锌在3种乔木中的积累及其亚细胞分布和化学形态

为了探索园林木本植物对重金属锌(Zn)的积累和耐性机制,本研究以栾树(Koelreuteria paniculata)、臭椿(Ailanthus altissima)和银杏(Ginkgo biloba)3种北京常见乔木为试验树种,通过盆栽污染模拟试验,研究不同浓度Zn处理(0、250、500、1000、2000 mg·kg^-1)对3种乔木的叶、枝、根生物量及叶片超微结构的影响,分析各器官中Zn积累含量及Zn在叶、根中的亚细胞分布和化学形态。结果表明: 各浓度Zn处理下3种乔木均能存活,但叶、枝、根的生物量较对照均有所下降。过量的Zn会导致栾树、臭椿的叶片细胞变形、细胞壁破裂、细胞器解体,而银杏叶片细胞尚能保持正常形态,说明银杏对Zn的耐受能力强于栾树和臭椿。随着Zn处理浓度的增加,3种乔木各器官的Zn含量呈上升趋势,栾树和臭椿体内的Zn含量显著高于银杏,说明栾树和臭椿对Zn的积累能力强于银杏。3种乔木叶和根中的Zn主要分布在细胞壁,分别占26.9%～71.8%和28.1%～82.6%,最高浓度Zn处理(2000 mg·kg^-1)下,Zn在可溶性组分(液泡为主)的占比可超过细胞壁。3种乔木叶片中的Zn主要以NaCl、HAc、HCl提取态存在,占57.4%～82.7%,根系中的Zn主要以NaCl、HAc提取态存在,占42.8%～67.2%,均是活性较低的形态。这说明细胞壁固持、液泡区隔化和将Zn以低活性的形态赋存可能是3种乔木积累和耐受Zn的重要机制。

Accumulation,subcellular distribution,and chemical forms of zinc in three tree species

In order to explore the mechanism underlying zinc (Zn) accumulation and tolerance in woody garden species, the effects of different Zn concentrations (0, 250, 500, 1000, 2000 mg·kg^-1) on leaf, branch, root biomass and leaf ultrastructure of Koelreuteria paniculata, Ailanthus altissima, and Ginkgo biloba were studied in a pot pollution simulation experiment. The concentration of Zn in plant organs, the subcellular distribution and chemical forms of Zn in leaves and roots were further analyzed. The results showed that all the three species could survive under diffe-rent Zn concentrations, but the biomass of leaves, stems and roots decreased compared with the control. Excessive Zn could lead to cell deformation, cell wall rupture and organelle disintegration of leaves in K. paniculata and A. altissima, while the cells in leaves of G. biloba could maintain normal morphology, indicating that G. biloba had a better tolerance to Zn than K. paniculata and A. altissima. With the increases of Zn concentration, Zn concentration in the organs of the three species showed an increasing trend, and the Zn concentration in K. paniculata and A. altissima was significantly higher than that in G. biloba, indicating that the Zn accumulation ability of K. paniculata and A. altissima was stronger than that of G. biloba. Zn was mainly distributed in the cell walls of leaves and roots, accounting for 26.9%-71.8% and 28.1%-82.6%, respectively. Under the treatment with the highest Zn concentration (2000 mg·kg^-1), Zn concentration in the soluble components (mainly vacuoles) could be higher than that in the cell walls. In addition, Zn mainly existed in NaCl-, HAc- and HCl-extracted forms in leaves, accounting for 57.4%-82.7%, and Zn mainly existed in NaCl- and HAc-extracted forms in roots, accounting for 42.8%-67.2%, all of which were forms with relatively low activity. Therefore, cell wall retention, vacuoles segregation and accumulating Zn in less active forms might be important mechanisms underlying Zn accumulation and tolerance in the three trees.