Arbuscular mycorrhizal fungi increase crop yields by improving biomass under rainfed condition: a meta-analysis.

BACKGROUND: Rainfed agriculture plays key role in ensuring food security and maintain ecological balance. Especially in developing areas, most grain food are produced rainfed agricultural ecosystem. Therefore, the increase of crop yields in rainfed agricultural ecosystem becomes vital as well as ensuring global food security. METHODS: The potential roles of arbuscular mycorrhizal fungi (AMF) in improving crop yields under rainfed condition were explored based on 546 pairs of observations published from 1950 to 2021. RESULTS: AMF inoculation increased 23.0% crop yields based on 13 popular crops under rainfed condition. Not only was crop biomass of shoot and root increased 24.2% and 29.6% by AMF inocula, respectively but also seed number and pod/fruit number per plant were enhanced markedly. Further, the effect of AMF on crop yields depended on different crop groups. AMF improved more yield of N-fixing crops than non-N-fixing crops. The effect of AMF changed between grain and non-grain crops with the effect size of 0.216 and 0.352, respectively. AMF inoculation enhances stress resistance and photosynthesis of host crop in rainfed agriculture. CONCLUSION: AMF increased crop yields by enhancing shoot biomass due to the improvement of plant nutrition, photosynthesis, and stress resistance in rainfed field. Our findings provide a new view for understanding the sustainable productivity in rainfed agroecosystem, which enriched the theory of AMF functional diversity. This study provided a theoretical and technical way for sustainable production under rainfed agriculture.

Effect of molecular weight of dissolved organic matter on toxicity and bioavailability of copper to lettuce.

To clarify the effects of molecular weight of dissolved organic matter (DOM) on the toxicity and bioavailability of copper (Cu) to plants, DOM extracted from chicken manure was ultra-filtered into four fractions according to their molecular weights by means of sequential-stage ultrafiltration technique. Lettuce seeds were germinated by being exposed to the solutions containing Cu2+ with or without different fractions of DOM. The concentration of copper in roots, leaves, sprouts and the length of roots were investigated. The results showed that not all fractions of DOM could improve copper availability or toxicity. The fraction of DOM with larger molecular weight more than 1 kDa had higher complexation stability with Cu2+ and caused lower concentration of free Cu2+ ion in the solution of copper plus the fraction, resulting in lower availability and toxicity of copper to lettuce, but the fraction with molecular weight less than 1 kDa had the opposite function. Therefore, the molecular weight of 1 kDa may be the division point to determine DOM to increase or decrease copper availability and toxicity.

Proteomic Analysis of Vernalization Responsive Proteins in Winter Wheat Jing841.

BACKGROUND: Vernalization is one of the pivotal ways for plants to flower. The twodimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionization time-offlight/ time-of-flight mass spectrometry (MALDI-TOF/TOF MS) were applied to analyze the changes in protein expression profiles in responding to vernalization in leaves of wheat seedling before (0d) and after (30d) of vernalization. OBJECTIVE: The main objective of this study was to analyze the vernalization-responsive proteins in winter wheat after vernalization. METHODS: Winter wheat seedling leaf proteins were extracted by phenol extraction coupled with ammonium acetate in methanol. 2-DE was conducted according to procedures described in the manual given by the GE manufacture. The selected protein spots were identified by MALDITOF/ TOF MS. Gene ontology (GO) classification was applied to classify the functions of the differentially expressed proteins. Pathway enrichment analysis identified significantly enriched metabolic pathways or signal transduction pathways relative to the whole proteins background. RESULTS: The results of 2-DE and MALDI-TOF/TOF MS showed that among the 65 differentially expressed proteins that were successfully identified under vernalization, 30 were up-regulated whereas 35 were down-regulated after vernalization, respectively. These vernalization-responsive proteins were found to play roles in carbohydrate metabolism, protein metabolism, photosynthesis, defense and stress-resistance and may therefore participate in many biological processes in responding to vernalization. The enhanced accumulation of proteins after vernalization, such as thiamine thiazole synthase, late embryogenesis abundant protein, and glutathione-S-transferase, probably play vital roles in the mechanisms underlying vernalization response in wheat. CONCLUSION: Our results indicated these vernalization-responsive proteins were found to be involved in protein metabolism, carbohydrate metabolism, photosynthesis, and stress resistance/ defense. The responses of plants to low temperature were very complex, involving in a wide range of cellular pathways for signal transduction, gene regulation, protein modifications, and metabolic regulation. Studying on wheat proteomic profiles in response to vernalization can improve our understanding the molecular mechanisms underlying vernalization in cereals. The results obtained in this study have provided a novel insight into the mechanisms underlying vernalization in cereal crops.

Influence of residue and nitrogen fertilizer additions on carbon mineralization in soils with different texture and cropping histories.

To improve our ability to predict SOC mineralization response to residue and N additions in soils with different inherent and dynamic organic matter properties, a 330-day incubation was conducted using samples from two long-term experiments (clay loam Mollisols in Iowa [IAsoil] and silt loam Ultisols in Maryland [MDsoil]) comparing conventional grain systems (Conv) amended with inorganic fertilizers with 3 yr (Med) and longer (Long), more diverse cropping systems amended with manure. A double exponential model was used to estimate the size (Ca, Cs) and decay rates (ka, ks) of active and slow C pools which we compared with total particulate organic matter (POM) and occluded-POM (OPOM). The high-SOC IAsoil containing highly active smectite clays maintained smaller labile pools and higher decay rates than the low-SOC MDsoil containing semi-active kaolinitic clays. Net SOC loss was greater (2.6 g kg(-1); 8.6%) from the IAsoil than the MDsoil (0.9 g kg(-1), 6.3%); fractions and coefficients suggest losses were principally from IAsoil's resistant pool. Cropping history did not alter SOC pool size or decay rates in IAsoil where rotation-based differences in OPOM-C were small. In MDsoil, use of diversified rotations and manure increased ka by 32% and ks by 46% compared to Conv; differences mirrored in POM- and OPOM-C contents. Residue addition prompted greater increases in Ca (340% vs 230%) and Cs (38% vs 21%) and decreases in ka (58% vs 9%) in IAsoil than MDsoil. Reduced losses of SOC from residue-amended MDsoil were associated with increased OPOM-C. Nitrogen addition dampened CO2-C release. Clay type and C saturation dominated the IAsoil's response to external inputs and made labile and stable fractions more vulnerable to decay. Trends in OPOM suggest aggregate protection influences C turnover in the low active MDsoil. Clay charge and OPOM-C contents were better predictors of soil C dynamics than clay or POM-C contents.