Variations in the migratory history of the tropical catadromous eels Anguilla bicolor bicolor and A. bicolor pacifica in south-east Asian waters

Fish movements between aquatic habitats of different salinity ranges (fresh, estuarine, marine) by the tropical catadromous eels Anguilla bicolor bicolor and A. bicolor pacifica were examined by analysing the otolith strontium and calcium concentrations of yellow (immature) and silver (mature) stage eels collected in south-east Asian (Indonesia, Malaysia and Vietnam) waters. The ratios suggest that all migratory-type eels, including freshwater, brackish water and marine residents, pass the river mouth. However, the habitat preference was different among the sites (countries). In Indonesia and Vietnam, most A. bicolor bicolor and A. bicolor pacifica were either marine or brackish water residents in this study. Alternatively, most A. bicolor bicolor were freshwater residents in Malaysia; such a typical catadromous migration pattern in these eels has not been found in previous studies. The wide range of otolith Sr:Ca in both subspecies indicates that the habitat use of these tropical eels was opportunistic among fresh, brackish and marine waters during their growth phases following recruitment to coastal areas. The geographical variability of migratory histories suggests that habitat use might be determined by the inter and intraspecific competition and environmental conditions at each site.     

Solarization in a forest nursery: effect on ectomycorrhizal soil infectivity and soil receptiveness to inoculation with Laccaria bicolor

 Field experiments were carried out in a forest nursery during the summer of 1994 to examine the effect of soil solarization on ectomycorrhizal soil infectivity (ESI) and soil receptiveness to inoculation with Laccaria bicolor. Soil samples from solarized, steamed, fumigated and untreated plots were periodically collected and assayed for ESI. Untreated soil exhibited high ESI. Solarization was as effective as steaming or fumigation in reducing ESI in the uppermost layer. Solarization with a double layer of polyethylene film and fumigation were the only treatments which reduced ESI deeper in the soil. During July, the temperature of covered beds reached 50  °C at a soil depth of 5 cm. Ectomycorrhizal fungi were among the soil-borne fungi most sensitive to solar heating. Soil solarization provides an effective disinfection method for controlled mycorrhization in forest nurseries. Accepted: 10 April 1997     

An ectomycorrhizal fungus alters sensitivity to jasmonate,salicylate, gibberellin,and ethylene in host roots

The phytohormones jasmonate, gibberellin, salicylate, and ethylene regulate an interconnected reprogramming network integrating root development with plant responses against microbes. The establishment of mutualistic ectomycorrhizal symbiosis requires the suppression of plant defense responses against fungi as well as the modification of root architecture and cortical cell wall properties. Here, we investigated the contribution of phytohormones and their crosstalk to the ontogenesis of ectomycorrhizae (ECM) between grey poplar (Populus tremula x alba) roots and the fungus Laccaria bicolor. To obtain the hormonal blueprint of developing ECM, we quantified the concentrations of jasmonates, gibberellins, and salicylate via liquid chromatography–tandem mass spectrometry. Subsequently, we assessed root architecture, mycorrhizal morphology, and gene expression levels (RNA sequencing) in phytohormone-treated poplar lateral roots in the presence or absence of L. bicolor. Salicylic acid accumulated in mid-stage ECM. Exogenous phytohormone treatment affected the fungal colonization rate and/or frequency of Hartig net formation. Colonized lateral roots displayed diminished responsiveness to jasmonate but regulated some genes, implicated in defense and cell wall remodelling, that were specifically differentially expressed after jasmonate treatment. Responses to salicylate, gibberellin, and ethylene were enhanced in ECM. The dynamics of phytohormone accumulation and response suggest that jasmonate, gibberellin, salicylate, and ethylene signalling play multifaceted roles in poplar L. bicolor ectomycorrhizal development.     

