The Role of the Ascorbic Acid-Glutathione Cycle in Young Wheat Ears' Response to Spring Freezing Stress.

Freezing stress in spring often causes the death and abnormal development of young ears of wheat, leading to a significant reduction in grain production. However, the mechanisms of young wheat ears responding to freezing are largely unclear. In this study, the role of the ascorbic acid-glutathione cycle (AsA-GSH cycle) in alleviating freezing-caused oxidative damage in young wheat ears at the anther connective tissue formation phase (ACFP) was investigated. The results showed that the release rate of reactive oxygen species (ROS) and the relative electrolyte conductivity in young ears of Jimai22 (JM22, freezing-tolerant) were significantly lower than those in young ears of Xumai33 (XM33, freezing-sensitive) under freezing. The level of the GSH pool (231.8~392.3 µg/g FW) was strikingly higher than that of the AsA pool (98.86~123.4 µg/g FW) in young wheat ears at the ACFP. Freezing significantly increased the level of the AsA pool and the activities of ascorbate peroxidase (APX) and monodehydroascorbate reductase (MDHAR) in the young ears of both varieties. The level of the GSH pool increased in the young ears of XM33 under freezing but decreased in the young ears of JM22. The young ears of JM22 showed higher activities of glutathione reductase (GR), glutathione-S-transferase (GST) and glutathione peroxidase (GPX) than the young ears of XM33 under freezing. Collectively, these results suggest that the AsA-GSH cycle plays a positive role in alleviating freezing-induced oxidative damage in young wheat ears. Furthermore, the ability of utilizing GSH as a substrate to scavenge ROS is an important factor affecting the freezing tolerance of young wheat ears. In addition, abscisic acid (ABA), salicylic acid (SA), 3-indolebutyric acid (IBA) and cis-zeatin (cZ) may be involved in regulating the AsA-GSH cycle metabolism in young wheat ears under freezing.

Label-Free Quantitative Proteomics Reveal the Mechanisms of Young Wheat (Triticum aestivum L.) Ears' Response to Spring Freezing.

Late spring frost is an important meteorological factor threatening the safe production of winter wheat in China. The young ear is the most vulnerable organ of the wheat plant to spring frost. To gain an insight into the mechanisms underpinning young wheat ears' tolerance to freezing, we performed a comparative proteome analysis of wheat varieties Xumai33 (XM33, freezing-sensitive) and Jimai22 (JM22, freezing-tolerant) under normal and freezing conditions using label-free quantitative proteomic techniques during the anther connective tissue formation phase (ACFP). Under freezing stress, 392 and 103 differently expressed proteins (DEPs) were identified in the young ears of XM33 and JM22, respectively, and among these, 30 proteins were common in both varieties. A functional characterization analysis revealed that these DEPs were associated with antioxidant capacity, cell wall modification, protein folding, dehydration response, and plant-pathogen interactions. The young ears of JM22 showed significantly higher expression levels of antioxidant enzymes, heat shock proteins, and dehydrin under normal conditions compared to those of XM33, which might help to prepare the young ears of JM22 for freezing stress. Our results lead to new insights into understanding the mechanisms in young wheat ears' response to freezing stress and provide pivotal potential candidate proteins required for improving young wheat ears' tolerance to spring frost.

One-time fertilization of controlled-release urea with compound fertilizer and rapeseed cake maintains rice grain yield and improves nitrogen use efficiency under reduced nitrogen conditions.

