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Copyright of Argentinian Horticulture / Horticultura Argentina is the property of Revista Horticultura Argentina and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Maize is cultivated under different agricultural management systems, which influence the ecological dynamics of the crop, and therefore the physiology of the plant. Questions: What is the effect of different agricultural management on the microclimate and the physiology of maize plants? Studied species: Zea mays L. Study site and dates: Nacajuca, Tabasco, Mexico; January to April 2017. Methods: Physiological performance of maize plants and microclimatic variation in the crop area was characterized under three management systems: maize monoculture, maize-bean, and maize-bean-squash intercropping. Each treatment was established in three 100 m2 plots (300 m2 per treatment). Four measurements were taken between days 33 and 99 after maize sowing, to characterize five microclimatic parameters (relative air humidity, air and soil temperature, vapor-pressure deficit and soil volumetric water content) and nine physiological parameters (photosynthesis, transpiration, water use efficiency, stomatal conductance, electron transport rate, quantum efficiency of photosystem II, non-photochemical quenching, foliar water potential and chlorophyll content). Results: Maximum soil temperature was up to 4.4 ºC less in the maize-bean system than in the monoculture at 15:00 h; soil in the maize-bean-squash intercropping retained up to 45 % more water than the monoculture throughout the day. Photosynthesis and electron transport rate in the maize-bean intercropping was up to 32 % higher than in the monoculture. The highest non-photochemical quenching and transpiration rate were observed in the maize-bean-squash system. Conclusions: The maize-bean and maize-bean-squash combination provides maize plants with lower soil temperature and higher water availability, allowing them better physiological performance compared to monoculture.

Copyright of Agronomía & Ambiente is the property of Universidad de Buenos Aires. Facultad de Agronomia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Approval for glyphosate-based herbicides in the European Union (EU) is under intense debate due to concern about their effects on the environment and human health. The occurrence of glyphosate residues in European water bodies is rather well documented whereas only few, fragmented and outdated information is available for European soils. We provide the first large-scale assessment of distribution (occurrence and concentrations) of glyphosate and its main metabolite aminomethylphosphonic acid (AMPA) in EU agricultural topsoils, and estimate their potential spreading by wind and water erosion. Glyphosate and/or AMPA were present in 45% of the topsoils collected, originating from eleven countries and six crop systems, with a maximum concentration of 2 mg kg − 1 . Several glyphosate and AMPA hotspots were identified across the EU. Soil loss rates (obtained from recently derived European maps) were used to estimate the potential export of glyphosate and AMPA by wind and water erosion. The estimated exports, result of a conceptually simple model, clearly indicate that particulate transport can contribute to human and environmental exposure to herbicide residues. Residue threshold values in soils are urgently needed to define potential risks for soil health and off site effects related to export by wind and water erosion. [ABSTRACT FROM AUTHOR]

Climate change may both exacerbate the vulnerabilities and open up new opportunities for farming in the Northeastern USA. Among the opportunities are double-cropping and new crop options that may come with warmer temperatures and a longer frost-free period. However, prolonged periods of spring rains in recent years have delayed planting and offset the potentially beneficial longer frost-free period. Water management will be a serious challenge for Northeast farmers in the future, with projections for increased frequency of heavy rainfall events, as well as projections for more frequent summer water deficits than this historically humid region has experienced in the past. Adaptations to increase resilience to such changes include expanded irrigation capacity, modernized water monitoring and irrigation scheduling, farm drainage systems that collect excess rain into ponds for use as a water source during dry periods, and improved soil water holding capacity and drainage. Among the greatest vulnerabilities over the next several decades for the economically important perennial fruit crop industry of the region is an extended period of spring frost risk associated with warmer winter and early spring temperatures. Improved real-time frost warning systems, careful site selection for new plantings, and use of misting, wind machine, or other frost protection measures will be important adaptation strategies. Increased weed and pest pressure associated with longer growing seasons and warmer winters is another increasingly important challenge. Pro-active development of non-chemical control strategies, improved regional monitoring, and rapid-response plans for targeted control of invasive weeds and pests will be necessary. [ABSTRACT FROM AUTHOR]

