Hikosaka Kouki, Takashima Teruyuki, Kabeya Daisuke, Hirose Tadaki, Kamata Naoto
Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan.
Ann Bot. 2005 May;95(6):1025-32. doi: 10.1093/aob/mci111. Epub 2005 Mar 10.
Both nutrient availability and defoliation affect the carbon-nutrient balance in plants, which in turn influences biomass allocation (e.g. shoot-to-root ratio) and leaf chemical composition (concentration of nitrogen and secondary compounds). In this study it is questioned whether defoliation alters biomass allocation and chemical defence in a similar fashion to the response to nutrient deficiency.
Current-year seedlings of Quercus serrata were grown with or without removal of all leaves at three levels of nutrient availability.
Plant nitrogen concentration (PNC), a measure of the carbon-nutrient balance in the plant, significantly decreased immediately after defoliation because leaves had higher nitrogen concentrations than stems and roots. However, PNC recovered to levels similar to or higher than that of control plants in 3 or 6 weeks after the defoliation. Nitrogen concentration of leaves produced after defoliation was significantly higher than leaf nitrogen concentration of control leaves. Leaf mass per plant mass (leaf mass ratio, LMR) was positively correlated with PNC but the relationship was significantly different between defoliated and control plants. When compared at the same PNC, defoliated plants had a lower LMR. However, the ratio of the leaf to root tissues that were newly produced after defoliation as a function of PNC did not differ between defoliated and control plants. Defoliated plants had a significantly lower concentration of total phenolics and condensed tannins. Across defoliated and control plants, the leaf tannin concentration was negatively correlated with the leaf nitrogen concentration, suggesting that the amount of carbon-based defensive compounds was controlled by the carbon-nutrient balance at the leaf level.
Defoliation alters biomass allocation and chemical defence through the carbon-nutrient balance at the plant and at the leaf level, respectively.
养分有效性和去叶处理都会影响植物的碳养分平衡，进而影响生物量分配（如茎根比）和叶片化学成分（氮和次生化合物的浓度）。本研究探讨去叶处理是否会以与养分缺乏反应类似的方式改变生物量分配和化学防御。
在三种养分有效性水平下，对当年生的枹栎幼苗进行去叶或不去叶处理。
植物氮浓度（PNC）是衡量植物碳养分平衡的指标，去叶后立即显著降低，因为叶片的氮浓度高于茎和根。然而，去叶后3或6周，PNC恢复到与对照植物相似或更高的水平。去叶后产生的叶片氮浓度显著高于对照叶片的氮浓度。单株植物质量的叶质量（叶质量比，LMR）与PNC呈正相关，但去叶植物和对照植物之间的关系显著不同。在相同的PNC下比较时，去叶植物的LMR较低。然而，去叶后新产生的叶与根组织的比例作为PNC的函数，去叶植物和对照植物之间没有差异。去叶植物的总酚和缩合单宁浓度显著较低。在去叶植物和对照植物中，叶片单宁浓度与叶片氮浓度呈负相关，表明碳基防御化合物的量受叶片水平的碳养分平衡控制。
去叶分别通过植物水平和叶片水平的碳养分平衡改变生物量分配和化学防御。
