Obovata Seedlings Research Articles

2,2',4,4'-Tetrabromodiphenyl Ether (BDE-47) at Environmental Levels Influenced Photosynthesis in the Mangrove Species Kandelia obovata.

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.

Effect of soil temperature on the morphological and physiological traits of Kandelia obovata seedlings

Effect of soil temperature on the morphological and physiological traits of Kandelia obovata seedlings

Effects of 5-HT on the cold resistance of mangrove Kandelia obovata seedlings.

5-hydroxytryptamine (5-HT) participates in plant growth and development, and can also delay senescence and cope with abiotic stress. To explore the role of 5-HT in regulating the abilities of mangrove in cold resis-tance, we examined the effects of cold acclimation and the spraying of p-chlorophenylalanine (p-CPA, 5-HT synthesis inhibitor) on leaf gas exchange parameters and CO2 response curves (A/Ca), as well as the endogenous phytohormone content levels in the mangrove species Kandelia obovata seedlings under low temperature stress. The results showed that low temperature stress significantly reduced the contents of 5-HT, chlorophyll, endogenous auxin (IAA), gibberellin (GA), and abscisic acid (ABA). It weakened the CO2 utilization abilities of plants and reduced net photosynthetic rate, which ultimately reduced carboxylation efficiency (CE). Under low temperature stress, exogenous p-CPA reduced the contents of photosynthetic pigments, endogenous hormones, and 5-HT in the leaves, which aggravated the damages caused by low temperature stress on photosynthesis. By enhancing cold acclimation abilities, the endogenous IAA content in the leaves could was reduced under low temperature stress, promoted the production of 5-HT, improved the contents of photosynthetic pigments, GA, and ABA, as well as enhanced photosynthetic carbon assimilation abilities, which would increase photosynthesis in the K. obovata seedlings. Under cold acclimation conditions, the spraying of p-CPA could significantly inhibit the synthesis of 5-HT, promote the production of IAA, and reduce the contents of photosynthetic pigments, GA, ABA, and CE, which would weaken the effects of cold acclimation by improving the cold resistance of mangroves. In conclusion, cold acclimation could improve the cold resistance abilities of K. obovata seedlings by regulating photosynthetic carbon assimilation capacity and the contents of endogenous phytohormone. 5-HT synthesis is one of the necessary conditions for improving the cold resistance abilities of mangroves.

Analysis of the expression and function of the CBL-CIPK network and MAPK cascade genes in Kandelia obovata seedlings under cold stress

Mangroves are an important component of coastal wetland ecosystems, and low temperature is the main factor that limits their extension to higher latitudes. Kandelia obovata as one of the most cold-tolerant species in mangrove ecosystems can provide basis for the northward migration of mangrove ecosystems. We took K. obovata seedlings from Zhoushan (Zhoushan, Zhejiang, China) as the research object in this study. Transcriptome sequencing based on the Illumina HiSeqTM 2500 platform was performed to compare the transcriptome changes of roots, stems, and leaves before and after freezing and to reveal the molecular mechanisms of frost resistance. A total of 1560, 370, and 416 genes were differentially expressed in the roots, stems, and leaves before and after cold snaps, respectively. Among these differentially expressed genes, 13 positive and negative regulators were attributed to the CBL-CIPK signaling network and MAPK cascade, which might be related to the frost resistance mechanism of K. obovata Transcription factors such as AP2/EREBP and bHLH were involved in regulating the synthesis pathways of ethylene, cytokinin, growth hormone, and flavonoids. Results provide new insights into the frost resistance mechanism of K. obovata seedlings.

Iron plaque crystallinity, heavy metal toxicity, and metal translocation in Kandelia obovata seedlings as altered by an iron-reducing bacterium under different flooding regimes

Iron plaque crystallinity, heavy metal toxicity, and metal translocation in Kandelia obovata seedlings as altered by an iron-reducing bacterium under different flooding regimes

Physiological and transcriptomic responses to cold waves of the most cold-tolerant mangrove, Kandelia obovata.

