摘要:选择人工湿地中常用的挺水植物美人蕉和鸢尾作为受试植物,配制不同氨氮浓度的模拟废水进行培养,每隔一段停留时间测试植株生理指标,以期得到植株的氨氮耐受性特征。研究脯氨酸、丙二醛、超氧化物歧化酶、净光合速率、蒸腾速率、气孔导度等表征植株耐受性指标的变化。结果表明,美人蕉叶片中脯氨酸和丙二醛含量均随氨氮胁迫时间的延长呈现先增高后降低的趋势,说明植株对氨氮的胁迫具有一定的适应性。鸢尾叶片中两种物质的含量均明显高于美人蕉。氨氮浓度为200 mg/L时,美人蕉SOD活性变化很小,而鸢尾则呈现先增高后降低的趋势;随着氨氮浓度升高,美人蕉和鸢尾叶片的SOD活性都呈先升高后降低的趋势,但鸢尾叶片SOD活性无法恢复到初始水平,SOD系统遭到损害。低浓度氨氮对美人蕉净光合速率具有明显的促进作用,且蒸腾速率呈现先升高后下降的趋势。表明在低氨氮浓度情况下,美人蕉表现出较强的耐受性。鸢尾净光合速率和蒸腾速率均有所下降,植物生长受到抑制。研究结果表明,美人蕉对高氨氮具有更强的耐受性,是人工湿地处理高氨氮废水时较为理想的湿地植物。
关键词:人工湿地;氨氮;植物生理指标;湿地植物
The Tolerance of Plants to High Concetration of Ammonia in Wastewater by Constructed Wetland
GONG Juan, WANG Yu-hui, ZHAO Xiao-xiang, SONG Xin-shan
Abstract: Two commonly used emergent plants for constructed wetland including Canna and Iris were used to be stressed by the configuration of simulated wastewater with different concentrations of ammonia. Plant physiological indicators were determined at fixed residence time intervals to obtain ammonia tolerance characteristics of the two plants. The plant tolerance indexes were proline, malondialdehyde, superoxide dismutase, photosynthetic rate, transpiration rate and stomatal conductance. The results showed that the contents of proline and MDA in Canna increased with prolonged stress time of ammonia at first and then decreased, indicating that Canna had a certain flexibility of ammonia nitrogen. The contents of proline and MDA in Iris were significantly higher than that of Canna. SOD activity of Canna changed little when the concentration of ammonia nitrogen was 200 mg/L, while the index of Iris increased at first and then decreased. As the concentration of ammonia nitrogen increased, the SOD activity of Canna and Iris increased at first and then decreased. While the SOD activity of Iris was not able to be restored to original level, indicating that the SOD enzyme system was compromised. The photosynthetic rate of Canna was significantly promoted when the concentration of ammonia nitrogen was low. The transpiration rate increased at first and then decreased, showing that Canna had stronger tolerance than Iris had when the concentration of ammonia nitrogen was low. Canna had a stronger tolerance to high concentration of ammonia nitrogen. It was the ideal wetland plants for constructed wetland to treat high concentration of ammonia nitrogen in wastewater. Key words: constructed wetland; ammonia nitrogen; physiological index of plant; wetland plant
湿地挺水植物是人工湿地主要组成部分,是湿地处理系统最明显的生物特征[5]。人工湿地脱氮是通过湿地植物吸收、微生物硝化-反硝化、基质吸附、氨挥发等,其中主要是硝化-反硝化过程去除[6]。有研究表明,植物吸收、存储仅占总氮去除量的10%左右[7]。但是,植物根系则具有很强的输氧作用,能够为微生物提供充足的氧气,并且能分泌有机质为微生物提供生长条件[8,9]。基质内部形成好氧区、缺氧区和厌氧区,满足硝化和反硝化作用的顺利进行[10]。然而,高浓度氨氮对植株具有胁迫作用,氨氮浓度过高,对植物细胞产生渗透胁迫,破坏植物细胞内自由基代谢平衡,导致膜脂过氧化,使膜系统受到伤害;同时影响正常光合作用,植株生长受到抑制。因此,研究常见人工湿地植物对氨氮的耐受性,有助于对湿地植物的选择,有利于人工湿地处理高氨氮废水的连续性和有效性。此外,植物根系还能在介质中形成许多间隙,减少介质封闭性,加强介质的水力传输能力[11]。
因此,以人工湿地中常见的美人蕉和鸢尾作为受试植物,研究植株在高氨氮胁迫作用下生理指标的变化响应,通过对比研究,以期得到植物对高氨氮的耐受性,为人工湿地处理高氨氮废水植物选择提供一定参考。
1 材料与方法
1.1 材料
2 结果与分析
2.1 不同浓度氨氮胁迫对植物脯氨酸含量的影响
2.2 不同浓度氨氮胁迫对植物丙二醛含量的影响
2.3 不同浓度氨氮胁迫对植物超氧化物歧化酶活性的影响
2.5 不同浓度氨氮胁迫对植物蒸腾速率的影响
2.6 不同浓度氨氮胁迫对植物气孔导度的影响
2.7 不同处理对植物胞间CO2浓度的影响
3 结论与讨论
美人蕉和鸢尾叶片中脯氨酸、丙二醛的含量都随着水中氨氮浓度的升高而逐渐增加,且鸢尾叶片的含量明显高于美人蕉。氨氮浓度为200 mg/L时,美人蕉的SOD活性变化很小,随着氨氮浓度升高,SOD活性变化明显,且可以恢复到初始水平。鸢尾叶片的SOD活性随着氨氮浓度的增高呈现先增高后下降的趋势。当氨氮浓度为400、600 mg/L时,SOD活性无法恢复到初始水平,说明SOD系统遭到损害。美人蕉的净光合速率和蒸腾速率远大于鸢尾。美人蕉在200和400 mg/L时的净光合速率高于不添加氨氮的水样下栽培的美人蕉,但在600 mg/L的浓度下则受到抑制。而氨氮对鸢尾叶片的净光合速率有十分明显的抑制作用。氨氮胁迫开始后,美人蕉叶片的气孔导度和胞间CO2浓度随着胁迫时间的延长呈现先增高后降低的趋势,而鸢尾叶片的气孔导度和胞间CO2浓度则呈现先降低后升高的趋势,但始终低于不受氨氮胁迫的植株。通过两种植物的生理生化特征对比可知,美人蕉对氨氮的耐受性更佳,是人工湿地系统处理高氨氮废水的理想工程植物。
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