Search Results (146)

Leaf phenology of trees responds to temperature and photoperiod cues, mediated by underlying genes and plasticity. However, uncertainties remain regarding how smaller-scale phenological variation in cold-limited regions has been affected by modified selection pressures from herbivores, pathogens, and climate conditions, and whether this leaves genetic signatures allowing for projections of future responses. We investigated environmental correlates and genetic variation putatively associated with spring and autumn leaf phenology in northern range margin oak (Quercus robur L.) populations in Sweden (55.6° N–60.8° N). Results suggested that budburst occurred later at higher latitudes and in locations with colder spring (April) temperatures, whereas leaf senescence occurred earlier at higher latitudes. Several candidate loci associated with phenology were identified (n = 40 for budburst and 47 for leaf senescence), and significant associations between these loci and latitude were detected. Functions associated with some of the candidate loci, as identified in previous studies, included host defence and heat stress tolerance. The proportion of polymorphic candidate loci associated with budburst decreased with increasing latitude, towards the range margin. Overall, the Swedish oak population seems to comprise genetic diversity in phenology-related traits that may provide resilience to a rapidly changing climate. Full article

Inselbergs are rocky outcrops with specialized vegetation, including woody species growing in poorly developed soils. We investigated whether populations of the lithophytic tree Pseudobombax petropolitanum A. Robyns (Malvaceae), a key species endemic to Atlantic Forest inselbergs, have convergent or divergent patterns of functional traits related to leaf chemistry. This study was carried out on three inselbergs located in southeastern Brazil. Green and senescent leaves from nine healthy trees and soil samples were collected in each inselberg. The carbon, nitrogen, phosphorus, potassium, calcium, and magnesium concentrations, and the natural abundances of δ¹³C and δ¹⁵N, were measured in leaves and soil, and the C/N, C/P, and N/P ratios were calculated. The specific leaf area (SLA) was measured, and the nutrient retranslocation rate between green and senescent leaves was estimated. Divergences between populations were observed in the concentrations of potassium and magnesium in the green and senescent leaves, as well as in the C/P and N/P ratios in senescent leaves. Our results suggest that nutrient and water dynamics may differ in some inselbergs due to specific nutrients or their relationships, even though there were convergences in most functional traits related to leaf chemistry among the Pseudobombax populations. The divergences among the populations could have important implications for species selection in the ecological restoration context. Full article

Northwestern Ontario has a shorter growing season but fertile soil, affordable land, opportunities for agricultural diversification, and a demand for canola production. Canola yield mainly varies with spatial heterogeneity of soil properties, crop parameters, and meteorological conditions; thus, existing yield estimation models must be revised before being adopted in Northwestern Ontario to ensure accuracy. Region-specific canola cultivation guidelines are essential. This study utilized high spatial-resolution images to estimate flower coverage and yield in experimental plots at the Lakehead University Agricultural Research Station, Thunder Bay, Canada. Spectral profiles were created for canola flowers and pods. During the peak flowering period, the reflectance of green and red bands was almost identical, allowing for the successful classification of yellow flower coverage using a recursive partitioning and regression tree algorithm. A notable decrease in reflectance in the RedEdge and NIR bands was observed during the transition from pod maturation to senescence, reflecting physiological changes. Canola yield was estimated using selected vegetation indices derived from images, the percent cover of flowers, and the M5P Model Tree algorithm. Field samples were used to calibrate and validate prediction models. The model’s prediction accuracy was high, with a correlation coefficient (r) of 0.78 and a mean squared error of 7.2 kg/ha compared to field samples. In conclusion, this study provided an important insight into canola growth using remote sensing. In the future, when modelling, it is recommended to consider other variables (soil nutrients and climate) that might affect crop development. Full article