Mangrove forests inhabit tropical or subtropical intertidal zones and have remarkable abilities in coastline protection. Kandelia obovata is considered the most cold-tolerant mangrove species and has been widely transplanted to the north subtropical zone of China for ecological restoration. However, the physiological and molecular mechanisms of K. obovata under colder climate was still unclear. Here, we manipulated the typical climate of cold waves in the north subtropical zone with cycles of cold/recovery and analyzed the physiological and transcriptomic responses of seedlings. We found that both physiological traits and gene expression profiles differed between the first and later cold waves, indicating K. obovata seedlings were acclimated by the first cold experience and prepared for latter cold waves. 1,135 cold acclimation-related genes (CARGs) were revealed, related to calcium signaling, cell wall modification, and post-translational modifications of ubiquitination pathways. We identified the roles of CBFs and CBF-independent transcription factors (ZATs and CZF1s) in regulating the expression of CARGs, suggesting both CBF-dependent and CBF- independent pathways functioned in the cold acclimation of K. obovata. Finally, we proposed a molecular mechanism of K. obovata cold acclimation with several key CARGs and transcriptional factors involved. Our experiments reveal strategies of K. obovata coping with cold environments and provide prospects for mangrove rehabilitation and management.

Multiple heavy metals affect root response, iron plaque formation, and metal bioaccumulation of Kandelia obovata

Multiple heavy metal pollution in mangrove wetlands is serious. Kandelia obovata seedlings were cultured in pots in which lead (Pb), zinc (Zn) and copper (Cu) were added separately and in combinations. The results showed that heavy metal stress improved the rate of root oxygen leakage, enhanced root activity, and reduced root porosity. The root under single heavy metal stress was impacted by the addition of other heavy metals, demonstrating antagonistic or synergistic effects. Iron plaque (IP) formation was improved under single Zn or Cu stress, and inhibited in binary stress of Pb + Cu. The adsorptions of IP on heavy metals in combined stress (Pb, 62–116 μg g−1; Zn, 194–207 μg g−1; Cu, 35–52 μg g−1) were higher than that in single stress (Pb, 18 μg g−1; Zn, 163 μg g−1; Cu, 22 μg g−1). K. obovata accumulated higher levels of heavy metals in root (Pb, 7–200 μg g−1; Cu, 4–78 μg g−1), compared with IP (Pb, 18–116 μg g−1; Cu, 22–52 μg g−1), stem (Pb, 3–7 μg g−1; Cu, 9–17 μg g−1), and leaf (Pb, 2–4 μg g−1; Cu, 4–7 μg g−1). Correlation analysis showed that single and binary stresses affected K. obovata, with more significant effect of trinary stress. Regression path analysis showed that multiple heavy metal stress firstly affected root, then indirectly contributed to IP formation, as well as heavy metal in IP and root; at last, heavy metal in IP directly contributed to heavy metal bioaccumulations in root.

Effects of cadmium and flooding on the formation of iron plaques, the rhizosphere bacterial community structure, and root exudates in Kandelia obovata seedlings

In the rhizosphere, plant root exudates (REs) serve as a bridge between plant and soil functional microorganisms, which play a key role in the redox cycle of iron (Fe). This study examined the effects of periodic flooding and cadmium (Cd) on plant REs, the rhizosphere bacterial community structure, and the formation of root Fe plaques in the typical mangrove plant Kandelia obovata, as well as the relationship between REs and Fe redox cycling bacteria. Based on two-way analysis of variance, flooding and Cd had a considerable effect on the REs of K. obovata. DOC, NH4+-N, NO3−-N, dissolved inorganic phosphorus, acetic acid, and malonic acid concentrations in REs of K. obovata increased considerably with the increase of Cd concentration under 5 and 10 h flooding conditions. Fe plaque development in the plant root was stimulated by flooding and Cd, although flooding was more effective. After Cd treatment, the ways in which Fe-oxidizing bacteria (FeOB) and Fe-reducing bacteria (FeRB) were enriched in the rhizosphere and rhizoplane of plants were different. Thiobacillus and Sideroxydans (dominant FeOB) were more abundant in the plant rhizosphere, whereas Acinetobacter (dominant FeRB) was more abundant in the rhizoplane. Cd considerably decreased the relative abundance of unclassified_f_Gallionellaceae in the rhizosphere and rhizoplane but dramatically enhanced the relative abundance of Thiobacillus, Shewanella, and unclassified_f_Geobacteraceae. Unclassified_f_Geobacteraceae and Thiobacillus exhibited substantial positive correlations with citric acid and DOC in REs in the rhizosphere and rhizoplane but strong negative correlations with Sideroxydans. The findings indicate that Cd and flooding treatments may play a role in the production and breakdown of Fe plaque in K. obovata roots by affecting the relative abundance of Fe redox cycling bacteria in the rhizosphere and rhizoplane.

