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Background and aim: Deep roots are important for crops to access water when the topsoil is dry. Root anatomy and activity play an important role in water uptake. However, little is known about the effects of root distribution and anatomical structure on water uptake and grain yield under different water conditions. This study aimed to reveal the contribution of deeper roots, root anatomy and root activity on grain yield and water use efficiency. Methods: A field experiment and Rhizobox experiment were performed to evaluate the effects of changes in root distribution, root anatomy and root activity on grain yield and water use efficiency under three water conditions. Three dryland wheat cultivars (BM1, CH58 and CH1) were compared. Results: BM1 formed a root system, which limited the acquisition of water in the subsoil, resulting in lower grain yield and water use efficiency in field and rhizobox experiments. In contrast, cultivars CH58 and CH1 exhibited greater root biomass and root length density in the subsoil, optimizing subsoil water uptake, thereby increasing grain yield and water use efficiency. CH58 had a smaller root diameter and vessel diameter, thicker cortex thickness, higher root cortex thickness-to-diameter ratio and higher root activity. Conclusion: This study demonstrated that, deeper roots, root anatomy and root activity are important traits in selecting wheat cultivars that maintain yield under low water conditions. Therefore, wheat crop development and breeding to improve grain yield should also consider optimizing root anatomy and improving root activity while promoting deep root development. [ABSTRACT FROM AUTHOR]

Diversified crop rotation with an appropriate sequence may be a promising strategy for increasing crop productivity while reducing greenhouse gas emissions (GHGs) and lowering carbon (C) footprint for more sustainable agricultural systems. The objectives of this study were to (i) assess the agronomic performance and C footprint of canola (Brassica napus L.) production in different cropping systems, and (ii) better understand how canola could be adapted to existing cropping systems in eastern Canada. A four-year canola-based phase rotation study, including maize (Zea mays L.), wheat (Triticum aestivum L.), and soybean (Glycine max L.), started in 2011 and continued for two cycles in Ottawa, ON; Montreal, QC; and Canning, NS. It was found that, compared to continuous monoculture (canola, maize or wheat), diversified cropping systems increased crop yields by an average of 32% and reduced the C footprint of all rotations by 33%, except under severe heat and drought conditions. The effect of rotation on yield and C footprint of canola production varied significantly among site-years. At Ottawa, the canola following soybean (SC) had 12% higher canola yield than monoculture canola (CC), 5 and 8% higher canola yield than canola following wheat (WC) or maize (MC). At Montreal, canola yield ranked as MC > SC > WC > CC. At Canning, the highest canola yield was in WC (21%) and SC (13%). Overall, most SC rotations had the lowest C footprint, and CC cropping had the highest C footprint, with only a few exceptions. Regardless of the cropping system, canola required more N input and was high in oil and protein in the harvested product, and produced the highest C footprint, while soybean had the lowest C footprint at all three sites. Our findings indicate that a diversified cropping system with canola production following soybean significantly improved canola yield while lowering the C footprint. However, profitable and sustainable canola production in eastern Canada is threatened by climate change-induced drought and heat stress. [ABSTRACT FROM AUTHOR]

While no significant differences in initial ovule number were found among oilseed rape Brassica napus genotypes, there was a large variation in effective ovule number (EON), which determines the final seeds per silique (SPS), a critical component of yield. In this study, we selected 18 oilseed rape Brassica napus genotypes with contrasting nitrogen utilization efficiency (NUtE) to unravel the main factors responsible for different EON and determine the critical period of EON formation under both a field and a pot experiments from 2016–2018. The high NUtE genotypes displayed significantly higher NUtE by 14.3%, along with greater yield per plant (29.4%) and SPS (21.1%) than the low NUtE genotypes. The greater productivity of the high NUtE genotypes was associated with 44.1% higher pollen grain number, 23.5% greater pollen viability, and 39.3% lower ovule abortion rate, compared to the low NUtE genotypes. In addition, the heart stage was the critical ovule development period for delineating the variability of EON among contrasting NUtE oilseed rape Brassica napus genotypes, when the high NUtE genotypes displayed higher silique net photosynthetic rate, surface area, biomass, and RNA expression levels. Taken together, this study indicated the pollen grain number, pollen viability and ovule abortion rate contributed to the final variation in EON and the heart stage was the critical period of determining the EON differences among contrasting NUtE genotypes. Increasing pollen grain number and pollen viability, and decreasing ovule abortion rate before heart stage should be the prerequisite for breeders to improve yield and NUtE of oilseed rape Brassica napus genotypes. [ABSTRACT FROM AUTHOR]