Aging affects all tissues in an organism, including the tracheobronchial tree, with structural and functional changes driven by mechanisms such as oxidative stress, cellular senescence, epigenetic modifications, mitochondrial dysfunction, and telomere shortening. Airway aging can be accelerated by intrinsic or extrinsic factors. This review brings together information from the literature on the molecular changes occurring in all layers of the tracheobronchial airway wall. It examines the biomolecular changes associated with aging in the mucosa, submucosa, cartilage, and smooth muscle of the airways. At the mucosal level, aging reduces ciliary function and disrupts mucin homeostasis, impairing mucociliary clearance and contributing to chronic respiratory diseases such as COPD (Chronic Obstructive Pulmonary Disease). Cellular senescence and oxidative stress drive extracellular matrix remodeling and chronic inflammation. Airway cartilage undergoes age-related changes in collagen and fibronectin composition, leading to increased stiffness, while heightened MMP (Matrix Metalloproteinases) activity exacerbates ECM (extracellular matrix) degradation. In airway smooth muscle, aging induces changes in calcium signaling, hypertrophy, and the secretion of pro-inflammatory mediators, further perpetuating airway remodeling. These changes impair respiratory function and increase susceptibility to chronic respiratory conditions in the elderly. By consolidating current knowledge, this review aims to provide a comprehensive overview of the molecular changes occurring in the respiratory tract with aging and to highlight new molecular perspectives for future research on this topic. Full article

Madhuca longifolia (M. longifolia), a tropical tree valued for its medicinal, nutritional, and industrial applications, exhibits severe sensitivity to low-temperature stress in subtropical regions, particularly during seedling establishment. To address this challenge, this study systematically identified 109 NAC genes in M. longifolia and characterized their functional roles in cold adaptation via multi-omics analyses. All NAC proteins were hydrophilic. Key members (e.g., MlNAC026, MlNAC077, MlNAC076) were localized in the nucleus. Phylogenetic analysis grouped them with ANAC072 (RD26), a homolog involved in leaf senescence and ABA-regulated cold stress responses. The NAC family expanded primarily through segmental duplication. And low Ka/Ks ratios (<1) indicated purifying selection. Promoter analysis highlighted the prevalence of dehydration-responsive DRE and LTR cis-acting elements. Transcriptomic profiling under cold stress identified five continuous differentially expressed genes (MlNAC026, MlNAC040, MlNAC059, MlNAC077, and MlNAC078) linked to regulatory functions. Homology modeling predicted 3D structures of cold-responsive NAC proteins, and STRING network analysis indicated independent regulatory mechanisms due to the absence of prominent interaction nodes. These findings advance our understanding of NAC-mediated cold tolerance and offer genetic targets to enhance M. longifolia resilience in subtropical climates. Full article

Within a dam reservoir landscape in the Western Black Sea Region of Türkiye, a dense young-mature stand composed diversely of oriental beeches, European hornbeams, sessile oaks, and silver lindens was chosen as a study field to analyze canopy parameters and to determine phenological patterns along the altitudinal gradients. Referring to the air-soil temperature and precipitation data, intra-annual eco-physiological characteristics of that stand tree canopies, were aimed to be determined regarding those altitudinal gradients. For each of the 10 altitudinal gradients, the mixed deciduous stand canopy physiological characteristics were analyzed by hemispherical photographing. Canopy parameters were acquired from those digital hemispherical photographs, which were confirmed with secondary LAI data from the LAI-2200C. Leaf Area Index, Light Transmission, Canopy Openness, and Gap Fraction were obtained during a total of 21 study field visits throughout the monitoring year. Beginning from a theoretical leafless stage with 0.51 m² m⁻², average LAI increased to 0.89 m² m⁻² during budburst stage, and then gradually up to 3.60 m² m⁻² during climax leaf period, and then to 1.38 m² m⁻² during senescence period, and gradually down to 0.50 m² m⁻² during the next theoretical leafless stage. However, average LT (64%, 61%, 9%, 36%, 74%), CO (65%, 62%, 9%, 37%, 75%), and GF (18%, 14%, 1%, 8%, 14%) followed opposite patterns. Though no apparent trend was valid for those canopy parameters from the lowest to the highest altitudinal gradient, their obvious intra-annual patterns emerged as compatible with the annual air-soil temperature data course. Full article

