Mitigative Effect of <i>Bacillus subtilis</i> QM3 on Root Morphology and Resistance Enzyme Activity of Wheat Root under Lead Stress

Abstract

Lead (Pb) is an environmental pollutant extremely toxic to plants and other living organisms including humans. In order to research the relieve effect of Bacillus subtilis QM3 on wheat roots ( Triticum aestivum L.), after wheat seeds germination for two days, wheat root caused, the experimental materials were divided into four large groups and each large group was placed in 6 petri dishes as six small groups, and then four large groups respectively cultivated with sterile water (CK), 10 8 CFU/ml B. subtilis QM3 (B1), 10 7 CFU/ml B. subtilis QM3 (B2) and 10 6 CFU/ml B. subtilis QM3 (B3) for 2 days, after that stressed with lead nitrate, Pb (NO) 2 , Pb 2+ concentration calculation at five concentrations (50, 250, 500, 1000, 2000 mg/L), sterile water and different Pb 2+ concentration liquid respectively cultivated the 6 small groups in each large group measuring root morpholog and assaying changes of antioxidant enzyme activity. The results showed that: with the increase of the Pb 2+ concentration, root morphology index and the activity of antioxidant enzyme increased first and then decreased. Root morphology index reached the maximum in 50 mg/L Pb 2+ concentration. B. subtilis QM3 clearly promoted the growth of the root and the antioxidant enzyme activity (p < 0.05). Without Pb stress, B. subtilis QM3 had the best improving effect on root morphology. When Pb 2+ concentration was 50 mg/L, superoxide dismutase (SOD) and ascorbate peroxidase (APX) reached the maximum. SOD activity, compared with CK, B1, B2 and B3 respectively, increased by 8.05%, 27.41% and 9.79%. APX activity, compared with CK, B1, B2 and B3 respectively, increased by 52.70%, 111.15% and 14.16%. Catalase (CAT) and peroxidase (POD) reached the maximum at the Pb 2+ concentration was 500 mg/L. CAT activity, compared with CK, B1, B2 and B3 respectively, increased by 59.93%, 83.46% and 70.59%. POD activity, compared with CK, B1, B2 and B3 respectively, increased by 2.88%, 10.11% and 7.67%. Result suggested that B. subtilis QM3 could improve root growth and antioxidant enzyme activity of the wheat root under lead stress.