Seed treatment technology: An attractive delivery system for controlling root parasitic weed Striga with mycoherbicide

Coating sorghum seeds with Fusarium oxysporum (Foxy 2) for control of the root parasitic weed Striga, appears to be an attractive option for minimizing the inoculum amount, establishing the biocontrol agent in the potential infection zone of the host plants, and offering a simple, easy and economical delivery system. Our investigations resulted in the selection of appropriate seed coating materials and a suitable type and form of fungal inoculum. The coating materials tested were arabic gum (AG10%, 20%, 40%), carboxymethylcellulose (CMC1%, 2%) and pectin (LS 440, LM-5 CS) 1%, while the fungal inoculum included microconidia and fresh and dried chlamydospores produced using different substrates. Foxy 2 survived the seed treatment processing and showed excellent viability on seeds for at least 8 months of storage after coating. In general, the performance of 40% arabic gum in combination with dried chlamydospores was the best among the other types of inoculum and coating material tested. Regardless of the type and form of inoculum and coating materials tested, Foxy 2 was able to colonize all roots, even root tips and hairs of the host (sorghum), thereby meeting important criteria of a promising candidate for controlling Striga when applied as a seed treatment. The efficacy of treated sorghum seed with Foxy 2 using different coating materials in reducing S. hermonthica infestation was evaluated in pot and root chamber trials. Foxy 2 markedly reduced Striga emergence and dry weight and increased the percentage of the diseased emerged Striga shoots. However, the efficacy of seed coating varied according to the type and form of fungal inoculum as well as coating material. Coating sorghum seed with dried chlamydospore inoculum homogenized into 20% arabic gum (as adhesive) showed the highest efficacy of 81 and 77% (i.e., percent reduction in healthy emerged Striga shoots compared to the control treatment) against Striga using either sterilized or non-sterilized soil, respectively. In root chamber bioassays, the application of Foxy 2 in combination with AG40% significantly caused disease in 77% of the germinated Striga seeds and in all tubercles after 25 days of sowing. These findings provide an optimized coating protocol as an attractive delivery system for bioherbicides for root parasitic weeds.     

Seed hemagglutinins

Substances which agglutinate red blood cells are widely distributed in nature, particularly in the seeds of leguminous plants. Some of these have been isolated in a high state of purity and carefully studied with respect to their chemical and physical properties, immunological behavior, and toxicological effects on animals. Of these, the hemagglutinins of the castor bean, jack bean, soybean, and varieties of Phaseolus vulgaris have received the most attention. The possible nutritional significance of those hemagglutinins which are found in edible legumes is discussed. A mechanism is proposed to explain the nature of the interaction of hemagglutinins with red blood cells, and their possible function in the plant.     

Seed biology

Seed biology is an intensive area of study,a reflection of the significance of seeds for several scientific areas.From an evolutionary perspective,the ability of plants to make seeds has conf erred major selective advantages,accounting,in part,for the success of seed plants as the largest and most species-rich group of land plants.The seed habit facilitates fertilization in non-aqueous environments,provides a level of physical and biological protect!on for the female gametophyte and embryo,allows for the massive accumulation of storage proteins,lipids,and/or carbohydrates in the embryo and/or endosperm to serve as a nutrient reserve for the germinating seed and developing seedling,and permits the embryo to remain in a developmentally arrested and metabolically quiescent state until environ mental conditions permit germination to occur(Steeves 1983).     

种子细胞——组织工程连载之三

种子细胞也是组织工程的核心研究内容,获得足够数量和质量的种子细胞是开展体外组织工程的必要基础。用于组织工程的种子细胞必须具有形成新组织结构的能力,主要来源于自体、同种异体或异种,在具体应用时各有利弊。一些成体干细胞由于不存在伦理争议以及发育分化条件相对简单等优势是重要的种子细胞,包括造血干细胞、骨髓干细胞、神经干细胞、脂肪干细胞、皮肤干细胞。人胚胎干细胞及其组织工程要真正在临床医学中得到应用,还有很长的一段路要走。其他一些细胞也可以作为组织工程种子细胞,包括内皮细胞、上皮细胞、成纤维细胞、骨细胞、成骨细胞、角质细胞、前脂肪细胞、脂肪细胞、肌腱细胞等。这些细胞已分化,分裂能力有限,但仍应用于组织工程。理想的种子细胞具有一定标准。     

种子感光的机理及影响种子感光性的因素

种子的萌发或休眠均取决于萌发时种子内所建立起来的Pfr含量和Pfr/(Pr Pfr)比值。种子内的Pfr水平受到诸多因素的影响。光中性种子在成熟时已存在适合萌发的Pfr水平;需光种子在不同程度地接受白光或红光照射后,方可达到适宜的Pfr水平;忌光种子萌发要求的Pfr水平较低,因此萌发需要较长时间的黑暗。种子的感光性不是绝对的,母株的生长条件、种子本身的成熟度、贮藏状况、光质、光流量、光周期、萌发温度、O2供应及某些化合物的处理等都可使种子的感光性发生改变。     

含水量对种子贮藏寿命的影响

建立以收集种子为主体的基因库乃是当今保护植物种质资源最为普遍且可靠易行的方式,在世界库存约 61 0 0 0 0 0份种质资源中,近 90 %是以种子形式保存于约 1 30 0个基因库中。低温贮藏仍是目前基因库中种子种质保存的主要方法。种子含水量和贮藏温度是影响种子在贮藏期间生活力和活力保持的关键因素。传统的经验认为控制温度比控制水分来得安全有效,因而趋向于向低温或超低温的贮藏方向发展。国际植物遗传资源研究所（ＩＰＧＲＩ）曾推荐 5%～ 6%的含水量和 - 1 8～- 2 0℃低温作为各国长期保存种子的理想条件。目前,世界各国都把更多的…     