Crop selection often leads to dramatic morphological diversification, in which allocation to the harvestable component increases. Shifts in allocation are predicted to impact (as well as rely on) physiological traits; yet, little is known about the evolution of gas exchange and related anatomical features during crop diversification., In Brassica rapa, we tested for physiological differentiation among three crop morphotypes (leaf, turnip, and oilseed) and for correlated evolution of circadian, gas exchange, and phenological traits. We also examined internal and surficial leaf anatomical features and biochemical limits to photosynthesis., Crop types differed in gas exchange; oilseed varieties had higher net carbon assimilation and stomatal conductance relative to vegetable types. Phylogenetically independent contrasts indicated correlated evolution between circadian traits and both gas exchange and biomass accumulation; shifts to shorter circadian period (closer to 24 h) between phylogenetic nodes are associated with higher stomatal conductance, lower photosynthetic rate (when CO2 supply is factored out), and lower biomass accumulation. Crop type differences in gas exchange are also associated with stomatal density, epidermal thickness, numbers of palisade layers, and biochemical limits to photosynthesis., Brassica crop diversification involves correlated evolution of circadian and physiological traits, which is potentially relevant to understanding mechanistic targets for crop improvement. [ABSTRACT FROM AUTHOR]

The cultivation of crops in a given area is highly dependent of climatic conditions. Assessment of how the climate is favorable is highly useful for planners, land managers, farmers and plant breeders who can propose and apply adaptation strategies to improve agricultural potentialities. The aim of this study was to develop an assessment method for crop-climate suitability that was generic enough to be applied to a wide range of issues and crops. The method proposed is based on agroclimatic indicators that are calculated over phenological periods (ecoclimatic indicators). These indicators are highly relevant since they provide accurate information about the effect of climate on particular plant processes and cultural practices that take place during specific phenological periods. Three case studies were performed in order to illustrate the potentialities of the method. They concern annual (maize and wheat) and perennial (grape) crops and focus on the study of climate suitability in terms of the following criteria: ecophysiological, days available to carry out cultural practices, and harvest quality. The analysis of the results revealed both the advantages and limitations of the method. The method is general and flexible enough to be applied to a wide range of issues even if an expert assessment is initially needed to build the analysis framework. The limited number of input data makes it possible to use it to explore future possibilities for agriculture in many areas. The access to intermediate information through elementary ecoclimatic indicators allows users to propose targeted adaptations when climate suitability is not satisfactory. [ABSTRACT FROM AUTHOR]

Abstract: To understand the reason for the success of weeds, we investigated the energetic cost of leaf construction, and certain ecophysiological traits of rice and its dominant weeds. On physiological basis among all weeds, Caesulia axillaris Roxburgh was found to be the most serious, followed by Echinochloa cruss-galli L. Beauv and Echinochloa colonum L. Link, while Fimbristylis miliaceae L. Vahl and Cyperus iria L. were moderate weeds of the rice fields. C. axillaris had the lowest leaf construction cost (LCC) both on a mass basis (1.15 g/g) and on a unit area basis (22.93 g/m2). Comparatively higher specific leaf area, photosynthetic rate, photosynthetic nitrogen use efficiency, leaf area ratio and leaf area index provided C. axillaris with further competitive advantage. Low LCC suggests that weeds utilize carbon resource more efficiently than the crop and potentially spend the saved energy on other competitive strategies viz. seed production, biomass production and high relative growth rate, which results in low crop yield and increase in weed seed bank. [Copyright &y& Elsevier]

Abstract: The concept of hierarchical levels and its implications for biological organisation have been recognised for many years, and various hierarchical models of biological organisation have been proposed. However, the increased tendency to analyse biological systems from the molecular perspective has overshadowed the integrated view of living beings. On the other hand, plant ecophysiological studies have shown that variations in environmental factors can affect the plant from the molecular to the whole-plant level in different ways. The main objective of this study was to demonstrate that a cross-scale multivariate approach is important to support more consistent conclusions about plant–environment interactions. A study with two tropical crops (a C3 and a C4 species) was performed to test the effects, in a single experiment, of high temperatures across different levels of plant organisation from the molecular to the whole-plant level. Simulations using principal component analysis (PCA) on variables grouped according to the nature of the data were performed to investigate the effect of the observational scale on the interpretation of plant responses to high temperature. Despite an efficient photosynthetic response to elevated temperature, indicating an acclimatisation of the photosynthetic apparatus, the results of growth analysis showed a significant reduction in the biomass of both species and in leaf area. The resulting PCAs showed that the distinct differences between the responses of each species to the two temperature regimes were dependent on the specific data set observed. Despite causal associations between the physiological variables in different temperature regimes, the PCA results demonstrate that focusing on specific datasets markedly influences the interpretation of plant environmental response. Thus, we suggest that the multivariate approach could improve the differentiation between a global disruptive disturbance and a local physiological adjustment within a plant. [Copyright &y& Elsevier]

