High NH4+/NO3− Ratio Inhibits the Growth and Nitrogen Uptake of Chinese Kale at the Late Growth Stage by Ammonia Toxicity

The aim of this study was to determine the effects of various NH4+/NO3− ratios in a nutrient solution on the growth and nitrogen uptake of Chinese kale under hydroponic conditions. The four NH4+/NO3− ratios in the nutrient solution were CK (0/100), T1 (10/90), T2 (25/75), and T3 (50/50). An appropriate NH4+/NO3− ratio (10/90, 25/75) promoted the growth of Chinese kale. T2 produced the highest fresh and dry weight among treatments, and all indices of seedling root growth were the highest under T2. A high NH4+/NO3− ratio (50/50) promoted the growth of Chinese kale seedlings at the early stage but inhibited growth at the late growth stage. At harvest, the nutrient solution showed acidity. The pH value was the lowest in T3, whereas NH4+ and NH4+/NO3− ratios were the highest, which caused ammonium toxicity. Total N accumulation and N use efficiency were the highest in T2, and total N accumulation was the lowest in T3. Principal component analysis showed that T2 considerably promoted growth and N absorption of Chinese kale, whereas T3 had a remarkable effect on the pH value. These findings suggest that an appropriate increase in NH4+ promotes the growth and nutrient uptake of Chinese kale by maintaining the pH value and NH4+/NO3− ratios of the nutrient solution, whereas excessive addition of NH4+ may induce rhizosphere acidification and ammonia toxicity, inhibiting plant growth.

Modeling the Growth of Four Commercial Broiler Genotypes Reared in the Tropics

Genetic improvement in commercial broilers worldwide is heavily focused on selection for higher final body weight at a given age. Although commercial broilers are mostly sold by their final body weight, it is important to pay attention to how this weight is attained and at what cost. The cost of feeding broilers, which constitutes about 70% of the total cost of broiler production, varies considerably at different stages of the bird. It is, therefore, important to pay attention to the growth curve of broilers and the parameters of the growth curve to maximise profitability of commercial broiler production. The objective of this study was to model the variations of the growth curves of 4 commercial broiler genotypes reared in Ghana using the Gompertz and polynomial growth functions. Data on body weights at 1, 7, 14, 21, 28, 35 and 42 days for 4 unsexed commercial broiler genotypes were used to model both the Gompertz and polynomial growth functions. The 4 genotypes ranked differently for Gompertz predicted early (1 - 28 days), late growth (28 – 42 days) and body weight at 42 days. Gompertz function predicted growth better for broiler chicken than the polynomial as the parameters of the Gompertz function are biologically meaningful and heritable. Selection of broiler genotypes for production based on their growth curve (slower early growth and faster late growth) could minimize cost of production and thereby increase the profitability of commercial broiler production in the tropics.

Examining the Patterns of Virtual Visit Uptake Across Clinical Disciplines Using Hospital Administrative Data During the COVID-19 Pandemic: A Descriptive Study. (Preprint)

BACKGROUND The COVID-19 pandemic resulted in a dramatic and rapid shift away from physical visits, resulting in an instantaneous and unplanned adoption of virtual (phone and video) visits. OBJECTIVE Administrative data at a large urban Canadian university-affiliated hospital network was analyzed to understand how clinical disciplines adopted phone and video visits early in the pandemic and how their use of virtual visits grew, sustained or was abandoned through the pandemic. METHODS Virtual visit adoption by clinical discipline was compared during both the early pandemic (Apr-May 2020) and peak reopening time periods (Oct-Nov 2020) in an attempt to categorize clinical disciplines by their adoption of virtual visits, and thus understand how best to provide change management support. RESULTS At our largest academic site, for which we had full data, 50.8% of ambulatory visits were provided by phone or video during the pandemic (94.5% phone, 5.5% video). There was considerable variability across services in terms of how they adopted virtual visits in the early pandemic and peak reopening. Phone was the dominant modality, but video had high usage (up to 95% of virtual visits) in select disciplines. CONCLUSIONS We identified 4 patterns that provide opportunities for dedicated support in some disciplines: early sustained adoption, non-adoption, late growth, and late abandonment. The phone was the dominant modality (>90% of virtual visits) but video had high use in some disciplines necessitating targeted support. Additional high-quality research examining phone vs. video visits across disciplines and contexts is critical; until then both should be supported.

The Response of Grain Yield and Root Morphological and Physiological Traits to Nitrogen Levels in Paddy Rice