Osmanthus fragrans is a highly valued ornamental tree species in China, but its short flowering period limits its ornamental appeal. Investigating the mechanisms of flower senescence in O. fragrans is therefore of significant importance. Ethylene, a key endogenous hormone, plays a central role in flower senescence, and the AP2/ERF gene family, which includes ethylene response factors, is known to regulate this process in various plants. Transcriptome sequencing and expression analysis identified OfERF17 as a critical gene influencing petal senescence in O. fragrans. Bioinformatics analysis revealed that OfERF17 lacks transmembrane transport structures but contains multiple phosphorylation sites and shares a close phylogenetic relationship with the Olea europaea var. Sylvestris. Subcellular targeting and yeast-based auto-activation tests revealed that OfERF17 resides in the nucleus and possesses a transcriptional self-activation capability. Transient expression studies conducted in O. fragrans petals indicated a decrease in the expressions of two genes associated with senescence, namely, OfSAG21 and OfACO3, when compared to the control group. Additionally, the levels of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) were markedly reduced. Transgenic Nicotiana tabacum blooms one day more than the wild type, and NtSAG12 and NtACO1 expressions were lower than wild type. These results suggest that OfERF17 functions to delay petal senescence in O. fragrans. This study enhances our knowledge of the molecular mechanisms underlying O. fragrans petal senescence and provides insights into strategies for prolonging its flowering period. Full article

‘Green island’ symptoms in the form of vivid green, round spots visible on the senescent leaves of many plants and trees are mostly the results of pathogenic colonization by fungi, and the greenish tissue is often dead. Therefore, this study investigates whether green spots observed on senescent Norway maple (Acer platanoides L.) leaves were still alive and photosynthetically active. The appearance of ‘green islands’ on the leaves of young Norway maple trees was observed from the autumn of 2019 to 2022 in an urban forest (Bialystok, eastern Poland). However, in the late summer (September) of 2023 and 2024, mostly tar spots caused by the fungus Rhytisma spp. on maple leaves could be observed, with only a few leaves having ‘green island’ symptoms. The percentage of ‘green island’ areas on senescent leaves observed during the 4 years (2019–2022) was influenced by a year of sampling (p < 0.001). A non-destructive physiological analysis of chlorophyll, flavonoids, and nitrogen balance index (NBI) in leaves revealed that these parameters were significantly lower in ‘green islands’ than in the summer leaves, but higher than in the senescent yellow area of the autumn leaves. In the case of anthocyanins, their level was significantly higher in ‘green islands’ than in yellow areas, although, in the summer leaves, anthocyanins were undetectable. The amount of chlorophyll and most photosynthetic parameters were significantly (p < 0.05) reduced in the ‘green islands’ of the senescent leaves compared to the mature green leaves. However, these parameters were significantly higher in the ‘green islands’ than in senescent yellow leaves. Carotenoid content in the ‘green island’ and yellow areas of senescent leaves were at the same level, twice as higher than in summer leaves. Green mature leaves and the ‘green islands’ on senescent leaves had the same structure and anatomy. The main differences concerned the chloroplasts, which were smaller and had less grana and starch grains, but had more plastoglobuli in ‘green island’ cells. The cells building the mesophyll in the yellow area of the leaf deteriorated and their chloroplasts collapsed. Epiphytes were present on the adaxial epidermis surface in all types of samples. Full article

Calcium (Ca) and Boron (B) are structural components of the cell wall with limited phloem mobility. The absorption, movement, and distribution of these two nutrients have a greater effect on leaves than on fruits since their transport is dependent on transpiration flow. This research aimed to study the absorption and movement of ⁴⁵Ca applied to the soil and the fruit of sweet cherry trees under B-deficient and B-adequate soil conditions. In the first experiment, ⁴⁵Ca was applied to the soil surface before the occurrence of leaf senescence. Soil and tree components were sampled and analyzed 6 months after ⁴⁵Ca application. The second experiment involved a ⁴⁵Ca application to the surface of small fruits with 5 mm diameters, which were analyzed after 45 days. The tree Ca allocation in the B-deficient soil condition was significantly fewer in shoots and higher in roots, contrary to the B-adequate soil. On the other hand, the fruit evidenced significant differences in Ca levels in the edible portion of the fruit (i.e., the flesh and peel), which was higher in the B-adequate soil condition. Therefore, under B-deficient soil, Ca was ‘retained’ in the root system and in the fruit pit, suggesting a synergistic mechanism between Ca and B. This mechanism might indicate a survival ecological function where B triggers biological signals to restore Ca homeostasis. Full article

