SODs involved in the hormone mediated regulation of H 2 O 2 content in Kandelia obovata root tissues under cadmium stress

Abstract(#br)Cadmium (Cd) pollution in mangrove wetlands has received increasing attention as urbanization expands rapidly. As a dominant mangrove species, Kandelia obovata is highly tolerant to Cd toxicity. Plant hormones and superoxide dismutase (SODs) play critical roles in the response to heavy metal stress in K. obovata roots. Although theirs important influence have been reported, the regulation mechanism between SODs and plant hormones in Cd detoxification by K. obovata roots remains limited. Here, we investigated relationships among SOD, plant hormones, and Cd tolerance in K. obovata roots exposed to Cd. We found that Cd was retained in the epidermis and exodermis of roots, and the epidermis and exodermis had highest hydrogen peroxide (H 2 O 2 ) content and SOD activity. Similarly, SOD isozymes also exhibited distinct activity in the different parts of root. Overexpressed KoCSD3 and KoFSD2 individually in Nicotiana benthamiana revealed that different SOD members contributed to H 2 O 2 content regulation by promote the activity of downstream antioxidant enzymes under Cd treatment. In addition, assays on the effects of hormones showed that increased endogenous indole-3-acetic acid (IAA) was observed in the cortex and stele, whereas the abscisic acid (ABA) content was enhanced in the epidermis and exodermis in roots during Cd treatment. The results of exogenous hormones treatment indicated that KoFSD2 upregulated under ABA and IAA treatment, but KoCSD3 only induced by ABA stimulation. Taken together, our results reveal the relationship between SODs and plant hormones, which expands the knowledge base regarding KoSODs response to plant hormones and mediating H 2 O 2 concentration under Cd stress

SODs involved in the hormone mediated regulation of H2O2 content in Kandelia obovata root tissues under cadmium stress.

Cadmium (Cd) pollution in mangrove wetlands has received increasing attention as urbanization expands rapidly. As a dominant mangrove species, Kandelia obovata is highly tolerant to Cd toxicity. Plant hormones and superoxide dismutase (SODs) play critical roles in the response to heavy metal stress in K. obovata roots. Although theirs important influence have been reported, the regulation mechanism between SODs and plant hormones in Cd detoxification by K. obovata roots remains limited. Here, we investigated relationships among SOD, plant hormones, and Cd tolerance in K. obovata roots exposed to Cd. We found that Cd was retained in the epidermis and exodermis of roots, and the epidermis and exodermis had highest hydrogen peroxide (H2O2) content and SOD activity. Similarly, SOD isozymes also exhibited distinct activity in the different parts of root. Overexpressed KoCSD3 and KoFSD2 individually in Nicotiana benthamiana revealed that different SOD members contributed to H2O2 content regulation by promote the activity of downstream antioxidant enzymes under Cd treatment. In addition, assays on the effects of hormones showed that increased endogenous indole-3-acetic acid (IAA) was observed in the cortex and stele, whereas the abscisic acid (ABA) content was enhanced in the epidermis and exodermis in roots during Cd treatment. The results of exogenous hormones treatment indicated that KoFSD2 upregulated under ABA and IAA treatment, but KoCSD3 only induced by ABA stimulation. Taken together, our results reveal the relationship between SODs and plant hormones, which expands the knowledge base regarding KoSODs response to plant hormones and mediating H2O2 concentration under Cd stress

Terrestrial-derived soil protein in coastal water: Metal sequestration mechanism and ecological function

Abstract(#br)Terrestrial fungi, especially arbuscular mycorrhizal (AM) fungi, enhance heavy metal sequestration and promote ecosystem restoration. However, their ecological functions were historically overlooked in discussions regarding water quality. As an AM fungi-derived stable soil protein fraction, glomalin-related soil protein (GRSP) may provide insights into the ecological functions of AM fungi associated with water quality in coastal ecosystems. Here, we first assessed the metal-loading dynamics and ecological functions of GRSP transported into aquatic ecosystems, characterized the composition characteristics, and revealed the mechanisms underlying Cu and Cd sequestration. Combining in situ sampling and in vitro cultures, we found that the composition characteristics of GRSP were significantly affected by the element and mineral composition of sediments. In situ , GRSP-bound Cu and Cd contributed 18.91–22.03% of the total Cu and 2.27–6.37% of the total Cd. Functional group ligands and ion exchange were the principal mechanisms of Cu binding by GRSP, while Cd binding was dominated by functional group ligands. During the in vitro experiment, GRSP sequestered large amounts of Cu and Cd and formed stable complexes, while further dialysis only released 25.74 ± 3.85% and 33.53 ± 3.62% of GRSP-bound Cu and Cd, respectively

Terrestrial-derived soil protein in coastal water: metal sequestration mechanism and ecological function.

