Yanhong Tang, Hiroshi Koizumi, Mitsumasa Satoh, Izumi Washitani
Division of Plant Ecology, National Institute of Agro-Environmental Sciences, 305, Tsukuba, Ibaraki, Japan.
Institute of Biological Sciences, University of Tsukuba, 305, Tsukuba, Ibaraki, Japan.
Oecologia. 1994 Dec;100(4):463-469. doi: 10.1007/BF00317868.
Photosynthetic-induction response and light-fleck utilization were investigated for the current-year seedlings of Quercus serrata, a deciduous tree found in temperate regions of Japan. The tree seedlings were grown under three light regimes: a constant low photosynthetic photon flux density (PFD) regime of 50 μmol m s, a constant high PFD regime of 500 μmol m s, and a lightfleck regime with alternated low (lasting 5 s) and high (lasting 35 s) PFD. The photosynthetic-induction response following a sudden increase of PFD from 50 to 500 μmol m s exhibited two phases: an initial fast increase complete within 3-5 s, and a second slow increase lasting for 15-20 min. Induction times required to reach 50% and 90% of steady-state assimilation rates were significantly shorter in leaves from the constant low PFD than those from the high PFD regime. During the first 60-100 s, the ratio of observed integrated CO uptake to that predicted by assuming that a steady-state assimilation would be achieved instantaneously after the light increase was significantly higher for leaves from the low PFD regime than from the high PFD regime. Lightfleck utilization was examined for various durations of PFD of 500 μmol m s on a background PFD of 50 μmol m s. Lightfleck utilization efficiency was significantly higher in low PFD leaves than in the high PFD leaves for 5-s and 10-s lightflecks, but showed no difference among different light regimes for 100-s lightflecks. The contribution of post-illumination CO fixation to total carbon gain decreased markedly with increasing lightfleck durations, but exhibited no significant difference among growth regimes. Photosynthetic performances of induction response and lightfleck utilization in leaves from the lightfleck regime were more similar to those in leaves from the low PFD regime. It may be the total daily PFD rather than PFD dynamics in light regimes that affects the characteristics of transient photosynthesis in Q. serrata seedlings.
对日本温带地区的落叶树枹栎当年生幼苗的光合诱导响应和光斑利用情况进行了研究。这些树苗在三种光照条件下生长：恒定低光合光子通量密度（PFD）为50 μmol m⁻² s⁻¹的条件、恒定高PFD为500 μmol m⁻² s⁻¹的条件，以及低（持续5秒）高（持续35秒）PFD交替的光斑条件。当PFD从50突然增加到500 μmol m⁻² s⁻¹时，光合诱导响应呈现两个阶段：初始快速增加在3 - 5秒内完成，第二个缓慢增加持续15 - 20分钟。达到稳态同化率50%和90%所需的诱导时间，在恒定低PFD条件下的叶片中显著短于高PFD条件下的叶片。在最初的60 - 100秒内，低PFD条件下的叶片中，观测到的累积CO₂吸收量与假设光照增加后立即达到稳态同化所预测的吸收量之比，显著高于高PFD条件下的叶片。在50 μmol m⁻² s⁻¹的背景PFD下，对500 μmol m⁻² s⁻¹的不同持续时间的PFD光斑利用情况进行了检测。对于5秒和10秒的光斑，低PFD叶片的光斑利用效率显著高于高PFD叶片，但对于100秒的光斑，不同光照条件之间没有差异。光照后CO₂固定对总碳增益的贡献随着光斑持续时间的增加而显著降低，但在不同生长条件之间没有显著差异。光斑条件下叶片的光合诱导响应和光斑利用的光合性能，与低PFD条件下的叶片更为相似。可能是每日总PFD而非光照条件下的PFD动态影响了枹栎幼苗瞬时光合作用的特征。
