Search Results (29)

Climbing vines have recently induced increasing threats to forest growth under favourable environmental changes. In mangrove forests, the native vine Derris trifoliata became invasive and is now one of the main threats. Yet current management relies on manual removal with low efficiency. Exploring an alternative, cost-effective method is required. To assess the potential of a proposed biological control method, this study performed a pot-plant experiment using Cuscuta japonica to infect D. trifoliata and three common mangrove species in Beihai, China. Results showed that D. trifoliata had a higher infection rate and high host mortality (90%) than mangrove (0%). It also had significantly decreased moisture by 4%, nitrogen by 14%, phosphorus by 27%, potassium by 49% and increased soluble sugar by 49% and protein by 20%, whereas only moisture (2% reduction) and one or two minerals of Excoecaria agallocha and Aegiceras corniculatum were influenced. Only Kandelia obovata had neither effective haustoria nor any nutrients impact from the infection. This study indicated that C. japonica can cause more damage to D. trifoliata than to mangrove species and has the potential to be used as a biological control agent for the threatened mangrove forests of A. corniculatum and K. obovata with monitoring and control. Further field tests are required to bring this method into practice. Full article

Although significant progress has been made in the remote sensing extraction of mangroves, research at the species level remains relatively limited. Kandelia obovata is a dominant mangrove species and is frequently used in ecological restoration projects in China. However, owing to the fragmented distribution of K. obovata within mixed mangrove communities and the significant spectral and textural similarities among mangrove species, accurately extracting large-scale K. obovata-based remote sensing data remains a challenging task. In this study, we conducted extensive field surveys and developed a comprehensive sampling database covering K. obovata and other mangrove species across mangrove-distributing areas in China. We identified the optimal bands for extracting K. obovata by utilizing time-series remote sensing data from Sentinel-1 and Sentinel-2, along with the Google Earth Engine (GEE), and proposed a method for extracting K. obovata communities. The main conclusions are as follows: (1) The spectral-temporal variability characteristics of the blue and red-edge bands play a crucial role in the identification of K. obovata communities. The 90th percentile metric of the blue wavelength band ranks first in importance, while the 75th percentile metric of the blue wavelength band ranks second; (2) This method of remote sensing extraction using spectral-temporal variability metrics with time-series optical and radar remote sensing data offers significant advantages in identifying the K. obovata species, achieving a producer’s accuracy of up to 94.6%; (3) In 2018, the total area of pure K. obovata communities in China was 4825.97 ha; (4) In the southern provinces of China, Guangdong Province has the largest K. obovata community area, while Macau has the smallest. This research contributes to the understanding of mangrove ecosystems and provides a methodological framework for monitoring K. obovata and other coastal vegetation using advanced remote sensing technologies. Full article

Endogenous melatonin (MEL) and abscisic acid (ABA) are involved in the adaptation of plants to environmental stresses. The application of exogenous serotonin (SER) to plants can enhance their tolerance to abiotic stress, such as cold. However, the mechanism associated with serotonin-mediated defense against cold-induced damage in mangroves is still poorly understood. In this study, we demonstrated that mangrove (Kandelia obovata) seedlings sprayed with 200 μmol·L⁻¹ serotonin exhibited enhanced cold tolerance, as shown by reduced damage to leaves and loss of photosynthesis when exposed to low-temperature conditions. The mechanism associated with the cold adaptation of K. obovata seedlings upon treatment with serotonin was subsequently investigated by transcriptomic analysis. Serotonin treatment caused changes in differentially expressed genes (DEGs) involved in the regulation of melatonin (MEL) and ABA biosynthesis and defense responses against cold stress. Under low-temperature stress, serotonin-treated seedlings showed a significant increase in the endogenous levels of melatonin and ABA. By contrast, under normal growth conditions, K. obovata seedlings treated with serotonin displayed no substantial change in melatonin level, whereas ABA level significantly increased. These findings demonstrated that serotonin treatment might play an important role in the enhanced resistance to cold in K. obovata and that such an effect would depend on the activation of endogenous melatonin and ABA synthesis. Full article

