An Inverse Correlation between Corn Temperature and Nitrogen Stress: A Field Case Study

Nitrogen is one of the most important yield-limiting nutrients for corn (Zea mays). The ability of thermal remote sensing to detect nitrogen deficiency in corn may enable precision agriculture to modify nitrogen rates according to field conditions. This study applies the exergy destruction principle as a theory to explain the inverse relationship between surface temperature and nitrogen rate. Two hypotheses were developed. First, it was hypothesized that agricultural crops experiencing greater growth and providing greater yield will have lower surface temperature. The second hypothesis was that corn grown under optimum levels of nitrogen will have lower surface temperatures compared to corn grown under nitrogen stressed conditions. Field studies were conducted during two summer seasons (2016 and 2017) on an established long-term field trial of corn yield response to varying rates of nitrogen. It was found that corn surface temperature decreased as the rate of nitrogen increased. A shallow but statistically significant (P < 0.05) negative slope was observed consistently with increasing rates of nitrogen. Surface temperature measurements, however, were variable. This variability was the result of external and weather dependent variables that influenced leaf surface temperature. Despite this variability, the exergy destruction principle provides a theory from which thermal remote sensing can be applied through the use of surface temperature measurements to detect physiological stress in crop plants.Natural Sciences and Engineering Research Council || Growing Forward

Weed-induced Crop Yield Loss: A New Paradigm and New Challenges

Direct competition for resources is generally considered the primary mechanism for weed-induced yield loss. A re-evaluation of physiological evidence suggests weeds initially impact crop growth and development through resource-independent interference. We suggest weed perception by crops induce a shift in crop development, before resources become limited, which ultimately reduce crop yield, even if weeds are subsequently removed. We present the mechanisms by which crops perceive and respond to weeds and discuss the technologies used to identify these mechanisms. These data lead to a fundamental paradigm shift in our understanding of how weeds reduce crop yield and suggest new research directions and opportunities to manipulate or engineer crops and cropping systems to reduce weedinduced yield losses

Spatial and temporal diversity in genomic instability processes defines lung cancer evolution.

Spatial and temporal dissection of the genomic changes occurring during the evolution of human non-small cell lung cancer (NSCLC) may help elucidate the basis for its dismal prognosis. We sequenced 25 spatially distinct regions from seven operable NSCLCs and found evidence of branched evolution, with driver mutations arising before and after subclonal diversification. There was pronounced intratumor heterogeneity in copy number alterations, translocations, and mutations associated with APOBEC cytidine deaminase activity. Despite maintained carcinogen exposure, tumors from smokers showed a relative decrease in smoking-related mutations over time, accompanied by an increase in APOBEC-associated mutations. In tumors from former smokers, genome-doubling occurred within a smoking-signature context before subclonal diversification, which suggested that a long period of tumor latency had preceded clinical detection. The regionally separated driver mutations, coupled with the relentless and heterogeneous nature of the genome instability processes, are likely to confound treatment success in NSCLC

Ecological Aspects Of Growth And Development Of Jerusalem Artichoke (helianthus Tuberosus L)

Jerusalem artichoke (Helianthus tuberosus L.) is a perennial species capable of reproduction by seed and of clonal growth from rhizomes and tubers. Natural populations are frequently found in highly unstable habitats, principally river and stream banks, man-disturbed waste areas and cultivated fields. It was postulated that variation among populations from different habitats, the allocation of resources within the plant during its life cycle and the regenerative potential of rhizomes and tubers from different soil depths may contribute to its ability to survive in a variety of habitats. Field and laboratory studies were conducted in 1982, 1983 and 1984 at the Plant Sciences Research Station, University of Western Ontario, London.;Populations of Jerusalem artichoke collected from different habitats showed considerable morphological variation when grown in a common garden. Leaf number and dry weight of tubers produced per plant accounted for the greatest variation between populations. Morphological differences in leaf number, rhizome length and tuber yield appeared to be correlated to habitat.;Jerusalem artichoke was able to allocate resources for growth of leaves, rhizomes and tubers even under conditions of severe defoliation. The annual allocation pattern of resources was characterized by a relatively large commitment of stored resources from overwintered rhizomes and tubers to structural increases in height, leaf number and lateral spread by rhizomes and tubers.;A comparison of two populations of Jerusalem artichoke indicated seasonal variations in ability to mobilize resources for the regeneration of shoots from buried rhizomes and tubers. The regenerative capacity for both populations was least for rhizomes and tubers removed from the maternal plants at the time of rapid flower and bud development.;The maintenance of genetic variability between populations and the ability to mobilize resources for vegetative and clonal growth, reproduction and regeneration does account for the ability of Jerusalem artichoke to survive in varying habitats

