New Rootsnap Sensor Reveals the Ameliorating Effect of Biochar on In Situ Root Growth Dynamics of Maize in Sandy Soil

We investigated if subsoil constraints to root development imposed by coarse sand were affected by drought and biochar application over two seasons. Biochar was applied to the subsoil of pots at 20–50 cm depth in concentrations of 0%, 1%, 2%, and 3% (B0, B1, B2,and B3). Maize was grown in the same pots 1 week and 12 months after biochar application. The maize plants were fully irrigated until flowering; thereafter, half of them were subjected to drought. A new method for observing root growth dynamics and rootlength density in situ, the Rootsnap sensor system, was developed. The sensors were installed at 50 cm depth just below the layer of biochar-amended subsoil. Using data from a smaller experiment with grass, the calculated root length densities from the sensors were compared with data from scanning of manually washed roots. In year 2, we investigated the effect of aged biochar on root growth using only the root wash and scanning method. The Rootsnap sensor revealed that the arrival time of the first root in B3at the 50 cm depth averaged 47 days after planting, which was significantly earlier than in B0, by 9 days. The tendency for faster root proliferation in biochar-amended subsoil indicates that biochar reduced subsoil mechanical impedance and allowed roots to gain faster access to deep soil layers. A linear regression comparing root length density obtained from the Rootsnap sensor with the scanning method yielded an r(2) of 0.50. Our analysis using the scanning method further showed that under drought stress, maizeroots responded with reduced root diameter and increased root length density at 50–70cm depth in the first and second year, respectively. The trend under full irrigation was less clear, with significant decrease in root length density for B1 and B2 in year 2. Overall, reduction in subsoil mechanical impedance observed as early arrival of roots to the subsoil may prevent or delay the onset of drought and reduce leaching of nutrients in biochar-amended soil with positive implications for agricultural productivity

Proper management of irrigation and nitrogen-application increases crop N-uptake efficiency and reduces nitrate leaching

Irrigation is, on one hand, expected to increase the risk of nitrate leaching through increased rates of percolation, but, on the other hand, enhances plant nutrient uptake and growth, thereby limiting the risk of leaching. To investigate this dichotomy, we analysed the effects of irrigation at three nitrogen (N)-application rates in spring barley (Hordeum distichum L., two experiments with 50, 100, and 150 kg N ha(-1)) and winter oilseed rape (Brassica napus L., one experiment with 50, 150, and 250 kg N ha(-1)) on a coarse sandy soil in Denmark in a humid climate, which facilitates nitrate leaching. Analyses comprised grain/seed dry matter yield, N-uptake, nitrogen use efficiency (partial nitrogen budget, PNB, and partial-factor productivity, PFP) and nitrate leaching. For both crops, increasing N-application without consideration of the crops' drought-stress responses lead to a relatively lower N-uptake in grain, lower yield, lower PNB and PFP and higher nitrate leaching, although responses were not proportionally to increasing N-application. The effect of irrigation at the lowest N-rates was limited. The non-irrigated treatments with the highest N-rates had a grain/seed yield of 3.2, 2.3 and 0.7 t ha(-1) and nitrate leaching rates of 64, 72 and 127 kg N ha(-1) compared to a grain/seed yield of 5.3, 5.0 and 2.6 kg N ha(-1) and nitrate leaching rates of 61, 42 and 85 kg N ha(-1) (for spring barley, spring barley and winter oilseed rape, respectively). These results show that synchronised management of both irrigation and N-application are essential for reducing the risk of nitrate leaching and to promote efficient crop N-uptake in periods of droughts

Can miscanthus C4 photosynthesis compete with festulolium C3 photosynthesis in a temperate climate?