Effects of decabromodiphenyl ether (BDE-209) on a mangrove plant, Kandelia obovata and the uptake, translocation and accumulation of BDE-209

Due to close proximity to urban development, mangroves exposed to the contamination of polybrominated diphenyl ethers (PBDEs). Decabromodiphenyl ether (BDE-209) is one of the most predominant PBDE congener. The present study aimed to investigate the toxic effects of BDE-209 on the antioxidative and non-antioxidative responses of Kandelia obovata, a very common mangrove species, under different concentrations of BDE-209, 0.1, 1, 5 and 10 mg l-1. BDE-209 did not exhibit any negative effects on the growth of K. obovata seedlings. The stimulatory effects of BDE-209 on the enzymes including superoxide dismutase, peroxidase and catalase only occurred in weeks 1 and 4 and diminished in week 8. The concentrations of total polyphenols (TP) and extractable condensed tannins (ECT) were not affected by BDE-209. The production of O2·- was induced only at the very high level of BDE-209 (10 mg l-1). H2O2 was induced only in weeks 1 and 4 under BDE-209 treatment. BDE-209 was taken up by the roots of K. obovata, translocated to above-ground tissues, and accumulated in plant tissues with the concentrations declined in the order of root > propagule > stem > leaf. Although BDE-209 has higher molecular weight and higher log Kow than other PBDE congeners, the K. obovata seedlings could absorb, translocate and accumulate BDE-209. These findings suggested that mangrove plants could take up, accumulate PBDEs, and BDE-209 are less toxic than other congeners but more difficult to be removed by mangrove systems.

Effects of exogenous organic acids and flooding on root exudates, rhizosphere bacterial community structure, and iron plaque formation in Kandelia obovata seedlings

The rhizosphere of coastal wetland plants is the active interface of iron (Fe) redox transformation. However, coupling mechanism between organic acids (OAs) exuded by plant roots and Fe speciation transformation participated by Fe redox cycling bacteria in the rhizosphere is still unclear. Effects of four common OAs (citric acid, malic acid, tartaric acid, and oxalic acid) on root exudation, rhizosphere bacterial community structure, root Fe plaque, and Fe redox cycling bacterial communities of Kandelia obovata were investigated in this study. Long-term flooding (10 h) was conducive to K. obovata seedlings exuding additional dissolved organic carbon (DOC) and nitrogen and phosphorus organic matter (NH4+–N, NO3−–N, and dissolved inorganic phosphorus [DIP]) under each OA level. DOC, NH4+–N, NO3−–N, and DIP in root exudates increased significantly with the increase of exogenous OA level. Notably, long flooding time corresponds to an evidently increasing trend. Exogenous OAs also significantly increased contents of formic and oxalic acids in root exudates. Exogenous OAs and flooding enhanced the rhizosphere effect of K. obovata and significantly enhanced bacterial diversity of the rhizosphere and relative abundance of dominant bacteria in rhizoplane. Bacterial diversity in the rhizosphere of K. obovata seedlings was significantly higher than that in the rhizoplane under the same level of OAs and flooding. Fe plaque content of K. obovata root decreased significantly and the relative abundance of typical Fe-oxidizing bacteria, such as Gallionella, unclassified_f__Gallionellaceae, and Sideroxydans, decreased significantly in the rhizosphere but increased significantly in the rhizoplane with the increase of the treatment level of exogenous OAs. This finding is likely due to the Fe3+ reduction caused by acidification of rhizosphere environment after exogenous OA treatment rather than the result of chemotactic colonization of Fe redox cycling bacteria in the rhizoplane.

