Department of Botany and Plant Sciences, University of California, 2150 Batchelor Hall, Riverside, CA 92521, USA.
Oecologia. 2012 Feb;168(2):311-9. doi: 10.1007/s00442-011-2099-5. Epub 2011 Aug 12.
We investigated how photosynthesis by understory seedlings of the lowland tropical tree species Alseis blackiana responded to 10 years of soil nutrient fertilization with N, P and K. We ask whether nutrients are limiting to light and CO(2) acquisition in a low light understory environment. We measured foliar nutrient concentrations of N, P and K, isotopic composition of carbon (δ(13)C) and nitrogen (δ(15)N), and light response curves of photosynthesis and chlorophyll fluorescence. Canopy openness was measured above each study seedling and included in statistical analyses to account for variation in light availability. Foliar N concentration increased by 20% with N addition. Foliar P concentration increased by 78% with P addition and decreased by 14% with N addition. Foliar K increased by 8% with K addition. Foliar δ(13)C showed no significant responses, and foliar δ(15)N decreased strongly with N addition, matching the low δ(15)N values of applied fertilizer. Canopy openness ranged from 0.01 to 6.71% with a mean of 1.76 ± 0.14 (± 1SE). Maximum photosynthetic CO(2) assimilation rate increased by 9% with N addition. Stomatal conductance increased with P addition and with P and K in combination. Chlorophyll fluorescence measurements revealed that quantum yield of photosystem II increased with K addition, maximum electron transport rate trended 9% greater with N addition (p = 0.07), and saturating photosynthetically active radiation increased with N addition. The results demonstrate that nutrient addition can enhance photosynthetic processes, even under low light availability.
我们研究了低地热带树种 Alseis blackiana 的林下幼苗的光合作用如何对 10 年的氮、磷和钾土壤养分施肥做出响应。我们想知道在低光照林下环境中，养分是否对光和 CO₂的获取有限制。我们测量了叶片的氮、磷和钾浓度、碳（δ¹³C）和氮（δ¹⁵N）的同位素组成，以及光合作用和叶绿素荧光的光响应曲线。在每个研究幼苗的上方测量了冠层开度，并将其包含在统计分析中，以解释光照可用性的变化。氮添加使叶片 N 浓度增加了 20%。磷添加使叶片 P 浓度增加了 78%，氮添加使叶片 P 浓度降低了 14%。钾添加使叶片 K 增加了 8%。叶片 δ¹³C 没有明显的响应，而叶片 δ¹⁵N 随着氮的添加而强烈降低，与应用肥料的低 δ¹⁵N 值相匹配。冠层开度范围为 0.01 至 6.71%，平均值为 1.76 ± 0.14（± 1SE）。氮添加使最大光合作用 CO₂同化率增加了 9%。气孔导度随着磷的添加以及磷和钾的共同添加而增加。叶绿素荧光测量显示，光合系统 II 的量子产量随着钾的添加而增加，最大电子传递率在氮添加时增加了 9%（p = 0.07），饱和光合有效辐射随着氮的添加而增加。结果表明，即使在低光照条件下，养分添加也可以增强光合作用过程。