Miscanthus, a perennial grass with C4 photosynthesis, is regarded as a promising energy crop due to its high biomass productivity. Compared with other C4 species, most miscanthus genotypes have high cold tolerances at 14ºC. However, in temperate climates, temperatures below 14ºC are common and our aim was to elucidate cold tolerances of different miscanthus genotypes and compare with a C3 perennial grass - festulolium. Eleven genotypes of M. sacchariflorus, M. sinensis, M. tinctorius, M. x giganteus as well as festulolium were grown under warm (24/20ºC, day/night) and three under cold (14/10ºC, 10/8ºC and 6/4ºC) conditions in a controlled environment. Measurements of photosynthetic light response curves, operating quantum yield of photosystem II (ΦPSII), net photosynthetic rate at a PAR of 1000 lmol m-2 s-1 (A1000) and dark-adapted chlorophyll fluorescence (Fv/Fm) were made at each temperature. In addition, temperature response curves were measured after the plants had been grown at 6/4ºC. The results showed that two tetraploid M. sacchariflorus and the standard triploid M. x giganteus cv. Hornum retained a significantly higher photosynthetic capacity than other miscanthus genotypes at each temperature level and still maintained photosynthesis after growing for a longer period at 6/4ºC. Only two of five measured miscanthus genotypes increased photosynthesis immediately after the temperature was raised again. The photosynthetic capacity of festulolium was significantly higher at 10/8ºC and 6/4ºC than of miscanthus genotypes. This indicates that festulolium may be more productive than the currently investigated miscanthus genotypes in cool, maritime climates. Within miscanthus, only one M. sacchariflorus genotype exhibited the same photosynthetic capacity as Hornum at both cold conditions and when the temperature was raised again. Therefore, this genotype could be useful for breeding new varieties with an improved cold tolerance vis-a-vis Hornum, and be valuable in broadening the genetic diversity of miscanthus for more widespread cultivation in temperate climates

Accurate estimates of land surface energy fluxes and irrigation requirements from UAV-based thermal and multispectral sensors

The two-source energy balance model estimates canopy transpiration (Tr) and soil evaporation (E) traditionally from satellite partitions of remotely sensed land surface temperature (LST) and the Priestley-Taylor equation (TSEB-PT) at seasonal time with limited accuracy. The high spatial–temporal resolution spectral data collected by unmanned aerial vehicles (UAVs) provide valuable opportunity to estimate Tr and E precisely, improve the understanding of the seasonal and the diurnal cycle of evapotranspiration (ET), and timely detect agricultural drought. The UAV data vary in spatial resolution and the uncertainty imposed on the TSEB-PT outcome has thus far not being considered. To address these challenges and prospects, a new energy flux modelling framework based on TSEB-PT for high spatial resolution thermal and multispectral UAV data is proposed in this paper. Diurnal variations of LST in agricultural fields were recorded with a thermal infrared camera installed on an UAV during drought in 2018 and 2019. Observing potato as a test crop, LST, plant biophysical parameters derived from corresponding UAV multispectral data, and meteorological forcing variables were employed as input variables to TSEB-PT. All analyses were conducted at different pixelation of the UAV data to quantify the effect of spatial resolution on the performance. The 1 m spatial resolution produced the highest correlation between Tr modelled by TSEB-PT and measured by sap flow sensors (R2 = 0.80), which was comparable to the 0.06, 0.1, 0.5 and 2 m pixel sizes (R2 = 0.76–0.78) and markedly higher than the lower resolutions of 2 to 24 m (R2 = 0.30–0.72). Modelled Tr was highly and significantly correlated with measured leaf water potential (R2 = 0.81) and stomatal conductance (R2 = 0.74). The computed irrigation requirements (IRs) reflected the field irrigation treatments, ET and conventional irrigation practices in the area with high accuracy. It was also found that using a net primary production model with explicit representation of temperature influences made it possible to distinguish effects of drought vis-a-vis heat stress on crop productivity and water use efficiency. The results showed excellent model performance for retrieving Tr and ET dynamics under drought stress and proved that the proposed remote sensing based TSEB-PT framework at UAV scale is a promising tool for the investigation of plant drought stress and water demand; this is particularly relevant for local and regional irrigations scheduling.info:eu-repo/semantics/publishedVersio

Accurate estimates of land surface energy fluxes and irrigation requirements from UAV-based thermal and multispectral sensors

