Evans blue staining method as described by Tamas et al. (2004) was used to determine cell viability of root tips. In brief, the plant seedling treated with the crude extract were stained in 0.25% (w/v) aqueous solution of evans blue for 15 min and then washed by distilled water for 30 min. Ten roots from each treatment were excised about 3-4 mm in length from the tip. They were subsequently soaked in 200 μL of N,N-dimethylformamide to extract the Evans blue stain for 24 hours at room temperature. The absorbance of the released Evans blue was measured at 600 nm.