit greenhouse)-grown Coleus blumei Benth. hybrid. We found that after leaves had been exposed to complete darkness, quantum yield was reduced by about 60%. Only very low light levels were needed for quantum yield to be fully restored, with 5 micromol quanta m(-2) s(-1) being sufficient for 85% of the quantum yield of fully induced leaves to be achieved. Leaves regained higher quantum yields upon exposure to higher light levels with an estimated time constant of 130 s. It was concluded that the loss of quantum yield would be quantitatively important only for leaves growing in very dense understoreys where maximum light levels might not exceed 5 micromol quanta m(-2) s(-1) even in the middle of the day. Most leaves, even in understorey conditions, do, however, experience light levels in excess of 5 micromol quanta m(-2) s(-1) over periods where they obtain most of their carbon so that the loss of quantum yield would affect total carbon gain of those leaves only marginally.
人们通常认为，在相同温度、二氧化碳和氧气浓度下，所有C3植物未受胁迫叶片的光合量子产率基本相同。然而，H.C. 蒂姆等人（2002年，《树木》16:47 - 62）最近的一些研究表明，叶片在黑暗中暴露一段时间后，量子产率可能会降低。为了研究在何种光照条件下量子产率会降低，我们对一种在部分遮荫（未照明温室）环境中生长的彩叶草杂交种的叶片进行了一系列实验。我们发现，叶片在完全黑暗中暴露后，量子产率降低了约60%。只需非常低的光照水平就能使量子产率完全恢复，5微摩尔光子·米⁻²·秒⁻¹就足以达到完全诱导叶片85%的量子产率。叶片在暴露于更高光照水平时，以估计130秒的时间常数恢复到更高的量子产率。得出的结论是，量子产率的损失仅对于生长在非常浓密下层植被中的叶片在数量上具有重要意义，在那里即使在中午，最大光照水平可能也不会超过5微摩尔光子·米⁻²·秒⁻¹。然而，大多数叶片，即使是在下层植被条件下，在获取大部分碳的时间段内确实会经历超过5微摩尔光子·米⁻²·秒⁻¹的光照水平，因此量子产率的损失只会对那些叶片的总碳获取产生轻微影响。
