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Arsenic Toxicity in Akitakomachi Rice in Presence of Fe3+-edta

Molla Rahman Shaibur
Department of Environmental Science & Health Management, Jessore Science & Technology University, Jessore 7408, Bangladesh.

Shigenao Kawai
Faculty of Agriculture, Iwate University, Morioka 020-8550, Japan.

Abstract/ Executive Summary:

An experiment was carried out hydroponically to investigate the arsenic (As) toxicity in rice (Oryza sativa L. cv. Akitakomachi) seedlings in presence of Fe³⁺ -EDTA. The As treatments (NaAsO₂ ) were 0, 6.7, 13.4, 26.8, and 33.5 µM for 14 days. The whitish chlorotic symptom was pronounced in the fully expanded young leaves at 13.4 µM As treatment, suggesting that As-induced chlorosis might be Fe (iron)-chlorosis. Chlorophyll indices and Fe concentrations were reduced much in the shoots of As-treated chlorotic seedlings as compared to the control seedlings. Our result showed that As-toxicity largely depended on the concentrations of inorganic As in the medium and the higher was the concentration of As the higher was the As-toxicity.

Keywords: Arsenic, Concentration, Fe-chlorosis, Rice, Young leaves, Investigate

Location: Jessore Science & Technology University, Jessore 7408, Bangladesh

Start Date: 00-06-2007

End Date: 00-07-2007

Program Area: Risk Management in Agriculture

Commodity: Rice

Objectives:

To investigate the arsenic (As) toxicity in rice (Oryza sativa L. cv. Akitakomachi) seedlings in presence of Fe³⁺ -EDTA.

Methodology:

Rice (Oryza sativa L. cv. Akitakomachi) seeds were surface sterilized with 2% Ca(OCl)₂ for 45 minutes and washed with tap water for 1 hour. Seeds were wrapped between moistened towels covered with colorless vinyl wrapping paper and were kept in an electric incubator for 60 hour at 25 ± 2?C. Germinated seeds were transferred on a plastic net in a yellow plastic box containing 2% CaCl₂ for 7 days in the greenhouse under natural conditions. Seedlings were raised in half-strength nutrient solution for another 14 days and were hand-transplanted in bucket (5 seedlings/bunch) at the 4-5^th leaf stage. Each bucket (5 l) containing 8 bunches. Treatments were started with full-strength solution containing 1 mM NH₄NO₃; 1 mM K₂SO₄; 0.8 mM MgSO₄ ; 0.5 mM CaCl₂; 0.5 mM NaH₂PO₄; 10 µM MnSO₄ ; 1 µM CuSO₄; 1 µM ZnSO₄ ; 3 µM H₃BO₃; 0.05 µM H₂MoO₄ and 10 µM Fe³⁺ -EDTA. The As treatments were 0, 6.7, 13.4, 26.8 and 33.5 µM (equal to 0, 0.5, 1.0, 2.0, and 2.5 mg As 1 ^-1 , respectively) for 14 days. Arsenic was added as sodium meta-arsenite (NaAsO₂ ). The pH of the nutrient solution was adjusted daily at 5.5 with a digital pH meter and with 1 MHCl and/or 1 M NaOH at around 4 p.m. during the experiment (June-July, 2007). Solution was renewed every week and was not aerated. The detailed methodology has been described earlier with some exception. The experiment was carried out in the greenhouse of Iwate University, Japan, with ambient light (roughly 14 hours day/10 hours night). Temperature fluctuation was between 25ºC to 12ºC in day and at night, respectively. The volume of the roots was determined by the traditional method. The root was placed in a 100 ml measuring cylinder filled with an appropriate volume of water. The total volume of the roots was measured by the apparent change in the water volume caused by the roots. The seedlings were collected and washed with deionized water properly. Shoots were separated from the roots with a stainless steel scissor. Additionally, the young leaves were separated from the old leaves to determine the nutrient concentrations, especially Fe, as the chlorosis was found in the young leaves. Samples were dried at 55-60? C for 48 hours in an electric oven and were digested with a nitric acid-perchloric acid mixture. Amounts of K, Ca, Mg, Fe, Mn, Zn and Cu were determined with atomic absorption spectroscopy (AAS). Phosphorus was determined colorimetrically using a UV-visible Spectrophotometer at 420 nm wavelengths after developing the yellow color with vanadomolybdate. Arsenic was measured by using Hydride Generation Atomic Absorption Flame Emission Spectrophotometer. Determination of chlorophyll index, calculation for the parameters and statistical analysis were described elsewhere.

Source of Information: Bangladesh J. Agril. Res. 36(4): 553-562, December 2011

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Our result showed that As-toxicity largely depended on the concentrations of inorganic As in the medium and the higher was the concentration of As the higher was the As-toxicity.

Knowledge Management: Journal