Search Results (455)

The role of endogenous salicylic acid (SA), a major signaling molecule, was addressed in relation to the waterlogging (WL) stress response, including redox homeostasis and senescence. Wild-type and salicylate hydroxylase-expressing (NahG) tobacco plants were studied to reveal the stress-related effects of the transgene, which is known to deplete the endogenous SA pool. In control conditions, SA levels of the top leaves of NahG plants were moderately lower than those of wild-type, while SA was considerably reduced in the bottom leaves. WL conditions triggered a rise in H₂O₂ concentrations in young leaves, which was exaggerated in NahG plants, pointing to a mitigating effect of SA against the stress-associated oxidative burden. The NahG transgenic leaves displayed lower protein levels than their wild-type counterparts, indicating a role of SA in protein retention. In non-stressed NahG plants, young (top) leaves showed an increased level of protein nitration. WL treatment triggered decreased protein contents in the leaves of both genotypes. This coincided with the high H₂O₂ content of old leaves exceeding that of young leaves in most cases. The expression of the senescence marker gene Cysteine protease 1 was upregulated in WL-stressed bottom leaves. According to this marker, senescence progressed faster in NahG leaves. Links between SA, protein nitration, and leaf senescence were discussed. Additionally, a stimulating effect of the NahG transgene was confirmed on adventitious roots (AR) formation, which may have helped root functions and thus probably contributed to maintaining the growth of the WL-stressed plants. Our results have implications for how endogenous SA levels influence plants in a WL stress situation. According to our findings, the depletion of SA may trigger protein loss and tyrosine nitration, but at the same time accelerates AR formation in WL-stressed tobacco. Full article

Ilex lanceifolia K.W.Xu & Lei Jiang, a new species from the western Pearl River Delta of Guangdong, China, is described based on morphological and molecular evidence. To test whether this newly discovered population represents a distinct lineage and to assess the congruence between leaf morphology and phylogeny, we integrated multivariate morphometrics, scanning electron microscopy, and phylogenetic analyses of nuclear ITS, ETS, and nepGS sequences. The new species resembles I. xiaojinensis and I. peiradena in shrubby habit and lanceolate leaves but differs by its prominently raised abaxial leaf veins forming distinct reticulate areoles, and green to purplish-black petioles and young branchlets. However, phylogenetic analyses unexpectedly place it within Ilex sect. Ilex forming a clade with I. graciliflora and six other species, rather than with its morphological look-alikes. This discordance strongly suggests that the lanceolate leaf shape has evolved convergently in multiple lineages of Ilex, likely as an adaptive strategy to the high-humidity, low-light understory conditions of subtropical lowland forests. The new species is currently known only from a single population in Jiangmen City, with several thousand individuals but an extremely restricted range (<20 km²), warranting conservation attention. This discovery highlights the underestimated biodiversity of lowland forests in the Pearl River Delta and underscores the need to prioritize remnant habitat fragments in rapidly urbanizing regions. Full article

Leaves of Persea americana Mill. are a potential source of bioactive compounds; however, current knowledge is limited by the lack of studies that simultaneously evaluate multiple cultivars and leaf developmental stages under comparable field conditions, as well as by inconsistent sampling criteria across studies. This study aimed to assess how leaf developmental stage and cultivar influence phenolic composition and antioxidant activity in avocado leaves grown under field conditions. Total polyphenols, total flavonoids, quercetin-3-O-galactoside, and chlorogenic acid were selected as representative compounds due to their relevance in plant defense and antioxidant capacity. These compounds, together with antioxidant activity, were quantified in young expanding (E1) and fully expanded (E6) leaves of seven avocado cultivars using spectrophotometric methods and HPLC-DAD, and analyzed through two-way ANOVA. Results showed that leaf developmental stage significantly influenced flavonoid content, chlorogenic acid, and antioxidant activity, which were consistently higher in E1 leaves. In contrast, total polyphenol content exhibited cultivar-dependent responses, increasing toward E6 only in specific genotypes, while quercetin-3-O-galactoside remained stable across developmental stages but varied among cultivars. Overall, the results indicate that phenolic metabolism in avocado leaves is regulated by both developmental stage and genotype in a compound-specific manner, with no consistent pattern associated with racial background. From a practical perspective, these findings provide a basis for selecting leaf material according to the intended application: young leaves for higher antioxidant capacity and flavonoid content, and specific cultivars at advanced stages for higher total polyphenol accumulation, supporting the functional valorization of avocado leaves as a source of bioactive compounds. Full article

