田间旱育条件下不同化感潜力水稻的生理特性分析

以国际公认的化感水稻品种“PI312777”和非化感水稻品种“Lemont”为材料, 研究了田间旱育条件下2 种水稻的生长特性及其对水分和杂草胁迫的生理响应。结果表明, 在水分和杂草双重胁迫下, 田间水稻生长势表现为“PI312777”(旱地)＞“Lemont”(湿地)≥“PI312777”(湿地)＞“Lemont”(旱地)。进一步分析发现, 在各处理小区, 以适度干旱小区化感水稻“PI312777”叶片的叶绿素含量、保护酶活性、光合速率、水分利用效率最高,蒸腾速率最低; 以适度干旱小区非化感水稻“Lemont”叶片的光合速率、保护酶活性、可溶性糖、可溶性蛋白和水分利用效率最低, MDA 含量积累最高。与非化感水稻“Lemon”相比, 化感水稻“PI312777”对水分的利用效率更高, 有更强的适应水分缺乏的能力。     

芒萁生化他感作用机理初探

芒萁常形成单优势植丛,其生化他感是重要成因之一。该研究以杂草刺苋和农作物大豆为受体植物,采用稀释和减压蒸馏的方法分别制得浓度为0.05、0.2、0.4 g(Fw)/ml的芒萁水提液,初步探讨了芒萁水提液对受体植物萌发种子淀粉酶活性、可溶性糖含量和叶绿素含量的生化他感作用机理。试验结果表明,芒萁水提液对受体植物萌发种子淀粉酶活性、可溶性糖含量及叶绿素含量呈现明显抑制作用。故对芒萁的生化他感物质的研究及对农业、林业生产实践具有一定意义。     

加拿大一枝黄花浸提液对蔬菜种子萌发和生长的影响

以加拿大一枝黄花(Solidago canadensis L.)水浸提液处理3种蔬菜种子,加拿大一枝黄花地上部分浸提液(0.025～0.1 g/mL)能降低苏州青和生菜种子的萌发率,地上部分和地下部分浸提液均能显著抑制苏州青、萝卜和生菜种子的发芽势.经浸提液处理的3种蔬菜种子萌发的鲜根重和根长有所下降,地上部分浸提液对生菜和萝卜的芽长也起显著的抑制作用.结果表明:加拿大一枝黄花可能通过水溶性化感物质抑制蔬菜种子萌发和生长.     

Allelopathic effect of some essential oils and components on germination of weed species

Abstract

In this study, allelopathic effects of some essential oil plants (Carum carvi L., Coriandrum sativum L., Foeniculum vulgare Mill., Lavandula stoechas L., Mentha spicata L.,Origanum onites L., Pimpinella anisum L., Rosmarinus officinalis L., Salvia officinalis L. and Thymbra spicata L.) were investigated against some common weed species (Alcea pallida Waldst. & Kit., Amaranthus retroflexus L., Centaurea salsotitialis L., Raphanus raphanistrum L., Rumex nepalensis Spreng., Sinapis arvensis L. and Sonchus oleraceus L.) that grow in field and horticultural crops. Different concentrations (3, 6, 10 and 20 µl) of the essential oils were tested against weed seeds in vitro and their effect on germination was determined. Inhibitory effects of essential oils and concentrations were analysed with Freadman's test and they were found significant. Essential oils from Carum carvi, Mentha spicata, Origanum onites and Thymbra spicata showed high inhibitory effect against weed seeds at lower concentrations. The main components (carvacrol, thymol, carvone, limonene) of these four essential oils were tested for seed germination at four different concentrations (500, 250, 125 and 62.5 µg/ml) against the same weeds.Thymol, carvacrol and carvone showed high inhibition even at low concentrations against weed seeds. Only Alcea pallida seeds showed resistance against all essential oils and components.     

Effects of alfalfa leaf extracts and phenolic allelochemicals on early seedling growth and root morphology of alfalfa and barnyard grass

Alfalfa (Medicago sativa L.) plants contain water-soluble substances that are autotoxic as well as allelopathic to other plants. Laboratory experimentation through a petri dish assay with imbibed seeds was conducted to evaluate the phytotoxic effects of alfalfa cv. “Vernal” leaf extracts, coumarin, trans-cinnamic acid, o-coumaric acid, and hydro-cinnamic acid on the seedling growth and anatomical responses of 6 day-old alfalfa and barnyard grass. With increasing concentration, the alfalfa leaf extracts significantly reduced root lengths of alfalfa and barnyard grass (Echinochloa crus-galli, Beauv. var. oryzicola Ohwi). Coumarin, trans-cinnamic acid, o-coumaric acid, and hydro-cinnamic acid at 10⁻⁴ M significantly reduced root lengths of alfalfa and barnyard grass. The root systems, especially root tips of alfalfa, were stunted and swollen by the aqueous alfalfa leaf extracts at 30 g l⁻¹ and coumarin at 10⁻³ M. This research suggests that alfalfa plant extracts significantly affected root growth and morphological differentiation of susceptible plants, resulting in reduction of their biomass in the presence of either autotoxic or allelopathic compounds. The results may have value in enabling weed control based on natural plant extracts.     