Wildfires significantly influence the environmental distribution of various elements through their fire-induced input and mobilization, yet little is known about their effects on the forest floor in Siberian forests. The present study evaluated the effects of spring wildfires of various severities on the levels of major and minor (Ca, Al, Fe, S, Mg, K, Na, Mn, P, Ti, Ba, and Sr) trace and ultra-trace (B, Co, Cr, Cu, Ni, Se, V, Zn, Pb, As, La, Sn, Sc, Sb, Be, Bi, Hg, Li, Mo, and Cd) elements in the forest floors of Siberian forests. The forest floor (Oi layer) samples were collected immediately following wildfires in Scots pine (Pinus sylvestris L.), larch (Larix sibirica Ledeb.), spruce (Picea obovata Ledeb.), and birch (Betula pendula Roth) forests. Total concentrations of elements were determined using inductively coupled plasma–optical emission spectroscopy. All fires resulted in a decrease in organic matter content and an increase in mineral material content and pH values in the forest floor. The concentrations of most elements studied in a burned layer of forest floor were statistically significantly higher than in unburned precursors. Sb and Sn showed no statistically significant changes. The forest floor in the birch forest showed a higher increase in mineral material content after the fire and higher levels of most elements studied than the burned coniferous forest floors. Ca was a predominant element in both unburned and burned samples in all forests studied. Our study highlighted the role of wildfires in Siberia in enhancing the levels of geochemical elements in forest floor and the effect of forest type and fire severity on ash characteristics. The increased concentrations of elements represent a potential source of surface water contamination with toxic and eutrophying elements if wildfire ash is transported with overland flow. Full article

2,2′,4,4′-tetra-bromodiphenytol ether (BDE-47) is one of the ubiquitous organic pollutants in mangrove sediments. To reveal the toxic effects of BDE-47 on mangrove plants, the mangrove species Kandelia obovate was used to investigate the photosynthetic capacity effects and the molecular mechanisms involved after BDE-47 exposure at environment-related levels (50, 500, and 5000 ng g⁻¹ dw). After a 60-day exposure, the photosynthetic capacity was inhibited in K. obovata seedlings, and a decrease in the stomatal density and damage in the chloroplast ultrastructure in the leaves were found. Transcriptome sequencing showed that, following exposure to BDE-47, gene expression in photosynthesis-related pathways was predominantly suppressed in the leaves. The bioinformatics analysis indicated that BDE-47 exerts toxicity by inhibiting photosystem I activity and chlorophyll a/b-binding protein-related genes in the leaves of K. obovata. Thus, this study provides preliminary theoretical evidence for the toxic mechanism effect of BDE-47 on photosynthesis in mangrove species. Full article

The decomposition of mangrove litter plays a crucial role in material circulation and energy flow within mangrove forests. Evaluating the decomposition-based variation in biogenic elements in litter is important for improving our understanding about their biogeochemical cycling in ecosystems. The main objective of this study was to examine the interaction effect during the decomposition process of mixed Kandelia obovata and Avicennia marina litter. Variations in C and N were also determined in the decomposing leaf litter mixtures. Our findings revealed that the decomposition rates were faster in summer than in winter, and increased with the proportion of A. marina litter. After 35 days of decomposition in summer, the remaining weights for different proportions of K. obovata (KO) and A. marina (AM) were 22.9% (KO:AM = 1:2), 27.2% (KO:AM = 1:1), and 31.2% (KO:AM = 2:1), respectively. Similarly, after 49 days of decomposition in winter, the remaining weights for the different KO:AM proportions were 27.7%, 35.4%, and 44.0%, respectively. Additionally, the decomposition of mixed K. obovata and A. marina litter had an influence on C content and N release dynamics. These results provide a scientific basis for understanding the decomposition of mixed mangrove litter and its implications for material circulation and energy flow within these ecosystems. Full article

