香豆素对苏丹草种子萌发和幼苗生长的影响

香豆素为黄花草木樨(Melilotus officinalis)水浸提液的主效化感物质,能抑制多种杂草种子的萌发和幼苗生长。为探明香豆素的化感抑草作用机理,本研究采用室内培养、生物检测的方法,研究了简单香豆素水溶液对苏丹草(Sorghum sudanense)种子萌发及其幼苗生长和生理生化指标的影响,并采用透射电镜观察了苏丹草幼苗根和茎的超微组织结构。结果表明,20~100μg·mL~(-1)香豆素水溶液能够显著抑制早期苏丹草种子的萌发(P0.05),且随浓度升高抑制作用增强,能够显著抑制苏丹草根伸长,随处理时间的延长和浓度的升高其抑制作用也增强,根变粗扭曲,而对茎长的影响存在浓度效应和时间效应,在4d时,20~100μg·mL~(-1)浓度的香豆素水溶液均促进茎长,6和8d则表现为低浓度促进、高浓度抑制;与加蒸馏水的对照组相比,100μg·mL~(-1)香豆素溶液处理显著(P0.05)提高了过氧化氢酶(CAT)活性,并降低了超氧化物歧化酶(SOD)活性,对过氧化物酶(POD)抑制作用表现为先降低后升高;香豆素处理显著(P0.05)提高了可溶性糖的含量,同时显著(P0.05)降低了叶绿素的含量;在香豆素处理下,淀粉含量先降低后升高,吲哚乙酸氧化酶(IAAO)活性仅在第4天时低于对照组。香豆素水溶液破坏了苏丹草根细胞的超微结构,出现液泡体积变大,细胞器数量和种类减少的现象,细胞核的核膜发生明显的歪曲,细胞核变小甚至消失;香豆素水溶液处理下的苏丹草幼苗叶绿体内淀粉粒数目显著(P0.05)增加,体积变大。以上结果显示,100μg·mL~(-1)的香豆素水溶液可以通过改变苏丹草抗氧化酶系统、增加渗透调节物质、降低叶绿素含量、影响酶活性以及破坏细胞超微结构等途径调节苏丹草的生长。

Effect of coumarin on Sorghum sudanense seed germination and seedling growth

Coumarin is the main allelochemical of Melilotus officinalis ,and can inhibit seed germination and seedling growth in a variety of weeds.In this study,we aimed to explore the allelopathy mechanism of couma-rin and its inhibition of grass.Petri dish experiments were conducted on Sorghum sudanense to study the effect of coumarin on the main growth and physiological and biochemical indices,and to observe ultrastructural chan-ges in the roots and stems by transmission electron microscopy.The following results were obtained.Coumarin concentrations in the range of 20 to 100 μg·mL-1 significantly (P <0.05)inhibited the early germination of S .sudanense and the degree of inhibition increased with an increase in coumarin concentration.Coumarin solu-tion significantly (P <0.05)inhibited root length,and with an increase in treatment time and coumarin concen-tration,the roots became more coarse and distorted.There were concentration and time effects on stem growth. At 4 d,a coumarin concentration of 20 ~100 μg·mL-1 promoted stem length,whereas at 6 and 8 d,a low coumarin concentration promoted stem length and a high concentration inhibited stem length.A 100 μg·mL-1 coumarin solution significantly (P <0.05)inhibited the growth of S .sudanense ,and the germination rate,root length,and stem length were all significantly (P <0.05)lower than in the control group;Coumarin solution significantly (P < 0.05 )increased the activity of catalase and reduced the activity of superoxide dismutase, whereas the activity of the peroxidase initially decreased and then significantly (P <0.05)increased.Coumarin solution significantly (P <0.05)enhanced the content of soluble sugars and reduced the content of chlorophyll. Furthermore,treatment with coumarin initially decreased and then increased the content of starch,and the ac-tivity of indole acetic acid oxidase in coumarin-treated plants was lower than that in the control group.Treat-ment with coumarin solution destroyed the ultrastructure of Sudan grass root cells,with vacuole volume be-coming larger,the number and types of organelles decreasing,the nuclear membrane being distorted,and the nuclei becoming smaller or even disappearing.Coumarin treatment also significantly (P <0.05 )increased the number of starch granules in the chloroplast of S .sudanense and their volume became larger.The above results indicate that 100 μg·mL-1 coumarin solution can regulate the growth of S .sudanense by changing antioxidant enzyme systems,increasing osmotic adjustment substances,decreasing chlorophyll content,affecting enzyme activity,and destroying cell ultrastructure.