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<jats:p>The balance of carbon (C) and nitrogen (N) metabolism influences plant growth and development as well as yield. A two-year field experiment was conducted in a hilly region in southwest China in 2019–2020 to investigate the correlation between the accumulation and balance of C and N, as well as the grain yield of maize cultivars with contrasting N efficiencies. Using Zhenghong 311 (ZH 311) and Xianyu 508 (XY 508) as research sources, the differences in C and N accumulation and balance in maize cultivars with contrasting N efficiencies were compared to analyze the correlation between the accumulation and balance of C and N with grain yield. According to the results, the ZH 311 cultivar had higher C and N accumulation in each stage and grain yield than the XY 508 cultivar, while the C/N ratio in each stage and organ was significantly lower in ZH 311 than in XY 508, with the greatest difference occurring in the silking stage and leaf, indicating that the N-efficient cultivar ZH 311 had evident advantages in accumulation and balance of C and N and grain yield than the N-inefficient cultivar XY 508. Moreover, the C and N accumulation and grain yield increased significantly with N application, while the C/N ratio in each stage and organ decreased significantly with N application, but the differences between ZH 311 and XY 508 increased first and then decreased with the increase of N level, the optimum N level when obtaining the highest grain yield of ZH 311 (273.21 kg ha<jats:sup>–1</jats:sup>) was significantly lower than that of XY 508 (355.88 kg ha<jats:sup>–1</jats:sup>). Furthermore, grain yield was positively correlated with C (<jats:italic>R</jats:italic><jats:sup>2</jats:sup> = 0.9251) and N (<jats:italic>R</jats:italic><jats:sup>2</jats:sup> = 0.9033) accumulation, affected by pre-anthesis N (<jats:italic>R</jats:italic><jats:sup>2</jats:sup> = 0.9198) and post-anthesis C (<jats:italic>R</jats:italic><jats:sup>2</jats:sup> = 0.8632) accumulation, and negatively correlated with the C/N ratio (<jats:italic>R</jats:italic><jats:sup>2</jats:sup> = 0.7664), with the highest correlation between grain yield and the C/N ratio in silking stage (<jats:italic>R</jats:italic><jats:sup>2</jats:sup> = 0.7984) and leaf (<jats:italic>R</jats:italic><jats:sup>2</jats:sup> = 0.7616). In conclusion, the N-efficient cultivar ZH 311 could better coordinate the C and N balance of the plant, especially the C and N balance in the silking stage and leaf, promote photosynthetic product storage and transport, prolong the leaf function period, and make the pre-anthesis and post-anthesis C and N accumulation of ZH 311 significantly higher than those of XY 508, allowing higher grain yields.</jats:p>

<jats:p>Defence phytohormone pathways evolved to recognize and counter multiple stressors within the environment. Salicylic acid responsive pathways regulate the defence response to biotrophic pathogens whilst responses to necrotrophic pathogens, herbivory, and wounding are regulated <jats:italic>via</jats:italic> jasmonic acid pathways. Despite their contrasting roles <jats:italic>in planta</jats:italic>, the salicylic acid and jasmonic acid defence networks share a common architecture, progressing from stages of biosynthesis, to modification, regulation, and response. The unique structure, components, and regulation of each stage of the defence networks likely contributes, in part, to the speed, establishment, and longevity of the salicylic acid and jasmonic acid signaling pathways in response to hormone treatment and various biotic stressors. Recent advancements in the understanding of the <jats:italic>Arabidopsis thaliana</jats:italic> salicylic acid and jasmonic acid signaling pathways are reviewed here, with a focus on how the structure of the pathways may be influencing the temporal regulation of the defence responses, and how biotic stressors and the many roles of salicylic acid and jasmonic acid <jats:italic>in planta</jats:italic> may have shaped the evolution of the signaling networks.</jats:p>

