Earthworms enhance plant regrowth in a grassland plant diversity gradient

Knowledge of the role of decomposers in the plant diversity–productivity relationship is scarce. In the framework of the Jena Experiment, we observed regrowth of grassland plant communities varying in plant species and functional group richness three weeks after mowing. We investigated earthworm subplots and subplots with reduced earthworm density in order to explore if earthworms enhance plant regrowth and if earthworm effects depend on plant diversity. Earthworms significantly enhanced each of the plant regrowth parameters (plant coverage and maximum and average height of the vegetation) suggesting that particularly fast growing species, such as grasses, benefit from earthworm activity. However, the average height of the vegetation was not affected in 16-species mixtures suggesting compensation of the impact of earthworms on plant regrowth in complex plant communities.     

Endangered plant life

This paper discusses ways and means of more effective action, on an international scale, for the protection of endangered plant life, and shows how, in places where people have become aware of possessing spectacular or unique examples of plant life, they have often added to amenities around sacred places and created inviolate parts of the world's heritage. Good results for conservation of representative areas have been reached locally through improved attitudes towards rational land-use planning, great caution in the employment of herbicides and pesticides, recognition in forestry of the need for a systems planning for natural areas, and awareness that the great diversity of the green plant cover, of flowers and trees, is among the most delightful features helping to keep the Earth as a livable and beautiful environment. Plant protection can be a very good and profitable way to promote local tourism.     

Forms and solubility of plant nutrient elements in tropical plant waste biochars

Thailand is an agriculture‐based country which produces large amounts of agricultural waste. Making biochar from this waste can reduce pollution, decrease costs of production, and increase C sequestration. The agronomic benefits of biochar are partly derived from the available plant nutrients in biochar. This study investigated the fertilizer value of biochars manufactured by slow pyrolysis. Pyrolysis temperature and feedstock type affect nutrient concentrations and nutrient element speciation in biochar. The physio‐chemical, mineralogical and structural properties of biochars made from 14 agriculture wastes (soybean cake, corncob, lemon peel, sugar palm fibre, durian shell, tamarind wood, coconut fibre, coconut shell, bamboo wood, rice husk, eucalyptus wood, oil palm fruit, coffee waste, and bagasse) were investigated. The plant nutrients in biochar mostly occurred in crystalline minerals which were present on the surface and inside the cell structure of biochar. Most biochars examined in this research contained calcite (CaCO₃). The presence in biochars of several K‐minerals [archerite (KH₂PO₄), chlorocalcite (KCaCl₃), kalicinite (KHCO₃), pyrocoproite (K₂MgP₂O₇), struvite‐K (KMgPO₄ · 6 H₂O), and sylvite (KCl)] encourages the use of biochar as a K‐fertilizer. Fibre, fruit and wood biochars contained considerable amounts of K, Ca, and P. Sugar palm and coconut fibres also contained high level of Na in halite. This study recommends the utilization of biochars manufactured from sugar palm fibre, coconut fibre, durian shell, and oil palm fruit as fertilizers. With their appreciable contents of plant nutrients in highly to moderately soluble compounds these biochars should be effective fertilizers, especially for use by organic farmers who cannot use any chemical fertilizers.     

The release and plant uptake of nitrogen from some plant and animal manures

Summary Field and laboratory experiments were used to examine the efficiency of N uptake from various manure forms, and at different rates of application. In a field experiment, wheat was grown on soils with different amounts of ¹⁵N-labelled legume residues. The amount of N taken up by the crop was directly proportional to the amount applied, with a recovery of between 15% and 23% of the legume N. In a second field experiment, inorganic N was applied at rates varying from 0 to 120 kg N ha^-1 in the presence and absence of poultry manure. The uptake of N by barley was 11 kg ha^-1 greater in the manured plots when no inorganic N was applied, and 23 kg ha^-1 greater when N was applied at the top rate. N uptake in a pot experiment was again shown to be directly proportional to the rate of manure application, but the amount of N taken up was strongly related to the N content of the manure. An incubation experiment demonstrated that net N mineralisation reached a maximum where residue concentrations were 1,5%. The significance of added nitrogen interactions in the context of manure-N additions is discussed.     

