Effects of aqueous extracts and decomposition of Mikania micrantha H.B.K. debris on selected agronomic crops

Laboratory and greenhouse experiments were conducted to determine the effects of aqueous extract and the debris of Mile-a-Minute ( Mikania micrantha H.B.K.) on the germination and growth of four test species, viz. tomato ( Lycopersicon esculentum Mill.), Chinese cabbage ( Brassica chinensis L.), corn ( Zea mays L.) and long bean ( Vigna sesquipedalis L.). Germination percentage, radicle length and fresh weight of two crops, Chinese cabbage and tomato, decreased progressively when plants were exposed to increasing concentrations (12.5, 25, 37.5 and 50 g L⁻¹) of aqueous extract of Mikania , but did not affect those of corn and long bean seedlings. The emergence of tomato and Chinese cabbage was greatly reduced when Mikania debris was incorporated into the soil, irrespective of the amount of debris and the decomposition period. In contrast, the emergence of corn and long bean seedlings was not affected. The application of fertilizer (NPK 15 : 15 : 15) enhanced the fresh weight of all seedlings tested as compared with those not supplied with the fertilizer. Four compounds were identified in the leaf extract of Mikania , viz. caffeic acid, p -hydroxybenzaldehyde, resorcinol and vanillic acid.     

Approach of allelopathy study with Arabidopsis thaliana (L.) Hevnh. and Neurospora crassa

Allelopathy in Arabidopsis seeds was investigated in the present study because there are few available reports of allelopathy studies regarding the early development stage of the plant life cycle, and because Arabidopsis is widely used as a model plant for molecular biology. When cockscomb ( Celosia cristata ) was incubated together with Arabidopsis seeds, the growth of cockscomb was promoted by Arabidopsis seeds. Exudate of Arabidopsis seeds showed a promotive activity on the growth of cockscomb and Arabidopsis itself. A new method for studying allelopathic mechanisms involving the interaction of the plant Arabidopsis thaliana (L.) Hevnh. and the fungus Neurospora crassa was suggested. Arabidopsis seed exudate and the water-soluble fraction of the exudate promoted Arabidopsis growth and reduced fungal germination, indicating that the seed exudate has a species-selective activity. Conversely, the ethylacetate-soluble fraction inhibited growth of all tested materials in the current study. These results demonstrate that the water-soluble substance(s) released from Arabidopsis seeds have species-selective activity on growth of both plants and microorganisms.     

铺地竹叶片对结球生菜种子发芽及幼苗生长的影响

采用基质盆栽试验,研究了铺地竹(Sasa argenteastriatus E.G.Camus)叶片对结球生菜(Lactucasativa L.var.capitata L.)种子萌发和幼苗生长的影响,结果表明,铺地竹叶片粉末对结球生菜种子的萌发和幼根生长具有一定的抑制作用,随着浓度的增加抑制作用增强,在50～200 g/m2的范围内,幼根抑制率为12.15%～28.91%。在50～100 g/m2的用量下,铺地竹叶片对结球生菜苗长表现为促进生长作用,而在200 g/m2时,则表现为抑制生长作用。施用铺地竹叶片后3 d、6 d、9 d和12 d,结球生菜幼苗的叶绿素含量特别是叶绿素a的含量显著减少,随着基质中叶片粉末浓度的增加,结球生菜叶绿素含量降低,叶绿素a含量高低依次为对照、低浓度处理、中浓度处理、高浓度处理。随着处理后时间的延长,竹叶对结球生菜叶片叶绿素a含量的影响减弱。这个结果进一步验证了自然条件下铺地竹叶片对植物生长的化感效应,说明其具有开发植物源除草剂的潜力,为研究铺地竹叶片中的化感物质提供了佐证。     

他感作用及其林学意义与思考

在全面介绍他感作用研究历史、概念和研究现状的基础上,分析认为苗圃育苗失败、边行优势、小老树、散生树种、林网胁地、干旱半干旱地区造林成活率保存率双低等常见林学问题,都是他感作用的结果,或其重要因素之一。结合相关论述,提供铅笔柏受群众杨他感抑制的一则实例,提出挥发性他感物质改变茎尖向性生长可能是一种他感作用形式,以及植物吐水作为他感物质释放的可能途径。从植物次生代谢和进化角度进一步阐释他感作用,结合植物生物学特点,分析认为他感作用是植物的攻击性防御手段,其效能强度依次为抑制竞争者种子萌发、根尖生长、茎尖生长、侧芽萌发、全株生长和种子生产。     

白三叶对黑麦草、弯叶画眉草的化感作用初探

针对白三叶Trifolium repens与黑麦草Lotium perenne、弯叶画眉草Eragrostis curvula混播时导致后2种植物数量减少甚至消失的现象,通过白三叶的根部、地上部和植株水提液对黑麦草和弯叶画眉草种子进行发芽实验,以及白三叶与黑麦草、白三叶与弯叶画眉草种子混播进行实验,研究表明:白三叶(幼苗、2年生植株根及茎叶)的水提取液在原液以及稀释20倍时对受体植物的胚根和胚芽的生长均产生明显的抑制作用,而在100倍稀释液时表现出一定的促进作用;白三叶与黑麦草及白三叶与弯叶画眉草种子混播实验,表明5∶1的比例为最佳混播比例.     