The two-source energy balance model estimates canopy transpiration (Tr) and soil evaporation (E) traditionally from satellite partitions of remotely sensed land surface temperature (LST) and the Priestley-Taylor equation (TSEB-PT) at seasonal time with limited accuracy. The high spatial-temporal resolution spectral data collected by unmanned aerial vehicles (UAVs) provide valuable opportunity to estimate Tr and E precisely, improve the understanding of the seasonal and the diurnal cycle of evapotranspiration (ET), and timely detect agricultural drought. The UAV data vary in spatial resolution and the uncertainty imposed on the TSEB-PT outcome has thus far not being considered. To address these challenges and prospects, a new energy flux modelling framework based on TSEB-PT for high spatial resolution thermal and multispectral UAV data is proposed in this paper. Diurnal variations of LST in agricultural fields were recorded with a thermal infrared camera installed on an UAV during drought in 2018 and 2019. Observing potato as a test crop, LST, plant biophysical parameters derived from corresponding UAV multispectral data, and meteorological forcing variables were employed as input variables to TSEB-PT. All analyses were conducted at different pixelation of the UAV data to quantify the effect of spatial resolution on the performance. The 1 m spatial resolution produced the highest correlation between Tr modelled by TSEB-PT and measured by sap flow sensors (R2 = 0.80), which was comparable to the 0.06, 0.1, 0.5 and 2 m pixel sizes (R2 = 0.76-0.78) and markedly higher than the lower resolutions of 2 to 24 m (R2 = 0.30-0.72). Modelled Tr was highly and significantly correlated with measured leaf water potential (R2 = 0.81) and stomatal conductance (R2 = 0.74). The computed irrigation requirements (IRs) reflected the field irrigation treatments, ET and conventional irrigation practices in the area with high accuracy. It was also found that using a net primary production model with explicit representation of temperature influences made it possible to distinguish effects of drought vis-a-vis heat stress on crop productivity and water use efficiency. The results showed excellent model performance for retrieving Tr and ET dynamics under drought stress and proved that the proposed remote sensing based TSEB-PT framework at UAV scale is a promising tool for the investigation of plant drought stress and water demand; this is particularly relevant for local and regional irrigations scheduling

Trade-offs in carbon-degrading enzyme activities limit long-term soil carbon sequestration with biochar addition

We would like to thank all the authors whose data and work are included in this meta-analysis. This study was supported by the National Natural Science Foundation of China (32071595, 41830756 and 42177022). We also thank the Fundamental Research Funds for the Central Universities (Program no. 2662019QD055). We acknowledge Cunbin Gao, Qianqian Zhao and Qin Liu for their assistance in data collection. J.C. received funding from Aarhus Universitets Forskningsfond (AUFF-E-2019-7-1), EU H2020 Marie Skłodowska-Curie Actions (839806), Danish Independent Research Foundation (1127-00015B), and Nordic Committee of Agriculture and Food Research (https://nordicagriresearch.org/2020-5/). The authors declare no competing interests.Peer reviewedPublisher PD

Duox, Flotillin-2, and Src42A Are Required to Activate or Delimit the Spread of the Transcriptional Response to Epidermal Wounds in Drosophila

The epidermis is the largest organ of the body for most animals, and the first line of defense against invading pathogens. A breach in the epidermal cell layer triggers a variety of localized responses that in favorable circumstances result in the repair of the wound. Many cellular and genetic responses must be limited to epidermal cells that are close to wounds, but how this is regulated is still poorly understood. The order and hierarchy of epidermal wound signaling factors are also still obscure. The Drosophila embryonic epidermis provides an excellent system to study genes that regulate wound healing processes. We have developed a variety of fluorescent reporters that provide a visible readout of wound-dependent transcriptional activation near epidermal wound sites. A large screen for mutants that alter the activity of these wound reporters has identified seven new genes required to activate or delimit wound-induced transcriptional responses to a narrow zone of cells surrounding wound sites. Among the genes required to delimit the spread of wound responses are Drosophila Flotillin-2 and Src42A, both of which are transcriptionally activated around wound sites. Flotillin-2 and constitutively active Src42A are also sufficient, when overexpressed at high levels, to inhibit wound-induced transcription in epidermal cells. One gene required to activate epidermal wound reporters encodes Dual oxidase, an enzyme that produces hydrogen peroxide. We also find that four biochemical treatments (a serine protease, a Src kinase inhibitor, methyl-ß-cyclodextrin, and hydrogen peroxide) are sufficient to globally activate epidermal wound response genes in Drosophila embryos. We explore the epistatic relationships among the factors that induce or delimit the spread of epidermal wound signals. Our results define new genetic functions that interact to instruct only a limited number of cells around puncture wounds to mount a transcriptional response, mediating local repair and regeneration

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe