Browsing by Author "Kitajima, Nobuyuki"

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Critical Toxicity Level of Arsenic and Elemental Composition of Arsenic-Induced Chlorosis in Hydroponic Sorghum
(Water Air Soil Pollut, 2008) Molla Rahman, Shaibur; Kitajima, Nobuyuki; Sugawara, Reiko; Kondo, Toshihito; Alam, Shah; Huq, S. M. Imamul; Kawai, Shigenao
Physiological and mineralogical responses of sorghum (Sorghum bicolor L. cv. Fast sorghum) in hydroponic culture at elevated concentrations of arsenic (As) were valuated. Seedlings were grown in the presence of 0, 6.7, 33.5 and 67 µM As levels (0, 0.5, 2.5 and 5 mg As l −1 ) up to 14 days after treatments (DAT). Shoot and root dry matter yield were repressed by higher As levels. At low As level (6.7 µM) shoot dry matter yield was enhanced by 2.3% but at 33.5 and 67 µM As levels, the yield decreased by 52 and 79%, respectively. The root growth was similarly enhanced (8%) at the lower As level while the growth decrement at the higher As levels were 33 and 68%, respectively for the two treatments. Considering 10% dry weight (DW) reduction, the critical toxicity level of As was calculated to be 11.7 µg g −1 DW for shoot and 367 µg g −1 DW for root, indicating that shoot was more sensitive to As-toxicity than root. A whitish chlorotic symptom was observed in the fully developed young leaves at the 67 µM As level. The lowest chlorophyll content was also observed at this As level. Arsenic oncentration increased both in shoot and in root with increase in solution As concentration. The concentrations of As and Fe were about 16, 28 and 17 times; and 2, 25 and 144 times higher in root than shoot at 6.7, 33.5 and 67 µM As levels, respectively. The concentrations of K, Fe and Cu were significantly lower while Ca, Mg and Mn oncentrations were higher in the shoot at the 67 µM As level compared to the control plants. On the other hand, Fe, Mn, Zn and Cu concentrations were higher in root at the 67 µM As level. In the shoot, accumulation and translocation of metal micronutrients, particularly that of Fe, decreased significantly because of the presence of As. The resent observations suggested that As might induce a toxic effect on sorghum by hampering the translocation of the metal micronutrients. It is suggested that “As-induced e-deficiency” caused chlorotic symptoms in the hydroponically grown sorghum.
Effects of temperature on plant growth and arsenic removal efficiency of Pteris vittata in purifying arsenic-contaminated water in winter: A two-year year-round field study
(Scopus, 2024) Kohda, Yi Huang-Takeshi; Miyauchi, Keisuke; Rahman, Farzana; Naruse, Haruki; Mito, Mitsuaki; Kitajima, Nobuyuki; Chien, Mei-Fang; Endo, Ginro; Inoue, Chihiro
Phytoremediation is a cost-effective and eco-friendly alternative method for arsenic (As) contaminated water treatment. This study conducted a two-year year-round field study (cycle1 and cycle2) in a temperate area (Sendai, Japan) using small As-hyperaccumulator Pteris vittata seedlings to reduce pre-cultivation time and associated costs. The number of seedlings was changed from 256 in the cycle1 period to 165 in the cycle2 period to evaluate the As removal efficiency of P. vittata for As-contaminated water in field conditions with different plant densities. Before the winter season, with continuously increasing fronds, rhizomes, and roots growth, this reduction did not affect the plant's As removal efficiency for As-contaminated water to decrease the As concentration from 30 μg/L to the environmental quality standard for As in water, set at 10 μg/L in Japan. During the winter season, we found that cold weather caused P. vittata to wither and release the accumulated As into water without a greenhouse (cycle1). In the meantime, the bioaccumulation factor (BAF) and the translocation factor (TF) values for fronds of P. vittata decreased (BAF for fronds: from 66,089 to 8,460; TF for fronds: from 13.4 to 3.4). On the other hand, with greenhouse protection (cycle2), P. vittata did not severely wither and kept accumulating As. Moreover, BAF and TF values for fronds of P. vittata increased (BAF for fronds: from 24,372 to 36,740; TF for fronds: from 5.2 to 17.2). Maintaining the air temperature inside the greenhouse, particularly around the rhizomes, above 0 °C may be the reason why P. vittata remained alive and functional during the cold winter. These results indicate that a single-layer polyethylene greenhouse was sufficient for the tropical-subtropical As-hyperaccumulator fern P. vittata to survive the cold winter and snow in the temperate area, enabling year-round phytoremediation treatment of As-contaminated water in the open field.
