Experimental site and period: Experiment was conducted at Department of Horticulture of the Sher-e-Bangla Agricultural University, Dhaka-1207, Bangladesh and at the Department of Botany of the Jahangirnagar University, Savar, Dhaka-1342, Bangladesh from October 2013 to April 2014.
Treatments and design: Arsenic was applied in the form of Arsenic trioxide (As2O3) @ 50 ppm at 7 days before transplanting of the wheat plant. P. vittata was inter-planted with wheat into pot as trap plant to mitigate (and/or reduce) arsenic accumulation into wheat plant. Experiment was consisted two densities of the trap plants and a control, viz. P0: No P. vittata (Control); P1: four P. vittata plants per m2 and P2: eight P. vittata plants per m2 following completely randomized design with three replication. Wheat seeds were sown broadcasting method where 12-14 plants were grown per m2 while trap plants were planted at the time of wheat seeds sowing. The pot size was 1.5 m in length, 0.5 m in width and 0.5 m in depth.
Data collection: Data were collected on plant height, number of tillers per plant, number of effective tillers per plant, Number of spikelets, ear length, total number of grains per spike, number of filled grains per spike, number of unfilled grains per spike, percentage of unfilled grains, 1000-grains weight, yield per plant, arsenic accumulation by wheat grain and straw, arsenic accumulation by P. vittata and reduction of arsenic accumulation in wheat by P. vittata over control.
Chemical analysis for arsenic: Plant biomass was collected and dried then weighted by u sing precision balance. After that samples were smashed by mortar and pastel machine. The arsenic analysis for was performed by using Atomic Absorption Spectrometer, where use of argon for carrier gas and arsenic was melted by 925ºC; which was approved by ISO organization in Bangladesh Council of Scientific Research Institute (BCSIR), Dhaka, Bangladesh. 50 and 1000 times dilution: (a) 5 ml concentrated HCl was taken at 50 ml volumetric flasks for transferring arsenic into arsenic trioxide and a little bit of distilled water was added. Then 1ml solution was taken very carefully from each volumetric flask to avoid bubble and KI (1 gm) wash added in solution with 150 ml distilled water. After that 0.5 gm sample was taken in volumetric flask and mixed distilled water up to 50 ml and solution turned into yellow color. Another volumetric flask made blank solution, where contain only HCl, KI and distilled water for arsenic analysis. (b) 2 ml solution was taken into 500 volumetric flasks, mixed with distilled water up to 500 ml and shaken very carefully. Then, 05 ml solution was taken into 250 ml volumetric flask and mixed with distilled water up to 250 ml. Again, 5 ml solution from 250 ml solution was taken into 25 ml volumetric flask then 2.5 ml HCl and 2.5 ml KI was added and mixed distilled water, shaking was done very smoothly until turn it into yellow color. Standard solution arsenic was added with HCl 2, 5, 10, 15, 20 ppb respectively.
Statistical analysis: Data were statistically analyzed using MSTAT-C computer package programme. Difference between treatments was assessed by Least Significance Difference (LSD) test at 5% level of significance ( Gomez and Gomez, 1984 ).