Sympatric butterflies in the same family (Pieridae) utilize the same genus of hostplant (Fabaceae), yet some are only found as caterpillars on young foliage, while others appear to eat mature foliage. Observations conducted over the course of a single year on five species of Inga (Fabaceae) in Monteverde, Costa Rica, revealed three butterflies whose caterpillars consumed their leaves. One species was more common throughout the year with caterpillars encountered on primarily mature foliage; two others were found only on species with new leaves and occurred seasonally, during months of increased new leaf production. In feeding preference tests, those species showed a marked preference for eating new leaves, whereas the more common species showed no preference. The seasonality of occurrence of the two species eating new leaves may be explained, in part, by availability of their preferred foliage. The coexistence of the three butterflies using the same host-plants may be facilitated by their leaf age preferences and differential oviposition patterns of the females. Full article

Atmospheric nitrogen (N) deposition is altering global forest ecosystems, with nitrate rising to rival ammonium as a dominant N form, yet how leaf ontogeny orchestrates carbon–nitrogen (C-N) metabolic coordination under contrasting N forms remains poorly understood. We conducted a field experiment investigating the physiological and metabolic responses of young and old leaves of Chinese fir (Cunninghamia lanceolata) to ammonium and nitrate addition. Young leaves, functioning as active sinks, exhibited enhanced photosynthetic performance and growth-oriented N assimilation under N addition, with disproportionately stronger responses to nitrate. In contrast, old leaves, acting as source tissues, showed limited photosynthetic plasticity but accumulated higher non-structural carbohydrates and elevated N assimilation enzyme activities, particularly under nitrate addition. Phytohormone profiles supported this ontogenetic divergence, with young leaves showing higher auxin levels while old leaves exhibited increased abscisic acid and salicylic acid contents. Metabolomic analysis further revealed age-dependent reprogramming of amino acid metabolism, identifying key metabolites coordinating C-N balance. These findings demonstrate a leaf ontogeny-mediated spatial division of metabolic labor in Chinese fir, wherein old leaves function as metabolic buffers stabilizing whole-plant C-N homeostasis under fluctuating N supply, providing new insights into plantation responses to contrasting N deposition regimes. Full article

Citrus production is increasingly constrained worldwide by rising soil salinity, particularly in arid and semi-arid regions. In Tunisia, the expansion of saline soils represents a major abiotic stress limiting orchard productivity. The identification of salt-tolerant rootstocks has therefore become a priority, especially as alternatives to sour orange (SO, Citrus aurantium L.), which is highly susceptible to Citrus tristeza virus. In recent years, several outbreaks of the disease have been reported in the Cap Bon citrus-growing region, posing an imminent threat to the sustainability of citrus production in Tunisia. This study evaluated the salt tolerance of commercial cultivars (HER, MAR, WN, NH) grafted onto Citrus volkameriana Ten. & Pasq. (CV, Citrus aurantium × Citrus limon (L.) Burm.f.) and three Poncirus trifoliata hybrids (CC, C35, CTR) under irrigation water salinity ranging from 1.1 to 4.1 mS/cm and soil salinity between 1.8 and 3.8 mS/cm. Data were collected between 2020 and 2021 in five young citrus orchards (KHB, OSN, BKN, BSJ, CHK) located in the main citrus-producing region of Tunisia, with key physiological measurements conducted during the high-evaporation period. Salinity increased across most sites during summer 2021, affecting ion homeostasis, Na⁺/K⁺ selectivity, stomatal traits, photosynthetic performance, and growth. The highest leaf Cl⁻ concentration (0.4 meq g⁻¹ dry weight) was recorded in the sensitive HER/CC combination at the OSN site. Increased salinity at OSN was associated with a 0.86% reduction in canopy growth compared to BSJ. Rootstock tolerance was strongly linked to the ability to restrict Cl⁻ accumulation in leaf tissues. Under higher salinity conditions, CV showed superior performance and represents a suitable alternative to SO. Full article

