Search

Traditional Se (selenium) fertilizers are poorly deposited on crop leaves and are easily washed away by rain; these factors limit plant Se absorption and pose potential environmental risks. To address this issue, a thermosensitive Se nanoparticles gel (CS-FA/BP-SeNPs) based on chitosan-ferulic acid (CS-FA) and β-glycerophosphate (β-BP) was developed to increase rain-washing resistance and Se uptake in grape leaves. The CS-FA derivative was synthesized via an amide reaction between chitosan and ferulic acid(1:2); this derivative demonstrated strong antibacterial and antioxidant activity, effectively dispersing the Se nanoparticles (SeNPs) and preventing their aggregation. β-glycerophosphate neutralized the pH value of the CS-FA/SeNPs solution, significantly increasing the stability of the SeNPs (stable for 30 days). Up to 37 °C, the solution rapidly formed a hydrogel, increasing its viscous modulus by 5.1 times and improving adhesion. Compared with SeNPs alone, CS-FA/BP-SeNPs showed superior spreading, reducing droplet splashing and retraction. In simulated rainfall experiments, the CS-FA/BP-SeNPs gel coating retained 91.1 % of the material on the leaf surface, while the corresponding value for SeNPs was 13.6 %, demonstrating excellent rainfastness in the former. In open-field cultivation trials, grape leaves treated with the CS-FA/BP-SeNPs gel coating presented a 141.3–192.7 % increase in the Se retention rate and a 51.3–62.3 % increase in Se uptake than those with SeNPs alone. Additionally, CS-FA/BP-SeNPs significantly reduced Fusarium oxysporum infection rates, demonstrating potential for use in challenging outdoor environments. This thermosensitive gel coating provides an effective strategy for enhancing nanoselenium utilization on crop leaves through its temperature-responsive properties and strong postgelation adhesion.

Ammonium and nitrate nitrogen are the two main forms of inorganic nitrogen (N) available to crops. However, it is not clear how mixtures of ammonium and nitrate N affect N uptake and partitioning in major rice cultivars in southern China. This study investigated the effects of different ammonium nitrogen and nitrate nitrogen mixture treatments (100:0, 75:25, 50:50, 25:75, and 0:100) on the growth, photosynthetic characteristics, nitrogen uptake, gene expression, and yield of different rice cultivars (Mei Xiang Zhan NO. 2: MXZ2; Nan Jing Xiang Zhan: NJXZ). Rice root biomass, tiller number, and yield were increased by 69.5%, 42.5%, and 46.8%, respectively, in the 75:25 ammonium-nitrate mixed treatment compared to the 100:0 ammonium-nitrate mixed treatment. The nitrogen content in rice roots, stems, leaves, and grains increased by 69.5%, 64.0%, 65.5%, and 17.5%, respectively. In addition, compared with MXZ2, NJXZ had a greater proportion of N allocated to leaves and grains. Analysis of root enzyme activities revealed that the 75:25 ammonium-nitrate mixed nutrient treatment increased rice root glutamine synthetase activity by an average of 35.0% and glutamate synthetase activity by an average of 52.0%. Transcriptome analysis revealed that the 75:25 mixed ammonium-nitrate nutrient treatment upregulated the expression of genes related to the nitrogen metabolism transporter pathway. Weighted correlation network analysis revealed that some differentially expressed genes (HISX and RPAB5) regulated the activities of nitrogen-metabolizing enzymes in rice and some (SAT2, CYSKP, SYIM, CHI1, and XIP1) modulated amino acid synthesis; greater expression of these genes was detected in the 75:25 ammonium-nitrate mixed nutrient treatment. The expression characteristics of the above genes were further confirmed by RT‒qPCR. Interestingly, the expression levels of the above genes were significantly correlated with the glutamate synthase activity, photosynthetic rate, and root volume. It is noteworthy that increasing the expression of the aforementioned genes coupled with nitrogen uptake was observed in the three main rice cultivars. These results suggest that the 75:25 ammonium-nitrate mixture may have increased nitrogen-metabolizing enzyme activities and promoted nitrogen uptake through the upregulated expression of nitrogen metabolism-related genes, thereby increasing tiller number and improving rice yield.

