六种湿地植物根际氧化还原电位的日变化

在野外条件下,研究人工湿地植物根际氧化还原电位(ORP)随时间的变化及其与主要环境因子的关系。研究了美人蕉(Canna indica Linn.)、风车草(Cyperus flabelliformis Rottb.)、芦苇(Phragmites australis Trin.ex Steud.)、水鬼蕉(Hymenocallis littoralis(Jack.)Salisb.)、紫芋(Colocasia tonoimo Nakai.)和鸢尾(Iris tectorum Maxim.)6种植物在潜流人工湿地中的根际ORP及其日变化。6种湿地植物的根际ORP日变化曲线相似,均为双峰型,双峰值出现在11:00—14:00之间,最大值出现在14:00。各植物的根际ORP日变化基本在130—350 m V之间,以水鬼蕉的变幅最大,风车草和芦苇的变幅较小。不同植物的根际ORP有较大差异,风车草和紫芋的日平均值最大,显著高于鸢尾、美人蕉和水鬼蕉(P0.05);芦苇显著高于鸢尾和美人蕉(P0.05)。ORP与光照强度和气温呈正相关,尤与气温的正相关最为显著。ORP日平均值与植物生物量有显著的正相关性,尤与地下部分生物量相关性最显著。结果表明,人工湿地植物根际ORP因不同植物、一天中不同的时间有较大差异,后者与光照和气温等环境因子密切相关。

Daily variation of the rhizosphere redox potential of six wetland plants

The objective of this study was to assess the daily variation of the rhizosphere redox potential (ORP) of wetland plants in constructed wetlands (CWs). Eighteen (18) small-scale monoculturesubsurface-flow wetlands were constructed (80 cm×50 cm×45 cm, upper diameter×lower diameter×height) stocked with six wetland plant species (Canna indica Linn.,Cyperus flabelliformis Rottb.,Phragmites australis Trin. ex Steud.,Hymenocallis littoralis(Jack.) Salisb.,Colocasia tonoimo Nakaiand Iris tectorum Maxim.)with three replicates or each plant species. The CWs were fed 30 L of domestic wastewater weekly. ORP was measured during sunny days (in early October) for the matured plants,ca. 1 m of C.indica,C.flabelliformis,P.australis and C. tonoimo, and ca. 0.7 m of I. tectorum, and ca. 0.5 m of H.littoralis.,in all the wetlands during the first growing season. ORP were measured at the position of 10 cm beneath the water surface and 2 mm off the new roots every 1 h from 07:00 to 19:00 with an ORP meter at the 5^th day after the domestic wastewaterirrigation. Light intensity and air temperature were measured at 20 cm above the shoot using the light meterand the stem thermometer. All the wetland plants showed a largevariation in daily ORP, with the ORP values at midday time significantly higher than thoseat early morning and late afternoon. The ORP of plants also showed similar bimodal variation patterns. The peak values appeared at 11:00-14:00, with 14:00 being the highest. The ORP ranged from130 mV to 350 mV in a daily measurement, with greater daily variation in H. littoralis than C. flabelliformis and P. australis.C.flabelliformis and C. tonoimo exhibited significantly higher ORP values than those of I. tectorum, C.indica and H.littoralis (P < 0.05) while P.australis showed a significantly higher value than those in I. tectorum and C.indica (P< 0.05). The ORP was positively correlated with air temperature, plant biomass and light intensity, especially for the air temperature and below-ground biomass. Results from this study indicated that the ORP of the wetland plants in the CWs varied greatly among species and during a daily cycle, and was significantly affected by the air temperature and light intensity.