Matching roots to their environment

Background

Plants form the base of the terrestrial food chain and provide medicines, fuel, fibre and industrial materials to humans. Vascular land plants rely on their roots to acquire the water and mineral elements necessary for their survival in nature or their yield and nutritional quality in agriculture. Major biogeochemical fluxes of all elements occur through plant roots, and the roots of agricultural crops have a significant role to play in soil sustainability, carbon sequestration, reducing emissions of greenhouse gasses, and in preventing the eutrophication of water bodies associated with the application of mineral fertilizers.

Scope

This article provides the context for a Special Issue of Annals of Botany on ‘Matching Roots to Their Environment’. It first examines how land plants and their roots evolved, describes how the ecology of roots and their rhizospheres contributes to the acquisition of soil resources, and discusses the influence of plant roots on biogeochemical cycles. It then describes the role of roots in overcoming the constraints to crop production imposed by hostile or infertile soils, illustrates root phenotypes that improve the acquisition of mineral elements and water, and discusses high-throughput methods to screen for these traits in the laboratory, glasshouse and field. Finally, it considers whether knowledge of adaptations improving the acquisition of resources in natural environments can be used to develop root systems for sustainable agriculture in the future.     

Development of Dactylaria eudermata Drechsler a predaceous fungi in Meloidogyne incognita

Dactylaria eudermata Drechsler is one of the important predaceous fungi occurring widely in different soils. The fungus produces hyphal bails and network compound in which nematodes are entangled. This hyphal nets as trapping structure which may be single dimensional to two or three dimensional and are formed through repeated hyphal anastomosis, which capture nematodes either through the adhesive material present on the surface of hyphal nets or due to physical entanglement. In the experiment it was observed that inflation of hyphal bails takes 30 to 50 minutes and capturing and killing the nematode by a single conidia in water takes 35–55 hours, were as time required for inflation of hyphal bails and real trapping and killing of a nematode in maize meal (MMA: water (1:10) medium) takes one minute and 30–50 hours respectively.     

Effect of Metalaxyl on the incidence and severity of Pearl millet downy mildew disease in Northern Nigeria

Pearl millet downy mildew (DM) incidence, severity and yield losses of two pearl millet varieties (local and improved) due to the disease were determined in the field. Significant differences in the disease incidence and severity were recorded in the plots sown with metalaxyl-treated seeds and those sown with non-treated seeds, indicating the efficacy of the fungicide on the fungus. Yield losses due to non-treatment of seeds with metalaxyl was 40.88 and 45.39% in a local variety and 43.00 and 18.60% in an improved variety in the 2000 and 2001 cropping seasons respectively. Significant differences between plots sown with metalaxyl-treated and those sown with non-treated seeds were obtained for other yield components such as 1000-grains weight, panicle length and weight.     

Bioactivity of Piper guineense Schum. & Thonn seed and Moringa oleifera Lam. leaf powder against Trogoderma granarium Everts (Coleoptera: Dermestidae)

Laboratory studies were carried out to investigate bioactivity of Piper guineense seeds and Moringa oleifera leaf powders applied singly or in a mixture against larvae and adult Trogoderma granarium Everts in airtight containers. Three levels (0.0 g, 0.5 g, and 1.0 g/20 g groundnut seeds) of the plant powders were used and pirimiphos-methyl was applied at 0.01 g/20 g seeds (recommended dose). Another control consisting of untreated seeds with aerated lids was included in the bioassay. Both larvae and adults were not killed in control with aerated lids throughout the experimental period and larvae were also tolerant to airtight storage conditions. Adults were more susceptible to plant powders than larvae and adult mortality recorded in P. guineense at 1.0 g, 0.5 g and M. oleifera at 1.0 g/20 g seeds were not significantly different from the mortality observed with the recommended dose of Pirimiphos methyl at five days after treatment (DAT). Larval mortality observed in a mixture of both plants (1:1; w/w) caused significantly higher mortality (77.5%) than other treatments at 5 DAT. All treatments (P. guineense and M. oleifera applied singly or in a mixture) were repellant to larvae T. granarium with 60% repellency recorded in the mixture of plants, 50% repellency in P. guineense and 30% repellency in M. oleifera slurry. The water absorption capacity of treated seeds was not affected by treatment with plant powders and ranged from 31.98% to 37.59%.     

