三种常见边坡植物对模拟干旱环境抗旱性能的研究

香根草、紫花苜蓿和高羊茅是工程边坡常见绿化植被,通过探究干旱胁迫对3种植物种子萌发、光合及生理生化指标的影响,评价分析其抗旱性,为水电边坡生态修复中的物种筛选、植物群落的重建给予参考。采用聚乙二醇(PEG)模拟干旱胁迫对植物种子进行4个PEG浓度水平的胁迫处理(5%、10%、15%、20%),研究3种植物种子在PEG干旱胁迫下的萌发特性;采用盆栽控水法分别对3种植物的幼苗进行4组土壤水分处理:正常供水(土壤含水量为最大田间持水量的75%~80%)、轻度土壤干旱胁迫(65%~70%)、中度土壤干旱胁迫(50%~55%)和重度土壤干旱胁迫(35%~40%),分别测定不同土壤干旱胁迫下3种植物光合、生理生化指标,运用隶属函数法对3种植物的抗旱性综合评价。结果表明由于干旱胁迫导致3种植物种子萌发数量减少、种子萌发活力下降,且随着干旱程度的加剧,影响程度逐渐加大,低浓度PEG胁迫对香根草种子的萌发具有引发作用。干旱程度导致3种植物净光合速率、蒸腾速率、胞间CO₂浓度、气孔导度和水分利用效率有不同程度的下降,香根草的净光合速率、蒸腾速率和胞间CO₂浓度下降最为显著,高羊茅的气孔导度和水分利用效率下降最为显著。随着干旱程度的增加,3种植物的丙二醛、脯氨酸和可溶性糖均显著增加。综合分析3种植物种子萌发率、萌发指数、光合及生理生化等多个单项指标,运用隶属函数平均值法鉴定出3种边坡植物的抗旱性,比较得出紫花苜蓿的抗旱性最强,高羊茅次之,香根草的抗旱性相对较差。

Drought resistance of three common slope plants determined in a simulated drought experiment

Vetiveria zizanioides,Medicago sativa,and Festuca elara are commonly used as greening plants on engineered slopes.The aim of this study was to determine the effects of drought stress on the seed germination,photosynthesis,and physiological and biochemical indices of V.zizanioides,M.sativa,and F.elata.Analyses of the drought resistance of these three plants will provide a reference for selecting species suited to community reconstruction and/or ecological restoration of engineered slopes (e.g.those created in hydropower schemes).Drought stress was imposed using polyethylene glycol (PEG) at 5％,10％,15％,and 20％,and seeds of V.zizanioides,M.sativa,and F.elata were germinated under this range of PEG concentrations.To explore the adaptability of the three plant species to natural soil water stress,their photosynthetic characteristics and physiological and biological indexes were measured under four treatments:normal water (soil moisture content 750％-80％ of field capacity),mild soil drought stress (65％-70％ of field capacity),moderate soil drought stress (50％-55％ of field capacity),and severe soil drought stress (35％-40％ of field capacity).The membership function method was used to evaluate the drought resistance of the three plant species.The number of germinated seeds and seedling vigor decreased with increasing drought stress for all three plant species.The higher PEG concentration significantly inhibited seed growth,and reduced the relative germination rate and relative germination index.In contrast,the seed relative germination rate and germination index of V.zizanioides were promoted in the 5％ PEG treatment.The net photosynthetic rate (Pn),transpiration rate (Tr),intercellular CO2 concentration (Ci),stomatal conductance (Gs),and water use efficiency (WUE) of the three species decreased to different degrees under drought stress.The largest decreases in Pn,Tr,and Ci under drought stress were in V.zizanioides,while the largest decreases in Gs and WUE under drought stress were in F.elata.The malonaldehyde (MDA),proline (Pro),and soluble sugars content significantly increased in all three plant species with increasing drought severity.As the severity of the drought stress increased,the largest increase in MDA content was in V.zizanioides and the smallest was in F.elata.The MDA and soluble sugars content in M.sativa leaves significantly increased and showed a strong response to drought stress.The increase in Pro and soluble sugars content in leaves was smaller in V.zizanioides than in the other two species.The drought resistance of the three plant species was evaluated based on their germination rate,germination index,and photosynthetic and physiological characteristics using the membership function method.The most drought resistant species was M.sativa,followed by F.elata,and then V.zizanioides.