摘要: 目的杨树的叶和细根在森林生态系统碳和养分（如氮、磷等）循环中起核心作用，但目前细根对臭氧（O ₃）胁迫响应的研究还较缺乏，尚不清楚叶和细根对O ₃胁迫的响应差异。本研究旨在阐明叶片和细根这2个快速分解器官对O ₃剂量的响应差异，为从植物地上-地下反馈角度理解杨树对O ₃污染的响应机制提供科学参考、�/sec> 方法本研究采用开顶室气室装置设置5个O ₃浓度水平，研究杨树叶片和细根功能性状指标对O ₃剂量的响应是否存在差异、�/sec> 结果叶片单宁和细根磷含量表现出显著的兴奋效应，即毒性阈值之前为应激正效应，毒性阈值之后为抑制负效应。叶片饱和光合速率、细根生物量以及叶片和细根可溶性糖含量出现毒性阈值，但未观察到显著兴奋效应。水分利用效率以及叶、茎、粗根和总根生物量对O ₃剂量呈现线性胁迫下降响应。碳、氮、可溶性糖、木质素含量以及木质素∶氮内稳性较强，沿O ₃浓度梯度在叶片和细根中的分配未发生变化。磷、淀粉和总非结构性碳水化合物随O ₃浓度升高分配到细根的比例增加；单宁表现为分配到叶片的比例先增加，当O ₃剂量达到37.25 μmol/mol·h时，分配到细根的比例增加、�/sec> 结论杨树叶片和细根的功能性状对O ₃剂量存在响应差异。O ₃胁迫增加了杨树细根中P和非结构性碳水化合物的储存比例，这可能是植物抵御O ₃胁迫的一种应对策略、�/sec>

关键诌�
• 臭氧胁迫/
• 杨树107/
• 细根/
• 叶片/
• 功能性状/
• 剂量响应

Abstract: ObjectivePoplar leaves and fine roots play a key role in the carbon and nutrient cycle (such as nitrogen and phosphorus) in the forest ecosystem. However, the response of fine roots to ozone (O ₃) stress has been poorly studied, and the difference in responses of leaves and fine roots to O ₃is still unclear. This study thus aimed to clarify the difference in responses to O ₃dose of leaves and fine roots, two rapidly decomposing organs, and to provide reference for understanding the response mechanism of poplar to O ₃pollution from the perspective of aboveground and belowground feedback. MethodFive O ₃concentration levels were set with the open-top chambers to explore whether the functional traits of poplar leaves and fine roots respond differently to O ₃dose. ResultThere was significant hormesis on the response of tannin content of leaves and P content of fine roots to O ₃stress, which showed a positive effect before toxicological O ₃threshold and a negative effect after toxicological O ₃threshold. Leaf saturated photosynthetic rate, fine root biomass and soluble sugar content of leaves and fine roots showed a toxicological O ₃threshold, but not significant hormesis. Water use efficiency and the biomass of leaves, stems, coarse roots and total roots decreased linearly with O ₃dose increasing. The ratio of fine roots to leaves in the content of C, N, soluble sugar, lignin, and lignin∶N did not change with O ₃dose increasing. The ratio of fine roots to leaves in the content of P, starch, and TNC increased with the O ₃dose increasing, while tannin content first declined and then rose with O ₃dose increasing (O ₃threshold value of 37.25 μmol/mol·h). ConclusionThese results indicate that the significant differences in the responses of leaves and fine roots to O ₃pollution will result in marked changes in the relative belowground roles of these two litter sources within poplar plantations. O ₃stress could induce more P and non-structural carbohydrates to fine roots for storage relative to leaves, which might be a coping strategy for poplar exposed to O ₃stress.

Key words:
• O₃stress/
• Populus euramericanacv. �?4/76‘�/a> /
• fine root/
• leaf/
• functional trait/
• dose response

�?nbsp; 1杨树光合生理特征、生物量积累和分配在5个O₃暴露剂量下的响应毓�/p>

AOT40. 试验期间小时O₃浓度超过40 nmol/mol的累计值，为O₃剂量指标。不同的小写字母表示不同臭氧处理的显著性差异（P< 0.05）。下同。AOT40, the accumulated hourly mean O₃concentration over 40 nmol/mol during fumigation, which is O₃-dose index. Lowercase letters indicate significant differences among O₃treatments (P< 0.05). The same below.