<jats:p>Northern corn leaf blight (NCLB), caused by the fungal pathogen <jats:italic>Exserohilum turcicum</jats:italic>, poses a grave threat to maize production worldwide. The resistance gene in A619<jats:italic>Ht3</jats:italic>, discovered decades ago, is an important genetic resource for NCLB control. By using a pair of near-isogenic lines (NILs) A619<jats:italic>Ht3</jats:italic> and A619, together with the resistant and susceptible bulks derived from the cross of A619<jats:italic>Ht3</jats:italic> and L3162 lines, we initially detected a <jats:italic>Ht3</jats:italic>-like (<jats:italic>Ht3L</jats:italic>) locus in bin 8.06 that was closely associated with NCLB resistance. We then performed five rounds of fine-mapping, which ultimately delimited the <jats:italic>Ht3L</jats:italic> locus to a 577-kb interval flanked by SNP markers KA002081 and KA002084. Plants homozygous for the <jats:italic>Ht3L</jats:italic>/<jats:italic>Ht3L</jats:italic> genotype exhibited an average reduction in diseased leaf area (DLA) by 16.5% compared to plants lacking <jats:italic>Ht3L locus</jats:italic>. The <jats:italic>Ht3L</jats:italic> locus showed extensive variation in genomic architecture among different maize lines and did not appear to contain any genes encoding canonical cell wall-associated kinases against NCLB. Moreover, the <jats:italic>Ht3L</jats:italic> locus was located ∼2.7 Mb away from the known <jats:italic>Htn1</jats:italic> locus. We speculate that the <jats:italic>Ht3L</jats:italic> locus may contain a bona fide <jats:italic>Ht3</jats:italic> gene or a novel NCLB resistance gene closely linked to <jats:italic>Ht3</jats:italic>. In practice, the <jats:italic>Ht3L</jats:italic> locus is a valuable resource for improving maize resistance to NCLB.</jats:p>

<jats:p>Nitrogen (N) fertilization is indispensable for high yields in agriculture due to its central role in plant growth and fitness. Different N forms affect plant defense against foliar pathogens and may alter soil–plant-microbe interactions. To date, however, the complex relationships between N forms and host defense are poorly understood. For this purpose, nitrate, ammonium, and cyanamide were compared in greenhouse pot trials with the aim to suppress two important fungal wheat pathogens <jats:italic>Blumeria graminis</jats:italic> f. sp. <jats:italic>tritici</jats:italic> (<jats:italic>Bgt</jats:italic>) and <jats:italic>Gaeumannomyces graminis</jats:italic> f. sp. <jats:italic>tritici</jats:italic> (<jats:italic>Ggt</jats:italic>). Wheat inoculated with the foliar pathogen <jats:italic>Bgt</jats:italic> was comparatively up to 80% less infested when fertilized with nitrate or cyanamide than with ammonium. Likewise, soil inoculation with the fungal pathogen <jats:italic>Ggt</jats:italic> revealed a 38% higher percentage of take-all infected roots in ammonium-fertilized plants. The bacterial rhizosphere microbiome was little affected by the N form, whereas the fungal community composition and structure were shaped by the different N fertilization, as revealed from metabarcoding data. Importantly, we observed a higher abundance of fungal pathogenic taxa in the ammonium-fertilized treatment compared to the other N treatments. Taken together, our findings demonstrated the critical role of fertilized N forms for host–pathogen interactions and wheat rhizosphere microbiome assemblage, which are relevant for plant fitness and performance.</jats:p>

<jats:p>Huanglongbing (HLB), the most destructive citrus disease, is associated with unculturable, phloem-limited <jats:italic>Candidatus</jats:italic> Liberibacter species, mainly <jats:italic>Ca.</jats:italic> L. asiaticus (Las). Las is transmitted naturally by the insect <jats:italic>Diaphorina citri</jats:italic>. In a previous study, we determined that the Oceanian citrus relatives <jats:italic>Eremocitrus glauca</jats:italic>, <jats:italic>Microcitrus warburgiana</jats:italic>, <jats:italic>Microcitrus papuana</jats:italic>, and <jats:italic>Microcitrus australis</jats:italic> and three hybrids among them and <jats:italic>Citrus</jats:italic> were full-resistant to Las. After 2 years of evaluations, leaves of those seven genotypes remained Las-free even with their susceptible rootstock being infected. However, Las was detected in their stem bark above the scion-rootstock graft union. Aiming to gain an understanding of the full-resistance phenotype, new experiments were carried out with the challenge-inoculated Oceanian citrus genotypes through which we evaluated: (1) Las acquisition by <jats:italic>D. citri</jats:italic> fed onto them; (2) Las infection in sweet orange plants grafted with bark or budwood from them; (3) Las infection in sweet orange plants top-grafted onto them; (4) Las infection in new shoots from rooted plants of them; and (5) Las infection in new shoots of them after drastic back-pruning. Overall, results showed that insects that fed on plants from the Oceanian citrus genotypes, their canopies, new flushes, and leaves from rooted cuttings evaluated remained quantitative real-time polymerase chain reaction (qPCR)-negative. Moreover, their budwood pieces were unable to infect sweet orange through grafting. Furthermore, sweet orange control leaves resulted infected when insects fed onto them and graft-receptor susceptible plants. Genomic and morphological analysis of the Oceanian genotypes corroborated that <jats:italic>E. glauca</jats:italic> and <jats:italic>M. warburgiana</jats:italic> are pure species while our <jats:italic>M. australis</jats:italic> accession is an <jats:italic>M. australis</jats:italic> × <jats:italic>M. inodora</jats:italic> hybrid and <jats:italic>M. papuana is</jats:italic> probably a <jats:italic>M. papuana</jats:italic> × <jats:italic>M. warburgiana</jats:italic> hybrid. <jats:italic>E. glauca</jats:italic> × <jats:italic>C. sinensis</jats:italic> hybrid was found coming from a cross between <jats:italic>E. glauca</jats:italic> and mandarin or tangor. <jats:italic>Eremocitrus</jats:italic> × <jats:italic>Microcitrus</jats:italic> hybrid is a complex admixture of <jats:italic>M. australasica</jats:italic>, <jats:italic>M. australis</jats:italic>, and <jats:italic>E. glauca</jats:italic> while the last hybrid is an <jats:italic>M. australasica</jats:italic> × <jats:italic>M. australis</jats:italic> admixture. Confirmation of consistent full resistance in these genotypes with proper validation of their genomic parentages is essential to map properly genomic regions for breeding programs aimed to generate new <jats:italic>Citrus</jats:italic>-like cultivars yielding immunity to HLB.</jats:p>