Water limitation and plant inter-specific competition reduce rhizosphere-induced C decomposition and plant N uptake

Plants can affect soil organic matter decomposition and mineralization through litter inputs, but also more directly through root-microbial interactions (rhizosphere effects). Depending on resource availability and plant species identity, these rhizosphere effects can be positive or negative. To date, studies of rhizosphere effects have been limited to plant species grown individually. It is unclear how belowground resources and inter-specific interactions among plants may influence rhizosphere effects on soil C decomposition and plant N uptake. In this study, we tested the simple and interactive effects of plant diversity and water availability on rhizosphere-mediated soil C decomposition and plant N uptake. The study was conducted in the greenhouse with five semi-arid grassland species (monocultures and mixtures of all five species) and two water levels (15 and 20% gravimetric soil moisture content). We hypothesized that microbial decomposition and N release would be less in the low compared to high water treatment and less in mixtures compared to monocultures. Rhizosphere effects on soil C decomposition were both positive and negative among the five species when grown in monoculture, although negative effects prevailed by the end of the experiment. When grown in mixture, rhizosphere effects reduced soil C decomposition and plant N uptake compared to monocultures, but only at the low-water level. Our results suggest that when water availability is low, plant species complementarity and selection effects on water and N use can decrease soil C decomposition through rhizosphere effects. Although complementarity and selection effects can increase plant N uptake efficiency, plant N uptake in the mixtures was still lower than expected, most likely because rhizosphere effects reduced N supply in the mixtures more than in the monocultures. Our results indicate that rhizosphere effects on C and N cycling depend on water availability and inter-specific plant interactions. Negative rhizosphere effects on soil C decomposition and N supply in mixtures relative to monocultures of the component species could ultimately increase soil C storage and possibly influence how plant communities in semi-arid grasslands respond to global climate change.     

Long-term plant growth legacies overwhelm short-term plant growth effects on soil microbial community structure

Plant-soil feedbacks are gaining attention for their ability to determine plant community development. Plant-soil feedback models and research assume that plant-soil interactions occur within days to weeks, yet, little is known about how quickly and to what extent plants change soil community composition. We grew a dominant native plant (Pseudoroegneria spicata) and a dominant non-native plant (Centaurea diffusa) separately in both native- and non-native-cultivated field soils to test if these species could overcome soil legacies and create new soil communities in the short-term. Soil community composition before and after plant growth was assessed in bulk and rhizosphere soils using phospholipid fatty acid analyses. Nematode abundance and mycorrhizal colonization were also measured following plant growth. Field-collected, native-cultivated soils showed greater bacterial, Gram (−), fungal, and arbuscular mycorrhizal PLFA abundance and greater PLFA diversity than field-collected, non-native-cultivated soils. Both plant species grew larger in native- than non-native-cultivated soils, but neither plant affected microbial composition in the bulk or rhizosphere soils after two months. Plants also failed to change nematode abundance or mycorrhizal colonization. Plants, therefore, appear able to create microbial legacies that affect subsequent plant growth, but contrary to common assumptions, the species in this study are likely to require years to create these legacies. Our results are consistent with other studies that demonstrate long-term legacies in soil microbial communities and suggest that the development of plant-soil feedbacks should be viewed in this longer-term context.     

Effects of plant diversity on plant biomass production and soil macrofauna in Amazonian pastures

We examined the effect of plant diversity on plant production and soil macrofauna density and diversity. Four plants species (Arachis pintoi, an herbaceous legume; Brachiaria brizantha, a perennial grass; Leucaena leucocephala, a legume shrub; Solanum rugosum, a non-legume shrub) were used in a field experiment and communities of all combinations of one, two, three or four species were established. Plant diversity neither significantly affected density and diversity of soil macrofauna nor total plant biomass, however, the biomass of specific plants was negatively affected by plant diversity. Earthworm and ant densities were significantly higher in the presence of A. pintoi although this plant influenced neither the density of the other group nor fauna diversity. Earthworm and diplopod densities increased significantly with shoot biomass of A. pintoi. Fauna diversity increased significantly with shoot biomass (specific and total). Root biomass did not affect fauna density and diversity. Our results suggest that fauna density is affected by litter quality and that it is more affected by resource quantity than quality. Our results also confirm the importance of nitrogen fixers to ecosystem function.     

