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Genetically modified crops are superior in their nitrogen use efficiency-A meta-analysis of three major cereals.
Li, M, Xu, J, Gao, Z, Tian, H, Gao, Y, Kariman, K
Scientific reports. 2020;(1):8568
Abstract
It is currently uncertain to what extent genetic transformations of strategic crops (targeting diverse traits) have improved their N use efficiency (NUE), and what the key factors affecting their NUE are. Based on data collected from 130 publications, the effect sizes of genetic transformations and the key factors influencing NUE for three major cereal crops (rice, maize, and wheat), were investigated using a meta-analysis approach. Genetic transformations increased yield, shoot biomass, N uptake efficiency (NUpE), and partial factor productivity of N (PFPN) in the crops, but decreased shoot NUE (SNUE) and grain NUE (GNUE). Transporter genes improved yield and NUE parameters more efficiently, than did the other gene types. The effect sizes for some NUE parameters varied according to crop species and experimental conditions but did not differ between the overexpression and ectopic expression methods. Most effect sizes did not correlate with gene overexpression levels. These results indicate a promising potential of genetic transformations approaches for improving certain NUE parameters.
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2.
Application of controlled release urea improved grain yield and nitrogen use efficiency: A meta-analysis.
Zhu, S, Liu, L, Xu, Y, Yang, Y, Shi, R
PloS one. 2020;(10):e0241481
Abstract
The application of controlled release urea (CRU) has been proposed as a crucial method to reduce the adverse environmental effects induced by conventional urea (CU). Yet, a systematic and quantitative analysis on how CRU affects staple crop production including wheat (Triticum aestivum L.), maize (Zea mays L.), and rice (Oryza sativa L.) is lacking. Here, a meta-analysis was conducted to determine how CRU influences soil chemical properties, total nitrogen (TN) uptake, grain yield, and nitrogen use efficiency (NUE) of staple crop in China. The results indicated that CRU application significantly increased soil organic carbon (SOC), TN, and available nitrogen (AN) by 5.93%, 3.89% and 13.98% respectively overall, while soil pH showed no significant changes. Compared to the application of CU, applying CRU significantly increased grain yield by 7.23%, which was mainly owing to the higher TN uptake (9.13%) across all the studies. In addition, the application of CRU significantly increased NUE, nitrogen agronomy efficiency (NAE), utilization rate of nitrogen fertilizer (NUR), and nitrogen physiological efficiency (NPE) by an average of 23.4%, 34.65%, 25.83% and 15.8% respectively which could be attributed to the slow nitrogen (N) release characteristics of CRU. The positive effect of CRU on grain yield and NUE of staple crop was greatest when the content of SOC and TN were extremely low, indicating that it was most effective to improve grain production of infertile soil by applying CRU. The finding of this study indicated that the application of CRU should be promoted for grain production, especially for infertile soil.
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3.
A meta-analysis of crop response patterns to nitrogen limitation for improved model representation.
Seufert, V, Granath, G, Müller, C
PloS one. 2019;(10):e0223508
Abstract
The representation of carbon-nitrogen (N) interactions in global models of the natural or managed land surface remains an important knowledge gap. To improve global process-based models we require a better understanding of how N limitation affects photosynthesis and plant growth. Here we present the findings of a meta-analysis to quantitatively assess the impact of N limitation on source (photosynthate production) versus sink (photosynthate use) activity, based on 77 highly controlled experimental N availability studies on 11 crop species. Using meta-regressions, we find that it can be insufficient to represent N limitation in models merely as inhibiting carbon assimilation, because in crops complete N limitation more strongly influences leaf area expansion (-50%) than photosynthesis (-34%), while leaf starch is accumulating (+83%). Our analysis thus offers support for the hypothesis of sink limitation of photosynthesis and encourages the exploration of more sink-driven crop modelling approaches. We also show that leaf N concentration changes with N availability and that the allocation of N to Rubisco is reduced more strongly compared to other photosynthetic proteins at low N availability. Furthermore, our results suggest that different crop species show generally similar response patterns to N limitation, with the exception of leguminous crops, which respond differently. Our meta-analysis offers lessons for the improved depiction of N limitation in global terrestrial ecosystem models, as well as highlights knowledge gaps that need to be filled by future experimental studies on crop N limitation response.
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4.
Nitrogen - essential macronutrient and signal controlling flowering time.
