The effect of laser pretreatment on seed germination indices and α-amylase activity and growth of Silybum marianum L. seedling in normal condition and under Pb stress

Recently, seed pre-treatment with helium-neon laser as one of the safest methods for enhancing seed germination, seedling growth and increasing stress tolerance of plants attracted the keen interest of scientific community. Therefore, in this study the effect of laser was investigated on the germination indices of Silybum marianum L. at normal condition and under Pb stress. The first, effect of various concentrations of lead nitrate (0, 125, 250, 500 and 1000 ppm) were evaluated on relative seed germination, root resistance index and germination tolerance index of Silybum marianum seeds at a completely randomize design. The results showed that 125 ppm lead nitrate had no significant effect on seed germination and root growth, but higher concentrations reduced above-mentioned parameters. Second experiment, the effect of various powers (5, 10 and 15 mW) and different times (0, 5, 10, 20, and 40 minutes) of He–Ne laser radiation on seed germination at a factorial experiment with completely randomize design showed that the maximum seed germination percentage, germination velocity, germination energy, seedling length and vigor index were obtained by He–Ne laser irradiation with 10 mW power for 20 min. In the third experiment, the interactive effect of irradiation times (0, 20 and 40 minutes) He–Ne laser with 10 mW power and lead nitrate concentrations (0, 250 and 500 ppm) was assessed at a factorial experiment with completely randomize design showed that He–Ne laser increased seed germination percentage, α-amylase activity and seedlings growth at a dose-dependent pattern at both with and without pb stress conditions.