The Role of Engineering Thermodynamics in Explaining the Inverse Correlation between Surface Temperature and Supplied Nitrogen Rate in Corn Plants: A Greenhouse Case Study

Nitrogen stress plays a critical role in corn yield reduction. Thermal remote sensing has many applications: as an assessment tool for urban heat island, as an ecological indicator of ecosystem development, and as a water-stress-detection tool. In this study, it was hypothesized that corn crops supplied with optimum or high rates of nitrogen would have lower surface temperatures compared to corn grown under nitrogen-stressed conditions. Two experiments were conducted in the greenhouse at the University of Guelph, Canada, from the period between 2015 and 2016, involving three rates of nitrogen (high, medium, and low rates) supplied to corn plants after seed emergence. Leaf and whorl temperatures were collected by using a high-resolution thermal camera, an infrared handheld point measurements gun, and a type T thermocouple, respectively. An approximate difference of 2 &deg;C was observed in temperatures between plants receiving high and low rates of nitrogen. These results supported the hypothesis that nitrogen-stressed plants have higher temperatures compared to less stressed plants, at a 0.05 significance level. This study investigated the application of the exergy destruction principle through thermal remote sensing, to detect crop stress at early growth stages under greenhouse conditions, to increase the production and reduce the harmful environmental impact

A critique of studies evaluating glyphosate effects on diseases associated with Fusarium spp.

With the large-scale adoption of glyphosate-resistant crops in North America, there are concerns that non-target microbial populations might be affected by increased frequency of glyphosate use. Stimulation of fungal species associated with crop diseases, including Fusarium spp., has been observed in laboratory and glasshouse experiments. Although field surveys in Saskatchewan detected positive associations between the incidence of Fusarium head blight and application of glyphosate formulations, few field experiments have been successful at demonstrating a stimulatory effect of glyphosate on crop diseases, including diseases associated with Fusarium spp. Taken at face value, there is little evidence from experimental field trials to support a causative link between glyphosate and crop diseases associated with Fusarium spp. However, we are concerned that the experimental field trials investigating links between glyphosate and Fusarium spp. are not representative of interactions that occur under actual farming conditions. In addition, inadequate consideration may have been given to microbial ecology during the design and maintenance of these experimental field trials. At this time, there is insufficient evidence to prove or disprove a link between glyphosate and crop diseases associated with Fusarium spp. and this area should receive high research priority, given the rapid and widespread increase in glyphosate use

The neonicotinoid insecticide thiamethoxam enhances expression of stress-response genes in Zea mays in an environmentally specific pattern

Recent studies indicate that thiamethoxam (TMX), a neonicotinoid insecticide, can affect plant responses to environmental stressors, such as neighboring weeds. The molecular mechanisms behind both stable and environmentally-specific responses to TMX likely involve genes related to defense/stress responses. We investigated the effect of a TMX seed treatment on global gene expression in maize coleoptiles both under normal conditions and under low red to far-red (R/FR) light stress induced by the presence of neighboring plants. The neighboring plant treatment upregulated genes involved in biotic and abiotic stress responses and also affected specific photosynthesis and cell-growth related genes. Low R:FR light may enhance maize resistance to herbivores and pathogens. TMX appears to compromise resistance. The TMX treatment stably repressed many genes that encode proteins involved in biotic stress responses, as well as cell-growth genes. Notably, TMX effects on many genes’ expression were conditional on the environment. In response to low R:FR, plants treated with TMX engage genes in the JA, and other stress-related, response pathways. Neighboring weeds may condition TMX treated plants to become more stress tolerant.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author