Biology and management of Phalaris minor in rice–wheat system

Phalaris minor Retz. (Littleseed canarygrass) is a pernicious weed, which infests several crops during the winter season, particularly the wheat crops in rice–wheat sequence. Considering the limitations of cultural and chemical methods of weed control, the understanding of its biology with respect to different environmental, edaphic and management factors may offer a useful key to strengthen weed management strategies. This review considers various aspects on dormancy, viability and agro-ecology with emphasis on management practices in host and succeeding crops. Due attention has been given to the approaches required to manage the resistant biotypes under present conditions and hence to avoid further escalation of the epidemic. The various studies indicate that P. minor utilizes beneficially the prevailing environmental and management conditions of both the wheat and succeeding rice crop in rice–wheat system for its survival and growth. Its seed is highly sensitive to variable moisture and temperature regimes for germination and exhibits tolerance to anoxia during anaerobic respiration in rice. Tillage options, residue management, spatial–temporal considerations and other factors influence the seed dynamics, pattern and depth of emergence and growth of P. minor. A comprehensive and conceptual understanding of these aspects may provide useful guidelines in formulating cautious and opportunistic weed management strategies.     

Activity and Persistence of Sorgoleone,a Long-Chain Hydroquinone Produced by Sorghum bicolor

Summary

Sorghum bicolor (L.) Moensch and other related Sorghum species produce sorgoleone-a long chain hydroquinone compound (MW = 358), which is exuded by living root systems. This compound exhibits potent activity as a photosynthetic inhibitor. A diverse group of sorghum germplasm was evaluated for sorgoleone production. Production was quite variable, with certain accessions producing up to 15 mg sorgoleone/g fresh root weight. The root exudate composition among accessions was less variable, with sorgoleone being the major constituent (76-99%) within the extract. The potential binding of sorgoleone to the D1 protein of the PSII complex was evaluated in triazine resistant and susceptible redroot pigweed (Amaranthus retroflexus L.) thylakoids. Sorgoleone, metribuzin and diuron exhibited competitive binding with atrazine in susceptible thylakoids, while no competition was evident in resistant thylakoids. Sorgoleone has an intermediate affinity between that of diuron and metribuzin from estimated binding constants. Computer-aided design programs have proven useful to further evaluate structural activity relationships for sorgo-leone, and PSII inhibitors. Sorgoleone at concentrations up to 40 ppmw significantly reduced shoot fresh weight in several broadleaf weed species when incorporated in soil, but had limited effect on root development. Sorgoleone at the same concentrations applied postemergence also caused significant growth reduction to a number of weed species. Recovery of soil impregnated with sorgoleone was most effective (up to 85%) when acetonitrile:water (80:20 v/v) was used as the extractant, in comparison to methanol:water or water alone. Recovery declined over a 42 day period after incorporation, but detectable sorgoleone levels were observed after 7 weeks.     

西瓜化感作用研究进展

西瓜连作引起化感物质积累,导致产量下降,研究西瓜化感作用对揭示西瓜连作障碍机理、
克服西瓜连作障碍具有重要的意义。本文对西瓜化感作用的研究进展进行了综述,包括西瓜化感现象的研
究现状、化感物质及其释放途径、化感物质的作用特点、以及化感作用在西瓜生产实践中的应用,并提出
西瓜化感作用未来的研究方向,旨在为制定增强西瓜抗逆性能和提高西瓜产量、品质的科学途径提供一定
理论参考。     

入侵植物南美蟛蜞菊不同组织部位浸提物的化感作用研究

以油菜和番茄为受试植物,以立枯丝核病原菌和西瓜枯萎病病原菌为受试菌种,研究了南美蟛蜞菊干茎、干叶、湿茎、湿叶酒精浸提物对这两种经济作物种子萌发时的化感作用活性以及对这两种病原菌生长的影响。结果表明,这4种浸提物对油菜种子的活力指数均有不同程度的抑制作用,干叶、湿叶浸提物对番茄种子的活力指数有不同程度的抑制作用;这4种浸提物对立枯丝核病原菌的生长均有明显的抑制作用,干叶、湿茎浸提物对西瓜枯萎病病原菌的生长有抑制作用,但干茎、湿叶浸提物对西瓜枯萎病病原菌的生长存在促进作用。     

白三叶化感作用相关基因CHS的克隆及生物信息学分析

白三叶(Trifolum repens)化感物质中含有多种化学成份,主要含有酚类与萜类及黄酮类物质,而查尔酮合成酶(CHS)是类黄酮途径的第一限速步骤,对于黄酮类物质的合成至关重要。本试验从白三叶中克隆了CHS基因cDNA序列,并对白三叶CHS基因进行了生物信息学分析。结果表明克隆到的CHS基因全长cDNA序列1473bp,其中包含了1170bp的开放阅读框(ORF),起始密码子为ATG,终止密码子为TAA,103bp的5′UTR和200bp 3′UTR编码389氨基酸。且白三叶的CHS基因与同属于豆科的苜蓿CHS、大豆CHS、鹰嘴豆CHS和豌豆CHS亲缘关系最近,处于同一分支,这与植物分类相一致。