Abstract:Two rice varieties Fe2+ tolerant Zhongyou 9288 and Fe2+ sensitive Shanyou No.10 screened from 19 rice varieties were used to study the biological characteristics of rice root border cells and their toxicity responses to ferrous iron stress. The experimental results showed that, the first border cell occurred almost synchronously with the emergence of primary root tip and the numbers of border cells reached maximum (1165 for Zhongyou 9288 and 1311 for Shanyou No.10) when the root was 25 mm long. The greatest activity of border cells of two rice varieties was observed at 20 mm root of length. The highest relative activity of Pectin methylesterase (PME) was achieved when the root was 2 mm long. With the increasing concentration of Fe2+, the number of root border cells in Zhongyou 9288 increased and reached the maximum at 100 mg/L of Fe2+, then decreased. The number of root border cells in Shanyou No.10 decreased all through. The activity of two rice varieties root border cells was reduced when concentration of Fe2+ was between 0 to 200 mg/L, but increased a little at 400 mg/L compared with that at 200 mg/L and decreased again when the concentration of Fe2+ reached 800 mg/L. With the increase of Fe2+ concentration, the PME activity of Zhongyou 9288 and Shanyou No.10 increased and reached the maximum at 200 mg/L and 100 mg/L, respectively, then decreased. The mechanism of ferrous iron toxicity on PME activity was discussed.