Effects of temperature on plant growth and arsenic removal efficiency of Pteris vittata in purifying arsenic-contaminated water in winter: A two-year year-round field study
(Scopus, 2024-08) Kohda, Yi Huang-Takeshi; Miyauchi, Keisuke; Rahman, Farzana; Naruse, Haruki; Mito, Mitsuaki; Kitajima, Nobuyuki; Chien, , Mei-Fang; Endo, Ginro; Inoue, Chihiro
Phytoremediation is a cost-effective and eco-friendly alternative method for arsenic (As) contaminated water treatment. This study conducted a two-year year-round field study (cycle1 and cycle2) in a temperate area (Sendai, Japan) using small As-hyperaccumulator Pteris vittata seedlings to reduce pre-cultivation time and associated costs. The number of seedlings was changed from 256 in the cycle1 period to 165 in the cycle2 period to evaluate the As removal efficiency of P. vittata for As-contaminated water in field conditions with different plant densities. Before the winter season, with continuously increasing fronds, rhizomes, and roots growth, this reduction did not affect the plant's As removal efficiency for As-contaminated water to decrease the As concentration from 30 μg/L to the environmental quality standard for As in water, set at 10 μg/L in Japan. During the winter season, we found that cold weather caused P. vittata to wither and release the accumulated As into water without a greenhouse (cycle1). In the meantime, the bioaccumulation factor (BAF) and the translocation factor (TF) values for fronds of P. vittata decreased (BAF for fronds: from 66,089 to 8,460; TF for fronds: from 13.4 to 3.4). On the other hand, with greenhouse protection (cycle2), P. vittata did not severely wither and kept accumulating As. Moreover, BAF and TF values for fronds of P. vittata increased (BAF for fronds: from 24,372 to 36,740; TF for fronds: from 5.2 to 17.2). Maintaining the air temperature inside the greenhouse, particularly around the rhizomes, above 0 °C may be the reason why P. vittata remained alive and functional during the cold winter. These results indicate that a single-layer polyethylene greenhouse was sufficient for the tropical-subtropical As-hyperaccumulator fern P. vittata to survive the cold winter and snow in the temperate area, enabling year-round phytoremediation treatment of As-contaminated water in the open field.
Physiological and Mineralogical Properties of Arsenic-Induced Chlorosis in Barley Seedlings 3 Grown Hydroponically
(Journal of Plant Nutrition, 2008) Molla Rahman, Shaibur; Kitajima, Nobuyuki; Sugawara, Reiko; Kondo, Toshihito; Huq, S. M. Imamul; Kawai, Shigenao
The experiment was carried out to investigate the effects of arsenic (As) on the physiological and mineralogical properties of barley (Hordeum vulgare L. cv. ‘Minorimugi’). The plants were grown in nutrient solution treated with 0, 6.7, 33.5, and 67 µMAs(0, 0.5, 2.5, and 5 ppm As, respectively) in the phytotron. Dry matter yield of shoots and roots decreased signiﬁcantly with the As treatments, indicating that barley plants are As-sensitive and As-toxicity depends on the As concentration in the rooting medium. Necrosis in older leaves and chlorosis symptoms (whitish color) in the fully developed young leaves were observed at the 33.5 and 67 µMAstreatments. Arsenic concentration, accumulation, and translocation increased with the increase of As concentration in the rooting medium. Arsenic was mostly concentrated in roots and a little amount wasmoved to shoots, indicating that As was not easily translocated to shoots of barley seedlings. Concentrations and accumulations of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), manganese (Mn), zinc (Zn), and copper (Cu) decreased signiﬁcantly in shoots for 33.5 and 67 µMAstreatments as compared to the 0 µMAstreatment. Concentrations of P, K, Ca, Mg, Mn, and Cu decreased in roots, but Zn concentration increased in roots at 67 µMAstreatment. Accumulations of P, K, Ca, Mg, Mn, Zn, and Cu in roots also decreased signiﬁcantly at 67 µMAstreatment. Accumulation of P and the cations showed negative relationship with As. Concentration of Fe decreased in shoots at 33.5 and 67 µMAstreatments where chlorosis was induced in the young leaf but increased in roots at 33.5 and 67 µMAstreatments. It was suggested that Asmight induce iron (Fe)-chlorosis in the plants. Among the micronutrients, Fe translocation was more affected than others by As. Phytosiderophore (PS) accumulation in roots, which is a symptom of Fe-deﬁciency in grasses, did not change signiﬁcantly between 0 and 33.5 µMAstreatments; indicating that As-induced chlorosis did not enhance PS accumulation in roots and decreased due to As-toxicity at 67 µMAstreatment.