An effective crop yield prediction is critical for making precise nitrogen (N) management decisions. A multi-site-year study was conducted across eastern Canada with the objectives to (1) construct machine-learning random forest regression (RFR) models for canola yield prediction; and (2) develop site-specific N recommendations using the RFR modelling approach. Soil characteristics, weather, plant growth and spectral index data collected from 2013 to 2015 were used to train the RFR models and the 2016 data for model validation in terms of making N decisions. Results showed that canola yields responded positively to N application rates in 16 out of the 18 site-year environments, with sometimes higher yields and an average of 8% higher N use efficiency for the split-N strategy than for the same amount of N applied only at preplant. Heat stress and precipitation distribution were identified as of critical importance in total yield variation. The RFR model by combining weather, soil and plant growth features with the spectral indices displayed highly improved prediction reliability, up to 85%, with 53–57% lower root mean square errors, compared with the model based only on leaf chlorophyll or normalized difference vegetation index. Based on the RFR algorithm, an average economic optimum N rate of 150 kg N ha−1 was recommended for most canola production scenarios in the test year. This study demonstrated that the machine learning-based RFR modelling approach can be used to implement optimal nutrient management strategies for sustainable crop production, which is sensitive and better adapted to environment-induced abiotic stresses. [ABSTRACT FROM AUTHOR]

Aims: Increasing post-flowering nitrogen (N) uptake is likely to improve seed N accumulation, ultimately leading to greater seed yield and N use efficiency (NUE). Methods: A comprehensive study on contrasting N utilization efficiency (NUtE) winter oilseed rape genotypes was conducted for three years (2017–2020) to unravel the effect of post-flowering N uptake on seed N accumulation. Results: Compared to the low NUtE genotype, the high NUtE genotype displayed respectively 31%, 28% and 70% greater root biomass, length and volume, along with 40%, 44%, 46% and 82% higher root nitrate reductase (NR), glutamine synthetase (GS), glutamate synthetase (GOGAT), and glutamate dehydrogenase (GDH) activities after flowering. These were accompanied by a significant increase (P < 0.05) in catalases (134%), peroxidase (45%), glutathione (45%) and ascorbate peroxidase (41%), leading to 27% higher seed N accumulation, 23% higher seed yield and 60% higher NUE. Conclusions: Stronger post-flowering N uptake potential for high NUtE genotype was a main contributor to the enhanced seed N accumulation, and ultimately increased seed yield and NUE. [ABSTRACT FROM AUTHOR]

Laser communication is essential part of maritime-terrestrial-air intelligent communication/sensor network. Among them, different modulation formats would play a unique role in specific applications. Based on Rytov theory, we discussed system performance of the maritime laser communication with repeated coding technology in several modulation schemes. The closed-form expression of average bit error rate (BER) from weak to moderate atmospheric turbulence described by log-normal distribution is given. Differential phase shift keying (DPSK) modulation, as a potential solution for future maritime laser communication, has attracted a lot of attention. We analyzed the effects of atmospheric turbulence parameters (visibility, refractive index structure coefficient, non-Kolmogorov spectral power-law exponent, turbulence inner scale) and DPSK system parameters (receiver aperture diameter, repeat time) on average BER in detail. Compared with the aperture-averaging effects, the system BER can be well suppressed through increasing repeat time. This work is anticipated to provide a theoretical reference for maritime laser communication systems. [ABSTRACT FROM AUTHOR]