<jats:p>Drought is one of the most destructive abiotic stresses that impact the growth, physiology, yield, and nutritional quality of seeds of crop plants. In modern agriculture, the use of nanoparticles can be beneficial due to their large surface area and higher potentiality to enter into the plant leaf during foliar application. This study aims to evaluate the effects of foliar spray containing varying doses (0, 100, and 200 ppm) of the nano-iron (Fe<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub>) on the growth, physiology, yield, and seed nutritional quality of soybean under drought (40% of field capacity, FC) and well-watered (80% of FC) conditions. Leaf water status, chlorophyll content of leaves, the height of the plant, fresh leaf weight, fresh stem weight, fresh petiole weight, total dry weight, seed yield, and protein and oil content in soybean seeds were found to be suppressed by the applied drought stress. Under both drought (40% of FC) and controlled well-watered (80% of FC) conditions, the foliar application of nano-iron substantially improved the growth, physiology, yield, and quality of soybean seeds. The nanoparticles at 200 ppm increased soybean seed yield by 40.12 and 32.60% in drought and well-watered conditions, respectively, compared to the untreated plants. Furthermore, nano-iron increased the oil content of soybean seeds by 10.14 and 7.87% under drought and well-watered conditions, respectively, compared to the untreated control. Our results indicate that the application of nano-iron improved drought tolerance, yield, and seed quality of soybean, so exogenous foliar sprays of 200 ppm Fe<jats:sub>3</jats:sub>O<jats:sub>4</jats:sub> were more effective than the other treatments in enhancing drought tolerance and can be utilized to reduce losses caused by drought stress in soybean-growing areas.</jats:p>

<jats:p>Pod size is one of the most important agronomic features of peanuts, which directly affects peanut yield. Studies on the regulation mechanism underpinning pod size in cultivated peanuts remain hitherto limited compared to model plant systems. To better understand the molecular elements that underpin peanut pod development, we conducted a comprehensive analysis of chronological transcriptomics during pod development in four peanut accessions with similar genetic backgrounds, but varying pod sizes. Several plant transcription factors, phytohormones, and the mitogen-activated protein kinase (MAPK) signaling pathways were significantly enriched among differentially expressed genes (DEGs) at five consecutive developmental stages, revealing an eclectic range of candidate genes, including <jats:italic>PNC</jats:italic>, <jats:italic>YUC</jats:italic>, and <jats:italic>IAA</jats:italic> that regulate auxin synthesis and metabolism, <jats:italic>CYCD</jats:italic> and <jats:italic>CYCU</jats:italic> that regulate cell differentiation and proliferation, and <jats:italic>GASA</jats:italic> that regulates seed size and pod elongation <jats:italic>via</jats:italic> gibberellin pathway. It is plausible that <jats:italic>MPK3</jats:italic> promotes integument cell division and regulates mitotic activity through phosphorylation, and the interactions between these genes form a network of molecular pathways that affect peanut pod size. Furthermore, two variant sites, <jats:italic>GCP4</jats:italic> and <jats:italic>RPPL1</jats:italic>, were identified which are stable at the QTL interval for seed size attributes and function in plant cell tissue microtubule nucleation. These findings may facilitate the identification of candidate genes that regulate pod size and impart yield improvement in cultivated peanuts.</jats:p>