Linkage Between Mangrove Seedling Colonization, Sediment Traits, and Nitrogen Input

Mangroves around the world settle along coasts and estuaries, where they usually encounter aquaculture effluent that causes eutrophication and regulates the nitrogen cycle in their ecosystems. Moreover, the physical–chemical features of sediment in mangrove habitats might be altered by coastal wind, waves, and currents more frequently under the condition of increasing extreme climatic events. These events affect the process of colonization/regeneration of mangroves. To study how exogenous nitrogen input and sediment texture affect root system establishment of mangrove propagules and the early growth of seedlings, in turn, we set up a mesocosm experiment to explore the morphological and physiological responses of the root system of two mangroves, i.e., Kandelia obovata and Sonneratia apetala. We found that the root morphological features of mangrove seedlings mostly showed significant differences across the sediment texture treatment; K. obovata seedlings were more intensively influenced than S. apetala seedlings. It could be ascribed that the roots of K. obovata seedlings were more sensitive to sediment texture than S. apetala seedlings. Conversely, the treatment of exogenous nitrogen input showed a slighter even non-significant influence on the root features of mangrove seedlings. These results suggest that the seedlings of S. apetala and K. obovata performed similarly. In estuaries and coasts featuring eutrophication and various sediment textures, the conservation and restoration of mangroves should consider these conditions to ensure the sustainable development of mangroves.

Physiological and Biochemical Responses of Kandelia obovata to Upwelling Stress

Mangroves growing in intertidal areas are faced with various stresses caused by coastal human activities and oceanic and atmospheric sources. Although the study of the physiological and biochemical characteristics of mangroves has been developing over the past four decades, the effect of upwelling on mangroves in plants stress resistance has seldom been investigated. Here, changes in the physiological and biochemical characteristics of the leaves of Kandelia obovata seedlings in response to upwelling were investigated (air temperature: 25 °C; water temperature: control 25 °C, 13 °C, and 5 °C; salinity: 10‰). The results revealed that upwelling treatment caused an increase in chlorophyll content but a decrease in photosynthetic fluorescence parameters. Hydrogen peroxide (H2O2) production and malondialdehyde activity (MDA) increased with the decrease in upwelling temperature. The proline content increased under upwelling stress, whereas the soluble sugar content decreased. Further, the activities of antioxidant enzymes, such as superoxide dismutase activity (SOD) and peroxidase activity (POD), showed an increasing trend during the treatment, while catalase activity (CAT) decreased. It was evidenced that upwelling stress triggered the physiological and biochemical responses of Kandelia obovata seedlings. This effect became more intense as the upwelling temperature decreased, and all these indicators showed different responses to upwelling stress. Through synthesizing more energy and regulating enzyme activity and osmotic pressure, the leaves of K. obovata formed a resistance mechanism to short-term upwelling.

Phytoextraction and Antioxidant Defense of Mangrove Seedling (Kandelia obovata) to Inorganic Arsenate Exposure

Increasing arsenic (As) pollution is posing potential endangerment to mangrove wetland ecosystems. Mangrove phytoextraction, translocation, and responses to As exposure must be urgently addressed. In this study, the growth and physiological response of Kandelia obovata seedlings were examined after addition of 25−200 mg kg−1 As under sediment culture conditions. Results showed that the seedling morphological variations were not significant below 100 mg kg−1 compared to the control group, indicating superoxide dismutase, peroxidase, and catalase synergetic interaction to resist the As exposure. High As concentrations (150–200 mg kg−1) inhibited the seedling growth accompanied by a significant increase in malondialdehyde content and decrease in activities of antioxidant enzymes. Toxicity symptoms and mortality appeared in 200 mg kg−1 As, presumably because the plant reached the limit of As tolerance. Besides, As accumulated mainly in roots, accounting for 87.04–97.85% of the total As, and the bioaccumulation factor (BCF) was >100%. However, the BCF and translocation factor (TF) in stems and leaves were below unity, illustrating a weak capacity of transferring As to aerial parts of the seedlings. Overall, K. obovata is a potential remediated species in polluted coastal wetlands due to high phytoextraction capacity and high tolerance to As exposure.

Effects of Exogenous Organic Acids and Flooding on Root Exudates, Rhizosphere Bacterial Community Structure, and Iron Plaque Formation in Kandelia Obovata Seedlings

Effects of Exogenous Organic Acids and Flooding on Root Exudates, Rhizosphere Bacterial Community Structure, and Iron Plaque Formation in Kandelia Obovata Seedlings

Mycorrhiza Formation in Pinus Sylvestris and Picea Obovata Seedlings in Forest Nurseries in Kazakhstan