Nitrogen (N) rate reduction and simplified fertilization can mitigate environmental impacts and reduce the involvement of manual labor in rice (Oryza sativa L.) production. Controlled-release urea (CRU) has been recommended as an effective alternative technique to conventional urea fertilization, and it can improve rice yield and N use efficiency (NUE) and reduce labor costs. However, the information on the effects of one-time fertilization with CRU on maintaining yield and improving NUE under reduced chemical N conditions is limited. In this study, controlled-release bulk blending fertilizer (CRF), consisting of CRU with release periods of 40 and 100 days, mixed with compound fertilizer, was applied as basal fertilizer. Increased ~20% plant density (ID) and rapeseed cake fertilizer (RC, increase 20% organic N) were combined with CRF, respectively. The N treatments with 20% chemical N reduction were as follows: reduced N fertilizer (RNF), CRF, CRF+ID, and CRF+RC. In addition, a conventional split fertilizer application with 300 kg ha-1 N was applied as the control (CK). Rice yield and its components, dry matter accumulation, N uptake, and NUE were investigated to evaluate whether one-time N fertilization realized stable yield and high NUE under reduced 20% chemical N conditions. Compared with CK, the CRF+RC treatment exhibited a comparable grain yield, while the other reduced N treatments (RNF, CRF, and CRF+ID) had a lower grain yield. Moreover, CRF+ID exhibited a higher rice grain yield than RNF or CRF under the same N level. Irrespective of exogenous organic N, CRF+RC exhibited significantly higher NUE than CK. The CRF+ID treatment showed a significantly higher N partial factor productivity (PFN) than CK but comparable N agronomic efficiency (NAE) and N recovery efficiency (NRE). Therefore, a one-time fertilizer application of CRF+RC maintained grain yield and improved the NUE while reducing the N rate and fertilization times, demonstrating its potential application in rice production.

Prevalence of Carbendazin Resistance in Field Populations of the Rice False Smut Pathogen Ustilaginoidea virens from Jiangsu, China, Molecular Mechanisms, and Fitness Stability.

Rice false smut (RFS), caused by Ustilaginoidea virens, is an important fungal disease of rice. In China, Methyl Benzimidazole Carbamates (MBCs), including carbendazim, are common fungicides used to control RFS and other rice diseases. In this study, resistance of U. virens to carbendazim was monitored for three consecutive years during 2018 to 2020. A total of 321 U. virens isolates collected from Jiangsu Province of China were tested for their sensitivity to carbendazim on PSA. The concentration at which mycelial growth is inhibited by 50% (EC50) of the carbendazim-sensitive isolates was 0.11 to 1.38 µg/mL, with a mean EC50 value of 0.66 µg/mL. High level of resistance to carbendazim was detected in 14 out of 321 isolates. The resistance was stable but associated with a fitness penalty. There was a statistically significant and moderate negative correlation (r= −0.74, p < 0.001) in sensitivity between carbendazim and diethofencarb. Analysis of the U. virens genome revealed two potential MBC targets, Uvß1Tub and Uvß2Tub, that putatively encode ß-tubulin gene. The two ß-tubulin genes in U. virens share 78% amino acid sequence identity, but their function in MBC sensitivity has been unclear. Both genes were identified and sequenced from U. virens sensitive and resistant isolates. It is known that mutations in the ß2-tubulin gene have been shown to confer resistance to carbendazim in other fungi. However, no mutation was found in the Uvß2Tub gene in either resistant or sensitive isolates. Variations including point mutations, non-sense mutations, codon mutations, and frameshift mutations were found in the Uvß1Tub gene from the 14 carbendazim-resistant isolates, which have not been reported in other fungi before. Thus, these results indicated that variations of Uvß1Tub result in the resistance to carbendazim in field isolates of Ustilaginoidea virens.

Degradable Self-Destructive Redox-Responsive System Based on Mesoporous Organosilica Nano-Vehicles for Smart Delivery of Fungicide.

The development of stimuli-responsive controlled release formulations is a potential method of improving pesticide utilization efficiency and alleviating current pesticide-related environmental pollution. In this study, a self-destruction redox-responsive pesticide delivery system using biodegradable disulfide-bond-bridged mesoporous organosilica (DMON) nanoparticles as the porous carriers and coordination complexes of gallic acid (GA) and Fe(III) ions as the capping agents were established for controlling prochloraz (PRO) release. The GA-Fe(III) complexes deposited onto the surface of DMON nanoparticles could effectively improve the light stability of prochloraz. Due to the decomposition of GA-Fe(III) complexes, the nano-vehicles had excellent redox-responsive performance under the reducing environments generated by the fungus. The spreadability of PRO@DMON-GA-Fe(III) nanoparticles on the rice leaves was increased due to the hydrogen bonds between GA and rice leaves. Compared with prochloraz emulsifiable concentrate, PRO@DMON-GA-Fe(III) nanoparticles showed better fungicidal activity against Magnaporthe oryzae with a longer duration under the same concentration of prochloraz. More importantly, DMON-GA-Fe(III) nanocarriers did not observe obvious toxicity to the growth of rice seedlings. Considering non-toxic organic solvents and excellent antifungal activity, redox-responsive pesticide controlled release systems with self-destruction properties have great application prospects in the field of plant disease management.

