叶片绒毛和气孔对冬小麦叶面吸收多环芳烃的影响

Effects of leaf trichome and stomata on PAHs uptake in the leaf of winter wheat

为探讨冬小麦叶面结构对多环芳烃(PAHs)吸收的影响,本研究采用室内模拟大气PAHs(1.25 mg·L^(-1)和6.00 mg·L^(-1))暴露试验,比较7种不同基因型冬小麦叶片绒毛和气孔的差异特征,分析其与叶片中PAHs之间的关系,揭示冬小麦叶片绒毛和气孔对PAHs吸收的影响及机制。结果表明:大多数冬小麦品种叶片背面比正面有更大的绒毛密度和长度,而气孔密度和面积则相反。在所有小麦品种中,‘中麦175’的叶片两面绒毛密度和长度均最高,而‘长武521’正面绒毛密度最低。‘中麦175’叶片正面气孔密度显著(P<0.05)高于‘仓麦6005’‘长武521’‘小偃22’,且‘长武521’‘小偃22’‘郑麦7698’叶片正面气孔面积显著(P<0.05)高于‘焦麦266’小麦品种。‘长武521’叶片5种PAHs的浓度显著低于其他小麦品种(P<0.05),这与其较小的气孔、绒毛长度及密度有关。在6.0 mg·L^(-1)暴露浓度下小麦叶片PAHs浓度随着分子量的增大而降低。此外,叶片正面绒毛密度和长度与叶片中菲(PHE)和PAHs总浓度呈显著正相关关系(P<0.05),PHE较高的挥发性和较低的分子量易被叶片富集。叶片正面气孔密度与叶片PHE和5种PAHs总浓度呈显著正相关关系(P<0.05),表明叶片正面气孔分布越密集,其对PHE吸收能力越强。主成分分析(PCA)也说明叶片绒毛密度是冬小麦叶片PAHs累积的关键驱动因子。因此,选择叶片绒毛稀疏的冬小麦品种可降低污染区PAHs的人体健康风险。

To explore the effects of leaf structure on polycyclic aromatic hydrocarbon(PAHs)uptake in winter wheat,an indoor-simulated atmospheric exposure experiment was conducted.The characteristics of trichomes and stomata of leaves of seven winter wheat varieties were compared,and the relationship between leaf structure and PAHs of leaves in winter wheat was analyzed.The results showed that trichome density and length on the leaf abaxial side were larger than those on the adaxial side,while the opposite was true for stomatal density and area for most varieties of winter wheat.Among all wheat varieties,the largest trichome density and length on the leaf abaxial and adaxial side were found in‘Zhongmai 175’,while the lowest trichome density on the leaf adaxial side was recorded in‘Changwu 521’.The stomatal density on the leaf adaxial side of‘Zhongmai 175’was significantly(P<0.05)higher than that of‘Cangmai 6005’‘Changwu 521’and‘Xiaoyan 22’,and the stomatal area on the leaf adaxial side of‘Changwu 521’‘Xiaoyan 22’and‘Zhengmai 7698’were significantly higher than that of‘Jiaomai 266’.The concentration ofΣ5PAHs in the leaf of‘Changwu521’were significantly lower than those of the other six varieties,which may be related to the smaller trichome and stomatal density and shorter trichome in the leaf.At an exposure concentration of 6.00 mg·L^(-1)Σ_(5)PAHs,PAH concentrations in the leaves decreased with increasing molecular weight of PAHs.In addition,trichome density and length on the leaf adaxial side and phenanthrene(PHE)andΣ5PAHs concentration showed a significant positive correlation.This result may be due to the higher volatility and lower molecular weight of PHE,which are easily attached to the leaf surface and then absorbed and enriched by leaves.There was a significant correlation between stomatal density on the leaf adaxial side and PHE(P<0.05)andΣ5PAHs(P<0.05)concentrations,indicating that the denser the stomatal distribution on the leaf adaxial side,the stronger the uptake capacity of PHE.PCA results further confirmed that leaf trichome density was the main limiting factor for PAHs accumulation in leaves.Therefore,selecting winter wheat varieties with a sparse leaf trichome distribution can reduce the human risk of PAHs in winter wheat in polluted areas.