Protein synthesis is catalyzed by the ribosome, a two-subunit enzyme comprised of four ribosomal RNAs and, in Arabidopsis (Arabidopsis thaliana), 81 ribosomal proteins (r-proteins). Plant r-protein genes exist as families of multiple expressed members, yet only one r-protein from each family is incorporated into any given ribosome, suggesting that many r-protein genes may be functionally redundant or development/tissue/stress specific. Here, we characterized the localization and gene-silencing phenotypes of a large subunit r-protein family, RPL23a, containing two expressed genes (RPL23aA and RPL23aB). Live cell imaging of RPL23aA and RPL23aB in tobacco with a C-terminal fluorescent-protein tag demonstrated that both isoforms accumulated in the nucleolus; however, only RPL23aA was targeted to the nucleolus with an N-terminal fluorescent protein tag, suggesting divergence in targeting efficiency of localization signals. Independent knockdowns of endogenous RPL23aA and RPL23aB transcript levels using RNA interference determined that an RPL23aB knockdown did not alter plant growth or development. Conversely, a knockdown of RPL23aA produced a pleiotropic phenotype characterized by growth retardation, irregular leaf and root morphology, abnormal phyllotaxy and vasculature, and loss of apical dominance. Comparison to other mutants suggests that the phenotype results from reduced ribosome biogenesis, and we postulate a link between biogenesis, microRNA-target degradation, and maintenance of auxin homeostasis. An additional RNA interference construct that coordinately silenced both RPL23aA and RPL23aB demonstrated that this family is essential for viability.

Mitigating the greenhouse gas emissions that arise durin manure is a crucial environmental challenge. We evalu effects of liquid manure timing (fall vs. spring) and nitrifi [2-chloro-6-(trichloromethyl) pyridine (nitrapyrin) vs. 3 phosphate (DMpp)] on n 2 O emissions, soil mineral n ley (Hordeum vulgare L.) productivity, and n uptake. E established in an incomplete split-plot design in Laco AB, Canada. Repeated measurements included n 2 O flu chambers, and soil ammonium (nH 4 -n) and nitrate (nO Relative to the manured soils without nIs, the use of n significantly reduced annual n 2 O emissions by 81% w with nitrapyrin in our Lacombe site; however, this diffe in the comparable spring treatments applied during the These beneficial effects were discernable in Lacombe, wetter than Edmonton, indicating the overriding role o n dynamics and fluxes. Following a 5-mo freezing wi caused at least 64% of annual n 2 O emissions from the f these intense episodic fluxes also revealed that the effic still continued during the early spring. On average, fal the n 2 O direct emission factors by about threefold com sponding spring treatments. Thus implementing liquid m nIs at the right timing has the potential opportunity to crops and simultaneously diminish global warming effect Abbreviations: CT, control treatment where the soil was disturb without soil disturbance); DM, dry matter; DMPP, 3, 4-dimethyl direct emission factors; FMD, fall-manured soil with DMPP, FMN nitrapyrin; FMW, fall-manured soil with no nitrification inhibitors; SMD, spring-manured soil with DMPP; SMN, spring-manured so spring-manured soil with no nitrification inhibitors.

Translation of nucleus-encoded messages in plants is conducted by the cytoplasmic ribosome, an enzyme that is comprised of two RNA/protein subunits. In Arabidopsis thaliana, the 81 different ribosomal proteins (r-proteins) of the cytosolic ribosome belong to gene families with multiple expressed members. Given that ribosomes generally contain only one copy of each r-protein, regulatory mechanisms must exist to ensure their stoichiometric accumulation. These mechanisms must be dynamic, allowing for adjustments to ribosome biogenesis to fulfill biological requirements for protein synthesis during development, and following stress induction of global changes in gene expression. In this study, we investigated whether r-protein paralogs are feedback regulated at the transcript level by obtaining a T-DNA knockout of one member, RPL23aB, from the two-member RPL23a family. Expression of the lone functional paralog in this line, RPL23aA, was compared to the expression of both paralogs in wildtype plants under non-stressed, low temperature-, and high light stresses. RPL23aA expression was not upregulated in RPL23aB knockouts to compensate for paralog-loss, and consequently knockouts showed reduced total abundance of RPL23a transcripts. However, no phenotype developed in RPL23aB knockouts, suggesting that this paralog is dispensable under experimental conditions examined, or that compensation by RPL23aA may occur post-transcriptionally. Patterns of RPL23aA and RPL23aB transcript accumulation in wildtype plants suggest that paralogs respond coordinately to developmental and stress stimuli.

Very few annuals produced seed during the season if they emerged after June, but some (< 45%) of these plants successfully overwintered. Summer annuals began dispersing mature seed 7 wk after emergence, but were also capable of persisting in a quiescent state for extended periods (up to 19 wk). Wheat and canola yield loss attributable to field violet was minimal. We compared domestic and European field violet accessions to determine if the study population represented a unique agroecotype. Plants from both cohorts grown in the greenhouse were near-identical, suggesting that differences resulted from phenotypic plasticity, rather than genetic divergence. Field violet appears to be well adapted to growing conditions and farming practices in Alberta, but is a poor competitor and is unlikely to cause serious crop production losses. La plante éclot en nombre variable, avec un pic au début de juin et en septembre. Lorsqu'elles germent après juin, très peu de violettes montent en graines, mais quelques plants survivent à l'hiver (moins de 45 %). Les annuelles alternatives répan-dent les graines matures sept semaines après la germination, mais elles peuvent persister longtemps (jusqu'à 19 semaines) au stade de repos. La violette cause des pertes de rendement minimes au blé et au canola. Les auteurs ont comparé les obtentions canadiennes et européennes afin d'établir si la population à l'étude constituait un écotype agricole particulier. Les plantes des deux cohortes cultivées en serre étaient presque identiques, signe que les variations résultent de la plasticité du phénotype et n'ont pas une origine génétique. La violette des champs semble bien adaptée aux conditions de croissance et aux pratiques agricoles de l'Alberta, mais s'avère une piètre compétitrice et il est peu probable qu'elle entraîne de grandes pertes pour l'agriculture.