梭梭林下土壤结皮发育对黄花补血草种群发育格局的影响

通过梭梭林下黄花补血草种群调查,研究土壤结皮发育过程中的无结皮沙地(前期NSC1、后期NSC2)、物理结皮沙地(前期PSC1、后期PSC2)和生物结皮沙地(前期BSC1、后期BSC2)的黄花补血草种群发育格局特征,以揭示梭梭林下土壤结皮发育对黄花补血草种群发育的影响以及植被恢复技术。结果表明:(1)梭梭林下土壤结皮的发育对黄花补血草的种群密度具有显著的促进作用,在BSC1样地达到最大,而对个体冠幅具有前期促进后期抑制的作用,在NSC2样地达到最大,故导致种群总盖度变化不稳定。(2)种群个体发育值呈先增加后减小的趋势,在NSC2样地达到最大;在NSC1-NSC2过程中,土壤结皮发育对种群个体发育具有促进作用,其值逐渐增大,而在NSC2-BSC2发育过程中,土壤结皮发育对种群个体发育的抑制作用逐渐增强,其值逐渐减小。(3)黄花补血草种群优势级层位于较低级层,随着土壤结皮的发育,呈先增加后减小的趋势,其峰值在BSC1样地,而种群级层越高,该级层的峰值则逐渐向土壤结皮发育前期移动,其峰值在NSC2或PSC1样地。研究认为,梭梭林下土壤结皮发育对黄花补血草种群密度具有促进作用,但对种群内植株个体发育具有前期促进后期抑制的作用,该结论对梭梭林下黄花补血草植被恢复具有积极的指导意义。     

Mesophyll CO2 conductance and leakiness are not responsive to short‐ and long‐term soil water limitations in the C4 plant Sorghum bicolor

Breeding economically important C₄ crops for enhanced whole‐plant water‐use efficiency (WUE_plant) is needed for sustainable agriculture. WUE_plant is a complex trait and an efficient phenotyping method that reports on components of WUE_plant, such as intrinsic water‐use efficiency (WUE_i, the rate of leaf CO₂ assimilation relative to water loss via stomatal conductance), is needed. In C₄ plants, theoretical models suggest that leaf carbon isotope composition (δ¹³C), when the efficiency of the CO₂‐concentrating mechanism (leakiness, ?) remains constant, can be used to screen for WUE_i. The limited information about how ? responds to water limitations confines the application of δ¹³C for WUE_i screening of C₄ crops. The current research aimed to test the response of ? to short‐ or long‐term moderate water limitations, and the relationship of δ¹³C with WUE_i and WUE_plant, by addressing potential mesophyll CO₂ conductance (g_m) and biochemical limitations in the C₄ plant Sorghum bicolor. We demonstrate that g_m and ? are not responsive to short‐ or long‐term water limitations. Additionally, δ¹³C was not correlated with gas‐exchange estimates of WUE_i under short‐ and long‐term water limitations, but showed a significant negative relationship with WUE_plant. The observed association between the δ¹³C and WUE_plant suggests an intrinsic link of δ¹³C with WUE_i in this C₄ plant, and can potentially be used as a screening tool for WUE_plant in sorghum.     

土壤节肢动物对箭竹凋落叶分解过程中酶活性的影响

为了解凋落物分解过程中土壤节肢动物与土壤酶活性的相互联系,以川西亚高山森林箭竹(Fargesia spathacea)凋落叶为对象,通过原位控制实验,于2016年4月至2018年4月研究了土壤节肢动物对凋落叶分解过程中碳、氮和磷转化相关酶活性的影响。结果表明:生物抑制剂施用降低了分解袋中土壤节肢动物49.7%~66.8%的个体密度和19.2%~46.3%的类群数量;对照和处理分解袋中凋落叶碳、氮和磷转化相关酶活性随分解过程呈现相似的动态;与处理相比,土壤节肢动物参与(对照)显著提高了凋落叶分解过程中蔗糖酶、β-葡聚糖苷酶、纤维素酶、多酚氧化酶、过氧化物酶、N-乙酰-β-D-氨基葡萄糖苷酶和酸性磷酸酶活性;土壤节肢动物对凋落叶分解过程中酶活性的贡献率在达到一个明显的峰值后快速降低;土壤温度和土壤节肢动物类群数量与蔗糖酶活性呈显著正相关,与β-葡聚糖苷酶、纤维素酶、多酚氧化酶、过氧化物酶、N-乙酰-β-D-氨基葡萄糖苷酶和酸性磷酸酶活性呈显著负相关。土壤节肢动物对凋落叶分解过程中酶活性促进效应随酶类型和分解时间变化存在差异,与土壤节肢动物群落结构和分解环境密切相关。     

