Photosynthetic acclimation and resource use by the C3 and C4 subspecies of Alloteropsis semialata in low CO2 atmospheres
Photosynthetic acclimation and resource use by the C3 and C4 subspecies of Alloteropsis semialata in low CO2 atmospheres
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DOI：
10.1111/gcb.12091
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发表时间：
2013-03
影响因子：
11.6
通讯作者：
B. Ripley;J. Cunniff;C. Osborne
中科院分区：
文献类型：
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作者：
B. Ripley;J. Cunniff;C. Osborne
在过去的2500万年，大气CO2分压（Ca）对C3比C4光合作用施加了更大的限制。这可能对植物氮经济和生物量分配产生重要的下游影响。在这里，我们报告的第一次亚环境钙对光合作用，生长和氮分配模式的综合影响的遗传控制比较，比较C3和C4亚种的Alloteropsis semialata。在低钙条件下，C3比C4亚种的植株大小下降更多，但氮库大小不变，所有植株分区的氮浓度均增加。C3，而不是C4亚种，优先分配生物量的叶片和增加比叶面积在低钙。在C3亚种中，叶氮增加与间冰期Ca的光合适应有关，通过更高的光合能力和更大的气孔导度介导。冰川钙进一步增加了C3亚种的生化驯化和氮浓度，但这些都不足以维持光合速率。相反，C4亚种保持光合速率，氮和水的利用效率和植物生物量在间冰期和冰期钙最小的生理调整。因此，在低Ca下，C4碳浓缩机制在整个植物规模的碳获取方面提供了优于C3类型的显著优势，显然是通过氮经济和水分损失介导的。有限的营养供应阻尼生物量响应钙和增加C4优势在所有的钙处理。研究结果强调了在整个植物的背景下考虑叶响应的重要性，并表明碳限制可能会以牺牲植物对土壤资源（如氮和水）的更大需求为代价来抵消。结果表明，低CO2和资源限制的综合影响有利于C3植物在冰川间冰期环境中的C4植物，但这种优势是减少在人为条件下。
During the past 25 Myr, partial pressures of atmospheric CO2 (Ca) imposed a greater limitation on C3 than C4 photosynthesis. This could have important downstream consequences for plant nitrogen economy and biomass allocation. Here, we report the first phylogenetically controlled comparison of the integrated effects of subambient Ca on photosynthesis, growth and nitrogen allocation patterns, comparing the C3 and C4 subspecies of Alloteropsis semialata. Plant size decreased more in the C3 than C4 subspecies at low Ca, but nitrogen pool sizes were unchanged, and nitrogen concentrations increased across all plant partitions. The C3, but not C4 subspecies, preferentially allocated biomass to leaves and increased specific leaf area at low Ca. In the C3 subspecies, increased leaf nitrogen was linked to photosynthetic acclimation at the interglacial Ca, mediated via higher photosynthetic capacity combined with greater stomatal conductance. Glacial Ca further increased the biochemical acclimation and nitrogen concentrations in the C3 subspecies, but these were insufficient to maintain photosynthetic rates. In contrast, the C4 subspecies maintained photosynthetic rates, nitrogen‐ and water‐use efficiencies and plant biomass at interglacial and glacial Ca with minimal physiological adjustment. At low Ca, the C4 carbon‐concentrating mechanism therefore offered a significant advantage over the C3 type for carbon acquisition at the whole‐plant scale, apparently mediated via nitrogen economy and water loss. A limiting nutrient supply damped the biomass responses to Ca and increased the C4 advantage across all Ca treatments. Findings highlight the importance of considering leaf responses in the context of the whole plant, and show that carbon limitation may be offset at the expense of greater plant demand for soil resources such as nitrogen and water. Results show that the combined effects of low CO2 and resource limitation benefit C4 plants over C3 plants in glacial–interglacial environments, but that this advantage is lessened under anthropogenic conditions.