The Toxicity of Salicylhydroxamic Acid and Its Effect on the Sensitivity of Ustilaginoidea virens to Azoxystrobin and Pyraclostrobin.

Rice false smut (RFS) caused by Ustilaginoidea virens has been one of the most severe rice diseases. Fungicide-based chemical control is a significant measure to control RFS. In the sensitivity determination of quinone outside inhibitor (QoI) fungicide in vitro, salicylhydroxamic acid (SHAM) has been commonly added to artificial culture media in order to inhibit alternative oxidase of phytopathogenic fungi. However, some studies showed that artificial media should not include SHAM due to its toxicity. Whether SHAM should be added in the assay of U. virens sensitivity to QoI fungicide remains unknown. In this study, two appropriate media, potato sucrose agar (PSA) and minimal medium (MM), were selected to test SHAM toxicity and sensitivity of U. virens to azoxystrobin and pyraclostrobin. The mycelial growth and sensitivity to azoxystrobin and pyraclostrobin had no significant difference between on PSA and MM. SHAM could significantly inhibit mycelial growth, conidial germination, peroxidase (POD) and esterase activity of U. virens. Average effective concentration for inhibiting 50% (EC50) values of SHAM against mycelial growth of ten U. virens were 27.41 and 12.75 µg/mL on PSA and MM, respectively. The EC50 values of SHAM against conidial germination of isolates HWD and JS60 were 70.36 and 44.69 µg/mL, respectively. SHAM at 30 µg/mL significantly inhibited POD and esterase activity of isolates HWD and JS60, and even SHAM at 10 µg/mL significantly inhibited POD activity of isolate HWD. In addition, SHAM significantly reduced EC50 values and EC90 values of azoxystrobin and pyraclostrobin on both PSA and MM. Even in the presence of SHAM at 10 µg/mL, average EC50 values of ten U. virens isolates for azoxystrobin decreased 1.7-fold on PSA and 4.8-fold on MM, and for pyraclostrobin that decreased 2.8-fold on PSA and 4.8-fold on MM. Therefore, these results suggest that SHAM should not be included in artificial media in the assay of U. virens sensitivity to QoI fungicides.

Zeolitic Imidazole Framework-90-Based Pesticide Smart-Delivery System with Enhanced Antimicrobial Performance.

Multimodal antimicrobial technology is regarded as a promising strategy for controlling plant diseases because it enhances antimicrobial efficacy by blocking multiple pesticide-resistance pathways. In this work, a pH-responsive multimodal antimicrobial system was constructed based on ZIF-90 for the controlled release of kasugamycin (KSM). A series of physicochemical characterizations confirmed the successful fabrication of ZIF-90-KSM. The results indicated that the loading capacity of ZIF-90-KSM for KSM was approximately 6.7% and that the ZIF-90 nanocarriers could protect KSM against photodegradation effectively. The acid pH at the site of disease not only decompose the Schiff base bonds between KSM and ZIF-90, but also completely dissolved the nanocarriers. The simultaneous release of KSM and Zn2+ ions was able to achieve multimodal antimicrobial functions during disease occurs. A bioactivity survey indicated that ZIF-90-KSM had superior fungicidal activity and longer duration against Magnaporthe oryzae than KSM aqueous solution. In addition, the phytotoxicity assessment of ZIF-90-KSM on rice plants did not reveal any adverse effects. Therefore, ZIF-90-KSM prepared by Schiff base reaction has great potential for achieving synergistic antifungal functions and provides an eco-friendly approach to manage rice diseases.

Hormetic Effects of Carbendazim on Mycelial Growth and Aggressiveness of Magnaporthe oryzae.