Mendoza Province is the major Argentinian vitivinicultural region, and its grape production is fundamental for the national vintage. The 1979-2009 climate-annual grape yield relationships are analyzed, and total grape yield is shown to depend significantly on regional 'summer' (October-March) precipitation. Precipitation negatively affects yields through plant disease and damage/destruction by hail. At interannual scales, summer regional precipitation variability can explains 25% of the yield variance. Summer precipitation modulates yield with a 6-8-yr period: wet (dry) summers can be associated with larger (smaller) grape damage/loss probability during the summer preceding the vintage, as well as lower (higher) grape yields in the subsequent annual campaign because of bud damage. With respect to monthly mean precipitation at Mendoza Observatory, wetter Novembers/Decembers can lead to lower yields. Hail during the summer of the previous harvest and during December could lower yields. Winter, late spring, and early summer mean maximum temperatures can impact current and subsequent annual yields: warmer (colder) months are linked to enhanced (decreased) yields. These relationships can be associated with circulation and SST conditions in the equatorial and extratropical Pacific Ocean basin and southern South America: SSTs within the southeastern South Pacific are related to western equatorial Pacific SSTs and convection, which modify circulation and water vapor transport over southern South America. Statistical multilinear modeling shows that the observed relationships among yield, precipitation, and temperature can explain at least 60% of the observed interannual yield variability. It is thus possible to quantitatively estimate, some months in advance, the upcoming vintage's yield. [ABSTRACT FROM AUTHOR]

Abstract: The integration of remotely sensed data into models of evapotranspiration (ET) facilitates the estimation of water consumption across agricultural regions. To estimate regional ET, two basic types of remote sensing approaches have been successfully applied. The first approach computes a surface energy balance using the radiometric surface temperature for estimating the sensible heat flux (H), and obtaining ET as a residual of the energy balance. This paper compares the performance of three different surface energy balance algorithms: an empirical one-source energy balance model; a one-source model calibrated using inverse modeling of ET extremes (namely ET=0 and ET at potential) which are assumed to exist within the satellite scene; and a two-source (soil+vegetation) energy balance model. The second approach uses vegetation indices derived from canopy reflectance data to estimate basal crop coefficients that can be used to convert reference ET to actual crop ET. This approach requires local meteorological and soil data to maintain a water balance in the root zone of the crop. Output from these models was compared to sensible and latent heat fluxes measured during the soil moisture–atmosphere coupling experiment (SMACEX) conducted over rain-fed corn and soybean crops in central Iowa. The root mean square differences (RMSD) of the estimation of instantaneous latent and heat fluxes were less than 50Wm−2 for the three energy balance models. The two-source energy balance model gave the lowest RMSD (30Wm−2) and highest r 2 values in comparison with measured fluxes. In addition, three schemes were applied for upscaling instantaneous flux estimates from the energy balance models (at the time of satellite overpass) to daily integrated ET, including conservation of evaporative fraction and fraction of reference ET. For all energy balance models, an adjusted evaporative fraction approach produced the lowest RMSDs in daily ET of 0.4–0.6mmd−1. The reflectance-based crop coefficient model yielded RMSD values of 0.4mmd−1, but tended to significantly overestimate ET from corn during a prolonged drydown period. Crop stress can be directly detected using radiometric surface temperature, but ET modeling approaches-based solely on vegetation indices will not be sensitive to stress until there is actual reduction in biomass or changes in canopy geometry. [Copyright &y& Elsevier]