Over two years, a randomized complete block field trial tested deficit irrigation [I: 70% ETc; NI] and ammonium nitrate [N₀, N₆₀, N₁₂₀; 0, 60, 120 kg N ha⁻¹] application in two northern Greece winegrape vineyards of cv. ‘Xinomavro’ (XM) and cv. ‘Cabernet Sauvignon’ (CS). Leaf-blade δ¹⁵N was measured at berry set, bunch closure, veraison, and technological maturity; berry-juice (must) δ¹⁵N at technological maturity and dormant cane δ¹⁵N in winter were also determined. In the first year, δ¹⁵N was additionally measured in petioles, unripe berries, trunks, and roots, along with arbuscular mycorrhizal fungal (AMF) colonization of fine roots. Fertilization increased δ¹⁵N in leaf blades and canes, whereas berry-juice δ¹⁵N responded weakly and inconsistently. Irrigation marginally lowered cane δ¹⁵N; cane δ¹⁵N varied between years, and berry-juice δ¹⁵N showed the highest variability across treatments. At berry set, intravine discrimination was evident: young berries and leaf blades were enriched, while fine roots and woody tissues were depleted. Root δ¹⁵N responses differed between cultivars and depended on AMF colonization in XM. Leaf and cane δ¹⁵N were positively related to vine N status, yield, and pruning weight but negatively to agronomic N-use efficiency indices. These findings indicate that δ¹⁵N serves as an integrative proxy of N cycling processes and fertilizer-use efficiency in vineyards, with potential implications for the assessment and optimization of sustainable vineyard management practices in the context of climate change. Full article

Remote sensing advancements have enhanced defoliation monitoring in forests, but distinguishing insect-specific damage from general canopy stress remains challenging due to overlapping spectral signatures. This study addresses this gap by analyzing multispectral reflectance changes in Eucalyptus dunnii caused by Gonipterus sp. n. 2 larval feeding and artificial defoliation (AD). A randomized complete block design with five replicates tested four treatments: No Damage, Medium (100 larvae/tree) and High (200 larvae/tree) larval inoculation, and AD (80% leaf removal). Twenty potted E. dunnii trees were monitored over 16 days using UAV-based multispectral 10-band imagery. Five multispectral flights were conducted during the experiment. The reduction in visible and near-infrared (NIR) reflectance likely reflects structural changes in canopy composition, namely an increased proportion of mature foliage. Both larval feeding and AD treatments decreased reflectance in these spectral regions, probably due to the removal of young leaves and exposure of older, darker leaves. This explanation is inferred from morphological observations; further biochemical measurements would be required to confirm the underlying mechanisms. Larval feeding and AD reduced chlorophyll-related vegetation indices (CVI, NDRE), decreased anthocyanin-related vegetation indices (mARI, ARI), and also caused a drop in relative carotene content (MTVI, CTRI/RE). The effects were strongest in the AD and peaked soon after the treatment, indicating that these pigment effects can mostly and also be attributed to the older leaves becoming more exposed. Statistically significant interactions between date and treatment were found for the pigment-sensitive indices, the Anthocyanin Reflectance Index (ARI) and the Chlorophyll Vegetation Index (CVI). They displayed opposite reflectance trends—CVI increased while ARI decreased—but followed a consistent pattern aligned with insect feeding. EVI values also exhibited a distinguishable pattern that matched this trend. Due to the inherent difficulty of studying insect feeding in natural settings, AD trials may serve as a practical proxy for assessing the impact of pest-induced damage on vegetation reflectance and physiological indices. Full article

Water availability represents a major limiting factor for crop production, particularly in Mediterranean agroecosystems. In parallel, water-stressed plants are often more susceptible to diseases, including Grapevine Trunk Diseases (GTDs), such as Botryosphaeria Dieback caused by Botryosphaeriaceae species. In Italy, the increasing prevalence of GTDs in young table grape plants and nursery material highlights the need to better understand the interaction between abiotic stress and pathogen dissemination in woody tissues. This study investigated the relationship between different water regimes (WRs) and infections by Neofusicoccum parvum. Grapevine cuttings (Vitis vinifera ‘Italia’ vines grafted onto the rootstock ‘140 Ruggeri’) were subjected to three WRs (20%, 50%, and 100% of crop evapotranspiration, ET_c) under controlled environmental conditions and, subsequently, inoculated with mycelial plugs of N. parvum at both the scion and rootstock levels. Plant responses were monitored non-destructively using low-cost proximal sensing tools, including leaf temperature (T_leaf) and the Normalized Difference Vegetation Index (NDVI). Disease development was assessed by measuring internal necrotic lesion extension. Reduced irrigation was associated with increased disease severity, while proximal sensing detected differences in plant physiological responses among water regimes. Overall, the results highlight the interplay between water availability, plant physiological status, and disease severity under controlled conditions. Full article