Combined effect of gamma radiation,hot water and sodium bicarbonate on quality and chemical constituents of stored mandarin fruits

The combined effect of gamma radiation and both hot water and sodium carbonate on physiological decay and chemical constituents of stored mandarin fruits was investigated in this work. In this consideration, the studied fruits were gamma irradiated at doses of 0, 0.3, 0.6, 1.2 and 2.4 KGy. Then, the irradiated and non-irradiated fruits were treated either by hot water or sodium bicarbonate to examine their capacity to give a further maintenance and increasing shelf life or storage periods of mandarin. Treated and non-treated fruit samples were taken at intervals of 10 days and up to 60 days. Physiological decay, total acidity, vitamin C, total sugars and TSS were investigated during the different intervals. Gamma radiation treatments showed a promising effect for maintaining the studied fruits and retarding the development of decay. On the other hand, applying both hot water and sodium bicarbonate as a further combined treatments induced a powerful effect on delaying decay development, keeping the chemical constituents near to the normal level and in turn maximizing shelf life and storage periods of the fruits under investigation.     

Use of some emulsified plant seed oils as a safe alternative for the management of Meloidogyne incognita infecting tomato

Abstract

The aim of the present study was to formulate six different plant seed oils namely canola, cotton, flax, olive, sesame and soybean as emulsifiable concentrates. The composition of the formulation comprises at least one organic solvent, one surfactant and one plant oil. Physico-chemical properties of the formulated oils (emulsion stability test, cold stability and heat stability tests) were measured. The successfully emulsified oils were evaluated for nematicidal activity against Meloidogyne incognita infecting tomato plants under greenhouse conditions. Emulsified canola oil proved to be the most effective oil as a protectant against M. incognita infection to tomatoes followed by soybean, cotton, flax and sesame oil. In addition, employing a high rate of the tested emulsified oils gave higher activity in suppressing nematodes both in the soil and in tomato roots than using a low rate. Moreover, all tested formulated oils at both rates of application had no adverse effect on the growth of tomato plants except sesame oil which significantly decreased the shoot length when compared to the control. The prepared plant oils might be used as potential sources for sustainable eco-friendly botanical nematicides to protect plants from nematode attack.     

民族植物学应重视“人类利用实践对植物资源影响”的研究

对民族民间利用植物资源的传统知识进行调查编目、探究相关传统知识形成的原因和影响因素一直是民族植物学研究的重点内容.作为“人与植物”之间关系中一个重要领域——人类利用实践对植物资源影响的研究却相对被忽略.重视这一研究领域,既可以为民族植物学方法及原理在植物资源保护与可持续利用实践提供理论依据,从而有助于推动民族植物学研究进入“应用阶段”,同时也拓展了民族植物学研究领域.其中,人类采集活动(尤其是越来越严重的商业性采集)对植物资源的影响应该受到民族植物学家的重点关注.     

Metabarcoding技术在植物鉴定和多样性研究中的应用

目前植物学研究已进入后植物志时代,iFlora的实现需要以传统植物分类学及相关研究为基础,整合基于高通量测序的DNA条形码（DNAbareoding）技术并开发便携式快速鉴定仪器及构建信息平台。传统植物鉴定多基于形态学分类,而近年来快速发展的DNA条形码快速鉴定技术被各界分类学家认可,在植物鉴定中也被广泛应用。但DNA条形码技术仍存在一些问题亟待解决,如种的鉴定需要多个条形码的解析、Sanger测序平台无法处理混合样品。本文介绍了传统植物分类技术和DNA条形码技术在植物研究中的应用和遇到的瓶颈;并重点介绍了基于高通量测序的metabarcoding技术在植物鉴定及多样性研究中的应用及前景,及其与iFlora的关系。