The vapour pressure deficit (VPD) in open-top chambers (OTCs) was analysed in relation to time of day and ambient meteorology. Effects of observed VPD differences (ΔVPD) between OTCs and the ambient air (AA) on stomatal conductance (g s) were simulated using 10 model functions from the literature. The dataset originated from 17 OTC crop experiments performed in Belgium, Germany and Sweden. ΔVPD is the resulting difference between the OTC effect on e s(T), which is the temperature-dependent saturation pressure of water vapour and the OTC effect on e a, which is the prevailing partial pressure of water vapour in the air (ΔVPD=Δe s(T)−Δe a). Both Δe s(T) and Δe a were positive during daylight hours. ΔVPD was small in comparison and sensitive to changes in Δe s(T) or Δe a. ΔVPD was negative between 07:30 and 10:30 and positive thereafter with a maximum at 20:30 (local time). The positive afternoon ΔVPD was due to an early decrease in Δe a, probably caused by ceased transpiration, while the positive Δe s(T) persisted throughout the evening, most likely because of restrained cooling in the OTCs. Both the negative morning ΔVPD and the positive evening ΔVPD were more pronounced during clear, warm and dry weather. Circumstances when VPD had a stronger limiting effect on g s inside the OTCs compared to in the ambient air coincided with high ambient ozone concentrations ([O3]). Calculated wheat O3 uptake over an [O3] threshold of 40nmolmol−1 was reduced by 8.7% in OTCs, assuming that VPD was the only factor limiting g s and that g s was the only resistance for O3 uptake. VPD is one factor of considerable importance for g s and the OTC impact on VPD may contribute to an underestimation of O3 effects expressed in relation to the external O3 exposure. [Copyright &y& Elsevier]

Antagonistic activity and root colonizing behaviour of 10 Trichoderma isolates collected from different agro-ecological zone of West Bengal were evaluated. Of these, T. viride from Bishnupur (red and lateritic zone) and T. roseum of Alipurduar (terai zone) were most prominent showing superior antagonistic effects and fast growth; both overgrew Rhizoctonia solani after 3 days of incubation in dual culture. Production of volatile and non-volatile substances was highest for T. viride of Falakata (terai) origin as evidenced by the greatest mycelial growth inhibition in R. solani, followed by T. roseum from Alipurduar. The highest growth stimulation of the antagonist by both exudates and extract of Bengal gram (Cicer arietinum Linn.) roots was found in T. harzianum of Kalyani (new alluvial zone) source. This isolate, however, was not only antagonistic to the pathogen, but also colonized the rhizosphere and maintained high population growth (224 x 106 cfu g-1 of soil at 30 days after sowing). Conversely, very low rhizosphere colonizing ability was found in T. roseum collected from Bardhaman's old alluvial zone. Colonization of non-rhizospheric soil by Trichoderma isolate was very low compared to that of rhizosphere (81.33 x 106 cfu g-1 of soil at 20 days after sowing for T. virens from Kalimpong hill zone). Significantly, the isolates showing high antagonism were not always highly rhizosphere competent. [ABSTRACT FROM AUTHOR]

Grass degradability declines as cell wall and lignin concentrations increase during maturation. The role of tissue development and lignification in decline of stem degradability was examined in maize (Zea mays L.) internodes sampled at 10 stages of growth from early elongation through plant physiological maturity. The fourth elongated internode above ground level was collected from three maize hybrids grown in a 2-yr, replicated field trial at St. Paul, MN. Internode cross-sections and ground samples were incubated in vitro for 24- and 96-h with rumen microbes. Tissue degradation was examined by light microscopy and degradability of cell wall polysaccharide components from ground internodes was determined. All tissues in elongating internodes were completely degradable except for protoxylem vessels, which was the only lignified tissue. After elongation, degradability of all tissues declined markedly except for phloem, which never lignified. Tissues with thick, lignified secondary walls (sclerenchyma and rind-region parenchyma) required longer incubation times for observable degradation. Cell wall polysaccharide components were highly degradable in immature internodes, but degradability declined after elongation and reached a minimum by Sampling Date 8, with glucose and xylose residues having the greatest reductions in degradability. Cell wall polysaccharide degradation was related to lignin concentration and ferulate cross-linking in a complex manner. [ABSTRACT FROM AUTHOR]