This work presents research materials, the purpose of which is to grow seedlings of coniferous trees in the open field using artificial substrates of mycorrhizal macromycetes in forest nurseries of Central, North and Northeast Kazakhstan. The success of mycorrhiza formation in seedlings Pinus sylvestris and Picea obovata from forest nurseries of Akmola and Karaganda regions, and the survival rate of seedlings from forest nurseries of Akmola, Karaganda and Pavlodar regions of Kazakhstan are analysed. In the future, we want to expand the range of studied species and compare artificially mycorrhized seedlings with naturally mycorrhized species from natural forests. If we compare the survival rate of seedlings in nurseries, the highest in P. sylvestris seedlings in Shaldai is about 78%, low in Novodolenskoe, about 27%, and for P. obovata, on average, 66%. In the future, we want to expand the range of studied species and compare artificially mycorrhized seedlings with naturally mycorrhized species from natural forests.

A comparative study of the seedling production technology of Picea obovata L. in the forest-steppe ecotone of northern Mongolia

The success of reforestation largely depends on the quality of the seedling. This study focuses on comparative assessments of the experimental planting of Picea obovata seedlings under various growing conditions, including in a greenhouse and open field. The objectives were to carry out a comparative study of the effect of different care regimes on the growth of seedling, and to choose the most optimal treatment that accelerates the growth of seedlings on the basis of the results taken from the comparative analysis. The study was carried out in the Experimental Forest Nursery of the Institute of Geography and Geoecology, MAS in the period between 2018 and 2020. The experimental planting design included four treatments with varying irrigation norms, air temperatures, air relative humidity, shading rates. Two of these experiments were put in greenhouses, and the remaining two treatments were in the open field. Repeated measurements and sampling were performed at the end of each growing season. The results showed high variation in seedling height (p < 0.0001; F = 38.6) and diameter (p < 0.0001; F = 43.2) growth and biomass accumulation (p < 0.0001). These variables therefore, positively corresponded to the air temperature, air relative humidity and moisture sufficiency in the soils. We found that the seedlings had faster growth in height (52.4%) and diameter (62.3%), and there was more biomass accumulation (128.1%) under greenhouse conditions than outdoors. With regard to the biomass allocation, a three-year observation showed a greater proportion of stem biomass in the total biomass, and, conversely, the predominant proportion of needle biomass accounted for open field treatments. However, the creation of stable condition in the greenhouse with a high relative humidity (more than 75%; daily watering norm of 20 liters per day) and an internal temperature of 25°C (40% shading) had the most positive effect on the growth and accumulation of biomass of seedlings. Consequently, we conclude that to meet the existing needs for seedlings for the restoration of natural Picea obovata forests, seedling production in greenhouses should be recommended.

Ecological criteria for assessing the content of petroleum hydrocarbons in the main soils of coniferous-deciduous forests and forest steppe.

The effect of pollution of Albicluvisols/Retisols, Calcaric Leptosols, Luvic Phaeozems, Greyzamic Phaeozems and Folic Fluvisols with oil (Solovatovsky oil field, Perm region) added in amounts of 1, 2, 3 and 5g oil/kg of soil on the organisms was studied in a model laboratory experiment. Oil addition showed phytotoxic effects on root length in Triticum aestivum L., Lepidium sativum L., Picea obovata Ledeb. and Pinus sylvestris L. in all soils. However, oil contamination of Calcaric Leptosols and Greyzamic Phaeozems led to growth stimulation in Picea obovata seedlings. A remarkable shift in the diversity and number of colony-forming units of heterotrophic and oil-oxidizing bacteria was detected in all soil types. The maximum decrease in biodiversity (45%) was noted for heterotrophic bacteria in Luvic Phaeozems. Aqueous extracts from all oil-contaminated soils had a toxic effect on Chlorella vulgaris Beijer, causing an increase in biomass by more than 30%, but did not show acute toxicity on Daphnia magna Straus. Oil addition in the range of 1-3g oil/kg soil posed no environmental risk to human health. However, oil addition at 5g oil/kg of soil led to an increase in the level of carcinogenic risk to children to the threshold values of acceptable risk and ranged from 0.95 × 10-4 for Greyzamic Phaeozems and Folic Fluvisols to 1.098 × 10-4 for Luvic Phaeozems. Our results suggest that the reaction of test organisms to oil pollution depends on the soil type, and their complex application makes it possible to identify the most sensitive factor and assess the dangerous level of pollution.

