Adejumo Sifau A, Oniosun Bosede, Akpoilih Okemena Agnes, Adeseko Abiodun, Arowo Dorcas Omotayo
Environmental Biology Unit, Department of Crop Protection and Environmental Biology Faculty of Agriculture, University of Ibadan, Ibadan, Nigeria.
Environ Geochem Health. 2021 Apr;43(4):1537-1549. doi: 10.1007/s10653-020-00649-5. Epub 2020 Jun 29.
Native plants growing on heavy-metal-contaminated sites are the potential candidates for phytoremediation of contaminated sites due to their tolerance and adaptation to toxic environment. For better application of the technology, in-depth knowledge and understanding of the anatomy and physiology of these plant species are essential. In this study, anatomical changes in roots and leaves of various plant species growing on Pb-contaminated sites as well as osmolytes (proline, PR; glycine betaine, GB; and phenolics, PH) production and distribution in different plant parts were investigated. The soil and plant samples were collected in triplicates from two different Pb-contaminated sites, while control plants were collected from the University of Ibadan. The plants were washed and partitioned into different parts for anatomical and biochemical studies, and soil adhering to the roots of different plant species was collected for the determination of Pb contents. Sporobolus pyramidalis, Cynodon dactylon, Imperata cylindrica, Eleusine indica, Gomphrena celosioides, Rhinconspora corymbosa and Echinochloa colona are the plant species common to these contaminated sites. Though with variations based on the site, thick epidermis and sclerenchyma, pronounced and numerous vascular bundles as well as trichomes were some of the anatomical characteristics of these metallophytes from contaminated sites compared to their counterparts from uncontaminated site. These plants also produced PR, GB and PH, with PH being the highest followed by PR and GB. Accumulation in different parts of the plants also varied depending on the plant species and the osmolyte. They were more in the leaf than other plant parts. Among the plant species, Sporobolus pyramidalis had the highest value of proline (3.26 and 2.63 µg/g FW) and glycine betaine (3.44 and 2.23 µg/FW) in the leaf and stem, respectively, followed by Cynodon dactylon having 2.20 and 0.89 µg/g FW proline and 2.02 and 0.94 µg/g FW glycine betaine. On the Pb accumulation in plant, more lead (Pb) was found in the roots than other plant parts. Gomphrena celosioides accumulated the highest Pb (4537.50 and 1081.50 mg/kg) in the root and shoot, respectively, followed by Eleusine indica (3988 and 699.00 mg/kg), while the lowest values were recorded for Echinochloa colona (36.87 and 5.97 mg/kg). In rhizospheric soils, G. celosioides had the highest Pb content (34,405.00 mg/kg) which was higher than other rhizospheric soils. In conclusion, phenolics were produced more in these metallophytes and all the osmolytes were more in leaf than root. Anatomical modifications in response to heavy metal exposure differed between plant species and level of contamination. Lead accumulation in plant also varied depending on plant species.
生长在重金属污染场地的本土植物因其对有毒环境的耐受性和适应性，是污染场地植物修复的潜在候选者。为了更好地应用该技术，深入了解和认识这些植物物种的解剖学和生理学知识至关重要。在本研究中，调查了生长在铅污染场地的各种植物物种根和叶的解剖学变化，以及不同植物部位中渗透调节物质（脯氨酸、PR；甘氨酸甜菜碱、GB；和酚类物质、PH）的产生和分布。从两个不同的铅污染场地采集土壤和植物样本，一式三份，同时从伊巴丹大学采集对照植物。将植物洗净并分成不同部分进行解剖学和生物化学研究，收集附着在不同植物物种根部的土壤用于测定铅含量。圆锥花序鼠尾粟、狗牙根、白茅、牛筋草、千日红、伞房花耳草和石茅是这些污染场地常见的植物物种。尽管因场地不同存在差异，但与未受污染场地的同类植物相比，这些来自污染场地金属植物的解剖学特征包括厚表皮和厚壁组织、明显且数量众多的维管束以及毛状体。这些植物还产生PR、GB和PH，其中PH含量最高，其次是PR和GB。不同植物部位中这些物质的积累也因植物物种和渗透调节物质的不同而有所差异。它们在叶中的含量高于其他植物部位。在植物物种中，圆锥花序鼠尾粟叶和茎中的脯氨酸（分别为3.26和2.63µg/g鲜重）和甘氨酸甜菜碱（分别为3.44和2.23µg/鲜重）含量最高，其次是狗牙根，其脯氨酸含量为2.20和0.89µg/g鲜重，甘氨酸甜菜碱含量为2.02和0.94µg/g鲜重。关于植物中铅的积累，根部的铅含量高于其他植物部位。千日红根部和地上部分积累的铅含量最高（分别为4537.50和1081.50mg/kg），其次是牛筋草（3988和699.00mg/kg），而石茅的铅含量最低（36.87和5.97mg/kg）。在根际土壤中，千日红的铅含量最高（34405.00mg/kg），高于其他根际土壤。总之，这些金属植物中酚类物质产生较多，所有渗透调节物质在叶中的含量高于根。不同植物物种和污染程度对重金属暴露的解剖学改变有所不同。植物中铅的积累也因植物物种而异。