Endurance performance is influenced by age- and sex-specific physiological determinants, while emerging evidence indicates an increasing prevalence of Relative Energy Deficiency in Sport (REDs) among both young and master endurance runners. Despite its clinical relevance, limited data exist on how long-term endurance training modulates REDs risk, skeletal muscle characteristics, and physiological ageing in comparison with inactive individuals. Methods: This cross-sectional study protocol will examine 112 participants stratified by sex, age (20–35 vs. 65–80 years), and training status (endurance runners vs. inactive controls). Cardiorespiratory fitness (VO₂max) is defined as the primary outcome. Secondary outcomes include body composition, musculoskeletal function, biochemical and hormonal markers, and REDs-related screening variables. Assessments will comprise cardiorespiratory testing, DXA-based bone and body composition analysis, isometric knee dynamometry, mobility testing, validated REDs screening tools (LEAF-Q, LEAM-Q, and IOC REDs CAT2), seven-day dietary and training monitoring, venous blood sampling, and skeletal muscle biopsies from the vastus lateralis. Results: This study is designed to generate an integrated overview of physiological, nutritional, metabolic, and muscle-cell characteristics across sex-, age-, and training-specific subgroups. Conclusions: This protocol provides comprehensive insight into how ageing and sex influence endurance physiology and REDs susceptibility and whether long-term endurance training preserves functional capacity across the lifespan. The findings aim to support evidence-based screening, prevention, and targeted interventions for REDs in endurance athletes. Full article

Coffea canephora cultivation areas in Brazil are frequently exposed to successive cycles of water deficit, triggering plant stress responses. In addition to water deficit, increased air temperature can act as a second stress factor. The recurrence of these stress factors may induce plant tolerance mechanisms, potentially mitigating future stress responses even of a different stress nature. We hypothesized that repeated cycles of water deficit can trigger tolerance mechanisms that make C. canephora leaves more resilient to supra-optimal temperatures. To test this hypothesis, young C. canephora plants were grown under non-limited water conditions for seven months (Ψ_mSoil > −20 kPa), after which they were subjected to two consecutive cycles of water deficit (Ψ_mSoil < −300 kPa), followed by rehydration. Two clones were used, ‘A1’ and ‘3V’, previously classified as drought sensitive and tolerant, respectively, considering the dynamics of physiological and architectural responses. After the second cycle, leaf discs were collected from completely expanded leaves formed during the two stress cycles and exposed to heat treatments (35 °C, 40 °C, 45 °C, 50 °C, and 55 °C) for 15 min in a water bath. Chlorophyll a fluorescence emission was then monitored, and the results were analyzed using OJIP transient kinetics and the JIP_Test. High temperatures induced negative changes in both OJIP kinetics and JIP_Test-derived parameters. A significant increase in F₀ and a reduction in F_M were observed mainly at 50 °C and 55 °C, due to changes in the stages of the OJIP curve. These changes impacted the “energy connectivity” and consequently the electron transport along the electron transfer chain (ETC), increasing energy dissipation, as confirmed by the JIP_Test variables. Despite the high temperature impacts, previous water deficit induced heat tolerance in clone ‘A1’, while it increased sensitivity in clone ‘3V’. This study suggests that selecting drought-resistant varieties should consider their subsequent response to short high-temperature stress to avoid cross-sensitivity caused by selecting for a single environmental factor. Full article

The effects of nitrogen (N) application rates and N topdressing at different leaf growth stages on the yield, N absorption, and utilization of japonica rice cultivar Nanjing 9108 were studied to screen the optimal N management mode for high yield and high N use efficiency. A field experiment was conducted from 2023 to 2024, with nine N regulation treatments (94–351 kg ha⁻¹) established through dynamic allocation of basal, tillering, and topdressing fertilizers. The results showed that with the increase of N application rate, the yield and N use efficiency of Nanjing 9108 first increased and then decreased. At a total N application rate of 270 kg ha⁻¹, the N6 treatment (basal N + tiller N + topdressing at the 13th leaf stage) demonstrated optimal overall performance, achieving the highest yield and N use efficiency. Topdressing at the 13th leaf stage (coinciding with young panicle differentiation) promoted spikelet differentiation and large panicle formation, increasing grains per panicle by 2.36–2.20% compared to other treatments under the same N rate. The N6 treatment exhibited enhanced N uptake and utilization: N accumulation increased by 39.27–67.12% during the elongating to heading stage and by 7.14–62.24% during heading to maturity, while N apparent efficiency and agronomic efficiency rose by 3.51–14.68% and 29.22–58.25%, respectively. At heading, the proportion of high-effective leaf area in N6 was 1.52–7.05% higher than in N4, N5, and N7 treatments, accompanied by a slower leaf area decay rate. These traits provided sustained photosynthetic support for dry matter accumulation in mid-to-late growth stages. Consequently, dry matter accumulation in N6 increased by 5.85–33.44% (elongating to heading) and 0.42–26.98% (heading to maturity), leading to a yield advantage of 3.8–17.2% over other treatments. In summary, the N management strategy combining basal, tiller, and 13th-leaf topdressing at 270 kg ha⁻¹ is most effective for achieving both high yield and high N efficiency in Nanjing 9108. Full article