Colonization by native species enhances the carbon storage capacity of exotic mangrove monocultures

BackgroundThe fast-growing introduced mangrove Sonneratia apetala is widely used for mangrove afforestation and reforestation in China. Some studies suggested that this exotic species outperforms native species in terms of carbon sequestration potential. This study tested the hypothesis that multi-species mangrove plantations might have higher carbon sequestration potential than S. apetala monocultures.ResultsOur field measurements at Hanjiang River Estuary (Guangdong province, China) showed that the carbon stock (46.0 ± 3.0 Mg/ha) in S. apetala plantations where the native Kandelia obovata formed an understory shrub layer was slightly higher than that in S. apetala monocultures (36.6 ± 1.3 Mg/ha). Moreover, the carbon stock in monospecific K. obovata stands (106.6 ± 1.4 Mg/ha) was much larger than that of S. apetala monocultures.ConclusionsOur results show that K. obovata monocultures may have a higher carbon accumulation rate than S. apetala monocultures. Planting K. obovata seedlings in existing S. apetala plantations may enhance the carbon sink associated with these plantations.

Comparative Proteomic Analysis Reveals the Regulatory Effects of H2S on Salt Tolerance of Mangrove Plant Kandelia obovata.

As a dominant mangrove species, Kandelia obovata is distributed in an intertidal marsh with an active H2S release. Whether H2S participates in the salt tolerance of mangrove plants is still ambiguous, although increasing evidence has demonstrated that H2S functions in plant responses to multiple abiotic stresses. In this study, NaHS was used as an H2S donor to investigate the regulatory mechanism of H2S on the salt tolerance of K. obovata seedlings by using a combined physiological and proteomic analysis. The results showed that the reduction in photosynthesis (Pn) caused by 400 mM of NaCl was recovered by the addition of NaHS (200 μM). Furthermore, the application of H2S enhanced the quantum efficiency of photosystem II (PSII) and the membrane lipid stability, implying that H2S is beneficial to the survival of K. obovata seedlings under high salinity. We further identified 37 differentially expressed proteins by proteomic approaches under salinity and NaHS treatments. Among them, the proteins that are related to photosynthesis, primary metabolism, stress response and hormone biosynthesis were primarily enriched. The physiological and proteomic results highlighted that exogenous H2S up-regulated photosynthesis and energy metabolism to help K. obovata to cope with high salinity. Specifically, H2S increased photosynthetic electron transfer, chlorophyll biosynthesis and carbon fixation in K. obovata leaves under salt stress. Furthermore, the abundances of other proteins related to the metabolic pathway, such as antioxidation (ascorbic acid peroxidase (APX), copper/zinc superoxide dismutase (CSD2), and pancreatic and duodenal homeobox 1 (PDX1)), protein synthesis (heat-shock protein (HSP), chaperonin family protein (Cpn) 20), nitrogen metabolism (glutamine synthetase 1 and 2 (GS2), GS1:1), glycolysis (phosphoglycerate kinase (PGK) and triosephosphate isomerase (TPI)), and the ascorbate–glutathione (AsA–GSH) cycle were increased by H2S under high salinity. These findings provide new insights into the roles of H2S in the adaptations of the K. obovata mangrove plant to high salinity environments.

Ecophysiological Analysis of Mangrove Seedlings Kandelia obovata Exposed to Natural Low Temperature at Near 30°N

In this study, mangrove seedlings Kandelia obovata were firstly introduced to Zhoushan in Eastern China at 29° 93′ N from Xuwen in South China at 20° 34′ N in April 2016. In order to analyze ecophysiological differences of K. obovata seedlings domesticated in Zhoushan, the growth status and antioxidant system of K. obovata exposed to natural low temperature were studied through situ measurements. The results showed that K. obovata seedlings introduced artificially to Zhoushan grew slowly when subjected to natural cold stress. The chlorophyll contents exhibited a decreased tendency. In addition, 2-butanol and 2,3-butanediol were firstly found in K. obovata after being moved to Zhoushan, which are specific substances produced by K. obovata under low-temperature stress. Moreover, there was a synergistic competition mechanism in the antioxidant enzyme system in K. obovata, in which superoxide dismutase (SOD) would convert oxygen radicals to hydrogen peroxide, and then catalase (CAT) and peroxidase (POD) could work together to remove hydrogen peroxide. This study provides a foundation for better understanding of the response of mangroves to natural low temperature at high latitudes.