This study examines the effects of drought timing on height growth and seasonal leaf phenology in pedunculate oak (Quercus robur L.) seedlings. Drought represents a significant threat to long-lived tree species, impacting growth, phenology, and recovery potential. This research aims to assess whether the timing of drought stress influences height growth and leaf phenology while also investigating possible compensatory mechanisms. The experiment involved five groups of seedlings: four exposed to drought at different periods during the 2022 and 2023 growing seasons, and one regularly irrigated control group. The key monitored parameters included height growth, spring flushing, autumn leaf senescence, and photosynthesis. Preliminary results revealed that late-spring and summer drought had a significant negative impact on height growth and delayed autumn senescence, whereas mid-spring drought allowed for compensatory growth. Spring leaf phenology remained largely unaffected by drought treatments. None of the drought-stressed plants showed increased photosynthesis during the recovery phase compared to the control. These findings highlight the critical role of drought timing in determining growth and phenological outcomes. Relatively late-season droughts were particularly detrimental, limiting recovery and resource allocation, while early-season droughts provided better opportunities for compensation. Further research on drought recovery mechanisms and nutrient interactions is needed to refine forestry management strategies under climate change. Full article

Tree peony (Paeonia suffruticosa Andr.), which is a traditional flower cultivated in China, is rapidly becoming an important species in the cut flower industry. Thus, extending the vase life of tree peony cut flowers is a major goal in the cut flower industry. Melatonin, which is a new type of antioxidant, plays an important regulatory role in the preservation of cut flowers. Therefore, this study employed the cut flower of tree peony “Diguan” as the test material to investigate the preservative effects of the antioxidant melatonin on the cut flower of tree peony “Diguan”. We examined tree peony cut flowers in terms of their morphology, lifespan, relative fresh weight, relative diameter, and water balance value after treatments with different melatonin concentrations (0.2, 0.3, 0.4, and 0.5 mg·L⁻¹) to select the optimal treatment concentration. Considered together, these analyses clarified the effects of melatonin on the preservation of “Diguan” tree peony cut flowers. Specifically, the exogenous application of melatonin positively affected the preservation of tree peony cut flowers by improving the water balance value and increasing the soluble protein content and antioxidant enzyme activities, thereby prolonging the ornamental period of tree peony cut flowers. The fresh weight of flower branches is significantly positively correlated with soluble protein, and cut flower lifespan increases with the values of soluble protein and the fresh weight of flower branches, with a large correlation coefficient. It can be used as an important indicator to measure cut flower lifespan in subsequent research. The 0.4 mg L⁻¹ melatonin treatment was optimal for preserving tree peony cut flowers because of its positive effects on the duration of the ornamental period and ornamental quality. Full article

Ficus trees (Moraceae) play a vital role in sustaining the stability of tropical and subtropical rainforests. The obligate mutualism between Ficus species and their pollinating fig wasps renders them an exemplary model for investigating insect–plant coevolution. In this study, we employed Ficus hispida Linn. f., an ecologically significant fig species in tropical rainforests, to conduct a wasp-introduction controlled experiment in the field. This method enabled us to precisely delineate the developmental stages of figs. We collected samples at specific intervals and examined the impact of pollinating fig wasp entry on the hormonal metabolism of male and female figs using liquid chromatography–tandem mass spectrometry analysis. The findings demonstrate that pollinator entry significantly decreases fig abscission. Moreover, it substantially altered the developmental indices of the figs. Unpollinated figs exhibit elevated levels of abscisic acid (ABA), which increases the likelihood of fig abortion and reduces the probability of pollinator entry into senescent figs. Following pollinator entry, indole-3-acetic acid (IAA) levels rise in both male and female figs. Male figs show higher concentrations of 1-aminocyclopropane-1-carboxylic acid (ACC), jasmonic acid (JA), and salicylic acid (SA), whereas these changes are less pronounced in female figs. Additionally, pollinated male figs display increased levels of cytokinins (CKs) and other hormones compared to female figs, suggesting a coordinated hormonal response to the stress induced by pollinator oviposition and gall development. Our findings suggest that the entry of pollinators likely triggers the transition from the female to the interfloral phase, with hormonal regulation playing a crucial role in the reproductive dimorphism of figs. This research can offer novel insights into the mechanisms underlying fig–wasp mutualism. Full article