Rice blast caused by Magnaporthe oryzae is one of the most destructive fungal diseases of rice worldwide. Stimulatory effects of low doses of fungicides on pathogens are closely relevant to disease management. In the present study, in potato dextrose agar (PDA) amended with carbendazim at a dose range from 0.003 to 0.3 µg/mL, stimulatory effects on the mycelial growth of three isolates sensitive to carbendazim were tested. Carbendazim at concentrations from 0.003 to 0.1 µg/mL showed stimulatory effects on mycelial growth of isolates Guy11 and H08-1a, while carbendazim at concentrations from 0.003 to 0.03 µg/mL stimulated the growth of isolate P131. The maximum stimulation magnitudes were 11.84% for the three isolates tested. Mycelial colonies grown on PDA amended with different concentrations of carbendazim were incubated at 28 °C in darkness for 7 days as the pretreatment. Pretreatment mycelia were inoculated on fresh fungicide-free PDA and subsequent mycelia growth stimulations were still observed, and the maximum stimulation magnitudes were 9.15% for the three isolates tested. Pretreatment mycelia did not significantly change the tolerance to H2O2 and NaCl, except that the tolerance to H2O2 was increased significantly (p < 0.05) when the carbendazim was at 0.3 µg/mL. After five generations of mycelial transference on fungicide-free PDA, the transgenerational hormesis of mycelial were exhibited when transferred onto PDA supplemented with carbendazim at 0.3 µg/mL, and the maximum percent stimulation was 51.28%. The time course of infection indicated that the visible initial necrotic symptoms could be detected at 2 DPI on leaves treated with carbendazim at 0.03 µg/mL, whereas no necrotic symptom could be discerned for the control. Statistical results of lesion area and lesion type at 7 DPI showed that there was a significant stimulation (p < 0.05) on aggressiveness of M. oryzae isolate Guy11 on detached rice leaves at 0.03 µg/mL carbendazim. These results will advance our understanding of hormetic effects of fungicides and provide valuable information for judicious application of fungicides.

Pectin functionalized metal-organic frameworks as dual-stimuli-responsive carriers to improve the pesticide targeting and reduce environmental risks.

Encapsulation of active ingredients into intelligent response controlled release carriers has been recognized as a promising approach to enhance the utilization efficiency and reduce the environmental risks of pesticides. In this work, an intelligent redox and pectinase dual stimuli-responsive pesticide delivery system was constructed by bonding pectin with metal-organic frameworks (FeMOF nanoparticles) which were loaded with pyraclostrobin (PYR@FeMOF-pectin nanoparticles). The successful fabrication of PYR@FeMOF-pectin nanoparticles was proved by a series of physicochemical characterizations. The results indicated that the loading capacity of PYR@FeMOF-pectin nanoparticles for pyraclostrobin was approximately 20.6%. The pectin covered on the surface of PYR@FeMOF nanoparticles could protect pyraclostrobin from photolysis and improve their spreadability on rice blades effectively. Different biological stimuli associated with Magnaporthe oryzae could trigger the release of pyraclostrobin from the pesticide-loaded core-shell nanoparticles, resulting in the death of pathogens. The bioactivity survey determined that PYR@FeMOF-pectin nanoparticles had a superior fungicidal activity and a longer duration against Magnaporthe oryzae than pyraclostrobin suspension concentrate. In addition, the FeMOF-pectin nanocarriers showed no obvious phytotoxicity and could enhance the shoot length and root length of rice plants. More importantly, PYR@FeMOF-pectin nanoparticles had an 8-fold reduction in acute toxicity to zebrafish than that of pyraclostrobin suspension concentrate. Therefore, the dual-responsive FeMOF-pectin nanocarriers have great potential for realizing site-specific pesticide delivery and promoting plant growth.

Improved physiological and morphological traits of root synergistically enhanced salinity tolerance in rice under appropriate nitrogen application rate.