Mangrove plant seedling cultivation is crucial for the protection, management, and restoration of the mangrove ecosystem. In this study, we focused on Kandelia obovata Sheue & al., a typical mangrove, and evaluated nursery cultivation with different combinations of three salinity levels (S1: 0 ppt, S2: 10 ppt, and S3: 20 ppt), three genealogies (EZD, JX, and YZ), and five growth media (M1: 100% loess, M2: 100% sandy, M3: 50% loess + 50% sandy, M4: 40% loess + 40% sandy + 20% peat, and M5: 40% loess + 40% sandy + 20% coir), by measuring the growth parameters such as mortality rate, seedling height, seedling diameter, and biomass partition. These growth indexes were significantly affected by salinity and medium, and genealogies also had significant effects on mortality rate and biomass accumulation. S2 or S3 both had lower mortality and higher growth indexes than S1. M1 was the medium that increased seedling height, diameter, and biomass the most and had the lowest death rate. EZD and JX were also at higher levels than YZ in these indicators, but the difference between them was not obvious. S3, M1, and EZD consistently performed well in fuzzy evaluation and quality assessment (Dickson quality index: 1.179, 1.478, and 1.089, respectively). Furthermore, combinations involving these treatments also produced highly favorable results. This indicates that the quality of seedlings produced under these conditions was high. These results furnish both a theoretical and practical foundation for advancing nursery cultivation techniques and germplasm breeding of K. obovata in mangroves. Full article

For decades in China, carbon neutrality policies have spurred the establishment of northern margin mangroves as artificial blue carbon ecosystems. However, there has been limited research on the impact of plantation and invasion on the stocks and sources of soil carbon and nitrogen in rehabilitated coastal wetlands. Non-native Kandelia obovata afforestation began on Ximen Island, Zhejiang, China, where Spartina alterniflora invasion had also occurred decades ago. Soil cores were collected from both mangrove and salt marsh habitats with depths from 0 to 50 cm and were analyzed for total carbon (TC), soil organic carbon (SOC), total nitrogen (TN), and the isotope of carbon and nitrogen in sediments. The results indicated that there were no significant differences in the TC, SOC, and C/N ratio between the K. obovata and the S. alterniflora, but there were significant differences in TN, isotope δ¹³C, and δ¹⁵N. The SOC content of both ecosystems in the 0–20 cm layer was significantly higher than that in the 30–50 cm layer. Our study has shown that the main sources of carbon and nitrogen for mangroves and salt marshes are different, especially under the impact of external factors, such as tidal waves and aquaculture. These findings provide insight into the ecological functioning of subtropical coastal wetlands and an understanding of the biogeochemical cycles of northern margin mangrove ecosystems. Full article

Kandelia obovata (Rhizophoraceae) is the most cold-tolerant mangrove species and has been widely used in coastal wetland ecological restoration due to its specific viviparous phenomenon, beautiful shape, and unique floral pattern. Due to long-term adaptation to their local environment, the phenotypic characteristics and stress resistance of widely distributed plants of the same species often differentiate across different locations. The capacity for cold resistance is closely linked to the physiological and structural characteristics of plants. Herein, we explored the temporal variations in the leaf structure and physiological status of K. obovata under −5.5 °C from different areas such as Jiulongjiang Estuary (JLJ, 24°25′ N), Fujian Province, and Longgang City (LG, 27°34′ N) and Jiaojiang District (JJ, 28°67′ N), Zhejiang Province. The morphological variations implied that the cold resistance of K. obovata obviously strengthened after the northward migration and acclimatization, in the following order: LG > JJ > JLJ. More specifically, after exposure to a sustained low temperature, the relative conductivity (REC), an index widely used to evaluate the degree of plant damage, remarkably increased from 33.62 ± 2.39 to 63.73 ± 3.81, 31.20 ± 1.63 to 49.48 ± 1.12, and 23.75 ± 0.13 to 54.24 ± 1.45 for JLJ, LG, and JJ, respectively (p < 0.05). Additionally, the palisade-to-spongy tissue ratio (P/I) of JLJ and JJ decreased from 0.78 ± 0.05 and 0.75 ± 0.03 to 0.5 ± 0.04 and 0.64 ± 0.02 (p < 0.05), whereas no significant changes were found in LG (p > 0.05). The SOD activity of LG significantly kept increasing, with values increased from 352.49 ± 10.38 to 477.65 ± 1.78 U·g⁻¹, whereas no apparent changes in JLJ and JJ were observed with the sustained low temperature. The results of this study improved our understanding of the response of K. obovata to freezing stress, which could provide a sound theoretical foundation for cultivating cold-resistant varieties, as well as expanding mangrove plantations in higher latitudes. Full article