Optimizing soil water and fertilizer management can benefit crop production and soil environment. Alginate oligosaccharides (AOS) are natural biostimulants with fertilizer efficiency- and growth-promoting functions. However, there are few application strategies of AOS in citrus production, especially in combination with water and fertilizer regulations. In this paper, a two-year field trial was conducted to investigate the effects of AOS (AOS0, AOS2.5, AOS5.0) strategies under different moisture conditions (W80, W70, W60) on citrus yield, quality, water and fertilizer use efficiency, plant growth and soil environment. The results showed that drip irrigation with 2.5 g L−1AOS 8–10 times under W70 (W70AOS2.5) increased fruit yield, the total soluble sugar and sucrose content by 11.93%–13.31%, 15.16–17.47% and 18.92–20.81%, and fruit potassium and water use efficiency increased by 51.09%–62.21% and 12.01%–13.34%, respectively, and the effect of increase was better than the application in W80 and W60. Citrus growth showed that net photosynthetic rate of W70AOS2.5 were significantly increased after 4th AOS application, and that total root length, surface area, and volume also increased at harvest. Soil analysis showed that drip-irrigated AOS reduced the loss rate of soil water under both W60 and W70, increased proportions of water stable aggregates >0.25 mm in the soil. The available potassium content increased significantly in the 0–20 cm soil layer but decreased significantly in the 20–40 cm soil layer, and soil cation exchange capacity also increased significantly in the 0–20 cm layer, suggesting that AOS may slow water and potassium loss under low moisture conditions. In addition, AOS also increased the organic carbon content and the abundance of Pseudolabrys which dominant bacteria associated with carbon and nitrogen. The W70AOS2.5 strategy exceeded other strategies in terms of overall evaluation score and net benefits, reducing irrigation water discharge to the environment by 620–700 m3 ha−1. Our study demonstrated the good potential of AOS in improving fruit production and soil properties.

Carbon dots (CDs), a novel type of nanomaterial, play crucial roles in the agriculture field. However, it remains unclear their impacts on the flavor quality of vegetables. The present study synthesized a novel chitooligosaccharide-peanut oligopeptide-carbon dots (COS-POP-CDs) material through the chitooligosaccharide (COS) and peanut oligopeptide (POP) high temperature Maillard reactions and studied its effect on the flavor quality of Chinese cabbage (Choy sum). Results indicated that COS-POP-CDs emit blue visible light that readily absorbed by chloroplasts, while also demonstrating some degree of antibacterial and antioxidant activities. After transplanting of Choy sum, foliar spraying 0.12 mg/mL COS-POP-CDs twice can increase the content of soluble proteins, Vitamin C, and enhance the strawberry and spicy flavors of Choy Sum. After harvest of Choy Sum, foliar spraying 0.12 mg/mL COS-POP-CDs once can slow down the spoilage. These results suggest that COS-POP-CDs have significant potential to improve crop quality.

Herein, four chitooligosaccharide derivatives (COS-RA, COS-FA, COS-VA, COS-GA) were prepared by laccase-catalyzed chitooligosaccharide modification with rosmarinic acid (RA), ferulic acid (FA), gallic acid (GA), and vanillic acid (VA), and structures were characterized. RA and FA resulted in higher amino-substitution in the chitooligosaccharides than GA and VA. COS-RA and COS-FA had greater DPPH scavenging rates than COS-GA and COS-VA. Compared with COS treatment, spraying 250 mg L−1 COS-RA or COS-VA 6 times (once per 7 days) increased soluble sugar and anthocyanin content by 18.6%–23.2% and 41.7%–46.7%, respectively, from the fruit expansion to harvest stage. COS-RA and COS-VA also enhanced gene expression related to anthocyanin synthesis (PAL, F3H, F3′5′H, DFR, and UFGT) and monomeric anthocyanin accumulation (Mal-3-O-glu, Petu-3-O-ace-glu, Del-3-O-glu). Therefore, chitooligosaccharide derivatives may improve grape fruit anthocyanin accumulation by regulating antioxidant systems, improving the photosynthetic rate and inducing gene expression related to anthocyanin synthesis.

