The Effect of Diffuse Light on Crops

Light is not evenly distributed in Dutch glass greenhouses, but this can be improved with diffuse light. Modern greenhouse coverings are able to transform most of the light entering the greenhouse into diffuse light. Wageningen UR Greenhouse Horticulture has studied the effect of diffuse light on crops for several years. Modelling and experimental studies showed that crops such as fruit vegetables with a high plant canopy as well as ornamentals with a small plant canopy can utilize diffuse light better than direct light. Diffuse light penetrates the middle layers of a high-grown crop and results in a better horizontal light distribution in the greenhouse. Diffuse light is absorbed to a better degree by the middle leaf layers of cucumber, resulting in a higher photosynthesis. The actual photosynthesis of four pot plant species was found to be increased and crop temperatures were lower during high irradiation. The yield of cucumbers was increased, and the growth rate of several potted plants was increased. These investigations have resulted in a quantitative foundation for the potentials of diffuse light in Dutch horticultural greenhouses and the selection and verification of technological methods to convert direct sunlight into diffuse light

Codivergence and multiple host species use by fig wasp populations of the Ficus pollination mutualism

<p>Abstract</p> <p>Background</p> <p>The interaction between insects and plants takes myriad forms in the generation of spectacular diversity. In this association a species host range is fundamental and often measured using an estimate of phylogenetic concordance between species. Pollinating fig wasps display extreme host species specificity, but the intraspecific variation in empirical accounts of host affiliation has previously been underestimated. In this investigation, lineage delimitation and codiversification tests are used to generate and discuss hypotheses elucidating on pollinating fig wasp associations with <it>Ficus</it>.</p> <p>Results</p> <p>Statistical parsimony and AMOVA revealed deep divergences at the <it>COI </it>locus within several pollinating fig wasp species that persist on the same host <it>Ficus </it>species. Changes in branching patterns estimated using the generalized mixed Yule coalescent test indicated lineage duplication on the same <it>Ficus </it>species. Conversely, <it>Elisabethiella </it>and <it>Alfonsiella </it>fig wasp species are able to reproduce on multiple, but closely related host fig species. Tree reconciliation tests indicate significant codiversification as well as significant incongruence between fig wasp and <it>Ficus </it>phylogenies.</p> <p>Conclusions</p> <p>The findings demonstrate more relaxed pollinating fig wasp host specificity than previously appreciated. Evolutionarily conservative host associations have been tempered by horizontal transfer and lineage duplication among closely related <it>Ficus </it>species. Independent and asynchronistic diversification of pollinating fig wasps is best explained by a combination of both sympatric and allopatric models of speciation. Pollinator host preference constraints permit reproduction on closely related <it>Ficus </it>species, but uncertainty of the frequency and duration of these associations requires better resolution.</p

Chaos en orde in de wereldlandbouw

Gebrek aan elasticiteit, solidariteit en autoriteit / door P.C. van den Noort ; Internationale arbeidsverdeling en marktorde / door J. de Hoogh ; Redes 6-12-1979 Wageninge

Evolution and functional cross-talk of protein post-translational modifications

Protein post-translational modifications (PTMs) allow the cell to regulate protein activity and play a crucial role in the response to changes in external conditions or internal states. Advances in mass spectrometry now enable proteome wide characterization of PTMs and have revealed a broad functional role for a range of different types of modifications. Here we review advances in the study of the evolution and function of PTMs that were spurred by these technological improvements. We provide an overview of studies focusing on the origin and evolution of regulatory enzymes as well as the evolutionary dynamics of modification sites. Finally, we discuss different mechanisms of altering protein activity via post-translational regulation and progress made in the large-scale functional characterization of PTM function

spFRET Using Alternating Excitation and FCS Reveals Progressive DNA Unwrapping in Nucleosomes

AbstractAccessibility to DNA wrapped in nucleosomes is essential for nuclear processes such as DNA transcription. Large conformational changes in nucleosome structure are required to facilitate protein binding to target sites within nucleosomal DNA. Transient unwrapping of DNA from nucleosome ends can provide an intrinsic exposure of wrapped DNA, allowing proteins to bind DNA that would otherwise be occluded in the nucleosome. The molecular details underlying these mechanisms remain to be resolved. Here we show how DNA unwrapping occurs progressively from both nucleosome ends. We performed single-pair fluorescence resonance energy transfer (spFRET) spectroscopy with alternating laser excitation (ALEX) on nucleosomes either in free solution or confined in a gel after PAGE separation. We combined ALEX-spFRET with a correlation analysis on selected bursts of fluorescence, to resolve a variety of unwrapped nucleosome conformations. The experiments reveal that nucleosomes are unwrapped with an equilibrium constant of ∼0.2–0.6 at nucleosome ends and ∼0.1 at a location 27 basepairs inside the nucleosome, but still remain stably associated. Our findings, obtained using a powerful combination of single-molecule fluorescence techniques and gel electrophoresis, emphasize the delicate interplay between DNA accessibility and condensation in chromatin