花叶滇苦菜浸提液对3种花卉种子萌发和幼苗生长的化感作用

为探讨花叶滇苦菜与常见草本花卉协同生长过程中的化感作用机制,采用培养皿生物测定法,研究了花叶滇苦菜地上部(DS)和地下部(DX)不同浓度浸提液对二月兰、石竹、观赏油菜3种花卉种子萌发、幼苗生长的生理指标及相关酶活性、丙二醛(MDA)含量的影响,以期为花卉植物大规模应用及杂草生物防治提供理论依据。结果表明:花叶滇苦菜浸提液对3种花卉种子萌发、幼苗生长均呈低浓度促进、高浓度抑制的趋势,在5 g·L^-1时2种浸提液中促进效应最大的是二月兰,其次是石竹,均在100 g·L^-1浓度下抑制效应达最大。2种浸提液提高了3种花卉幼苗的超氧化物歧化酶(SOD)活性,二月兰、观赏油菜在50 g·L^-1时达到峰值,石竹在25 g·L^-1时达到峰值,100 g·L^-1时均高于对照组,过氧化物酶(POD)和过氧化氢酶(CAT)活性均呈先升高后降低的趋势,丙二醛含量随浸提液浓度的升高而增加。石竹种子POD活性与种子发芽率呈极显著正相关;观赏油菜POD活性与茎长和根长呈显著正相关;二月兰根长与POD、CAT...     

不同腐解方式下棉秆腐解液对棉花种子萌发的化感效应

针对新疆棉区长期连作与棉花秸秆还田的普遍现象,分别采用自然腐解与接种微生物人工腐解的方式处理棉秆,研究了2种腐解液对棉花种子萌发的化感作用.结果表明,棉秆自然腐解液对棉花种子萌发具有较强的自毒作用,在腐解液浓度达到5 g/L时,种子发芽率与发芽指数即开始显著(P<0.05)降低;而已发芽种子的生长活力受影响较小,可耐受高达30 g/L的腐解液浓度.经人工腐解,棉秆腐解液的自毒化感效应得到极大消除,在50 g/L腐解液浓度的试验范围内,种子萌发率未受显著抑制,反而发芽种子的活力指数及胚根干重均有极显著增加(P<0.01).两种腐解方式下种子萌发情况的差异性检验表明,人工腐解处理的种子发芽势、发芽率、发芽指数与活力指数等指标值较之自然腐解处理有极显著增高(P<0.01),胚根干重增加显著(P<0.05).     

辣椒根系分泌物的化感作用及其化感物质分析

 利用生物测定和GC-MS分析的方法,研究了辣椒根系分泌物各组分的化感作用及其优势组分的化感物质。结果表明：辣椒根系分泌物各组分对莴苣的化感作用不同,以乙醚洗脱组分的化感作用最强;对乙醚洗脱组分进行再分离,最后得出80%乙醚＋20％乙酸乙酯洗脱组分的化感作用最强;对80%乙醚＋20％乙酸乙酯洗脱组分进行GC-MS分析鉴定,确定辣椒根系分泌的主要化感物质为邻苯二甲酸二丁酯、邻苯二甲酸-丁基-环己烷基酯、邻苯二甲酸-丁基-异丁酯、邻苯二甲酸二叔丁酯、二苯胺、4,4’-叔丁基二苯酚、苯萘胺、邻苯二甲酸,其中,邻苯二甲酸二丁酯的含量最高。     

Performance of Bangladesh indigenous rice in a weed infested field and separation of allelopathy from resource competition

This study aimed to identify the potential allelopathic indigenous rice (Oryza sativa L. ssp. indica) varieties from Bangladesh using a performance study in a weed‐infested field and to assess the extent of allelopathic interference relative to resource competition in a glasshouse experiment. Six varieties – namely, “Boterswar,” “Goria,” “Biron” and “Kartiksail” as the most allelopathic, “Hashikolmi” as weakly allelopathic and “Holoi” as nonallelopathic – were raised following a nonweed control method. The infestation levels of weed species were calculated using Simpson's Diversity Index (SDI), which ranged from 0.2 to 0.56. However, a significant correlation coefficient (0.87, P < 0.001) was obtained from these field data compared with the root inhibition percentage from the laboratory bioassay, and the “Boterswar” variety was the most allelopathic. The interactions between the allelopathic variety “Boterswar,” weakly allelopathic variety “Hashikolmi” and Echinochloa oryzicola via a target (rice)‐adjacent (E. oryzicola) cogrowth culture were determined in a hydroponic arrangement. The relative competitive intensity (RCI) and the relative neighbor effect (RNE) values showed that the crop–weed interaction was facilitation for “Boterswar” and competition for “Hashikolmi” and E. oryzicola in rice/E. oryzicola cogrowth cultures. The allelopathic effects of “Boterswar” were much higher than the resource competition in rice/E. oryzicola cogrowth cultures. The converse was observed for “Hashikolmi.” Moreover, the mineral content of E. oryzicola was severely affected by “Boterswar”/E. oryzicola cogrowth cultures’ exudate solution. Therefore, the allelopathic potential of “Boterswar” variety might be useful for developing the weed‐suppressing capacity of rice, which will likely have a significant influence on paddy weed control.