Diagnostic techniques for cereals based on plant analysis I. Stage of plant development

Abstract

The feasibility of using plant nutrient analysis results in the development of quantitative models for the evaluation and control of the nutritional status and grain yield of lowland rice was studied in a growth chamber experiment. Rice plants were grown under varying basal applications of N, P, K as well as several topdressing levels of N. Concentrations of N, P, K, Ca, Mg and Na in the above ground portions of the plants were measured four times during the growing period and at plant maturity.

Grain yield was closely related to the nutritional status of plants at 2.0 g Dry Hatter weight (DMw) per hill, as indicated by clear and reproducible relationships between the grain yield and concentrations of individual nutrient elements. Interactions between the various nutrient elements were minimum at this DMw. Therefore, 2.0 g DMw per hill was selected as a representative stage of plant development for identifying the reference values for the nutritional status of young rice plants for developing quantitative methods for the evaluation and control of nutritional status and yield.     

基于结构-功能互反馈机制的植物生长可视化建模与仿真(简报)

为确定植物生长可视化建模的一般方法,在总结国内外相关研究成果的基础上,归纳了基于结构-功能反馈机制的植物生长可视化建模的步骤,研究了建模过程中涉及的植物形态结构描述模型、结构模型与功能模型的结合、可视化模型以及模型的有效性检验等关键性技术问题,最后以具体作物生长可视化建模为例阐述了该技术的应用,并对关键性技术问题进行了讨论.研究结果表明,基于结构-功能反馈机制的作物生长模型,不但能可视化模拟不同环境因素下作物的生长发育状况,而且可在作物理想株型培育、群体产量预测、栽培管理等领域发挥实际作用.     

Aerosol deposition on plant leaves

An aerosol generator and wind tunnel system designed for use in aerosol deposition are described. Gross deposition on rough pubescent leaves was nearly seven times greater than on smooth, waxy leaves. Results suggest that aerosol deposition, on a per unit area basis, for single horizontal streamlining leaves is similar to that for arrays of leaves under similar flow conditions. Wind re-entrainment of PbCl₂ particles was negligible while 2.54 cm of simulated rainfall was sufficient to remove 85% of recently applied aerosol.     

Non-streptomycete actinomycetes as biocontrol agents of soil-borne fungal plant pathogens and as plant growth promoters

Among soil microorganisms, bacteria and fungi and to a lesser extent actinomycetes, have received considerable attention as biocontrol agents of soil-borne fungal plant pathogens and as plant growth promoters. Within actinomycetes, Streptomyces spp. have been investigated predominantly, mainly because of their dominance on, and the ease of isolation from, dilution plates and because of the commercial interest shown on the antibiotics produced by certain Streptomyces spp. Many of non-streptomycete actinomycetes (NSA) taxa are therefore rarely reported in literature dealing with routine isolations of biocontrol agents and/or plant growth promoters from plant and soil. It is clear that special isolation methods need to be employed in routine isolations to selectively isolate NSA. Some interesting information exists, albeit in relatively few reports compared to that on other microorganisms, on the biological activities of NSA, especially in relation to their mechanisms of action in the biological control of soil-borne fungal plant pathogens and plant growth promotion. This review presents an overview of this information and seeks to encourage further investigations into what may be considered a relatively unexplored area of research. Certain soil environmental factors, especially in horticultural systems, could be manipulated to render the soil conducive for the biological activities of NSA. A variety of NSA isolated by selective methods have not only shown to be rhizosphere competent but also adapted for an endophytic life in root cortices. Some of the NSA, including endophytic strains that have shown potential to suppress soil-borne fungal plant pathogens, are able to employ one or more mechanisms of antagonism including antibiosis, hyperparasitism and the production of cell-wall degrading enzymes. Strains of NSA promote plant growth by producing plant growth regulators. Enhancement of plant growth by the antagonists are considered to help the host by producing compensatory roots that mask the impact of root diseases.     

