模拟阴坡鱼腥草对梯度水分变化的响应

设置重度干旱、中度干旱、轻度干旱、轻度湿润、中度湿润、重度湿润、水淹及对照8个水分梯度，研究模拟自然阴坡环境土壤水分梯度对鱼腥草（Houttuynia cordata Thunb）生长和生理水平的影响。结果表明：重度干旱显著抑制鱼腥草茎叶含水量、生物量，但明显提高根冠比；重度干旱和中度干旱明显降低根状茎和根的含水量、株高、根长和叶面积指数，根数增加；水淹时，显著提高茎叶含水量，根数减少，根长增加。过氧化氢酶（CAT）和过氧化物酶（POD）活性对水分变化响应不明显，而超氧化物歧化酶（SOD）活性具有较显著的敏感性，水分的增加或减少均显著提高SOD活性。中等程度以上的干旱或湿润均显著提高丙二醛（MDA）含量。除轻度湿润组外，叶绿素含量随干旱或湿润胁迫程度的加剧明显依次下降，显著响应梯度水分变化。重度湿润时，MDA含量、相对膜伤害率、抗氧化酶活性最高，且叶绿素含量较低，表明其受到了严重水渍胁迫。综上所述，模拟阴坡条件下，轻度干旱和中度湿润之间的水分条件更加适宜于鱼腥草的栽培。

Response of Houttuynia cordata to Moisture Gradient in Shading

The effect of soil moisture gradient was studied on the growth and physiological level of Houttuynia cordata in shading.Eight different kinds of moisture treatments were conducted to simulate the dynamic change of soil water content in the natural habitat of shading,including the treatments of heavy drought,moderate drought,light drought,control,light moisture,moderate moisture,heavy moisture,and waterlogging.Heavy drought significantly reduced water content and total biomass,however,advanced root-shoot ratio;Both heavy and moderate drought significantly reduced water content of underground,plant height,root length,and leaf area index,while the number of root was increased;Waterlogging significantly enhanced water content of aboveground and promoted the growth of root length,whereas decreased the number of root.Moisture content had little effect on the activities of catalase(CAT)and peroxidase(POD)enzymes,however,superoxide dismutase(SOD)activity was sensitive to the change in soil moisture gradient,with the activity being significantly enhanced with either decrease or increase of gradient moisture.The contents of malondialdehyde(MDA)were significantly elevated under conditions beyond moderate moisture or drought.Chlorophyll content greatly responded to the change in soil moisture gradient,i.e.,the content decreased with increasing stress,except for light moisture treatment.Note that the maximal content of MDA,relative membrane injury rate,and activities of CAT,POD and SOD together with lower chlorophyll content were observed in the heavy moisture treatment,implying that they might encounter the serious stress of moisture.The results indicated that moisture between light drought and moderate moist conditions was more suitable for cultivation of Houttuynia cordata in shading.