Visualization of Toyoura sand-grown plant roots by X-ray computer tomography

Plants establish their root system as a three-dimensional structure, which is then used to explore the soil to absorb resources and provide mechanical anchorage. Simplified two-dimensional growth systems, such as agar plates, have been used to study various aspects of plant root biology. However, it remains challenging to study the more realistic three-dimensional structure and function of roots hidden in opaque soil. Here, we optimized X-ray computer tomography (CT)-based visualization of an intact root system by using Toyoura sand, a standard silica sand used in geotechnology research, as a growth substrate. Distinct X-ray attenuation densities of root tissue and Toyoura sand enabled clear image segmentation of the CT data. Sorghum grew especially vigorously in Toyoura sand and it could be used as a model for analyzing root structure optimization in response to mechanical obstacles. The use of Toyoura sand has the potential to link plant root biology and geotechnology applications.     

高粱SUT基因家族的生物信息学分析

蔗糖转运蛋白(sucrose transporters,SUTs)属于跨膜转运蛋白,大多数参与蔗糖的吸收和转运。迄今为止,对高粱蔗糖转运蛋白知之甚少,为进一步研究高粱蔗糖转运蛋白家族(SbSUTs),本研究利用生物信息学方法对SbSUTs的6个成员(编号SbSUT1~SbSUT6)进行蛋白理化性质、基因结构、蛋白结构、同源性及系统进化树构建等分析。结果表明:SbSUTs是一种无信号肽、定位于质膜和叶绿体类囊膜上的疏水性膜蛋白;SbSUTs均具有GPH结构功能域,是高度保守的蛋白;α-螺旋和无规卷曲是主要的二级结构元件,其三级结构较为相似。本研究为探究SbSUTs蛋白家族在高粱的蔗糖吸收及转运中的功能提供理论依据。     

Food preferences of Shorelarks Eremophila alpestris,Snow Buntings Plectrophenax nivalis and Twites Carduelis flavirostris wintering in the Wadden Sea

Capsule Seeds of plants from lower salt marsh communities are preferred, with insects less important.

Methods Droppings of Shorelarks Eremophila alpestris, Snow Buntings Plectrophenax nivalis and Twites Carduelis flavirostris sampled in the German Wadden Sea were analysed and compared with food abundance to assess preferences.

Results Shorelarks prefer seeds of Salicornia sp., Suaeda maritima, Atriplex sp., Halimione portulacoides and unidentified small grass seeds. Insects are eaten mainly in periods of seed shortage, but are consumed in smaller amounts during the winter. The food composition of Snow Buntings is very similar, but additionally Triglochin maritimum is commonly eaten. Twites are specialized on seeds of Salicornia sp. and Suaeda maritima and rarely ingest other seeds and insects. All seeds consumed were of plants from lower salt marsh communities. Many halophyte seeds, and especially those that birds feed on, are rich in energy. Large seeds and those which need a long handling time are avoided.

Conclusion Changes in the lower salt marshes of the Wadden Sea by embankments and intensified grazing might have been responsible for the rapid population decline from the 1960s to 1980s.     

Response of near‐isogenic sorghum lines,differing at the P locus for plant colour,to grain mould and head smut fungi

Leaves and stalks of many sorghum genotypes accumulate dark red or purple pigments upon wounding while some plants, called ‘tan,’ do not. Grains with unpigmented ‘white’ pericarps grown on tan plants are more desirable for food. The hypothesis tested was that pigments in plants protected grain against the panicle diseases grain mould and head smut. Near‐isogenic tan or purple plant colour genotypes with white grain were planted at Lincoln and Ithaca, NE and Corpus Christi, TX. The field grown grain was plated onto semi‐selective media to detect the presence of grain colonisation by mould genera Alternaria, Fusarium and Curvularia. More Fusarium and Curvularia spp. were recovered from grain grown at Corpus Christi than the Nebraska locations; however, there was no indication that the grain from purple plants was more resistant to the three fungal genera. Most fungi were identified morphologically as Alternaria alternata. Molecular identification of Fusarium species, using translation elongation factor 1‐α gene sequences, showed that Fusarium thapsinum and Fusarium proliferatum infected grain at all three locations. Head smut disease of panicles, caused by the fungus Sporisorium reilianum, was assessed at Corpus Christi; surprisingly, purple plants had significantly greater disease incidence than tan plants. We propose that the tan plant colour lines with white grain are promising for development of food‐grade sorghums not more susceptible than pigmented lines to grain mould and head smut.