铜胁迫对植物生长发育影响与植物耐铜机制的研究进展

铜(Cu)是植物生长发育必需的微量营养元素,在光合作用、呼吸作用、抗氧化系统及激素信号转导等多种生理过程中发挥至关重要的作用,其在植物体内含量过高或不足均会影响植物的正常生理代谢。近年来由于含铜杀菌剂的广泛使用及工业含铜污染物的排放,铜污染对植物生长发育的危害备受关注。研究铜离子对植物生长发育的影响以及植物响应铜胁迫的分子机制,对人们了解植物的耐铜性和铜污染区的植物修复具有重大意义。本文从植物对铜离子的吸收转运及积累,铜胁迫对植物生长发育的影响及植物对铜胁迫的抗性机制3个方面,系统总结了国内外关于植物铜胁迫的研究进展,并提出了需要进一步加强铜胁迫分子调控机制及植物修复方面的研究。     

Effects of irrigation water quality on loquat plant nutrition: Sensitivity of loquat plant to salinity

An investigation was conducted to study the possible use of municipal wastewater for watering loquat plants, and to determine the effects of this water on nutrient status of two‐year‐old loquat plants (Eriobotriae japonica L.) during two complete vegetative cycles. The plants, grafted on franco and Anger stocks, were planted on major soils of the area of La Marina Babea. Plants (grafted on franco stock), irrigated with this wastewater, suffered from foliar necrosis, and all of them died at the end of the experiment, whereas only 12.5% of the plants watered with municipal drinking water died at the same period of time. The Anger stock proved to be much more resistant to salinity than the franco stock. Therefore, medium quality waters (wastewater and saline water) can be used for the irrigation of loquat trees grafted on Anger stock, without causing damages on plant nutrition.     

平衡栽培体系中的有益元素(上)

其实必需元素、有益元素和有害元素之间没有明显的界限.任何一种元素对植物的作用不仅决定于其化学性质,还决定于其农度以及它和其它元素的比例关系是否适合某种植物在一定株龄时的平衡需求或耐受能力.     

Elemental composition of different plant species

Element concentrations in leaves and needles of different plant species (Rhizophora mangle, Aster tri‐polium, Vaccinium vitis—idaea and Pinus sylvestris) are presented in the form of element concentration cadasters with reference to their abundance. The concentration cadasters of the two halophytes (Rhizophora mangle and Aster tripolium) show that the elements Na, Cl, Br and Sr occur at high concentrations in halophytes. The changes in chemical abundances of halophytes can be attributed to the extreme habitat conditions, i. e. physiological drought, under which they grow. Certain elements are preferentially accumulated in specific plants, e. g. Mn in Vaccinium vitis‐idaea.     

植物转录因子功能分析方法

植物转录因子在植物的生长发育及其对外界环境的反应中起着重要的作用。通过各种途径已经分离出大量经序列分析推断为转录因子的基因，但由于方法的局限性，其功能特征还研究得很不够。综述概述了当前常用的研究植物转录因子功能的分子生物学方法，同时介绍了一些研究植物转录因子功能的新方法，如双链RNA和基于糖皮质激素受体的基因诱导表达。     

Iron mobilization by heathland plant extracts

Aqueous extracts of leaves and shoots of Calluna vulgaris, Erica tetralix, and Betula pendula were reacted with iron compounds in the laboratory. Extracts of B. pendula were found to be most active in solubilizing iron. The iron mobilizing capacity of extracts of C. vulgaris depended upon plant age, season, and soil conditions. C. vulgaris shoots were found to be more readily leached of their soluble organic matter than those of B. pendula but yielded little soluble inorganic material. C. vulgaris extracts were the most acid (pH 4.2–4.5) of those examined.