There is limited knowledge about the effects of the severity and timing of drought stress on oat (Avena sativa) yield and the critical stages at which water management could be effectively implemented. A controlled study was conducted to identify a variety-specific critical stage, and to examine the physiological mechanisms of drought stress on photosynthesis (Pn) and yield formation in two contrasting genotypes. We found that compared with sufficient water supply (AW), grain yield was reduced by 36%, 69% and 44% in 'Shadow', and by 31%, 33% and 41% in 'Bia' under the severe stress imposed either at jointing, heading or post-anthesis stage. The grain/leaf area (LA) ratio increased by 18–32% and biomass distribution to stems + leaves decreased by 5.2–6.2% of Bia under moderate stress (MS) as compared to AW. This, along with the improved harvest index, led to a comparable yield. Under AW, Shadow displayed 13–16% larger LA duration (LAD) and had significantly higher Pn at the heading and post-anthesis stages, leading to 13% to 20% more spikelets panicle−1 and 13–21% greater groat yields than Bia. It can be concluded that (1) water stress at heading for Shadow and at post-anthesis for Bia was detrimental to grain yield through reduced LA and LAD with a reduced sink size, (2) under the MS, greater grain yield of the hulled Bia was attributable to a stronger sink activity, and (3) higher groat yield of the naked Shadow under AW was associated mainly with a higher source activity and more spikelets panicle−1. [ABSTRACT FROM AUTHOR]

Understanding the interaction of macro- and micronutrients is a prerequisite to targeting nutrient balance in crop production. A 3-year field study was conducted to determine mineral nutrient uptake of maize hybrids with N fertilizer application under different rotation systems. The experiment was arranged in a split-plot design with rotation [maize-alfalfa (MA), maize-soybean (MS), and continuous maize (MM)] by N rate (0, 50, 100 and 150 kg N ha−1) as the mainplot and hybrid as the subplot. Two additional treatments (200 and 250 kg N ha−1) were tested in MM. Maize plant total Mg, Zn, and Cu content were in the order: MA > MS > MM. Plant Fe uptake was the lowest in MA and not affected by N input. The increased Cu uptake with increasing N rates indicated the synergism of these two nutrients, whereas dilution effects of N application on stover Zn and Mg concentrations were recorded. Rotation systems and N rates interactively affected nutrient harvest index and internal efficiency of Zn, Mg, Fe, and Cu. Relationships of plant N with Cu and Mg concentrations, and N with Zn, Mg, and Cu content at the V6 stage were established, but they were not necessarily preserved at maturity due to the progressive synergistic and dilution effects. The findings of nutrient uptake of Cu, Zn, Mg and Fe and their relationships with N nutrition in maize with stacked transgenic traits are important for developing best management practices to achieve concurrent improvements in nutrient use efficiency and crop productivity. [ABSTRACT FROM AUTHOR]

Background and aims: An understanding of the root traits in overcoming the constraints to canola growth imposed by heat and drought stresses is increasingly needed. This research examines the feasibility of using an electrical measurement method to screen canola root traits and its response to heat and drought stresses. Methods: Two genotypes were assessed under two temperature regimes (normal: 23/17 °C, vs. high: 27/24 °C, day/night) combined with three water levels in a controlled environment. All pots were subjected to root electrical capacitance (EC) and impedance (EI) measurements, followed by root morphological evaluation using a destructive method. Results: Both heat and drought stresses suppressed root morphological parameters significantly, accompanied with a decreasing EC and increasing EI. Both 1 KHz and 10 KHz are acceptable current frequencies for effective measurement of EC and EI. A linear correlation was found between EC and most root parameters for canola plants grown in soil. Conclusions: This research illustrates the feasibility of using EC measurements to assess root morphological parameters of canola plants grown in soil. It is possible to apply this non-destructive method for studying the dynamics of roots subjected to abiotic stress. High EC can be associated with tolerance to heat and drought stresses. [ABSTRACT FROM AUTHOR]

Heterojunctions near infrared (NIR) photodetectors have attracted increasing research interests for their wide-ranging applications in many areas such as military surveillance, target detection, and light vision. A high-performance NIR light photodetector was fabricated by coating the methyl-group terminated Si nanowire array with plasmonic gold nanoparticles (AuNPs) decorated graphene film. Theoretical simulation based on finite element method (FEM) reveals that the AuNPs@graphene/CH3-SiNWs array device is capable of trapping the incident NIR light into the SiNWs array through SPP excitation and coupling in the AuNPs decorated graphene layer. What is more, the coupling and trapping of freely propagating plane waves from free space into the nanostructures, and surface passivation contribute to the high on-off ratio as well. [ABSTRACT FROM AUTHOR]