Terrestrial fungi, especially arbuscular mycorrhizal (AM) fungi, enhance heavy metal sequestration and promote ecosystem restoration. However, their ecological functions were historically overlooked in discussions regarding water quality. As an AM fungi-derived stable soil protein fraction, glomalin-related soil protein (GRSP) may provide insights into the ecological functions of AM fungi associated with water quality in coastal ecosystems. Here, we first assessed the metal-loading dynamics and ecological functions of GRSP transported into aquatic ecosystems, characterized the composition characteristics, and revealed the mechanisms underlying Cu and Cd sequestration. Combining in situ sampling and in vitro cultures, we found that the composition characteristics of GRSP were significantly affected by the element and mineral composition of sediments. In situ, GRSP-bound Cu and Cd contributed 18.91-22.03% of the total Cu and 2.27-6.37% of the total Cd. Functional group ligands and ion exchange were the principal mechanisms of Cu binding by GRSP, while Cd binding was dominated by functional group ligands. During the in vitro experiment, GRSP sequestered large amounts of Cu and Cd and formed stable complexes, while further dialysis only released 25.74 ± 3.85% and 33.53 ± 3.62% of GRSP-bound Cu and Cd, respectively

Environmental fragility and land use of the Pindaíba Creek Hydrographic Basin, Uberlândia, MG, Brazil

This paper presents an environmental analysis of the fragility of Pindaíba Creek Hydrographic Basin using the analysis of natural and anthropic components interactions in the study area. The main objective of this research was to identify and map the environmental fragility of this basin. The specific objectives consisted in the physical characterization of land use and land cover. To accomplish this research, several field campaigns were conducted throughout the basin. The cartographic base was compiled using the Taboca and Pau Furado charts at 1:25.000 scale that were digitized using the software Cartalinx. The thematic maps of geology, geomorphology, and land use were compiled using the software Arcview 3.2. The fragility map was also derived based on the software Arcview 3.2 using the tool Geoprocessing Wizard. The methodology developed by Ross (1990, 1994) was used for the evaluation of the landscape fragility. This methodology attributes values to environment variables according to their potentialities. Results allowed the identification of major natural and anthropic actions in the study area represented in a map of fragility potential. These results indicate that land use has to be changed in order to adjust to the landscape morphology, considering not only natural resources, but also the needs of the people who live in the study area

Phosphorus and cadmium interactions in Kandelia obovata (S L) in relation to cadmium tolerance

National Important Scientific Research Program of China [2013CB956504]; National Natural Science Foundation of China [31170471, 30970527]This study focused on the cadmium (Cd) tolerance of mangroves with application of phosphate (P) in order to explore whether exogenous P can alleviate Cd stress on these intertidal species. Kandelia obovata (S. L.) seedlings were cultivated in rhizoboxes under different levels of Cd and P concentrations. The speciation distributions of Cd in the rhizosphere and non-rhizosphere sediments were examined by sequential extraction procedures; organic acid in plant tissues and soil solution was measured by high-performance liquid chromatography; Cd and P accumulation in the plants was also determined. Results showed that considerable differences existed in Cd speciation distributions between rhizosphere and non-rhizosphere sediments. Root activity influenced the dynamics of Cd, P application increased the organic acid content in root tissues, P also increased Cd accumulation in roots whilst lowering Cd translocation from root to the above-ground tissues, and a significant positive correlation was found between Cd and P in roots (r = 0.905). It is postulated that Cd detoxification of K. obovata (S. L.) is associated with higher Cd immobilization in the presence of higher P and organic acid contents in root tissue

Formation of iron plaque on mangrove Kandalar Obovata (SL) root surfaces and its role in cadmium uptake and translocation

In this study, a pot experiment was conducted to investigate the formation of iron plaque under Cd stress and its role in Cd uptake and translocation by mangrove Kandalar. Obovata (S.L.). Results showed:. 1.the Fe in dithionite-citrate-bicarbonate (DCB) extracts increased with an increasing rate of Cd treatments.2.the Cd in DCB extracts and in roots and above-ground tissues significantly increased with an increasing Cd application;3.significant positive correlation between concentration of Cd and Fe in DCB extracts existed (p<0.05); and that4.the proportion of Cd in DCB extracts was significantly lower than that in roots or above-ground tissues (p<0.001).In conclusion, formation of Fe plaque can precipitate Cd on root surfaces and impede its uptake and translocation in Kandalar. Obovata (S.L.). However, in comparison with root tissues, Fe plaque is of little significance. It is the mangrove root tissue that acts as the main buffer to Cd uptake and translocation. ? 2013 Elsevier Ltd