Spatial variability within soil profiles can substantially influence plant growth and productivity by modifying soil water and nutrient availability. In this study, we evaluated the relationship between soil physicochemical properties and productivity in a young almond orchard established on a Calcaric Solimovic Regosol under Mediterranean conditions. The soil profile comprised three horizons showing marked variability in depth and texture. Based on these differences, the experimental plot was divided into two zones: Zone A, characterized by a thicker upper horizon and a lower proportion of sand in the subsoil, and Zone B, with a thinner topsoil and higher sand content in the buried horizon. Within each zone, the almond cultivars ‘Marta’ and ‘Marinada’ were planted in a balanced design using two rootstocks: INRA GF-677 and GARNEM^®. Almond productivity was the parameter most strongly affected by soil heterogeneity, showing pronounced differences among soil zones and rootstock–cultivar combinations. Almond productivity followed the sequence Marta > Marinada/GF-677 > Marinada/GARNEM^®, and was reduced in Zone B by 37%, 68%, and 72%, respectively, compared with Zone A. In contrast, soil zones had no significant effect on leaf and kernel mineral nutrient concentrations, which varied mainly according to cultivar. Full article

This study evaluates the textile potential of five underexplored Agave varieties (Agave salmiana crassispina, A. salmiana salmiana, A. ingens marginata, A. tecta, and A. mapisaga) through combined analyses of extraction behaviour, microstructure, and single-fibre mechanical performance. Fibres extracted from basal, middle, and upper leaf sections were characterised using scanning electron microscopy (SEM) and single-fibre tensile testing under controlled conditions. All varieties produced spinnable fibres and exhibited significant longitudinal variability in mechanical behaviour along the leaf axis (p < 0.05). Mechanical performance depended strongly on both species and leaf position, with fibres from the middle leaf section generally showing higher tenacity. Variations in Young’s modulus reflected differences in fibre maturity and internal microstructural organisation. Fractographic observations revealed predominantly brittle fracture with microfibrillar rupture and longitudinal fibrillation. Overall, the results demonstrate that agave species and leaf position are key parameters governing fibre performance. These agave varieties therefore represent promising candidates for sustainable textile applications, provided that appropriate fibre selection and blending strategies are implemented to ensure homogeneous yarn properties. Full article

Cephalotaxus hainanensis, a valuable medicinal and endangered conifer, requires scientific conservation and precision management to ensure the sustainable utilization of its genetic and ecological resources. Nitrogen (N) is a key nutrient that regulates plant growth and metabolism; rapid and accurate nitrogen diagnosis is vital for optimizing fertilization, reducing nutrient losses, and promoting healthy plant development. This study employed a combined approach integrating stepwise regression, correlation analysis, and Least Absolute Shrinkage and Selection Operator (LASSO) regression to identify leaf color features strongly correlated with leaf nitrogen content (LNC). A support vector regression (SVR) model, suitable for small-sample datasets, was then employed to accurately estimate LNC across canopy layers. Nine color variables were found to be highly associated with LNC, among which the Green Minus Blue index (GMB) consistently appeared across all correlation methods, demonstrating strong robustness and generality. Color features effectively reflected LNC variations among nitrogen treatments—especially between N1 and N4—and across canopy layers, with the most pronounced contrasts observed between upper and lower leaves. The Spearman-based SVR model revealed that the middle canopy maintained the highest and most stable LNC. However, the lower leaves were most sensitive to nitrogen deficiency, while the upper leaves were more sensitive to nitrogen excess. Comprehensive analysis identified N2 as the optimal nitrogen treatment, representing a balanced nutrient state. Overall, this study confirms the reliability of color features for LNC estimation and highlights the importance of vertical canopy LNC distribution in nitrogen diagnostics, providing a theoretical and methodological foundation for color-based nitrogen diagnosis and precision nutrient management in evergreen conifers. Full article