Synergistic effects of zinc and cadmium on phytoremediation potential of Christmas moss (Vesicularia montagnei).

The hyperaccumulation potential of zinc (Zn) and cadmium (Cd) and their synergistic effects were examined in relation to Christmas moss (Vesicularia montagnei (Bél) Broth., Hypnaceae), an aquatic and terrestrial moss, dosed with Cd (Cd1 and Cd2), Zn (Zn1 and Zn2) and combined Zn and Cd (Cd1Zn1 and Cd2Zn2). Zinc promoted plant growth and development, particularly in the highest Zn and combined Zn/Cd treatments (Zn2 and Cd2Zn2). The Zn treatment resulted in substantial moss chlorophyll content and highest percentage relative growth rate in biomass value (0.23 mg L-1 and 106.8%, respectively); however, the Cd2Zn2 treatment achieved maximal production of chlorophyll a and total chlorophyll (0.29 and 0.51 mg L-1, respectively) due to synergistic effects. These findings suggest that Christmas moss is a highly metal-tolerant and adaptable bryophyte species. Zinc was essential for reducing the detrimental effects of Cd while simultaneously promoting moss growth and biomass development. Furthermore, Christmas moss exhibited hyperaccumulation potential for Cd and Zn in the Cd2Zn2 and Zn alone treatments, as evidenced by highest Cd and Zn values in gametophores (1002 and 18,596 mg per colony volume, respectively). Using energy dispersive X-ray fluorescence (EDXRF) spectrometry, atomic percentages of element concentrations in moss gametophores in the Zn2, Cd2 and combined Zn/Cd treatments were generally in the order: K > Ca > P > Zn > Cd. When comparing the atomic percentages of Zn and Cd in gametophores, it is likely that the higher atomic percentage of Zn was because this element is essential for plant growth and development.

Evaluation of Soil Streptomyces spp. for the Biological Control of Fusarium Wilt Disease and Growth Promotion in Tomato and Banana.

Fusarium oxysporum f. sp. lycopersici (Fol) and Fusarium oxysporum f. sp. cubense (Foc), are the causal agent of Fusarium wilt disease of tomato and banana, respectively, and cause significant yield losses worldwide. A cost-effective measure, such as biological control agents, was used as an alternative method to control these pathogens. Therefore, in this study, six isolates of the Streptomyces-like colony were isolated from soils and their antagonistic activity against phytopathogenic fungi and plant growth-promoting (PGP) activity were assessed. The results showed that these isolates could inhibit the mycelial growth of Fol and Foc. Among them, isolate STRM304 showed the highest percentage of mycelial growth reduction and broad-spectrum antagonistic activity against all tested fungi. In the pot experiment study, the culture filtrate of isolates STRM103 and STRM104 significantly decreased disease severity and symptoms in Fol inoculated plants. Similarly, the culture filtrate of the STRM304 isolate significantly reduced the severity of the disease and symptoms of the disease in Foc inoculated plants. The PGP activity test presents PGP activities, such as indole acetic acid production, phosphate solubilization, starch hydrolysis, lignin hydrolysis, and cellulase activity. Interestingly, the application of the culture filtrate from all isolates increased the percentage of tomato seed germination and stimulated the growth of tomato plants and banana seedlings, increasing the elongation of the shoot and the root and shoot and root weight compared to the control treatment. Therefore, the isolate STRM103 and STRM104, and STRM304 could be used as biocontrol and PGP agents for tomato and banana, respectively, in sustainable agriculture.

Growth and Phytoremediation Efficiency of Winged Bean in Fluorene- and Pyrene-Contaminated Soil.

Winged bean is a tropical legume that has been reported to enhance polycyclic aromatic hydrocarbon (PAH) biodegradation in soil. However, there is insufficient information about the susceptibility of winged bean to PAH toxicity in long term study. In this study, winged bean was planted in soil contaminated with either fluorene (124.5 mg/kg) or pyrene (98.4 mg/kg) for 90 days. Plant growth parameters and PAH disappearances from soil were measured every 30 days. Neither fluorene nor pyrene led to decreased shoot and root length of winged bean and all the winged bean plants flowered on day 90. However, the chlorophyll b content in the leaves decreased since day 60 and further decreased significantly by day 90 when winged bean was grown in the presence of fluorene or pyrene. The presence of fluorene and pyrene led to reduced root nodule formation at 30 and 60 days. Despite the reduced chlorophyll b content and decreased number of root nodules, winged bean could enhance pyrene removal significantly on day 30 compared to unplanted soil. Subsequently, pyrene degradation in the unplanted soil caught up and there was no statistically significant difference between the two treatments at 60 or 90 days. Negligible amounts of PAHs were accumulated in the shoot and root tissues of winged bean. These results showed that winged bean can speed up the removal of high MW PAHs from contaminated soil and we conclude that this plant is suitable for PAH phytoremediation.

Removal of Anthracene and Fluoranthene by Waxy Corn, Long Bean and Okra in Lead-Contaminated Soil.

The ability of waxy corn, long bean and okra to remove two polycyclic aromatic hydrocarbons (PAHs) from soil containing 0.63 mg Pb kg(-1) dry soil was assessed. The presence of Pb did not reduce the ability of these plants to remove the PAHs from soil. About 49 % of anthracene and 77 % of fluoranthene were removed from Pb-spiked or non-spiked soil, respectively, after 30 days. Among the plants, okra was the most efficient at removing anthracene and fluoranthene in the presence or absence of Pb in soil after 30 days. Pb did not affect fluoranthene removal, but stimulated the removal of anthracene, by long bean, waxy corn and okra. However, growth of long bean and waxy corn was poor in Pb-spiked soil and waxy corn plants died around 22 days after transplantation. The results show some promise in using plants to remove PAHs from soil which is also co-contaminated with Pb.