Figure 1.Response ratios of photosynthetic physiological characteristics, biomass accumulation and distribution of poplar under 5 O₃exposure doses

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�?nbsp; 2杨树叶片和细根的化学性状�?个O₃浓度水平的响应差弁�/p>

CF. 过滤大气浓度� < 40 nmol/mol；NF. 环境大气浓度；NF40. NF + 40 nmol/mol；NF60. NF + 60 nmol/mol；NF80. NF + 80 nmol/mol。CF, filtered ambient air concentration, < 40 nmol/mol; NF, ambient air concentration; NF40, NF + 40 nmol/mol; NF60, NF + 60 nmol/mol; NF80. NF + 80 nmol/mol.

Figure 2.Response difference of chemical properties of poplar leaves and fine roots at five O₃concentration levels

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�?nbsp; 3杨树叶片和细根的化学性状�?个O₃暴露剂量下的响应毓�/p>

Figure 3.Response ratios of chemical traits in leaves and fine roots in poplar to five O₃doses

下载: 全尺寸图牆�/a> 幻灯牆�/a>

�?nbsp; 4O₃浓度升高梯度下杨树细根和叶片的化学性状比倻�/p>

Figure 4.Ratio of fine roots to leaves of chemical traits in poplar along an elevated O₃gradient

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�?nbsp; 1杨树叶片化学性状之间的相关�?/p>

Table 1.Pearson’s correlation matrix for chemical traits in poplar leaves

叶片性状 Leaf trait	N	P	C∶N	N∶P	C∶P	可溶性糖 Soluble sugar	淀粈�br/>Starch	TNC	木质紟�br/>Lignin	木质素∶N Lignin∶N	单宁 Tannin
C	0.19	0.03	�?.05	0.11	�?.040	0.07	�?.20	�?.14	�?.13	�?.12	0.02
N		0.48	�?.99***	0.21	�?.777**	0.32	0.01	0.19	�?.33	�?.52*	0.13
P			�?.50	�?.76**	�?.910***	0.16	0.27	0.32	�?.02	�?.14	0.02
C∶N				�?.18	0.810***	�?.35	�?.08	�?.27	0.36	0.54*	�?.14
N∶P					0.440	0.09	�?.29	�?.20	�?.24	�?.24	0.09
C∶P						�?.27	�?.23	�?.36	0.19	0.36	�?.08
可溶性糖 Soluble sugar							�?.08	0.50	�?.89***	�?.90***	0.69**
淀� Starch								0.82***	�?.01	�?.04	�?.28
TNC									�?.52*	�?.54*	0.15
木质� Lignin										0.98***	�?.79***
木质∶N Lignin∶N											�?.73**
注：C. 碳；N. 氮；P. 磷；TNC. 总非结构性碳水化合物：�sup>***表示P< 0.001：�sup>**表示P< 0.01：�sup>*表示P< 0.05。下同。Notes: C, carbon; N, nitrogen; P, phosphorus; TNC, total non-structure carbohydrate;***indicatesP< 0.001;**indicatesP< 0.01;*indicatesP< 0.05. The same below.

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�?nbsp; 2杨树细根化学性状之间的相关�?/p>

Table 2.Pearson’s correlation matrix for chemical traits in poplar fine roots

细根性状 Fine root trait	C	N	P	C∶N	N∶P	C∶P	可溶性糖 Soluble sugar	淀粈�br/>Starch	TNC	木质紟�br/>Lignin	木质素∶N Lignin∶N
N	�?.32
P	0.26	0.59*
C∶N	0.49	�?.98***	�?.50
N∶P	�?.41	0.12	�?.95***	�?.17
C∶P	�?.35	�?.04	�?.97***	�?.02	0.99***
可溶性糖 Soluble sugar	0.27	0.37	0.25	�?.30	�?.15	�?.18
淀� Starch	0.27	0.18	0.16	�?.10	�?.29	�?.29	0.17
TNC	0.35	0.38	0.27	�?.29	�?.26	�?.29	0.86***	0.65**
木质� Lignin	�?.33	0.00	0.23	�?.07	�?.19	�?.22	�?.49	�?.10	�?.43
木质∶N Lignin∶N	�?.19	�?.36	0.02	0.29	�?.22	�?.20	�?.58*	�?.14	�?.53*	0.93***
单宁 Tannin	0.30	�?.48	�?.16	0.48	�?.03	0.04	�?.23	�?.54*	�?.46	�?.27	�?.09

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