无论在自然生态环境还是在人工农田环境下,植株残体进入土壤后都会对土壤的物理化学性质以及后茬植物的生长产生重要影响。西洋参(<em>Panax quinquefolium</em> L.)为人参属多年生名贵药材,在栽培生产中存在严重的连作障碍问题。为了探明秋后残留在土壤中的须根降解产物对来年植株生长的影响,以及收获后残留在田间的根茬对连作西洋参生长的作用,以3年生西洋参苗为研究对象,采用室内水培试验以及田间盆栽试验,通过添加西洋参根的粉碎物模拟根残体,测定其对西洋参生长的影响。水培试验中全营养液中分别添加0.02、0.1、0.5 mg/mL西洋参根粉碎物,处理后每隔5d测定植株叶片展开情况、株高、冠幅等生长指标。盆栽试验在土壤中添加0.1 mg/g根粉碎物,于栽种后1-2月测定西洋参叶片展开情况、株高、冠幅等生长指标;水培及盆栽试验均于展叶期、现蕾期、结果期测定地上部及地下部生物量。采用高效液相色谱法(HPLC)测定根围土壤中8种酚酸类化合物的含量。试验结果表明,水培溶液中添加0.02-0.5 mg/mL根残体,可显著抑制西洋参自身地上部分生长,推迟展叶期,结果期生物量降低14.9%-45.0%;对地下部分的影响主要表现为在展叶期显著促进须根生长(<em>P</em><0.05)。与水培试验相比,盆栽土壤中添加0.1 mg/g根残体同样导致西洋参展叶期推迟;不同的是处理组的地上、地下部及须根的平均生物量均高于对照。另外,添加根残体后盆栽西洋参根围土壤中丁香酸、香草醛、<em>p-</em>香豆酸、阿魏酸等酚酸类化感物质含量下降49.1%-81.4%,但作为逆境信号物质的水杨酸含量升高59.9%。以上结果可以确认根残体对西洋参早期生长具有自毒和促进的双重作用,表现为抑制地上部分生长,导致生物量显著下降;同时在生长早期促进须根生长。但在田间环境下,自毒作用可能受根残体降解速度以及土壤对降解产物吸附的影响有所减弱,使促进作用更为明显。;Both in the natural ecological system and in agricultural system, plant debris in soil may significantly influence the physical and chemical features of soil that consequently affect the plant growth. American ginseng (<em>Panax quinquefolium</em> L.), a member of <em>Panax</em> genus, as a highly valuable perennial herb for its medicinal properties, was cultivated with serious continuous cropping problem in cultivating places. The objectives of the study were to determine the effects of degraded annually-maintained root tissues in soil on plant growth and the influence of the postharvest root debris left in soil on the development of continuous American ginseng system. This study used the 3-year old American ginseng seedlings planted in solution and in soil mixed with ground root pieces as simulated root litter to determine their effects on plant growth. Then the effects of root litter on the growth of American ginseng were measured in the hydroponic and field cultural condition respectively. Based on previous studies, this study used nutrient solution amended with 0.02 mg, 0.1 mg, 0.5 mg American ginseng root debris per mL of solution. The plant growth data were collected every 5 days starting from mixing root debris in the solution including expansion of leaves, plant height, canopy growth and etc. The biomass of above and under ground parts were measured at seedling leaf expansion, blooming and fruit set stages. Potted soil was added with 0.1 mg root debris pieces per gram of soil. The measurements of leaf expansion, plant height, canopy growth and etc were conducted every month after planting date. The biomass of above and under ground parts at leaf expansion, blooming and fruit set stages were measured. American ginseng bulk soil samples were collected 30 days after planting date, their phenolic allelochemical contents were determined using high performance liquid chromatography (HPLC). The results showed that in the nutrient solution mixed with 0.02-0.5 mg/mL root debris, the growth of above-ground part of American ginseng were inhibited, leaf expansion was delayed, and the biomass was significantly reduced by 14.9%-45.0% in fruit set stages. The growth of root system was promoted also in such solutions (<em>P<</em>0.05) only during the leaf expansion period. Comparatively, for the potted plants, soil mixed with 0.1 mg/g of root debris also delayed the leaf expansion, plant biomass in both above and under ground parts were all greater than those of the non-debris control. Besides, the results also showed that some phenolic allelochemical contents in the American ginseng bulk soil, such as syringic acid, vanillin, <em>p</em>-coumaric acid, ferulic acid, were decreased by 49.1%-81.4%. However, the salicylic acid content in the treated soil, a stress-induced signal substance in many plants, was increased by 59.9% compared to the control group. In this study, we concluded that the American ginseng root debris had both effects on the inhibiting the growth of above-ground plants and promoting growth of American ginseng roots. This inhibiting effect consequently resulted in a significant decrease in biomass production. However, in the field soil, the degradation rate and the soil adsorption of the root decomposition might reduce the autotoxicity of roots, leading to the effects on growth promotion more significant.
Search from 250 M+ research papersSearch from 250 M+ research papers
Oct 30, 2014
K Lee + 6
Open Access