<jats:p>National Forest Park is an important place for the public to carry out forest recreation activities and recognize natural habitats. With the popularization of forest tourism and the increase of forest recreational activities, the pressure on forest habitats has increased. The development of national forest parks is accompanied by opportunities and challenges. The main purpose of this paper is to analyze and study the impact of ecotourism design on plant protection based on sensor network technology. This paper analyzes the impact of tourism on the ecological environment, establishes an ecological environment monitoring system and an ecological tourism resource evaluation system, and studies the functional division of forest parks. Experimental research shows that, as a strictly protected area, the ecological conservation area basically does not conduct scenic spot development and resource mining, nor is it open to tourists. The total area is 852.92 ha, accounting for 22.31% of the total area of the forest park, allowing the ecology of the ecological conservation area to achieve sustainable and healthy development.</jats:p>

<jats:p>Dinoflagellate inhabitants of the reef-building corals exchange nutrients and signals with host cells, which often benefit the growth of both partners. Phytohormones serve as central hubs for signal integration between symbiotic microbes and their hosts, allowing appropriate modulation of plant growth and defense in response to various stresses. However, the presence and function of phytohormones in photosynthetic dinoflagellates and their function in the holobionts remain elusive. We hypothesized that endosymbiotic dinoflagellates may produce and employ phytohormones for stress responses. Using the endosymbiont of reef corals <jats:italic>Breviolum minutum</jats:italic> as model, this study aims to exam whether the alga employ analogous signaling systems by an integrated multiomics approach. We show that key gibberellin (GA) biosynthetic genes are widely present in the genomes of the selected dinoflagellate algae. The non-13-hydroxylation pathway is the predominant route for GA biosynthesis and the multifunctional GA dioxygenase in <jats:italic>B. minutum</jats:italic> has distinct substrate preference from high plants. GA biosynthesis is modulated by the investigated bleaching-stimulating stresses at both transcriptional and metabolic levels and the exogenously applied GAs improve the thermal tolerance of the dinoflagellate. Our results demonstrate the innate ability of a selected Symbiodiniaceae to produce the important phytohormone and the active involvement of GAs in the coordination and the integration of the stress response.</jats:p>

<jats:p>The effects of selenium (Se) on plant metabolism have been reported in several studies triggering plant tolerance to abiotic stresses, yet, the effects of Se on coffee plants under chilling stress are unclear. This study aimed to evaluate the effects of foliar Se application on coffee seedlings submitted to chilling stress and subsequent plant recovery. Two <jats:italic>Coffea</jats:italic> species, <jats:italic>Coffea arabica</jats:italic> cv. Arara, and <jats:italic>Coffea canephora</jats:italic> clone 31, were submitted to foliar application of sodium selenate solution (0.4 mg plant<jats:sup>–1</jats:sup>) or a control foliar solution, then on day 2 plants were submitted to low temperature (10°C day/4°C night) for 2 days. After that, the temperature was restored to optimal (25°C day/20°C night) for 2 days. Leaf samples were collected three times (before, during, and after the chilling stress) to perform analyses. After the chilling stress, visual leaf injury was observed in both species; however, the damage was twofold higher in <jats:italic>C. canephora.</jats:italic> The lower effect of cold on <jats:italic>C. arabica</jats:italic> was correlated to the increase in ascorbate peroxidase and higher content of starch, sucrose, and total soluble sugars compared with <jats:italic>C. canephora</jats:italic>, as well as a reduction in reducing sugars and proline content during the stress and rewarming. Se increased the nitrogen and sulfur content before stress but reduced their content during low temperature. The reduced content of nitrogen and sulfur during stress indicates that they were remobilized to stem and roots. Se supply reduced the damage in <jats:italic>C. canephora</jats:italic> leaves by 24% compared with the control. However, there was no evidence of the Se effects on antioxidant enzymatic pathways or ROS activity during stress as previously reported in the literature. Se increased the content of catalase during the rewarming. Se foliar supply also increased starch, amino acids, and proline, which may have reduced symptom expression in <jats:italic>C. canephora in</jats:italic> response to low temperature. In conclusion, Se foliar application can be used as a strategy to improve coffee tolerance under low-temperature changing nutrient remobilization, carbohydrate metabolism, and catalase activity in response to rewarming stress, but <jats:italic>C. arabica</jats:italic> and <jats:italic>C. canephora</jats:italic> respond differently to chilling stress and Se supply.</jats:p>