One of the most productive ecosystems in the world, mangroves are susceptible to cold stress. However, there is currently insufficient knowledge of the adaptation mechanisms of mangrove plants in response to chilling stress. This study conducted a comparative analysis of transcriptomics and metabolomics to investigate the adaptive responses of Kandelia obovata (chilling-tolerant) and Avicennia marina (chilling-sensitive) to 5 °C. The transcriptomics results revealed that differentially expressed genes (DEGs) were mostly enriched in signal transduction, photosynthesis-related pathways, and phenylpropanoid biosynthesis. The expression pattern of genes involved in photosynthesis-related pathways in A. marina presented a downregulation of most DEGs, which correlated with the decrease in total chlorophyll content. In the susceptible A. marina, all DEGs encoding mitogen-activated protein kinase were upregulated. Phenylpropanoid-related genes were observed to be highly induced in K. obovata. Additionally, several metabolites, such as 4-aminobutyric acid, exhibited higher levels in K. obovata than in A. marina, suggesting that chilling-tolerant varieties regulated more metabolites in response to chilling. The investigation defined the inherent distinctions between K. obovata and A. marina in terms of signal transduction gene expression, as well as phenylpropanoid and flavonoid biosynthesis, during exposure to low temperatures. Full article

Plant basic helix-loop-helix (bHLH) transcription factors play pivotal roles in responding to stress, including cold and drought. However, it remains unclear how bHLH family genes respond to these stresses in Kandelia obovata. In this study, we identified 75 bHLH members in K. obovata, classified into 11 subfamilies and unevenly distributed across its 18 chromosomes. Collineation analysis revealed that segmental duplication primarily drove the expansion of KobHLH genes. The KobHLH promoters were enriched with elements associated with light response. Through RNA-seq, we identified several cold/drought-associated KobHLH genes. This correlated with decreased net photosynthetic rates (P_n) in the leaves of cold/drought-treated plants. Weighted gene co-expression network analysis (WGCNA) confirmed that 11 KobHLH genes were closely linked to photoinhibition in photosystem II (PS II). Among them, four Phytochrome Interacting Factors (PIFs) involved in chlorophyll metabolism were significantly down-regulated. Subcellular localization showed that KobHLH52 and KobHLH30 were located in the nucleus. Overall, we have comprehensively analyzed the KobHLH family and identified several members associated with photoinhibition under cold or drought stress, which may be helpfulfor further cold/drought-tolerance enhancement and molecular breeding through genetic engineering in K. obovata. Full article

Aquaporins (AQPs) are essential channel proteins that play central roles in maintaining water homeostasis. Here, a novel aquaporin gene, named KoPIP2;1, was cloned from the mangrove plant Kandelia obovata by RACE technology. The KoPIP2;1 gene was 1404 bp in length with an open reading frame (ORF) of 852 bp, encoded with 283 amino acids. Database comparisons revealed that KoPIP2;1 protein shared the highest identity (91.26%) with the aquaporin HbPIP2;2, which was isolated from Hevea brasiliensis. Gene expression analysis revealed that the KoPIP2;1 gene was induced higher in leaves than in stems and roots of K. obovata under cold stress. Transient expression of KoPIP2;1 in Nicotiana benthamiana epidermal cells revealed that the KoPIP2;1 protein was localized to the plasma membrane. Overexpressing KoPIP2;1 in Arabidopsis significantly enhanced the lateral root number of the transgenic lines. KoPIP2;1 transgenic Arabidopsis demonstrated better growth, elevated proline content, increased superoxide dismutase (SOD) and peroxidase (POD) activities, and reduced malondialdehyde (MDA) content compared with the wild-type Arabidopsis when exposed to cold stress. The findings suggest that overexpression of KoPIP2;1 probably conferred cold tolerance of transgenic Arabidopsis by enhancing osmoregulation and antioxidant capacity. This present data presents a valuable gene resource that contributes to the advancement of our understanding of aquaporins and their potential application in enhancing plant stress tolerance. Full article

