The effects of long-day lighting and removal of young leaves on tomato yield

While low intensity long-day (LD) lighting has been shown to enhance the growth of young plants under low light levels, its effect on the yield of a long-season glasshouse tomato crop has not been previously examined. LD were provided by the use of tungsten lamps (2.8 μmol m-2 s-1 at approx. 0.5 m from the ground) between 04.00 h to sunrise and from sunset until 20.00 h (GMT). LD lighting increased leaf chlorophyll contents, and the numbers of flowers and fruits set per truss when the plants were young. However, this treatment did not affect the total yield of tomatoes. Different leaf removal treatments were applied within each glasshouse compartment. A previous experiment had shown that reducing the leaf area index (LAI) from 5.2 to 2.6, by removing old leaves, did not affect yield. It was also thought that removal of young leaves reduced the total vegetative sink-strength and favoured assimilate partitioning into the fruit. Therefore, removal of young leaves could increase fruit yield. In the present experiments, one-third of the leaves were removed in March (those immediately below each truss) and, subsequently, every third leaf was removed at an early stage of its development. This reduced the LAI from 4.1 to 2.9 and resulted in a loss of yield from 3 – 4 weeks after leaf removal until the end of the experiment, at which point there was an 8% loss of cumulative yield due to a reduction in the average number of fruits set per truss and in mean fruit weight. We postulate that the light which would have been intercepted by young photosynthetically-efficient leaves at the top of the canopy was intercepted instead by older leaves which were less efficient, reducing overall net canopy photosynthesis

Star Formation History and Extinction in the central kpc of M82-like Starbursts

We report on the star formation histories and extinction in the central kpc region of a sample of starburst galaxies that have similar far infrared (FIR), 10 micron and K-band luminosities as those of the archetype starburst M82. Our study is based on new optical spectra and previously published K-band photometric data, both sampling the same area around the nucleus. Model starburst spectra were synthesized as a combination of stellar populations of distinct ages formed over the Hubble time, and were fitted to the observed optical spectra and K-band flux. The model is able to reproduce simultaneously the equivalent widths of emission and absorption lines, the continuum fluxes between 3500-7000 Ang, the K-band and the FIR flux. We require a minimum of 3 populations -- (1) a young population of age < 8 Myr, with its corresponding nebular emission, (2) an intermediate-age population (age < 500 Myr), and (3) an old population that forms part of the underlying disk or/and bulge population. The contribution of the old population to the K-band luminosity depends on the birthrate parameter and remains above 60% in the majority of the sample galaxies. Even in the blue band, the intermediate age and old populations contribute more than 40% of the total flux in all the cases. A relatively high contribution from the old stars to the K-band nuclear flux is also apparent from the strength of the 4000 Ang break and the CaII K line. The extinction of the old population is found to be around half of that of the young population. The contribution to the continuum from the relatively old stars has the effect of diluting the emission equivalent widths below the values expected for young bursts. The mean dilution factors are found to be 5 and 3 for the Halpha and Hbeta lines respectively.Comment: 20 pages, uses emulateapj.cls. Scheduled to appear in ApJ Jan 1, 200

Photometric Properties of 47 Clusters of Galaxies: I. The Butcher-Oemler Effect

We present gri CCD photometry of 44 Abell clusters and 4 cluster candidates. Twenty one clusters in our sample have spectroscopic redshifts. Fitting a relation between mean g, r and i magnitudes, and redshift for this subsample, we have calculated photometric redshifts for the remainder with an estimated accuracy of 0.03. The resulting redshift range for the sample is 0.03<z<0.38. Color-magnitude diagrams are presented for the complete sample and used to study evolution of the galaxy population in the cluster environment. Our observations show a strong Butcher-Oemler effect (Butcher & Oemler 1978, 1984), with an increase in the fraction of blue galaxies (f_B) with redshift that seems more consistent with the steeper relation estimated by Rakos and Schombert (1995) than with the original one by Butcher & Oemler (1984). However, in the redshift range between ~ 0.08 and 0.2, where most of our clusters lie, there is a wide range of f_B values, consistent with no redshift evolution of the cluster galaxy population. A large range of f_B values is also seen between ~ 0.2 and 0.3, when Smail at al. (1998) x-ray clusters are added to our sample. The discrepancies between samples underscore the need for an unbiased sample to understand how much of the Butcher-Oemler effect is due to evolution, and how much to selection effects. We also tested the idea proposed by Garilli et al. (1996) that there is a population of unusually red galaxies which could be associated either with the field or clusters, but we find that these objects are all near the limiting magnitude of the images (20.5<r<22) and have colors that are consistent with those expected for stars or field galaxies at z ~ 0.7.Comment: 35 pages including 8 figures, submitted to A

Ocean dominated expansion and contraction of the late Quaternary tropical rainbelt

The latitude of the tropical rainbelt oscillates seasonally but has also varied on millennial time-scales in response to changes in the seasonal distribution of insolation due to Earth’s orbital configuration, as well as climate change initiated at high latitudes. Interpretations of palaeoclimate proxy archives often suggest hemispherically coherent variations, some proposing meridional shifts in global rainbelt position and the ‘global monsoon’, while others propose interhemispherically symmetric expansion and contraction. Here, we use a unique set of climate model simulations of the last glacial cycle (120 kyr), that compares well against a compilation of precipitation proxy data, to demonstrate that while asymmetric extratropical forcings (icesheets, freshwater hosing) generally produce meridional shifts in the zonal mean rainbelt, orbital variations produce expansion/contractions in terms of the global zonal mean. This is primarily a dynamic response of the rainbelt over the oceans to regional interhemispheric temperature gradients, which is opposite to the largely local thermodynamic terrestrial response to insolation. The mode of rainbelt variation is regionally variable, depending on surface type (land or ocean) and surrounding continental configuration. This makes interpretation of precipitation-proxy records as large-scale rainbelt movement challenging, requiring regional or global data syntheses