IntroductionSelenium (Se) is an essential trace element required for proper human and animal health.MethodsIn this paper, we investigated the uptake and distribution characteristics of a new Se fertilizer, which comprises algal polysaccharides–selenium nanoparticles (APS-SeNPs), in rice plants in both hydroponic and pot experiments.ResultsThe results from the hydroponic experiments revealed that the rice root uptake of APS-SeNPs fitted the Michaelis–Menten equation, with a Vmax of 13.54 μg g−1 root dry weight (DW) per hour, which was 7.69 and 2.23 times those of selenite and selenate treatments, respectively. The root uptake of APS-SeNPs was inhibited by AgNO3 (64.81%–79.09%) and carbonyl cyanide 3-chlorophenylhydrazone (CCCP; 19.83%–29.03%), indicating that the uptake of APS-SeNPs by rice roots is mainly via aquaporins and is also affected by metabolic activity. Moreover, sulfur deficiency caused rice roots to absorb more APS-SeNPs, but treatment with APS-SeNPs increased the expression of the sulfate transporter OsSULTR1;2 in the roots, suggesting that OsSULTR1;2 is probably involved in the uptake of APS-SeNPs. The application of APS-SeNPs significantly increased the Se content in rice plants and the apparent Se uptake efficiency compared with selenate and selenite treatments. Most of the Se in the roots of rice plants was distributed in the cell wall, while it was primarily located in the cytosol in the shoots when treated with APS-SeNPs. The results from the pot experiments indicated that the application of Se enhanced the Se content of each rice tissue. It is worth noting that the Se content in brown rice under APS-SeNP treatment was higher than that under selenite or selenate treatment and was mainly concentrated in the embryo end, with the Se in organic form.DiscussionOur findings provide important insights into the uptake mechanism and the distribution of APS-SeNPs in rice plants.

Alginate oligosaccharides (AOS) are functional substances in seaweed extracts that regulate crop quality and stress tolerance. In this paper, the effects of AOS spray application on the antioxidant system, photosynthesis and fruit sugar accumulation in citrus was investigated through a two-year field experiment. The results showed that 8-10 spray cycles of 300-500 mg L-1 AOS (once per 15 days) increased soluble sugar and soluble solid contents by 7.74-15.79% and 9.98-15.35%, respectively, from citrus fruit expansion to harvesting. Compared with the control, the antioxidant enzyme activity and the expression of some related genes in citrus leaves started to increase significantly after the 1st AOS spray application, while the net photosynthetic rate of leaves increased obviously only after the 3rd AOS spray cycle, and the soluble sugar content of AOS-treated leaves increased by 8.43-12.96% at harvest. This suggests that AOS may enhance photosynthesis and sugar accumulation in leaves by antioxidant system regulation. Moreover, analysis of fruit sugar metabolism showed that during the 3rd to 8th AOS spray cycles, AOS treatment increased the activity of enzymes related to sucrose synthesis (SPS, SSs), upregulated the expression of sucrose metabolism (CitSPS1, CitSPS2, SUS) and transport (SUC3, SUC4) genes, and promoted the accumulation of sucrose, glucose and fructose in fruits. Notably, the concentration of soluble sugars in citrus fruits was significantly reduced at all treatments with 40% reduction in leaves of the same branch, but the loss of soluble sugars in AOS-treated fruits (18.18%) was higher than that in the control treatment (14.10%). It showed that there was a positive effect of AOS application on leaf assimilation product transport and fruit sugar accumulation. In summary, AOS application may improve fruit sugar accumulation and quality by regulating the leaf antioxidant system, increasing the photosynthetic rate and assimilate product accumulation, and promoting sugar transfer from leaves to fruits. This study shows the potential application of AOS in the production of citrus fruits for sugar enhancement.

Cadmium (Cd) is present in many soils and, when entering the food chain, represents a major health threat to humans. Reducing Cd accumulation in plants is complicated by the fact that most known Cd transporters also operate in the transport of essential nutrients such as Zn, Fe, Mn, or Cu. This work summarizes the current knowledge of mechanisms mediating Cd uptake, radial transport, and translocation within the plant. It is concluded that real progress in the field may be only achieved if the transport of Cd and the above beneficial micronutrients is uncoupled, and we discuss the possible ways of achieving this goal. Accordingly, we suggest that the major focus of research in the field should be on the structure−function relations of various transporter isoforms and the functional assessment of their tissue-specific operation. Of specific importance are two tissues. The first one is a xylem parenchyma in plant roots; a major “controller” of Cd loading into the xylem and its transport to the shoot. The second one is a phloem tissue that operates in the last step of a metal transport. Another promising and currently underexplored avenue is to understand the role of non-selective cation channels in Cd uptake and reveal mechanisms of their regulation.