Changes in vegetation activities driven by climate change serve as both a sensitive indicator and a key driver of climate impacts, underscoring the need for accurate phenological predictions. Delays in leaf senescence due to rising air temperatures increase the risk of damage from early frost, potentially affecting growth and survival in subsequent years. This study aimed to quantify long-term changes in leaf senescence timing for palmate maple and ginkgo trees, explore their associations with environmental factors, and compare the performance of multiple modeling approaches to identify their strengths and limitations for phenological predictions. Using data from 48 sites across South Korea (1989–2020), this study analyzed trends in the timing of leaf senescence for maple and ginkgo trees and compared the performance of process-based models (CDD_T, CDD_P, TP_T, TP_P), a linear regression model, and machine-learning models (random forest, RF; gradient-boosting decision tree, GBTD). Leaf senescence timing for both species has progressively been delayed, with ginkgo trees showing a faster rate of change (0.20 vs. 0.17 days per year, p < 0.05). Delayed senescence was observed in most regions (81% for maple and 75% for ginkgo), with statistically significant delays (p < 0.05) at half of the sites. Machine-learning models demonstrated the highest training accuracy (RMSE < 4.0 days, r > 0.90). Evaluation with independent datasets revealed that the RF and process-based TP_P (including minimum temperature and photoperiod) using a site-specific approach performed best (RMSE < 5.5 days, r > 0.75). Key environmental factors identified by RF included autumn minimum or mean temperatures and a summer photoperiod. By conducting this comparative assessment, the study provides insights into the applicability of different modeling approaches for phenology research and highlights their implications for vegetation management and climate change adaptation. Full article

Artificial light at night (ALAN) is an expanding environmental issue, particularly in urban areas. This review aimed to present the state of the art regarding the impact of ALAN on specific and interrelated aspects related to physiological processes and life cycle events in tree species. The reviewed studies highlighted the multifaceted effects of artificial light on plants, offering insights and perspectives to guide future research in this evolving and stimulating field. ALAN disrupts circadian rhythms, alters photoperiodic responses, and affects photosynthesis and carbohydrate metabolism. Changes in phenology such as delayed senescence and altered budburst timing demonstrated species-specific responses, often compounded by other urban stressors like heat and drought. Despite an increased interest, knowledge gaps remain concerning the species-specific responses and the effects of light spectra as well as the long-term consequences on tree physiology. These gaps highlight the need for integrated research approaches and urban planning strategies to mitigate ALAN effects, ensuring the resilience of urban trees and preserving ecosystem services in the context of growing urbanization and climate change. Full article

Increased water limitations due to climate change will pose severe challenges to forest ecosystems in Europe. We investigated the response of potted saplings of Fagus sylvatica L., one of the major European tree species, to a spring and a summer water-withholding period with control–control (C-C), control–drought (C-D), drought–control (D-C) and drought–drought (D-D) treatments. We focused on recovery capacity and phenological and growth traits and questioned the extent to which an earlier drought influenced the response to a second drought in the same growing season. To examine the impact of the level of drought stress, a distinction was made between saplings with less or more than half of their leaves desiccated due to the spring drought (D<50 and D>50). The timing of the drought influenced the immediate post-drought response: saplings severely affected by the spring drought (D>50) resprouted, whereas saplings severely affected by the summer drought (C-D and D<50-D) did not. The spring treatment influenced the onset of visual symptoms in the summer drought, with saplings less affected in the spring drought (D<50-D) developing symptoms three days later than the saplings not subjected to drought in the spring (C-D), whereas severely affected saplings (D>50-D) had not yet display symptoms seventeen days after the first visual symptoms in the spring control saplings (C-D). The timing of autumnal leaf senescence displayed the legacies of the spring treatment. The saplings heavily affected by the spring drought showed a slower decrease in relative chlorophyll content and delayed leaf senescence (D>50-C and D>50-D), which may enable the repair of damaged tissues. The saplings that were less affected by the spring drought (D<50-C) showed earlier autumnal leaf senescence, which is likely an acclimation response. Interestingly, a larger diameter increment in autumn for all of the saplings that experienced the summer drought (C-D, D<50-D and D>50-D) may indicate the recovery of hydraulic capacity by new xylem growth. Our results underline the plasticity of young F. sylvatica saplings in response to (repeated) drought. Full article