Effect of alpha-naphthalene acetic acid and thidiazuron on seedling of economic crops grown in endosulfan sulfate-spiked sand.

The effect of two plant growth regulators, alpha-naphthalene acetic acid (NAA) and thidiazuron (TDZ) on the growth of sweet corn (Zea mays), cowpea (Vigna sinensis) and cucumber (Cucurmis sativus) seedling planted in 1-100 mg kg(-1) of endosulfan sulfate spiked sand was investigated. Endosulfan sulfate had no apparent toxicity as seedlings of these crop plants grew normally in endosulfan sulfate spiked sand. Concentration of endosulfan sulfate in sand affected the response of seedling induction by NAA or TDZ. Induction of crop seeds by NAA or TDZ did not promote growth of sweet corn, cowpea and cucumber to an appreciable extent. Both plant regulators at concentration of 10 mg l(-1) seemed to exert adverse effect on crop seedling. TDZ decreased shoot length, root length and chlorophyll contents in leaves of sweet corn and cowpea growing in endosulfan sulfate spiked sand. In contrast, NAA was not toxic and promoted growth of sweet corn and cowpea seedling. However, cucumber was affected by NAA and TDZ more than other plants. TDZ significantly decreased biomass and root length of cucumber. Also, NAA significantly decreased cucumber root length and tended to increase cucumber root dried weight when grown in 100 mg kg(-1) of endosulfan sulfate spiked sand.

Comparing anthracene and fluorene degradation in anthracene and fluorene-contaminated soil by single and mixed plant cultivation.

The ability of three plant species (sweet corn, cucumber, and winged bean) to remediate soil spiked with 138.9 and 95.9 mg of anthracene and fluorene per kg of dry soil, respectively, by single and double plant co-cultivation was investigated. After 15 and 30 days of transplantation, plant elongation, plant weight, chlorophyll content, and the content of each PAH in soil and plant tissues were determined. Based on PAH removal and plant health, winged bean was the most effective plant for phytoremediation when grown alone; percentage of fluorene and anthracene remaining in the rhizospheric soil after 30 days were 7.8% and 24.2%, respectively. The most effective combination of plants for phytoremediation was corn and winged bean; on day 30, amounts of fluorene and anthracene remaining in the winged bean rhizospheric soil were 3.4% and 14.3%, respectively; amounts of fluorene and anthracene remaining in the sweet corn rhizospheric soil were 4.1% and 8.8%, respectively. Co-cultivation of sweet corn and cucumber could remove fluorene to a higher extent than anthracene from soil within 15 days, but these plants did not survive and died before day 30. The amounts of fluorene remaining in the rhizospheric soil of corn and cucumber were only 14% and 17.3%, respectively, on day 15. No PAHs were detected in plant tissues. This suggests that phytostimulation of microbial degradation in the rhizosphere was most likely the mechanism by which the PAHs were removed from the spiked soil. The results show that co-cultivation of plants has merit in the phytoremediation of PAH-spiked soil.

Phytotoxicity of heptachlor and endosulfan sulfate contaminants in soils to economic crops.

The intensive use of organochlorine in the past decades has resulted in contamination of soil worldwide. The phytotoxicity of two organochlorine pesticide, endosulfan sulfate and heptachlor, on the early growth stage of sweet corn (Zea mays), waxy corn (Zea mays) cowpea (Vigna sinensis), cucumber (Cucumis sativus) and water morning glory (Ipomoea aquatica) were studied. In the range of concentration found in Thai agricultural soil, 0.4-40 mg kg(-1) of each pesticide, did not affect the percentage of seed germination. Heptachlor seemed to affect the shoot and root length of test plants more than endosulfan sulfate. The combined effect of both pesticides to corn seedling growth was tested. There was no significant effect on combined treatment of both pesticides to corn growth. The 0.4-40 mg kg(-1) concentration of endosulfan sulfate and heptachlor did not produced significant effect on early growth of plants.

Enhanced biodegradation of anthracene in acidic soil by inoculated Burkholderia sp. VUN10013.

The ability of Burkholderia sp. VUN10013 to degrade anthracene in microcosms of two acidic Thai soils was studied. The addition of Burkholderia sp. VUN10013 (initial concentration of 10(5) cells g(-1) dry soil) to autoclaved soil collected from the Plew District, Chanthaburi Province, Thailand, supplemented with anthracene (50 mg kg(-1) dry soil) resulted in complete degradation of the added anthracene within 20 days. In contrast, under the same test conditions but using autoclaved soil collected from the Kitchagude District, Chanthaburi Province, Thailand, only approximately 46.3% of the added anthracene was degraded after 60 days of incubation. In nonautoclaved soils, without adding the VUN10013 inocula, 22.8 and 19.1% of the anthracene in Plew and Kitchagude soils, respectively, were degraded by indigenous bacteria after 60 days. In nonautoclaved soil inoculated with Burkholderia sp. VUN10013, the rate and extent of anthracene degradation were considerably better than those seen in autoclaved soils or in uninoculated nonautoclaved soils in that only 8.2 and 9.1% of anthracene remained in nonautoclaved Plew and Kitchagude soils, respectively, after 10 days of incubation. The results showed that the indigenous microorganisms in the pristine acidic soils have limited ability to degrade anthracene. Inoculation with the anthracene-degrading Burkholderia sp. VUN10013 significantly enhanced anthracene degradation in such acidic soils. The indigenous microorganisms greatly assisted the VUN10013 inoculum in anthracene degradation, especially in the more acidic Kitchagude soil.