Abstract: Alfalfa(Medicago sativa L.) is a kind of perennial leguminous forage grass with rapid growth,high yield,rich protein content,strong tolerance ability,and broad adaptation and usually be named the king of forage grasses.However,we have to face the stress factors acting on the yield of alfalfa in acid and iron-rich soil.Traditional researches primarily use the sour soil cultivation on the spot to simulate the real environmental stresses.But it’s unable to concretely investigate the effectiveness of single stress factor and unable to determine the dominate stress factor and to propose the corresponding countermeasure under different circumstances.In order to determine the most suitable range of Fe²⁺ concentration for alfalfa growth in acid soils,the effect of Fe²⁺ and acidity on the physiological characteristics of alfalfa seedlings were studied using sand culture with different Fe²⁺ concentration(10,50,100,150,and 200 mg·kg^-1) under acid environment of pH 4.5 and pH 6.0.The results show that the change of chlorophyll content was mainly induced by acidity and root activity was more sensitive to the Fe²⁺ content of than acidity.Chlorophyll fluorescence characteristic,soluble sugar content,and membrane permeability were simultaneously influenced by the effect of acidity and Fe²⁺ content;100 and 150 mg·kg^-1 Fe²⁺ was the highest tolerance level by alfalfa seedlings at pH 4.5 and pH 6.0,respectively.Physiological characteristics of alfalfa seedlings had better performance than other treatments under environment of pH 6.0 and 50 mg·kg^-1 Fe²⁺(P<0.05).The range of Fe²⁺ concentration from 10 to 50 mg·kg^-1 was the most suitable range for alfalfa seedling at both pH 4.5 and 6.0 and the root activity,PSII activity(Fv/Fo),and PSII photochemical efficiency(Fv/Fm) of alfalfa seedling were higher than those under the Fe²⁺ concentration from 100 to 200 mg·kg^-1(P<0.05).

Key words: Medicago sativa L., Acid stress, Fe²⁺, Physiological characteristics

摘要： 为探明酸环境和亚铁离子胁迫对紫花苜蓿(Medicago sativa L.)幼苗各生理特性指标的影响,寻求酸性土壤中适宜紫花苜蓿生长发育的环境亚铁离子浓度区间,于2007年2月以苜蓿品种W525为试验材料,采用砂培的方法研究了酸性(pH=4.5)和弱酸性(pH=6)环境中Fe²⁺(10 mg/kg、50 mg/kg、100 mg/kg,150 mg/kg和200mg/kg)对苜蓿幼苗生理特性的影响。结果表明:酸铁胁迫共存的环境中,叶绿素含量变化主要由环境酸度引起;根系活力对Fe²⁺浓度变化更为敏感;而光系统Ⅱ光化学效率(Fv/Fm)和潜在活性(Fv/Fo)、可溶性糖含量和膜透性同时受酸环境和Fe²⁺浓度的共同影响;酸性环境(pH=4.5)中100 mg/kg的Fe²⁺含量已达到苜蓿幼苗的耐受极限;弱酸环境(pH=6)下150 mg/kg的Fe²⁺含量才达到苜蓿幼苗的耐受极限,而50 mg/kg的Fe²⁺浓度尚能促进的苜蓿生长;10 mg/kg~50 mg/kg的Fe²⁺含量是苜蓿在两种酸度土壤中共同的最适生长区间,两种酸度环境下该Fe²⁺浓度范围内的根系活力、光化学效率(Fv/Fm)和光系统Ⅱ潜在活性(Fv/Fo)均显著高于100 mg/kg~200mg/kg的Fe²⁺处理(P<0.05)。

关键词: 紫花苜蓿, 酸胁迫, 亚铁离子, 生理特性