Host defense peptides (HDPs) are components of plant defensive barriers that resist microbial infection. Members of the Snakin/GASA protein family in plants have functions of regulating plant growth, defense, and bacteriostasis. Most mangrove plants grow in coastal zones. In order to survive in harsh environments, mangrove plants have evolved complex adaptations against microbes. In this study, Snakin/GASA family members were identified and analyzed in the genomes of three mangrove species. Twenty-seven, thirteen, and nine candidate Snakin/GASA family members were found in Avicennia marina, Kandelia obovata, and Aegiceras corniculatum, respectively. These Snakin/GASA family members were identified and categorized into three subfamilies via phylogenetic analysis. The genes coding for the Snakin/GASA family members were unevenly distributed on chromosomes. Collinearity and conservative motif analyses showed that the Snakin/GASA family members in K. obovata and A. corniculatum underwent multiple gene duplication events. Snakin/GASA family member expression in normal leaves and leaves infected with pathogenic microorganisms of the three mangrove species was verified using real-time quantitative polymerase chain reaction. The expression of KoGASA3 and 4, AcGASA5 and 10, and AmGASA1, 4, 5, 15, 18, and 23 increased after microbial infection. This study provides a research basis for the verification of HDPs from mangrove plants and suggests directions for the development and utilization of marine biological antimicrobial peptides. Full article

Kandelia obovata (S., L.) Yong and Sonneratia caseolaris (L.) Engl. are two dominant mangrove species in the subtropical coastlines of the Pearl River Estuary, China. The main aim of this study was to investigate the specific causes of K. obovata mortality versus S. caseolaris vitality on the west coast of Bao’an, Shenzhen, China and to propose sustainable management strategies for mangrove protection and future ecological planting restoration. Results showed that although both mangroves possessed simple and unstable community structures, S. caseolaris had a more tenacious vitality than the native species K. obovata, indicating that the former possesses stronger adaptability under adversity conditions. Moreover, the salinity of the seawater collection point 5 from the K. obovata plot was found to be lower than that of seawater collection point 1–3 from the S. caseolaris sample plots, indicating that no hydrologic connectivity existed in the K. obovata plots. In addition, the location of the drain outlet (seawater collection point 8) might be another potential risk factor for the dead of near K. obovata forests, implying that they were badly affected by poor oxygen and serious inorganic pollution, such as ammonium nitrogen, total phosphorus, and other inorganic substances. Depending on local circumstances, we should consider strengthening infrastructure construction to activate hydrological connectivity, reinforcing the stability of man-made mangrove communities, and controlling the pollution sources for sustainable mangrove protection and management on the western coast of Bao’an, Shenzhen, China. Full article

We report on the kinetics of pyrolysis of bark wood of four coniferous tree species: fir (Abies sibirica), larch (Larix sibirica), spruce (Picea obovata), and cedar (Pinus sibirica) denoted as FB, LB, SB, and CB, respectively. Thermogravimetry (TG) and differential scanning calorimetry (DSC) methods were used to study the influence of KCl and K₃PO₄ compounds on the process of thermal decomposition of fir bark and determine the main thermal effects accompanying this process. As a result of the studies carried out, it was found that KCl additives practically do not affect the decomposition of hemicelluloses, but they shift the maximum decomposition of the cellulose peak in the direction of decreasing temperature to 340.9 °C compared to untreated bark (357.5 °C). K₃PO₄ promotes the simultaneous decomposition of hemicelluloses and cellulose in the temperature range with a maximum of 277.8 °C. In both cases, the additions of KCl and K₃PO₄ reduce the maximum rate of weight loss, which leads to a higher yield of carbon residues: the yield of char from the original fir bark is 28.2%, in the presence of K₃PO₄ and KCl it is 52.6 and 65.0%, respectively. Using the thermogravimetric analysis in the inert atmosphere, the reaction mechanism has been established within the Criado model. It is shown that the LB, SB, and CB thermal decomposition can be described by a two-dimensional diffusion reaction (D2) in a wide range (up to 0.5) of conversion values followed by the reactions with orders of three (R3). The thermal decomposition of the FB occurs somewhat differently. The diffusion mechanism (D2) of the FB thermal decomposition continues until a conversion value of 0.6. As the temperature increases, the degradation of the FB sample tends to R3. It has been found by the thermogravimetric analysis that the higher cellulose content prevents the degradation of wood. The bark wood pyrolysis activation energy has been calculated within the Coats–Redfern and Arrhenius models. The activation energies obtained within these models agree well and can be used to understand the complexity of biomass decomposition. Full article