Temperature-responsive hydrogel prepared from carboxymethyl cellulose-stabilized N-vinylcaprolactam with potential for fertilizer delivery.

The growth of plants is highly dependent on sufficient water and suitable fertilizer nutrients, but the soil often loses moisture and the fertilizers are low efficiency. To address this issue, the temperature-responsive hydrogels were developed using the N-vinylcaprolactam (NVCL) dispersed in water through the emulsification of carboxymethyl cellulose (CMC) and acrylamide (AM), and urea was loaded into the hydrogel as a fertilizer. The amount of CMC and monomer have an effect on the structure, mechanical properties, swelling ability, and temperature sensitivity of the hydrogel. Therefore, the maximum swelling ratio of the hydrogel can reach 2056 % with the increasing hydrophilic groups, and the hydrogel exhibits a deswelling behavior as the temperature rises to higher than LCST due to the temperature responsiveness. Moreover, the fertilizer can rapidly release when the temperature is higher than LSCT, and exhibits similar release behavior in water and soil. Thus, the temperature-responsive hydrogel shows a great potential application for the controlled release of water and fertilizer in agriculture and forestry.

Selenium nanoparticles are effective in penetrating pine and causing high oxidative damage to Bursaphelenchus xylophilus in pine wilt disease control.

BACKGROUND: Research on selenium nanoparticles (SeNPs) in chemical defense and chemotherapy of plants has developed rapidly owing to their high microbial toxicity, environmental safety, and degradability. Pine wilt disease (PWD) threatens pine forests worldwide; however, it is difficult to kill the nematodes (Bursaphelenchus xylophilus) inside the tree that cause PWD using traditional pesticide formulations. SeNPs could be the key to controlling PWD. RESULTS: In this study, approximately 50 nm SeNPs were prepared using a simple and green method, and chitosan was used to increase their biocompatibility and stability. The preparation and characterization results showed that the prepared SeNPs coated with chitosan (SeNPs@CS) were spherical and evenly dispersed. The bioassay results showed that SeNPs@CS had an LC50 of 15.627 mg L-1 against B. xylophilus. In addition, the killing mechanism of SeNPs@CS against B. xylophilus was studied. Confocal microscopy and transmission electron microscopy demonstrated that B. xylophilus were killed by reactive oxygen species, and the penetration of nano-form materials to B. xylophilus was higher than that of non-nano-form materials. To verify the effective penetration of SeNPs in pine tissues, Cy5-labeled SeNPs@CS was observed inside pine needles and branches using frozen sections and confocal microscopy. In addition, the cytotoxicity of SeO2 and SeNPs@CS was tested, and the results showed that the cytotoxicity of SeNPs@CS to MC3T3-E1 cells was reduced. CONCLUSION: These results show that SeNPs are expected to be used as a new strategy for the control of PWD with oxidative damage and high penetration to B. xylophilus and effective target penetration and biosafety. © 2022 Society of Chemical Industry.

Using tank-mix adjuvant improves the physicochemical properties and dosage delivery to reduce the use of pesticides in unmanned aerial vehicles for plant protection in wheat.

BACKGROUND: Unmanned aerial vehicles (UAVs) are widely used to improve the efficiency of pesticide applications. Low-volume spraying operations require more efficient deposition of droplets on the target surface. Therefore, pesticide deposition and retention on plant surfaces is a serious challenge for modern precision agriculture. Tank-mix adjuvants have been used to improve spray dilutions performance; however, their effects on the physicochemical properties of spray dilutions, dosage delivery, and pesticide dosage are unclear. RESULTS: Tank-mix adjuvant 8860 significantly improved the physicochemical properties of spray dilutions, inhibited spray droplets rebound, improved the wetting and spreading performance of spray dilutions on wheat leaves, and increased the effective deposition of tebuconazole on wheat leaves. Even when its dosage was reduced by one-third, the spray solution still showed excellent disease control and effective deposition of the active ingredient on wheat leaves. CONCLUSION: The use of appropriate tank-mix adjuvants in UAV-based plant protection for wheat can significantly improve the performance of spray dilutions, increase the efficiency of pesticide dosage delivery, and improve disease control. These adjuvants can also help reduce the pesticide use while ensuring their effectiveness. © 2022 Society of Chemical Industry.

Sunlight-Induced Synthesis of Non-Target Biosafety Silver Nanoparticles for the Control of Rice Bacterial Diseases.

Silver is an important and efficient bactericide. Nanoscale silver has a large specific surface area, high target adhesion, strong permeability and high bactericidal activity. At present, the control of plant bacterial diseases is difficult, and the resistance of plant bacterial pathogens develops rapidly. Silver nanoparticles are expected to become a new generation of agrochemical to control plant bacterial diseases. In this study, a simple and green natural sunlight-induced method was used to prepare carboxymethylcellulose sodium-stabilized silver nanoparticles (CMC-SNs) with a particle size of around 13.53 ± 4.72 nm. CMC-SNs were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), energy-dispersive spectrometry (EDS), X-ray diffraction (XRD) and UV-vis spectroscopy and found to be spherical and evenly dispersed. The bacteriostatic activity of the CMC-SNs toward Xanthomonas oryzae pv. oryzae (Xoo) was tested. The minimum inhibitory concentration (MIC) of CMC-SNs to Xoo was 1 mg/L, and the minimum bactericidal concentration (MBC) was 2 mg/L. In addition, the antibacterial mechanism was studied by scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM), which confirmed that the CMC-SNs had high antibacterial activity. In order to verify its impact on the environment, we conducted an acute toxicity test on zebrafish and found that Half lethal concentration (LC50) > 100 mg/L in zebrafish, or no acute toxicity. The ability of CMC-SNs to control rice bacterial blight was verified by a pot experiment.

Efficient Degradation of Phenoxyalkanoic Acid Herbicides by the Alkali-Tolerant Cupriavidus oxalaticus Strain X32.

Phenoxyalkanoic acid (PAA) herbicides are mainly metabolized by microorganisms in soils, but the degraders that perform well under alkaline environments are rarely considered. Herein, we report Cupriavidus oxalaticus strain X32, which showed encouraging PAA-degradation abilities, PAA tolerance, and alkali tolerance. In liquid media, without the addition of exogenous carbon sources, X32 could completely remove 500 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) or 4-chloro-2-methylphenoxyacetic acid within 3 days, faster than that with the model degrader Cupriavidus necator JMP134. Particularly, X32 still functioned at pH 10.5. Of note, with X32 inoculation, we observed 2,4-D degradation in soils and diminished phytotoxicity to maize (Zea mays). Furthermore, potential mechanisms underlying PAA biodegradation and alkali tolerance were then analyzed by whole-genome sequencing. Three modules of tfd gene clusters involved in 2,4-D catabolism and genes encoding monovalent cation/proton antiporters involved in alkali tolerance were putatively identified. Thus, X32 could be a promising candidate for the bioremediation of PAA-contaminated sites, especially in alkaline surroundings.