Plant herbivores often stimulate lignin deposition in injured plant tissue, but it is not known whether corn ( Zea mays L.) reacts to European corn borer (ECB, Ostrinia nubilalis Hubner) injury in this manner. Bt ( Bacillus thuringiensis) genetic modification is also reported to affect lignin in corn. This study evaluated the effects of ECB injury and the Bt gene on the chemical composition and decomposition of corn tissues. Eight near isolines (Bt and NBt) were grown in pots and half were infested with ECB. The experiment was repeated in 2 years. ECB injury increased the lignin concentration in corn leaves in one of 2 years and lowered the C:N ratio in injured stems. Lignin concentration in leaves was greater in Bt than NBt corn in 1 year and Bt stems had greater N concentration than NBt stems in 1 year of the 2 year study. ECB injury affected the composition of lignin-derived phenols, however ECB infested and non-infested stems lost the same amount of mass after 5 months in buried field litterbags. In conclusion ECB injury and the Bt gene had subtle effects on the chemical composition of corn tissue, which did not alter the short-term decomposition of corn residues. [ABSTRACT FROM AUTHOR]

Real time PCR assays were developed to detect and quantify the transgene DNA of a commercially released Bacillus thuringiensis (Bt) corn ( Zea mays L.) hybrid (DKC42-23), which was derived from the event MON863 and also carried a neomycin phosphotransferase gene (the nptII gene). We applied the real time PCR assays to investigate the persistence of the transgene DNA in a field trial grown with DKC42-23 over 3 years, in combination with bacterial natural transformation. The results showed that under continuous cultivation of DKC42-23, its transgene DNA was detectable in the field plots all year around. Meanwhile, when soil DNA extracts from DKC42-23 plots were used as donor in bacterial natural transformation, successful recovery of kanamycin resistant (Km) transformants indicated that the nptII gene carried by DKC42-23 could be taken up and integrated into naturally competent Pseudomonas stutzeri pMR7 cells, leading to the restoration of the antibiotic resistance of P. stutzeri pMR7. However, after the cultivation of a soybean line in the same plots for the subsequent growing season, the presence of transgene DNA of DKC42-23 was reduced to undetectable levels at the end of that growing season. Therefore, existing corn-soybean crop rotation practices reduce the availability of transgene DNA in soil and thus minimize the risks that might be attributable to horizontal gene transfer. The real time PCR assays are useful for investigating the persistence of transgene DNA derived from the MON863 event in soil environments. [ABSTRACT FROM AUTHOR]

Abstract  Nitrogen (N) fertilizer rates applied spatially according to crop requirements can improve the efficiency of N use. The study compares the performance of two commercial sensors, the Yara N-Sensor/FieldScan (Yara International ASA, Germany) and the GreenSeeker (NTech Industries Inc., Ukiah, California, USA), for assessing the status of N in spring wheat (Triticum aestivum L.) and corn (Zea mays L.). Four experiments were conducted at different locations in Quebec and Ontario, Canada. The normalized difference vegetation index (NDVI) was determined with the two sensors at specific growth stages. The NDVI values derived from Yara N-Sensor/FieldScan correlated with those from GreenSeeker, but only at the early growth stages, where the NDVI values varied from 0.2 to 0.6. Both sensors were capable of describing the N condition of the crop or variation in the stand, but each sensor had its own sensitivity characteristics. It follows that the algorithms developed with one sensor for variable-rate N application cannot be transferred directly to another sensor. The Yara N-Sensor/FieldScan views the crop at an oblique angle over the rows and detects more biomass per unit of soil surface compared to the GreenSeeker with its nadir (top-down) view of the crop. The Yara N-Sensor/FieldScan should be used before growth stage V5 for corn during the season if NDVI is used to derive crop N requirements. GreenSeeker performed well where NDVI values were >0.5. However, unlike GreenSeeker, the Yara N-Sensor/FieldScan can also record spectral information from wavebands other than red and near infrared, and more vegetation indices can be derived that might relate better to N status than NDVI. [ABSTRACT FROM AUTHOR]

Acute carotid blowout syndrome (CBS) was defined as free rupture of the carotid artery associating with catastrophic hemorrhage. Most radiation acute CBSs in nasopharyngeal carcinoma (NPC) are found in petrous segment of the internal carotid artery (ICA) because of high-dose radiation in this area associated with nearby osteonecrosis. The occurrence of acute CBSs in the small branch of the external carotid artery and cervical ICA following radiotherapy in NPC patient is very rare. We present a rare case of NPC with radiation acute CBSs in the ascending pharyngeal and cervical ICA in a 3-month interval that were successfully managed by endovascular embolization. [ABSTRACT FROM AUTHOR]