Ögren Erling, Sundin Ulrika
Department of Plant Physiology, Umeå University, S-901 87, Umeå, Sweden.
Oecologia. 1996 Apr;106(1):18-27. doi: 10.1007/BF00334403.
Photosynthetic responses to variable light were compared for species from habitats differing in light availability and dynamics. Plants were grown under the same controlled conditions and were analysed for the kinetics of photosynthetic induction when photon flux density (PFD) was increased from 25 to 800 μmol ms. Gas exchange techniques were used to analyse the two principal components of induction, opening of stomata and activation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). On average, 90% of the final photosynthetic rate was attained after 7 min for obligate shade plants (two species), 18 min for fast-growing sun plants (seven species from productive habitats) and 32 min for slow-growing sun plants (nine species from unproductive habitats). The rapidity of response of the shade plants was explained by stomata remaining more open in the low-light period prior to induction. This was also observed in two species of deciduous trees, which therefore resembled shade plants rather than other fast-growing sun plants. The slow response of the slow-growing sun plants was the result of lower rates of both Rubisco activation and stomatal opening, the latter being more important for the final phase of induction. The lower rate of Rubisco activation was confirmed by direct, enzymatic measurements of representative plants. With increasing leaf age, the rate of stomatal opening appeared to decrease but the rate of Rubisco activation was largely conserved. Representative species were also compared with respect to the efficiency of using light-flecks relative to continuously high light. The shade plants and the slow-growing sun plants had a higher efficiency than the fast-growing sun plants. This could be related to the presence of a higher electron transport capacity relative to carboxylation capacity in the former group, which seems to be associated with their lower photosynthetic capacities. Representative species were also compared with respect to the ability to maintain the various induction components through periods of low light. Generally, the fast-growing sun plants were less able than the other two categories to maintain the rapidly reversible component. Thus, although the rate of induction appears to be related to the ecology of the plant, other aspects of photosynthetic dynamics, such as the efficiency of using lightflecks and the ability to maintain the rapidly reversible component, seem rather to be inversely related to the photosynthetic capacity.
对来自光照可用性和动态变化不同的栖息地的物种，比较了它们对可变光照的光合响应。植物在相同的受控条件下生长，并在光子通量密度（PFD）从25增加到800 μmol m⁻² s⁻¹时，分析其光合诱导动力学。采用气体交换技术分析诱导的两个主要成分，即气孔开放和1,5-二磷酸核酮糖羧化酶/加氧酶（Rubisco）的激活。平均而言，专性阴生植物（两个物种）在7分钟后达到最终光合速率的90%，速生阳生植物（来自高产栖息地的七个物种）在18分钟后达到，慢生阳生植物（来自低产栖息地的九个物种）在32分钟后达到。阴生植物响应迅速的原因是在诱导前的低光照期气孔保持更开放。在两种落叶树中也观察到了这一点，因此它们类似于阴生植物，而不是其他速生阳生植物。慢生阳生植物响应缓慢是Rubisco激活速率和气孔开放速率较低的结果，后者对诱导的最后阶段更为重要。通过对代表性植物的直接酶促测量证实了Rubisco激活速率较低。随着叶片年龄的增加，气孔开放速率似乎降低，但Rubisco激活速率在很大程度上保持不变。还比较了代表性物种在利用光斑相对于持续高光的效率方面的差异。阴生植物和慢生阳生植物的效率高于速生阳生植物。这可能与前一组中相对于羧化能力存在更高的电子传递能力有关，这似乎与它们较低的光合能力有关。还比较了代表性物种在低光照期维持各种诱导成分的能力。一般来说，速生阳生植物比其他两类植物更难维持快速可逆成分。因此，尽管诱导速率似乎与植物的生态有关，但光合动力学的其他方面，如利用光斑的效率和维持快速可逆成分的能力，似乎与光合能力呈负相关。