Accumulation, distribution and toxicological effects induced by chromium on the development of mangrove plant Kandelia candel (L.) Druce

A study was performed for investigating accumulation, distribution and toxicological effects induced by chromium (Cr) on the development of the mangrove seedling Kandelia candel (L.) Druce. Seedlings treated with increasing concentrations of CrCl3 solution (0, 0.5, 1, 1.5, 2, 2.5, 3 mg L-1, respectively) were grown in a basic nutrient solution for three months. The five month old seedlings were harvested for the experiment. This study showed that Cr treatment significantly decreased growth of K. candel in terms of seedling height, leaf number and total biomass. At the highest 3 mg L-1 Cr exposure, there was a 34.47% decrease in final seedling height, 68.95% decrease in leaf number and a 60.65% decrease in total biomass. The present study demonstrates that Cr accumulation ability of K. candel seedlings increased with the increase of treatment strength up to certain level. The concentrations of Cr in root, hypocotyl, stem and leaf ranged from 22.87 to 1.43 mg kg-1, 1.30 to 0.68 mg kg-1, 2.42 to 0.91 mg kg-1, and 1.74 to 0.74 mg kg-1, respectively. When comparing Cr concentration in different plant parts with respect to their controls, the results showed that treated plant root bioaccumulated high amounts of Cr. Almost 80% of Cr was accumulated mainly in roots. The distribution pattern of Cr in K. candel was Root > Stem > Leaf > Hypocotyl. Our findings indicated that the high concentration of Cr supply may interfere with several metabolic processes of seedlings, causing toxicity to plants as exhibited by chlorosis, necrosis, and finally, plant death

Effect of Mangroves on the Horizontal and Vertical Distributions of Rare Earth Elements in Sediments of the Zhangjiang Estuary in Fujian Province, Southeastern China

National Natural Science Foundation of China [30970526, 30970527, 41006043, 31170471]To examine the influence of the mangrove environment on the distribution of rare earth elements (REE) in estuarine sediments, surface and core sediments were collected from regions of mangrove forest, forest fringe, and adjacent mudflat in the Zhangjiang estuary, SE China. Concentrations of REE were determined in surface sediments and core samples using inductively coupled plasma mass spectrometry. Light REE were more enriched than heavy REE, with a relatively weak negative europium anomaly with respect to the North American shale composite in sediments of the Zhangjiang estuary. Significant differences for REE were found among sampling sites and locations, following the order mangrove forest, to forest edge, to mudflat. The main source for REE in the estuary is the weathered continental materials from the Zhangjiang River drainage basin. The mangrove environment affected the physicochemical features and thus affected the REE spatial distributions in sediments. Vertical REE distributions in core samples were altered by mangrove root activity. Mangroves played a significant role in controlling the horizontal and vertical distribution of REE in sediments of the Zhangjiang estuary

Effects of salinity on leaf delta C-13 in three dominant mangrove species along salinity gradients in an estuarine wetland, southeast China

Many previous studies demonstrate that carbon stable isotope composition (usually expressed as isotopic ratio, delta C-13) can reflect the integrated response of physiological processes to environment, but little is known of the variation in delta C-13 of mangrove plants as affected by salinity, especially in response to long term saline environment. The variation in delta C-13 of three dominant mangroves growing in long-term saline environments in the field was assessed. Mature leaves of Avicennia marina (Forsk) Vierh., Kandelia candel (L.) Duce., and Aegiceras corniculatum Blanco. were collected at seven sample sites covering seven salinity levels (14.07%-19.83%) at a natural mangrove wetland located in southeast China. The delta C-13 values varied from -31.46% to -27.33 parts per thousand, with increasing salinity, reflecting the typical C-3 pathway of CO2 fixation. The delta C-13 was positively related to salinity in K. candel and A. marina, and the reverse was observed in A. corniculatum, even though the correlations were not statistically significant for A. corniculatum and A. marina. The mean delta C-13 at high salinity was, in descending order, K candel > A. marina > A. corniculatum. It is concluded that responses of delta C-13 to salinity is species-dependent and assessment of carbon isotopic composition is helpful for evaluating the salt tolerance of mangrove species, but it should be used with caution when comparing the salt tolerance between different species, particularly when they have the different patterns of delta C-13 in response to salinity