The protective role of sulfur and α-tocopherol in detoxification of selenium in mung bean cuttings ( Phaseolus aureus Roxb.)

Abstract

Abstract :The role of sulfur (S) and α-tocopherol (α-T) in alleviating selenium (Se) toxicity has been studied physiologically by using water culture as balanced environment in terms of adventitious root formation. However, the toxic level of selenium and the optimal promotory concentrations of both S and α-T were supplied to mung bean cuttings ''as experimental system'' that taken from 10-day-old light grown seedlings (continuous light, light irradiance 1600 – 1800 lux, temperature 25 ± 1˚C and 60 – 70% relative humidity). The results revealed the followings:A significant increase in root number of cuttings which treated with Hoagland solution (half strength).1-The toxic level of selenium was 1.5 µM that reduced rooting response of cuttings to lower than 50% .2-The best rooting response was recorded in cuttings supplied with S (2mg/l) and α-T (0.1 µM) were 29.5% and > 75% respectively over control.3-Sulpher has no significant effect on selenium detoxification when supplied before or after (during the 1st day and 2nd day) whereas, it is capable to detoxify Se as well as inducing > 100% of rooting response when supplied simultaneously.4-α-tocopherol was unable to detoxify selenium when supplied before and after Se (seemingly, Se may inhibit part of α-T action during the 1st and 2nd day). However, when both α-T (promotory) and Se (inhibitory) were supplied together during first day (24 h) their antagonistic effects could balanced the situation and detoxifying Se as well as raising the rooting response to a level that equal to control (Hoagland treatment) statistically (0.05).5-The effect of S and α-T in terms of Se detoxification, when supplied together before and after Se (during the 1st day only or during the 2nd day only) was inhibitory. Whereas, when supplied together with Se at the same time (simultaneously), their effect not only completely ameliorate Se-toxicity but raising the rooting response to the level that equaled to control (Hoagland treatment) with no statistical differences.