Gas Exchange of Five Warm‐Season Grain Legumes and their Susceptibility to Heat Stress     

H. Herzog  W. Chai‐Arree 《Journal of Agronomy and Crop Science》2012,198(6):466-474

Objective of this study was to compare the heat stress performance of four pulses from dry and hot areas (mungbeans, limabeans, and teparybeans and cowpeas) with that of soybeans. Two experiments were conducted in growth chambers, and data were pooled because results of both experiments were similar. Plants were raised up to flowering at 24/17 °C (day/night) and were then either exposed to these temperatures until maturity or stressed with 33/24 °C for 2 weeks starting at day 1 or 15 after onset of flowering (early vs. late stress). Before, during and after these stress intervals, gas exchange of representative upper leaves was examined; additionally, immediate effects of increasing leaf temperatures from 24 to 32 or 40 °C on chlorophyll fluorescence were assessed. Without heat stress rates of photosynthesis (P_n), and of transpiration (TR), stomatal and mesophyll conductance (g_s, g_m) and intrinsic transpiration efficiency (iTE) differed significantly among the five crops at each date. However, because of crop‐specific time‐courses ranking among unstressed crops was instable with time, so values were integrated or averaged over time. This procedure revealed high P_n potentials in mung‐ and teparybeans and high iTE values in limabeans compared to the other crops. Heat stress lowered P_n and g_s considerably, but increased TR in all five crops. Relative lowering of P_n during heat stress displayed a crop‐specific pattern with limabeans being least susceptible to both early and late heat stress, while cowpeas were highly susceptible to early stress. Effects on P_n were mainly attributable to lowering of g_s and only in part to g_m. The latter was supported by very small changes (<10 %) of various chlorophyll fluorescence signals shortly after raising leaf temperature to 32 °C in all species. However, in limabeans, a decreased electron transport rate (e‐rate, ?18 %) and an increased non‐photochemical quenching (Q_N, +16 %) pointed to an adaptive mechanism to avoid oxidative strains under heat. Leaf temperatures of 40 °C immediately provoked stronger changes in all fluorescence signals than 32 °C; substantial damages at 40 °C were indicated by effective quantum yield, photochemical quenching and ratio of fluorescence decrease in mungbeans and low ones in cowpeas and soybeans. Nevertheless, some adaptive responses of e‐rates and Q_N were observed in all crops and were most expressed in limabeans.  相似文献   

Pamela Walker: Growing good things to eat in Texas: Profiles of organic farmers and ranchers across the state     

Patrick T. Lillard 《Agriculture and Human Values》2010,27(4):527-528

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The effects of applied crop residues on losses of Fe, Mn, Cu and Zn in run-off from a soil prone to crusting     

J. M. Mirás Avalos  I. Bertol    P. Sande Fouz  C. Carballeira  Díaz  E. Vidal Vázquez  & A. Paz  Gonzalez 《Soil Use and Management》2009,25(2):193-200

Tillage practices may reduce the organic matter content in near-surface soil horizons causing crust formation. Surface conditions may cause an increase in surface run-off, thus enhancing contaminant transfer of heavy metals or an acceleration in nutrient loss. This study examines the effect of applying crop residues to the surface of tilled soils on heavy metal losses by run-off. Losses in iron (Fe), manganese (Mn), zinc (Zn) and copper (Cu) were analysed. Run-off and sediment yield were measured on 1 m² plots using a rainfall simulator with a constant 65 mm/h intensity. Four successive rainfall applications were performed, the first three at 25 mm each and the last at 65 mm. Added corn straw varied between 0 and 4 t/ha in the five studied treatments. After 140 mm cumulative rainfall, total heavy metal losses were as follows: Fe from 137 to 950 mg/L, Mn from 2.3 to 12.83 mg/L, Cu from 0.09 to 0.72 mg/L and Zn from 0.31 to 2.46 mg/L. Dissolved fractions were as follows: Fe from 0.014 to 0.229 mg/L, Mn from 0.034 to 1.45 mg/L, Cu from 0.002 to 0.013 mg/L and Zn from 0.02 to 0.12 mg/L. Total concentrations of the studied elements decreased exponentially due to the effect of corn straw on soil loss. However, dissolved contents of Fe and Cu scarcely varied. Significant positive linear correlations were observed between total heavy metal content and soil and sediment loss by run-off. It is concluded that the addition of straw to a soil of low fertility prevents heavy metal loss.  相似文献   

Is variable compensation always win-win?     

