Relative enhancement of photosynthesis and growth at elevated CO2 is greater under sunflecks than uniform irradiance in a tropical rain forest tree seedling
Relative enhancement of photosynthesis and growth at elevated CO2 is greater under sunflecks than uniform irradiance in a tropical rain forest tree seedling
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DOI：
10.1046/j.1365-3040.2002.00944.x
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发表时间：
2002-12-01
影响因子：
7.3
通讯作者：
Watling, JR
中科院分区：
文献类型：
--
作者：
Leakey, ADB;Press, MC;Watling, JR
在东南亚热带雨林的浓荫下，龙脑果幼苗的生存受到其维持正碳平衡的能力的限制。日照期间的光合作用是碳吸收的重要组成部分。为了研究CO2浓度升高对日照条件下光合作用和生长的影响，在可控的环境条件下，研究了CO2浓度升高对麻风藻幼苗生长的影响。等日总光子通量密度(类似7.7molm(-2)d(-1))以均匀辐照度(类似于170mumol m(-2)S(-1))或阴影/斑点序列(类似于30mumol m(-2)S(-1)/类似于525mumol m(-2)S(-1))提供。高CO2处理促进了光合作用和生长，而斑点光照处理则抑制了光合作用和生长。光合作用能力的适应发生在对二氧化碳浓度升高的响应中，而不是点状光照。重要的是，与均匀光照(生长25%，碳增益59%)相比，在日照下(生长60%，碳增益89%)，高二氧化碳的相对增强效应更大。这是由两个因素驱动的：(1)更高的动态光合作用效率(光合作用诱导得与失，光照后气体交换)；(2)在很低的PFD时，光合作用增强最大。这使得在光斑聚集期(73%)和深影间隔期(99%)获得了更好的碳增量。在日照下CO2浓度升高时，生长和光合作用相对较大的促进对苗木更新过程具有重要的潜在影响，从而对森林结构和组成具有重要的潜在影响。
The survivorship of dipterocarp seedlings in the deeply shaded understorey of South-east Asian rain forests is limited by their ability to maintain a positive carbon balance. Photosynthesis during sunflecks is an important component of carbon gain. To investigate the effect of elevated CO2 upon photosynthesis and growth under sunflecks, seedlings of Shorea leprosula were grown in controlled environment conditions at ambient or elevated CO2. Equal total daily photon flux density (PFD) (similar to7.7 mol m(-2) d(-1)) was supplied as either uniform irradiance (similar to170 mumol m(-2) s(-1)) or shade/fleck sequences (similar to30 mumol m(-2) s(-1)/similar to525 mumol m(-2) s(-1)). Photosynthesis and growth were enhanced by elevated CO2 treatments but lower under flecked irradiance treatments. Acclimation of photosynthetic capacity occurred in response to elevated CO2 but not flecked irradiance. Importantly, the relative enhancement effects of elevated CO2 were greater under sunflecks (growth 60%, carbon gain 89%) compared with uniform irradiance (growth 25%, carbon gain 59%). This was driven by two factors: (1) greater efficiency of dynamic photosynthesis (photosynthetic induction gain and loss, post-irradiance gas exchange); and (2) photosynthetic enhancement being greatest at very low PFD. This allowed improved carbon gain during both clusters of lightflecks (73%) and intervening periods of deep shade (99%). The relatively greater enhancement of growth and photosynthesis at elevated CO2 under sunflecks has important potential consequences for seedling regeneration processes and hence forest structure and composition.