Rice (Oryza sativa L.) is an important crop in China. Although it is known that its yield is restricted by nitrogen (N) supply, the response of the root system to N supply specifically has not been systematically explored. This study aimed to investigate the effect of N uptake on grain yield to clarify the relationships between root morphophysiological traits and N uptake, and to understand relation between phytohormones and root morphophysiological traits. Two N-efficient absorption cultivars (NEAs) and two N-inefficient absorption cultivars (NIAs) were grown in the field, and three N conditions, deficient N (60 kg ha–1), intermediate N (180 kg ha–1), and sufficient N (240 kg ha–1), were applied during the growing season. The results showed higher dry matter and grain yield in NEAs than in NIAs, which was mainly attributed to increased N uptake in the mid- and late growth stages under all N conditions. And NEAs have different root regulation methods to obtain higher N accumulation and yield under different N supply conditions. Under lower N conditions, compared with NIAs, NEAs shown greater total root length, root oxidation activity, and root active absorbing surface area and smaller root diameter owing to higher indole-3-acetic acid and cytokinin content and lower 1-aminocyclopropane-1-carboxylic acid content in the early growth stages to respond to low N stress faster, laying a morphophysiological basis for its high N-uptake capacity in the mid- and late growth stages. Under higher N conditions, NEAs had higher root oxidation activity and root active absorbing surface area for N uptake and yield formation owing to higher abscisic acid and cytokinin content in the mid- and late growth stages, which improved the seed setting rate, thereby increasing the rice grain yield. These results suggest that NEAs can optimize the morphophysiological characteristics of roots through phytohormone regulation to adapt to different nutrient conditions, thereby promoting N accumulation and yield formation in rice.

Effects of Temporally Heterogeneous Hydrological Experiences On Subsequent Performance And Plasticity of Exotics And Natives From Different Habitats

Aims Temporally heterogeneous environments have crucial influences on plant survival and growth, leading to greater variations in plasticity, but direct experimental evidence is rare. Our objective was to investigate how early experience with temporally heterogeneous water conditions may affect the subsequent performance and plasticity of plants in response to water availability.Methods We subjected eight plant species from xeric, mesic or hydric habitats, four exotic and four native to North America, to initial exposure to either an alternating drought and inundation treatment (Ehet, heterogeneous experience) or a consistently moderate water supply (Ehom, homogeneous experience), and to a second round of drought, moderate watering or inundation treatments.Results Compared to Ehom, Ehet increased the final total mass across all species, but did not affect mortality. For species in groups, Ehet relative to Ehom decreased the initial total mass of native species, but increased the mass of exotic species, but natives had greater late growth than exotics after Ehet. Ehet also increased the total mass and late growth of mesic species more than xeric and hydric species.Conclusions Our findings suggest that previous exposure to temporal heterogeneity in water supply may be not beneficial immediately, but can be beneficial for plant late growth and plastic responses under water stress. Species from different habitats, and exotics vs. natives showed contrasting abilities to exploit such benefits from early heterogeneous experience, regardless of their final performance. This revealed the importance of modulating future plastic responses, or “metaplasticity”.

Agronomic and Physiological Evaluation of Wheat Cultivars under Deficit Irrigation Condition

Improving crop productivity under drought conditions contributes largely to the sustainable agriculture globally. In this study, the agronomic traits and physiological processes related to osmolyte accumulation and reactive oxygen species (ROS) homeostasis during late growth stage in wheat under drought stress were studied. Three cultivars viz., Shimai 22 (drought tolerant), Zhongxinmai 99 (median drought-tolerant, control), and Shi 4185 (drought sensitive) sharing contrasting drought tolerance were grown under normal irrigation (NI: with irrigations prior to sowing, and at jointing and flowering stages) and deficit irrigation (DI, with irrigations prior to sowing and at jointing) conditions. Data regarding yields, osmolyte (i.e., proline and soluble sugar) contents, and antioxidant enzyme activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), and malondialdehyde (MDA) contents were recorded. Under deficit irrigation, the cultivars displayed modified agronomic and physiological traits. Among cultivars, Shimai 22 showed best agronomic traits (6.47 to 7.23% higher yield than control), osmolyte contents and AE activities (10.12 to 22.18% higher than control), and least MDA accumulation (12.30 to 17.06% lower than control). In contrast, Shi 4185 cultivar performed worst regarding above said traits. The transcripts of the genes in ��1-Pyrroline-5-carboxylate synthetase (P5CS) family that regulates proline biosynthesis and those in AE families that modulate ROS homeostasis were evaluated. Results revealed that the P5CS genes TaP5CS2 and TaP5CS5 and the AE ones TaSOD3, TaCAT2 and TaCAT5 were modified on transcripts across the cultivars under DI condition, showing to be significant upregulated compared with NI. These results suggested the essential roles of osmolyte accumulation and AE proteins in improving the drought tolerance of wheat during late growth stages. In addition, this study suggested that the elevated transcription efficiencies of distinct P5CS and AE family genes under water deprivation contribute to the enhanced drought tolerance in drought-tolerant cultivars. © 2021 Friends Science Publishers

Visualisation and biovolume quantification in the characterisation of biofilm formation in Mycoplasma fermentans

The ability of mycoplasmas to persist on surfaces has been widely acknowledged, despite their fastidious nature. However, the organism’s capability to form a recognisable biofilm structure has been identified more recently. In the current study Mycoplasma fermentans was found to adhere to the glass surface forming highly differentiated biofilm structures. The volumes of biofilm microcolonies were quantified and observed to be greater at late growth stage than those at early growth stage. The channel diameters within biofilms were measured with Scanning Electron Microscopy images and found to be consistent with the size observed in Confocal Laser Scanning Microscope images. The combination of imaging methods with 3D visualisation provides key findings that aid understanding of the mycoplasma biofilm formation and true biofilm architecture. The observations reported here provide better understanding of the persistence of these minimalist pathogens in nature and clinical settings.