T Melbo 《Journal of the American Veterinary Medical Association》1999,215(2):188-189

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Effect of glyphosate on the tripartite symbiosis formed by Glomus intraradices,Bradyrhizobium japonicum,and genetically modified soybean     

Jeff R. Powell  Rachel G. Campbell  Kari E. Dunfield  Robert H. Gulden  Miranda M. Hart  David J. Levy-Booth  John N. Klironomos  K. Peter Pauls  Clarence J. Swanton  Jack T. Trevors  Pedro M. Antunes 《Applied soil ecology》2009,41(1):128-136

Most soybeans grown in North America are genetically modified (GM) to tolerate applications of the broad-spectrum herbicide glyphosate; as a result, glyphosate is now extensively used in soybean cropping systems. Soybean roots form both arbuscular mycorrhizal (AM) and rhizobial symbioses. In addition to individually improving host plant fitness, these symbioses also interact to influence the functioning of each symbiosis, thereby establishing a tripartite symbiosis. The objectives of this study were to (1) estimate the effects of glyphosate on the establishment and functioning of AM and rhizobial symbioses with GM soybean, and (2) to estimate the interdependence of the symbioses in determining the response of each symbiosis to glyphosate. These objectives were addressed in two experiments; the first investigated the importance of the timing of glyphosate application in determining the responses of the symbionts and the second varied the rate of glyphosate application. Glyphosate applied at recommended field rates had no effect on Glomus intraradices or Bradyrhizobium japonicum colonization of soybean roots, or on soybean foliar tissue [P]. N₂-fixation was greater for glyphosate-treated soybean plants than for untreated-plants in both experiments, but only when glyphosate was applied at the first trifoliate soybean growth stage. These data deviate from previous studies estimating the effect of glyphosate on the rhizobial symbiosis, some of which observed negative effects on rhizobial colonization and/or N₂-fixation. We did observe evidence of the response of one symbiont (stimulation of N₂-fixation following glyphosate) being dependent on co-inoculation with the other; however, this interactive response appeared to be contextually dependent as it was not consistent between experiments. Future research needs to consider the role of environmental factors and other biota when evaluating rhizobial responses to herbicide applications.  相似文献   

Genetic mapping of the prion protein gene (PRNP) on bovine chromosome 13     

J. Schlpfer  N. Stahlberger‐Saitbekova  J. Küffer  G. Dolf 《Zeitschrift für Tierzüchtung und Züchtungsbiologie》2000,117(4):288-288

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An Analysis of Urban Size and Territorial Location Effects on Employment Probabilities: The Spanish Case     

ANA VIÑUELA‐JIMÉNEZ  FERNANDO RUBIERA‐MOROLLÓN  BEGOÑA CUETO 《Growth and change》2010,41(4):495-519

The probability of being employed varies depending on several factors. Many of these are related to personal characteristics such as educational level, age, gender, or number and age of children. Nevertheless, other factors may be relevant, in particular the geographical environment. The purpose of this paper is to analyse the relevance of urban size and the position of each territory (in terms of its distance from large metropolises) for the probability of being employed in the Spanish economy. Following the set of economic regions suggested by Polése, Shearmur and Rubiera (2007 ), we try to explain the spatial patterns of employment distribution. Our results show some relevant differences between these alternative economic areas. We find that municipalities with similar sizes and located at a similar distance from a metropolis but belonging to different Autonomous Communities or provinces share similar employability patterns.  相似文献   

Mechanical transmission of maize rayado fino marafivirus (MRFV) to maize and barley by means of the vascular puncture technique     

K. Madriz-Ordeñana  R. Rojas-Montero  T. Lundsgaard  P. Ramírez  H. Thordal-Christensen  & D.B. Collinge 《Plant pathology》2000,49(2):302-307

Maize rayado fino marafivirus (MRFV) was mechanically transmitted to kernels of three Costa Rican maize cultivars by the vascular puncture technique. A transmission rate of up to 43.2% was obtained for cultivar HC-57. The rate of MRFV transmission to maize was possibly affected by the morphology of the kernel, which may influence physical access to the vascular tissue after water imbibition. Transmission to maize was confirmed by western blot and immunosorbent electron microscopy. By slight modifications of the procedure, MRFV was also transmitted to barley. This is the first report of MRFV infecting a species outside the supertribe Andropogonodae. Virus infection and replication in barley were confirmed by RT-PCR detection of MRFV RNA and by detection of the virus by ELISA.  相似文献   

Elastic Training for the Prevention of Mandibular Drift Following Mandibulectomy in Dogs: 18 Cases (2005–2008)     

Yoav Bar‐Am  Frank J. M. Verstraete 《Veterinary surgery : VS》2010,39(5):574-580

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Some properties of alfalfa mosaic virus isolated from Buddleia davidii in the UK     

C. J. PERKINS  R. G. T. HICKS 《Plant pathology》1989,38(3):443-446

Alfalfa mosaic virus (AMV) and cucumber mosaic virus (CMV) were isolated from clones of Buddleia davidii collected at Long Ashton Research Station for assessment of horticultural characteristics. The AMV isolate investigated in this study (AMV-B) infected 18 species and cultivars of herbaceous test plants. The in vitro properties of AMV-B were determined. The virus was purified by permeation chromatography on controlled-pore glass beads and an antiserum prepared. AMV-B appeared to be serologically indistinguishable from AMV isolate 15/64. The sizes and shapes of the virus particles were those of classical AMV components. The capsid protein was a single polypeptide of Mr 24 375. Buddleia seedlings inoculated with AMV-B showed only mild chlorosis and slight distortion of leaves.  相似文献