Numerous papers studied the relations between nitrogen rate and rice yield in saline soils, whereas the rice root morphological and physiological characteristics mediating nitrogen rates in yield formation under varied salinity levels remain less concerns. Through a field experiment applied with five nitrogen rates (0, 210, 255, 300, 345, and 390 kg ha-1) in saline land, we found that rice yield peaked at 7.7 t ha-1 under 300 kg ha-1 nitrogen, and excessive N was not conductive for increasing yield. To further elucidate its internal physiological mechanism, a pot experiment was designed with three N rates (210 [N1], 300 [N2], 390 [N3] kg ha-1) and three salt concentrations (0 [S0], 1.5 [S1], 3.0 [S2] g kg-1 NaCl). Results showed that the average grain yield was decreased by 19.1 and 51.1% under S1 and S2, respectively, while notably increased by 18.5 and 14.5% under N2 and N3, respectively. Salinity stress significantly inhibited root biomass, root length and surface area, root oxidation capacity (ROC), K+ and K+/Na+ ratio, and nitrogen metabolism-related enzyme activities, whereas root Na+ and antioxidant enzyme activities were notably increased. The mechanism of how insufficient N supply (N1) affected rice yield formation was consistent at different salinity levels, which displayed adverse impacts on root morphological and physiological traits, thereby significantly inhibiting leaf photosynthesis and grain yield of rice. However, the mechanism thorough which excessive N (N3) affected yield formation was quite different under varied salinity levels. Under lower salinity (S0 and S1), no significant differences on root morphological traits and grain yield were observed except the significantly decline in activities of NR and GS between N3 and N2 treatments. Under higher salinity level (S2), the decreased ROC, K+/Na+ ratio due to increased Na+, antioxidant enzyme activities, and NR and GS activities were the main reason leading to undesirable root morphological traits and leaf photosynthesis, which further triggered decreased grain yield under N3 treatment, compared to that under N2 treatment. Overall, our results suggest that improved physiological and morphological traits of root synergistically enhanced salinity tolerance in rice under appropriate nitrogen application rate.

The Starch Physicochemical Properties between Superior and Inferior Grains of Japonica Rice under Panicle Nitrogen Fertilizer Determine the Difference in Eating Quality.

Nitrogen fertilizer is essential for rice growth and development, and topdressing nitrogen fertilizer at panicle stage has a huge impact on rice grain quality. However, the effect of panicle nitrogen fertilizer (PNF) on starch physicochemical properties and fine structure remain unclear. In this study, four PNF levels (0, 60, 120, 180 kg N ha-1) were grown with the same basal and tiller fertilizer (150 kg N ha-1). The starch physicochemical properties, fine structure, texture properties and eating quality of two japonica rice were determined. We found that the content of total protein, crude fat and amylose between superior and inferior grains were significantly different. Compared with inferior grains, superior grains had low relative crystallinity, good pasting characteristics and outstanding eating quality. With the increase of nitrogen application rates, the starch volume mean diameter was lower; the average chain length of amylopectin was longer; and the relative crystallinity of starch was higher. The changes above in starch structure resulted in an increase in starch solubility, swelling power and gelatinization enthalpy, and led to a decrease in retrogradation enthalpy, retrogradation percentage and pasting viscosity, consequently contributing to the increase in hardness and stickiness of rice and the deterioration of taste value. These results indicated that topdressing PNF lengthened the amylopectin chain, decreased starch granule size, enhanced crystallization stability and increased gelatinization enthalpy, which were the direct reasons for the deterioration of cooking and eating quality.

Rice Yield Estimation Based on Continuous Wavelet Transform With Multiple Growth Periods.

Yield is an important indicator in evaluating rice planting, and it is the collective result of various factors over multiple growth stages. To achieve a large-scale accurate prediction of rice yield, based on yield estimation models using a single growth stage and conventional spectral transformation methods, this study introduced the continuous wavelet transform algorithm and constructed models under the premise of combined multiple growth stages. In this study, canopy reflectance spectra at four important stages of rice elongation, heading, flowering and milky were selected, and then, a rice yield estimation model was constructed by combining vegetation index, first derivative and wavelet transform based on random forest algorithm or multiple stepwise regression. This study found that the combination of multiple growth stages significantly improved the model accuracy. In addition, after two validations, the optimal model combination for rice yield estimation is first derivative-wavelet transform-vegetation index-random forest model based on four growth stages, with the coefficient of determination (R2) of 0.86, the root mean square error (RMSE) of 35.50 g·m-2 and the mean absolute percentage error (MAPE) of 4.6% for the training set, R2 of 0.85, RMSE of 33.40 g.m-2 and MAPE 4.30% for the validation set 1, and R2 of 0.80, RMSE of 37.40 g·m-2 and MAPE of 4.60% for the validation set 2. The research results demonstrated that the established model could accurately predict rice yield, providing technical support and a foundation for large-scale statistical estimating of rice yield.