Multiaperture UBVRIzJHKUBVRIzJHK Photometry of Galaxies in the Coma Cluster

We present a set of $UBVRIzJHK_s$ photometry for 745 $J+H$ band selected objects in a $22.5' \times 29.2'$ region centered on the core of the Coma cluster. This includes 516 galaxies and is at least 80% complete to H=16, with a spectroscopically complete sample of 111 cluster members (nearly all with morphological classification) for $H < 14.5$. For each object we present total \cite{kron80} magnitudes and aperture photometry. As an example, we use these data to derive color-magnitude relations for Coma early-type galaxies, measure the intrinsic scatter of these relations and its dependence on galaxy mass, and address the issue of color gradients. We find that the color gradients are mild and that the intrinsic scatter about the color-magnitude relation is small ($\sim 0.05$ mag in $U-V$ and less than $\sim 0.03$ in $B-R$, $V-I$ or $J-K$). There is no evidence that the intrinsic scatter varies with galaxy luminosity, suggesting that the cluster red sequence is established at early epochs over a range of $\sim 100$ in stellar mass.Comment: 41 pages, 5 figures, 18 data tables attached to source files or available on request from R. De propris. Accepted for publication in Astrophysical Journal Supplement Serie

Influences of thermal environment on fish growth

Indexación: Scopus.Thermoregulation in ectothermic animals is influenced by the ability to effectively respond to thermal variations. While it is known that ectotherms are affected by thermal changes, it remains unknown whether physiological and/or metabolic traits are impacted by modifications to the thermal environment. Our research provides key evidence that fish ectotherms are highly influenced by thermal variability during development, which leads to important modifications at several metabolic levels (e.g., growth trajectories, microstructural alterations, muscle injuries, and molecular mechanisms). In Atlantic salmon (Salmo salar), a wide thermal range (ΔT 6.4°C) during development (posthatch larvae to juveniles) was associated with increases in key thermal performance measures for survival and growth trajectory. Other metabolic traits were also significantly influenced, such as size, muscle cellularity, and molecular growth regulators possibly affected by adaptive processes. In contrast, a restricted thermal range (ΔT 1.4°C) was detrimental to growth, survival, and cellular microstructure as muscle growth could not keep pace with increased metabolic demands. These findings provide a possible basic explanation for the effects of thermal environment during growth. In conclusion, our results highlight the key role of thermal range amplitude on survival and on interactions with major metabolism-regulating processes that have positive adaptive effects for organisms.http://onlinelibrary.wiley.com/doi/10.1002/ece3.3239/ful

Produtividade da agricultura: resultados para o Brasil e estados selecionados.

Este trabalho analisa a produtividade da agricultura nos anos recentes, em especial no período de 2000 a 2012. O artigo estima indicadores de produtividade não apenas para o Brasil, mas também para uma seleção de estados. Estes foram escolhidos pela sua relevância na produção nacional de grãos e carnes. Para isso, foram escolhidos os estados da Bahia, Minas Gerais, São Paulo, Paraná, Rio Grande do Sul, Mato Grosso e Goiás. Utilizou-se o conceito de produtividade total dos fatores (PTF) porque ele oferece uma definição mais abrangente de produtividade do que medidas que comparam o produto a apenas um insumo, como trabalho ou terra. Esta última forma de mensuração da produtividade é chamada produtividade parcial. A PTF considera, em sua definição, a reunião de todos os produtos das lavouras e da pecuária e os relaciona com todos os insumos usados na produção

SPITZER IRS spectra of Virgo early type galaxies: detection of stellar silicate emission

We present high signal to noise ratio Spitzer Infrared Spectrograph observations of 17 Virgo early-type galaxies. The galaxies were selected from those that define the colour-magnitude relation of the cluster, with the aim of detecting the silicate emission of their dusty, mass-losing evolved stars. To flux calibrate these extended sources we have devised a new procedure that allows us to obtain the intrinsic spectral energy distribution and to disentangle resolved and unresolved emission within the same object. We have found that thirteen objects of the sample (76%) are passively evolving galaxies with a pronounced broad silicate feature which is spatially extended and likely of stellar origin, in agreement with model predictions. The other 4 objects (24%) are characterized by different levels of activity. In NGC 4486 (M 87) the line emission and the broad silicate emission are evidently unresolved and, given also the typical shape of the continuum, they likely originate in the nuclear torus. NGC 4636 shows emission lines superimposed on extended (i.e. stellar) silicate emission, thus pushing the percentage of galaxies with silicate emission to 82%. Finally, NGC 4550 and NGC 4435 are characterized by polycyclic aromatic hydrocarbon (PAH) and line emission, arising from a central unresolved region. A more detailed analysis of our sample, with updated models, will be presented in a forthcoming paper.Comment: 6 pages; ApJ Letters, accepte

Spectroscopy of Broad Line Blazars from 1LAC

We report on optical spectroscopy of 165 Flat Spectrum Radio Quasars (FSRQs) in the Fermi 1LAC sample, which have helped allow a nearly complete study of this population. Fermi FSRQ show significant evidence for non-thermal emission even in the optical; the degree depends on the gamma-ray hardness. They also have smaller virial estimates of hole mass than the optical quasar sample. This appears to be largely due to a preferred (axial) view of the gamma-ray FSRQ and non-isotropic (H/R ~ 0.4) distribution of broad-line velocities. Even after correction for this bias, the Fermi FSRQ show higher mean Eddington ratios than the optical population. A comparison of optical spectral properties with Owens Valley Radio Observatory radio flare activity shows no strong correlation.Comment: Accepted for publication in Ap