The agrestal field violet, a pervasive weed in Europe, has been identified in reduced-tillage cereal fields in Alberta. The efficacy of herbicides in direct-seeded spring wheat was assessed on natural field violet infestations in Alberta in 2002 and 2003. Only fluroxypyr + 2,4-D, applied postemergence, provided control of field violet in 2002 when rainfall was limiting. Over both years, this herbicide combination reduced biomass by 59 to 69% and plant density by 83 to 91%, relative to nontreated plots. The herbicides metsulfuron, sulfosulfuron, and thifensulfuron + tribenuron only suppressed weed growth under drought conditions in 2002 but controlled the weed in 2003 when rainfall was greater, reducing plant density by 82 to 92% and rendering remaining plants sterile. Suppression was also observed with MCPA + mecoprop + dicamba in 2002 and 2003 and with metribuzin only in 2003. Effective control of field violet was conferred by a pre–crop emergence application of glyphosate at 445 g ae/ha in 2003, the only year that this treatment was evaluated. Activity of herbicides on three- to four-leaf seedlings was also evaluated in a greenhouse dose– response assay. All herbicides had greater efficacy in the greenhouse, and those that provided control in situ reduced field violet dry weight by 85% at less than the recommended rate used in field experiments. Management of field violet is possible with herbicides registered for use on spring wheat in Alberta. However, the weed does not appear to cause significant crop production losses; hence, herbicide selection should be based on knowledge of all weed species present within the field.

Field violet is a winter or summer annual plant that is a serious weed of canola crops in Europe. It is a weed of increasing concern within reduced tillage fields in central Alberta, where its response to registered herbicides has not been evaluated. Two commercial fields within the Aspen Parkland ecoregion of Alberta were used to evaluate the efficacy of postemergence (POST) herbicides against field violet in conventional, imidazolinone-resistant (IMI-resistant) and glufosinate-resistant canola cultivars, as well as to evaluate the plant's response to various timings and rates of glyphosate in glyphosate-resistant canola. Control of field violet was lower in field experiments conducted in 2002 compared with 2003, probably because of abnormally low rainfall in 2002. The POST herbicides evaluated provided inadequate control of field violet in conventional canola. Glufosinate control at 500 g ai/ha was unacceptable unless the crop canopy closed shortly after application. In IMI-resistant canola, thifensulfuron did not significantly reduce plant density and biomass under the extremely dry conditions experienced in 2002, but in 2003, it conferred respective reductions of 79 and 86% relative to nontreated controls. Imazamox plus imazethapyr did not affect plant growth. Field violet was controlled by pre- and postcrop emergence glyphosate at 445 g ae/ha. Postharvest application of glyphosate provided good control throughout the following growing season when spring emergence was minimal. Herbicide activity was also evaluated on two- to four-leaf seedlings in a greenhouse experiment. Dose– response curves reflected the activity observed in field experiments. Strategies for effective field violet control with herbicides are dependent on cultivar selection and the management system, but are improved by timing application to young, actively growing plants.

An estimated one-third of organic farmers in Alberta are located within a 150 km radius of Edmonton, a commercial center with a population of close to one million. A random sample of these producers were administered and an in-depth survey in 2002 to obtain knowledge of their crop and commodity selection practices, land usage, fertility management, perceived research needs and recognized constraints to sector viability. The study area contained a 4-fold greater proportion of land cropped to cereals (40%) and double the proportion of farms raising organic cattle (45%), but had less than half the amount of pasture and forage land (35%) than the province as a whole. Albertan organic farmers felt they were constrained by markets, soil fertility, weeds, and production costs. They would like to see more research focused on improving and protecting soil productivity, developing profitable and sustainable crop rotations, identifying alternative livestock vaccines and feed supplements, and comparing organic and conventional farming systems. Overcoming challenges Rory Degenhardt is a graduate student at facing this emerging sector will require the combined assistance of government, industry and research sectors.

• Nitrapyrin has been tested in fallow field trials in cereal and oilseed growing regions of Canada.• Nitrapyrin maintained N in the ammonium form through critical loss periods.• Nitrapyrin preserved more mineral N in the soil relative to non-stabilized fertilizer. AbstractSoil N loss is a significant impediment to maximizing yield and profitability for farmers in Canada. Maintaining N in the stable and plant-available NH 4 + form via use of nitrification inhibitors limits the potential for soil N losses from denitrification or leaching. Between 2013 and 2015, twenty-one research trials were established across the major cereal and oilseed growing regions of Canada to evaluate the efficacy of two commercially available formulated nitrapyrin products, eNtrenchTM and N-Serve, at stabilizing soil N in the NH 4 + form and protecting against N loss. Urea, urea ammonium nitrate (UAN) or NH 3 fertilizer treatments were banded in the fall or spring on fallow land, and the soil was sampled to a depth of 60 cm at multiple time intervals after application. Fall applications of nitrapyrin resulted in 21-63% more NH 4 N, and 10-19% more total mineral N, at spring sampling after soil thaw relative to non-stabilized fertilizer. Spring applications of nitrapyrin resulted in larger pools of NH 4 -N for at least 8 weeks after treatment, and they increased total mineral N by up to 25%, compared with non-stabilized treatments. Results suggest that eNtrench and N-Serve are useful tools for growers looking to protect their N investment, optimize crop yield potential, and enhance flexibility of their N application timing.