Grain yields of rainfed agriculture in Australia are often low and vary substantially from season to season. Assimilates stored prior to grain filling have been identified as important contributors to grain yield in such environments, but quantifying their benefit has been hampered by inadequate methods and large seasonal variability. APSIM-Nwheat is a crop system simulation model, consisting of modules that incorporate aspects of soil water, nitrogen (N), crop residues, crop growth and development. Model outputs were compared with detailed measurements of N fertilizer experiments on loamy soils at three locations in southern New South Wales, Australia. The field measurements allowed the routine for remobilization of assimilates stored prior to grain filling in the model to be tested for the first time and simulations showed close agreement with observed data. Analysing system components indicated that with increasing yield, both the observed and simulated absolute amount of remobilization generally increased while the relative contribution to grain yield decreased. The simulated relative contribution of assimilates stored prior to grain filling to grain yield also decreased with increasing availability of water after anthesis. The model, linked to long-term historical weather records was used to analyse yield benefits from assimilates stored prior to grain filling under rainfed conditions at a range of locations in the main wheat growing areas of Australia. Simulation results highlighted that in each of these locations assimilates stored prior to grain filling often contributed a significant proportion to grain yield. The simulated contribution of assimilates stored prior to grain filling to grain yield can amount to several tonnes per hectare, however, it varied substantially from 5–90% of grain yield depending on seasonal rainfall amount and distribution, N supply, crop growth and seasonal water use. High N application often reduced the proportion of water available after anthesis and decreased the relative contribution of remobilization to grain yield as long as grain yields increased, particularly on soils with greater water-holding capacity. Increasing the capacity or potential to accumulate pre-grain filling assimilates for later remobilization by 20% increased yields by a maximum of 12% in moderate seasons with terminal droughts, but had little effect in poor or very good seasons in which factors that affect the amount of carbohydrates stored rather than the storage capacity itself appeared to limit grain yield. These factors were, little growth due to water or N deficit in the weeks prior to and shortly after anthesis (when most of the assimilates accumulate for later remobilization), poor sink demand of grains due to low grain number as a result of little pre-anthesis growth or high photosynthetic rate during grain filling. Increasing the potential storage capacity for remobilization is expected to increase grain yield especially under conditions of terminal drought. [ABSTRACT FROM AUTHOR]

Grain yields of rainfed agriculture in Australia are often low and vary substantially from season to season. Assimilates stored prior to grain filling have been identified as important contributors to grain yield in such environments, but quantifying their benefit has been hampered by inadequate methods and large seasonal variability. APSIM-Nwheat is a crop system simulation model, consisting of modules that incorporate aspects of soil water, nitrogen (N), crop residues, crop growth and development. Model outputs were compared with detailed measurements of N fertilizer experiments on loamy soils at three locations in southern New South Wales, Australia. The field measurements allowed the routine for remobilization of assimilates stored prior to grain filling in the model to be tested for the first time and simulations showed close agreement with observed data. Analysing system components indicated that with increasing yield, both the observed and simulated absolute amount of remobilization generally increased while the relative contribution to grain yield decreased. The simulated relative contribution of assimilates stored prior to grain filling to grain yield also decreased with increasing availability of water after anthesis. The model, linked to long-term historical weather records was used to analyse yield benefits from assimilates stored prior to grain filling under rainfed conditions at a range of locations in the main wheat growing areas of Australia. Simulation results highlighted that in each of these locations assimilates stored prior to grain filling often contributed a significant proportion to grain yield. The simulated contribution of assimilates stored prior to grain filling to grain yield can amount to several tonnes per hectare, however, it varied substantially from 5–90% of grain yield depending on seasonal rainfall amount and distribution, N supply, crop growth and seasonal water use. High N application often reduced the proportion of water available after anthesis and decreased the relative contribution of remobilization to grain yield as long as grain yields increased, particularly on soils with greater water-holding capacity. Increasing the capacity or potential to accumulate pre-grain filling assimilates for later remobilization by 20% increased yields by a maximum of 12% in moderate seasons with terminal droughts, but had little effect in poor or very good seasons in which factors that affect the amount of carbohydrates stored rather than the storage capacity itself appeared to limit grain yield. These factors were, little growth due to water or N deficit in the weeks prior to and shortly after anthesis (when most of the assimilates accumulate for later remobilization), poor sink demand of grains due to low grain number as a result of little pre-anthesis growth or high photosynthetic rate during grain filling. Increasing the potential storage capacity for remobilization is expected to increase grain yield especially under conditions of terminal drought. [ABSTRACT FROM AUTHOR]

The article presents a survey of the changes observed in Laminariaceae found in the Island of Arran in Scotland from 1952 to 1955. Decrease in the crop of Laminariaceae from 1952 to 1953 and from 1954 to 1955 was observed. The decrease in the crop is suggested to follow a trend in other areas of Scotland particularly during a peak in 1947 followed by progressive decreases in 1953 which would be succeeded with increases on the following year. Laminaria saccharina Lamour remained the dominant species throughout the study period. This species underwent considereble seasonal and perennial changes.