Low Nitrogen Enhances Apoplastic Phloem Loading and Improves the Translocation of Photoassimilates in Rice Leaves and Stems.

The grain filling of rice depends on photoassimilates from leaves and stems. Phloem loading is the first crucial step for the transportation of sucrose to grains. However, phloem loading mechanisms in rice leaves and stems and their response to nitrogen (N) remain unclear. Here, using a combination of electron microscopy, transportation of a phloem tracer and 13C labeling, phloem loading was studied in rice leaves and stems. The results showed that the sieve element-companion cell complex lacked a symplastic connection with surrounding parenchyma cells in leaves and stems. The genes expression and protein levels of sucrose transporter (SUTs) and sugars will eventually be exported transporters (SWEETs) were detected in the vascular bundle of leaves and stems. A decrease in the 13C isotope remobilization from leaves to stems and panicles following treatment with p-chloromercuribenzenesulfonic acid indicated that rice leaves and stems actively transport sucrose into the phloem. Under low-N (LN) treatment, the activities of α-amylase, ß-amylase and sucrose phosphate synthase (SPS) in stems and activity of SPS in leaves increased; genes expression and protein levels of SUTs and SWEETs in leaves and stems increased; the 13C isotope reallocation in panicles increased. These indicated that LN enhanced apoplastic phloem loading in stems and leaves. This improved the translocation of photoassimilates and consequently increased grain filling percentage, grain weight and harvest index. This study provides evidence that rice leaves and stems utilize an apoplastic loading strategy and respond to N stimuli by regulating the genes expression and protein levels of SUTs and SWEETs.

Baseline Sensitivity and Control Efficacy of Two Quinone Outside Inhibitor Fungicides, Azoxystrobin and Pyraclostrobin, Against Ustilaginoidea virens.

Rice false smut caused by the filamentous fungus Ustilaginoidea virens is a devastating grain disease in rice. Fungicides have been an important measure for the control of this disease. In this study, baseline sensitivities of 179 isolates of U. virens to the quinone outside inhibitor (QoI) fungicides azoxystrobin and pyraclostrobin were established. The distribution of the 50% effective concentration (EC50) values of each fungicide was unimodal. The frequency distribution of logarithmically transformed EC50 values fit or fit closer to a normal distribution. The ranges of EC50 values for azoxystrobin and pyraclostrobin were 0.001 to 0.864 and 0.001 to 0.569 µg/ml, with means and standard errors of the mean values of 0.203 ± 0.012 and 0.079 ± 0.006 µg/ml, respectively. There was a statistically significant and moderately positive correlation (n = 100, r = 0.469, P = 0.001) in sensitivity between these two fungicides. No cross-resistance was found between azoxystrobin, pyraclostrobin, and carbendazim or sterol demethylation inhibitor fungicides. Each fungicide had a significantly higher mean preventive efficacy compared with its curative efficacy. Field assays showed that the control efficacy of pyraclostrobin against rice false smut was greater than that of azoxystrobin. Pyraclostrobin had the best control of rice false smut in three rice varieties, with the control efficacy ranging from 81.5 to 95.5%, whereas azoxystrobin decreased the disease index by 64.1 to 69.2% under the same conditions. These results provide us a reference point in the management of U. virens and future QoI fungicide resistance monitoring programs.

Pre-Gelatinisation of Rice Flour and Its Effect on the Properties of Gluten Free Rice Bread and Its Batter.

In order to improve the quality of the gluten free rice bread (GFRB), pre-gelatinised rice flour (PGRF) was made and used to partially replace natural rice flour in the production of GFRB. The pre-gelatinisation parameters were optimised and the effects of PGRF on the quality of the GFRB and its batter were studied. The results showed that optimal PGRF was obtained when 50% total water was mixed with 1.0% rice flour and the mixture heated at 80 °C for 2 min. Supplementation with PGRF significantly improved the properties of GFRB by affecting its baking properties, textural properties, colour, and crumb grain features. Effects of PGRF on GFRB were mainly caused by the more closely packed gel structure of rice starch in the bread batter, the higher onset temperature during gelatinisation and the complex effect of PGRF on water-binding capacity in bread batter during the baking process. As the pre-gelatinisation parameters of flours and their effect on gluten-free baked products varied with grain variety, processing properties should be studied before using them, and emphasis should be placed on new techniques such as flour pre-gelatinisation to obtain gluten-free foods with improved quality.