Weber, K, Burow, M
Physiologia plantarum. 2018;(2):251-260
Abstract
Nitrogen, as limiting nutrient for plant growth and crop yield, is a main component of fertilizers and heavily used in modern agriculture. Early reports from over-application of fertilizers in crop production have shown to repress the transition from vegetative to reproductive phase. For the model plant Arabidopsis thaliana, there is evidence that low nitrogen conditions promote early flowering, while high nitrogen as well as nitrogen starvation conditions display the opposite effect. To gain a better understanding of how nitrogen affects the onset of flowering, we reviewed the existing literature for A. thaliana and carried out a meta-analysis on available transcriptomics data, seeking for potential genes and pathways involved in both nitrogen responses and flowering time control. With this strategy, we aimed at identifying potential gateways for integration of nitrogen signaling and potential regulators that might link the regulatory networks controlling nitrogen and flowering in A. thaliana. We found that photoperiodic pathway genes have high potential to be involved in nitrogen-dependent flowering.
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5.
Modulation of intestinal microbiota, control of nitrogen products and inflammation by pre/probiotics in chronic kidney disease: a systematic review.
Lopes, RCSO, Balbino, KP, Jorge, MP, Ribeiro, AQ, Martino, HSD, Alfenas, RCG
Nutricion hospitalaria. 2018;(3):722-730
Abstract
Dysbiosis may favor the occurrence of inflammation and oxidative stress in chronic kidney disease (CKD). It has been suggested that the intake of pre/probiotics may control the progression of chronic kidney disease. Thus, the objective of this study was to systematically review the literature on the effects of pre/probiotic intake on the intestinal microbiota, control of nitrogen products, oxidative stress, and inflammation in CKD patients.The literature search was conducted on MEDLINE, LILACS, Cochrane Library of Clinical Trials, and Science Direct. After careful evaluation by the reviewers, ten potentially relevant articles were selected for this study. Based on previous studies, intake of prebiotics appears to have the following effects: increased bifidobacteria and lactobacillus counts; reduced formation of uremic toxin, p-cresol, and its serum concentrations; improved lipid profiles; reduced systemic inflammatory state and concentrations of oxidative stress markers. Similarly, consumption of probiotics can reduce blood urea and serum phosphate concentrations. Furthermore, an increase in fecal volume and intestinal Bifidobacteriumand a reduction in p-cresol serum and blood urea concentrations were observed in response to symbiotic intake. These results suggest that consumption of pre/probiotics may modulate the intestinal microbiota, and promote the growth and metabolism of anaerobic bacteria by decreasing the production of uremic solutes, further causing oxidative stress and systemic inflammation in CKD patients.
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6.
Nutrient-limited conditions determine the responses of foliar nitrogen and phosphorus stoichiometry to nitrogen addition: A global meta-analysis.
You, C, Wu, F, Yang, W, Xu, Z, Tan, B, Yue, K, Ni, X
Environmental pollution (Barking, Essex : 1987). 2018;:740-749
Abstract
To test the hypothesis that nutrient-limited conditions can determine the responses of nitrogen (N) and phosphorus (P) stoichiometry to N addition, a meta-analysis was conducted to identify the different responses of foliar N and P concentrations and N-to-P ratios to N addition under N limitation, N and P co-limitation and P limitation. N addition increased the foliar N-to-P ratios and N concentrations by 46.2% and 30.2%, respectively, under N limitation, by 18.7% and 19.7% under N and P co-limitation, and by 4.7% and 12.9% under P limitation. However, different responses of foliar P concentrations to N addition were observed under different nutrient limitations, and negative, positive, and neutral effects on P concentrations were observed under N limitation, P limitation and N and P co-limitation, respectively. Generally, the effects of N addition on N-to-P ratios and N concentrations in herbaceous plants were dramatically larger than those in woody plants (with the exception of the N-to-P ratio under N limitation), but the opposite situation was true for P concentrations. The changes in N-to-P ratios were closely correlated with the changes in N and P concentrations, indicating that the changes in both N and P concentrations due to N addition can drive N and P stoichiometry, but the relative sizes of the contributions of N and P varied greatly with different nutrient limitations. Specifically, the changes in N-to-P ratios may indicate a minimum threshold, which is consistent with the homeostatic mechanism. In brief, increasing N deposition may aggravate P limitation under N-limited conditions but improve P limitation under P-limited conditions. The findings highlight the importance of nutrient-limited conditions in the stoichiometric response to N addition, thereby advancing our ability to predict global plant growth with increasing N deposition in the future.