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), 108 CFU/ml B. subtilis QM3 (B1), 107 CFU/ml B. subtilis QM3 (B2) and 106 CFU/ml B.
subtilis QM3 (B3) for 2 days,
after that stressed with lead nitrate, Pb (NO)2, Pb2+ concentration
calculation at five concentrations (50, 250, 500, 1000, 2000 mg/L), sterile
water and different Pb2+ 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 Pb2+ 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 Pb2+ 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 Pb2+ 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 Pb2+ 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.