Fabrication of pH-responsive nanoparticles for high efficiency pyraclostrobin delivery and reducing environmental impact.

In this work, a pH-responsive pesticide delivery system using mesoporous silica nanoparticles (MSNs) as the porous carriers and coordination complexes of Cu ions and tannic acid (TA-Cu) as the capping agent was established for controlling pyraclostrobin (PYR) release. The results showed the loading capacity of PYR@MSNs-TA-Cu nanoparticles for pyraclostrobin was 15.7 ± 0.5% and the TA-Cu complexes deposited on the MSNs surface could protect pyraclostrobin against photodegradation effectively. The nanoparticles had excellent pH responsive release performance due to the decomposition of TA-Cu complexes under the acid condition, which showed 8.53 ± 0.37%, 82.38 ± 1.67% of the encapsulated pyraclostrobin were released at pH 7.4, pH 4.5 after 7 d respectively. The contact angle and adhesion work of PYR@MSNs-TA-Cu nanoparticles on rice foliage were 86.3° ± 2.7° and 75.8 ± 3.1 mJ/m2 after 360 s respectively, indicating that TA on the surface of the nanoparticles could improve deposition efficiency and adhesion ability on crop foliage. The control effect of PYR@MSNs-TA-Cu nanoparticles against Rhizoctonia solani with 400 mg/L of pyraclostrobin was 85.82% after 7 d, while that of the same concentration of pyraclostrobin EC was 53.05%. The PYR@MSNs-TA-Cu nanoparticles did not show any phytotoxicity to the growth of rice plants. Meanwhile, the acute toxicity of PYR@MSNs-TA-Cu nanoparticles to zebrafish was decreased more than 9-fold compared with that of pyraclostrobin EC. Thus, pH-responsive PYR@MSNs-TA-Cu nanoparticles have great potential for enhancing targeting and environmental safety of the active ingredient.

Preparation of biochar-interpenetrated iron-alginate hydrogel as a pH-independent sorbent for removal of Cr(VI) and Pb(II).

Herein, a pH-independent interpenetrating polymeric networks (Fe-SA-C) were fabricated from graphitic biochar (BC) and iron-alginate hydrogel (Fe-SA) for removal of Cr(VI) and Pb(II) in aqueous solution. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and scanning electron microscope (SEM) results demonstrated that graphitic BC interpenetration increased surface porosity and distorted surfaces of Fe-SA, which boosted availability of hydroxyl (-OH) group. Fe3+ as a cross-linking agent of the alginate endowed Fe-SA-C with positive surfaces (positive zeta potential) and excellent pH buffering capacity, while excessive Fe3+ was soldered on Fe-SA-C matrix as FeO(OH) and Fe2O3. Cr(VI) removal at pH of 3 by Fe-SA-C (20.3 mg g-1) were 30.3% and 410.6% greater than that by Fe-SA and BC, respectively. Fe-SA-C exhibited minor pH dependence over pH range of 2-7 towards Cr(VI) retention. Greater zeta potential of Fe-SA-C over Fe-SA conferred a better electrostatic attraction with Cr(VI). FTIR and XPS of spent sorbents confirmed the reduction accounted for 98.5% for Cr(VI) removal mainly due to participation of -OH. Cr(VI) reduction was further favored by conductive carbon matrix in Fe-SA-C, as evidenced by more negative Tafel corrosion potential. Reductively formed Cr(III) was subsequently complexed with carboxylic groups originating from oxidation of -OH. Thus, Cr(VI) removal invoked electrostatic attraction, reduction, and surface complexation mechanisms. Pb(II) removal with excellent pH independence was mainly ascribed to surface complexation and possible precipitation. Thus, the functionalized, conductive, and positively-charged Fe-SA-C extended its applicability for Cr(VI) and Pb(II) removal from aqueous solutions in a wide pH range. This research could expand the application of hydrogel materials for removal of both cationic and anionic heavy metals in solutions over an extended pH range.

[Life history traits of an Echinochloa crus-galli var. crus-galli population with extreme adaptations to rice planting systems]. / 特异性适应稻作系统的稗草种群生活史特性.