Seed Rain and Seed Bank Reveal that Seed Limitation Strongly Influences Plant Community Assembly in Grasslands

Dispersal is an important factor in plant community assembly, but assembly studies seldom include information on actual dispersal into communities, i.e. the local propagule pool. The aim of this study was to determine which factors influence plant community assembly by focusing on two phases of the assembly process: the dispersal phase and the establishment phase. At 12 study sites in grazed ex-arable fields in Sweden the local plant community was determined and in a 100-m radius around the centre of each site, the regional species pool was measured. The local seed bank and the seed rain was explored to estimate the local propagule pool. Trait-based models were then applied to investigate if species traits (height, seed mass, clonal abilities, specific leaf area and dispersal method) and regional abundance influenced which species from the regional species pool, dispersed to the local community (dispersal phase) and which established (establishment phase). Filtering of species during the dispersal phase indicates the effect of seed limitation while filtering during the establishment phase indicates microsite limitation. On average 36% of the regional species pool dispersed to the local sites and of those 78% did establish. Species with enhanced dispersal abilities, e.g. higher regional abundance, smaller seeds and dispersed by cattle, were more likely to disperse to the sites than other species. At half the sites, dispersal was influenced by species height. Species establishment was however mainly unlinked to the traits included in this study. This study underlines the importance of seed limitation in local plant community assembly. It also suggests that without information on species dispersal into a site, it is difficult to distinguish between the influence of dispersal and establishment abilities, and thus seed and microsite limitation, as both can be linked to the same trait.     

Seed Number, Seed Size and Seed Diversity in Washington Lupin (Lupinus polyphyllus Lindl.)

Over 20 000 seeds of the Washington lupin (Lupinus polyphyllusLindl.) were examined and measured in an experiment carriedout over a 10 year period (1989–1999). Four differentgroups of Washington lupin seeds were found: dark, patterned,grey and light seeds. During the 10 year experiment, the totalaverage number of seeds per plant decreased from 2654 (1990)to 1220 (1999), there was a slight decrease in seed weight perplant and an increase in the average weight per seed. Therewas a clear seed size/number trade-off at the intraspecificlevel. The relative proportions of each seed group also changedwith patterned seeds becoming dominant (50% at the beginningand 90% at the end of the experiment), grey seeds remained constant(constituting 10% of the total seeds) and the proportion ofboth dark (33% at the beginning and 5% at the end) and light(10% at the beginning and 5% at the end of the experiment) seedsdecreased. Six hundred and sixty nine seeds were found to havea different testa ornamentation; they were distributed amongthe different groups as follows: 48% patterned seeds, 29% darkseeds, 12% grey seeds and 11% light seeds. There were no significantdifferences in the physical dimensions of the ornamented seedscompared with all other seeds. The results suggest that theWashington lupin is a mixture of different species and botanicalforms; this is discussed in relation to possible selection pressuresto produce both smaller and larger seeds. The possibility thatchanges in testa ornamentation are influenced by genes controllingthe synthesis of the seed coat pigment is discussed. Copyright2001 Annals of Botany Company Lupinus polyphyllus Lindl., lupine, plant biotechnology, plant parameters, selection pressure, seed size/number trade-off, testa ornamentation     

沙葱种皮特性、种胚及种子浸提液与种子休眠的关系

本文以沙葱休眠种子为试材,检测其种皮透水性、透气性、超微结构、种胚休眠及种子浸提液。结果表明,酸蚀种子吸水12h达饱和,吸水率是完整种子的2倍;其呼吸强度最大值是完整种子的1.36倍。酸蚀处理使种子表面结构破损,角质层脱落,种孔露出。沙葱种子离体胚接种培养后2～3d,种胚开始萌发,萌发率达85％。沙葱完整种子与粉碎种子的浸提液对白菜种子发芽率、苗高、根长均有抑制作用,且随着浓度的提高而增强。     

Amaranthus hypochondriacus: Seed Structure and Localization of Seed Reserves

The mature seed of Amaranthus hypochondriacus L. consists ofa peripheric embryo surrounding the nutritive tissue which isthe perisperm. Endosperm remnants are close to the root tip.Cytochemical analysis revealed that the embryo and endospermcells had a quite homogenous internal organization, with proteinbodies embedded in a lipid matrix. The embryo, however, appearsvariable in tissue organisation, due to the differentiationof the three primary meristematic tissues: the procambium appearsas a single bundle in the embryonic axis or as small bundlesthroughout the cotyledons length, these provascular cells aresmall and elongated and with fewer reserves and more cellularorganelles than the large protoderm and ground meristem cells.These latter cells have more protein bodies, and they show ahigher number of larger globoid crystal inclusions than theothers. The perisperm is a starchy tissue, and its cells havethin walls and are full of angular starch grains.Copyright 1994,1999 Academic Press Amaranth, Amaranthus hypochondriacus, seed structure, seed reserves     

植物的种子引发

就种子引发方法、引发条件、引发效应、生理生化和分子机制的研究进展作了介绍,并对种子引发研究和应用前景作了讨论。     

Seed predator responses

Summary An examination of Enterolobium contortisiliquum predispersal seed predation by beetles suggests that simple tests of the importance of seed density or seed distance from the parent tree must be interpretated with caution.     

Iris Seed Dormancy

Iris embryos were treated in several ways to study the cause of delayed germination. The results of this work indicate that a chemical inhibitor is present in the endosperm and mechanical inhibition of embryo growth also occurs. The mechanical inhibition reduces excised Iris embryo growth to the same extent as does the chemical inhibitor.     

植物种子脂氧合酶

概述了植物种子脂氧合酶蛋白和编码其基因的特性、各种突变体及其遗传规律、基因表达和调控以及生理功能的研究进展.