硝氮胁迫对不同沉水植物生理生长的影响

Effects of Nitrate-Nitrogen Stress on the Growth and Physiological Indices of Two Submerged Macrophytes

沉水植物是水生生态系统的初级生产者，对调控生态系统能量的循环和传递，维持水生态系统的结构和功能。都有极为重要的作用。为了解硝态氮浓度对不同种类沉水植物生理生长的综合影响，实验采用6种浓度的硝态氮对苦草和黑藻进行胁迫处理，在实验开始后的6、24h测定植株抗氧化物酶（SOD、POD、CAT）的活性;并于实验处理7d后考察植株的叶绿素含量和各项生长指标。结果表明，缺氮条件下苦草和黑藻的SOD、POD反应强烈，40mg／L下苦草和黑藻的SOD、CAT酶活性几乎无变化；从处理时间上看，苦草总体表现为各浓度处理的SOD、CAT随胁迫时间增加活性上升，POD活性下降;黑藻生理活性表现则相反。胁迫处理7d后，苦草5mg／L处理下生物量积累最大，1～20mg／L内黑藻生物量积累没有差异，苦草的叶绿素、鲜重增量生长指标总体远低于黑藻。研究表明，10mg／L是苦草能够耐受的最高硝态氮浓度．黑藻在1～20mg／L内均能较好生长；黑藻较苦草对硝态氮胁迫具有更大的耐受性。

Solution culture method was adopted to study the responses of Vallisneria natans and Hydrilla verticillata to the stress of nitrate-nitrogen （NO3-N） with six different concentrations. The vitalities of superoxide disrnutase （SOD）, catalase （CAT） and peroxidase （POD） were surveyed after the plants had been treated for 6 and 24 hours, respectively. The vitalities of SOD and CAT in both species were found to vary in a similar way when NO3-N was missing, and the vitalities of the three enzymes had little variation even the concentrations of NO3-N reaching 40 mg/L. After seven day stress treatment, the contents of chlorophyll and other growth indices of Vallisneria natans such as bio-mass were much lower compared with that of Hydrilla verticillata. The results have shown that in terms of NO3-N concentrations, 10 mg/L would be the tolerable limit for Vallisneria natans, while Hydrilla verticillata could be well growing in the range of 1-20 mg/L, i.e., the latter species was more tolerant of NO3-N stress than the former one.