Long-term herbicide application may facilitate the adaptive evolution of weed populations. With Echinochloa crus-galli var. crus-galli population A from a rice field used for the experiment of effectiveness of herbicide in Nanling County, Anhui Province, we conducted common garden experi-ments with seeds of population A and three control populations collected from normal rice fields. Compared with the three control populations, population A had significantly lower seed production for individual plant, but higher 1000-seed weight. Population A had faster in seedling growth, higher in number of reproductive tillers, shorter life span, lower in height and biomass of individual plant, as well as lower in sensitivity to herbicide penoxsulam. Individuals from population A survived from 2× label dose (60 g·hm-2) of penoxsulam treatment at the three- to four-leaf stage showed significantly reduction in plant height, biomass, and mature seed production (1066 seeds per plant), but no difference in heading period, number of reproductive tillers, number of seeds per raceme and 1000-seed weight. The short lifespan, heavy seeds, dwarf architecture, more reproductive tillers and penoxsulam resistance made E. crus-galli var. crus-galli population A extremely adapting to rice planting systems, which should be prevented to spread to normal rice fields.

Quantitative monitoring of leaf area index in wheat of different plant types by integrating NDVI and Beer-Lambert law.

Normalized difference vegetation index (NDVI) is one of the most important vegetation indices in crop remote sensing. It features a simple, fast, and non-destructive method and has been widely used in remote monitoring of crop growing status. Beer-Lambert law is widely used in calculating crop leaf area index (LAI), however, it is time-consuming detection and low in output. Our objective was to improve the accuracy of monitoring LAI through remote sensing by integrating NDVI and Beer-Lambert law. In this study, the Beer-Lambert law was firstly modified to construct a monitoring model with NDVI as the independent variable. Secondly, experimental data of wheat from different years and various plant types (erectophile, planophile and middle types) was used to validate the modified model. The results showed that at 130 DAS (days after sowing), the differences in NDVI, leaf area index (LAI) and extinction coefficient (k) of the three plant types with significantly different leaf orientation values (LOVs) reached the maximum. The NDVI of the planophile-type wheat reached saturation earlier than that of the middle and erectophile types. The undetermined parameters of the model (LAI = -ln (a1 × NDVI + b1)/(a2 × NDVI + b2)) were related to the plant type of wheat. For the erectophile-type cultivars (LOV ≥ 60°), the parameters for the modified model were, a1 = 0.306, a2 = -0.534, b1 = -0.065, and b2 = 0.541. For the middle-type cultivars (30° < LOV < 60°), the parameters were, a1 = 0.392, a2 = -0.881, b1 = 0.028, and b2 = 0.845. And for the planophile-type cultivars (LOV ≤ 30°), those parameters were, a1 = 0.596, a2 = -1.306, b1 = 0.014, and b2 = 1.130. Verification proved that the modified model based on integrating NDVI and Beer-Lambert law was better than Beer-Lambert law model only or NDVI-LAI direct model only. It was feasible to quantitatively monitor the LAI of different plant-type wheat by integrating NDVI and Beer-Lambert law, especially for erectophile-type wheat (R2 = 0.905, RMSE = 0.36, RE = 0.10). The monitoring model proposed in this study can accurately reflect the dynamic changes of plant canopy structure parameters, and provides a novel method for determining plant LAI.

The effects of field pre-harvest sprouting on the morphological structure and physicochemical properties of rice (Oryza sativa L.) starch.

This study investigates the effects of field pre-harvest sprouting (PHS) on the morphological structure and physicochemical properties of starches from four rice varieties during the rice harvesting period. The results of the study showed that PHS significantly affected the grain characteristics, starch structure, and physicochemical properties of the four rice varieties. Moreover, PHS led to a significant decrease in the grain processing quality and protein content of the four varieties, pitting and unevenness on the surface of the starch granules, and smaller starch granules. In addition, PHS led to starches with lower amylose content, which resulted in a higher swelling power, solubility, and relative crystallinity. Higher gelatinization enthalpy and lower gelatinization temperature were also observed under PHS conditions. The results indicated that PHS can lead to degradation in grain processing and appearance quality, but it can also lead to some improvements in the gelatinization properties of starch.