Abstract:
Contamination of soils by
lead (Pb) is of widespread occurrence as
result of human, agricultural and industrial
activities. A pot study was carried out to
evaluate physio-biochemical responses
(chlorophyll content, soluble protein,
proline content and activities of enzymatic
antioxidants) of 10 bread wheat genotypes
to inoculation of plant growth promoting
rhizobacteria (combination of Azospirillum
brasilense and Azotobacter chroococcum)
under Pb stress (0 and 65 mg kg-1). Result
revealed that lead stress averagely decreased
grain yield of wheat cultivars by 41.4 %.
Lead stress increased lipid peroxidation and
induced a significant accumulation of
proline in leaves. Protein content decreased
from 8–25.4% in different cultivars in Pbcontaminated
soils. Activities of antioxidant
enzymes, such as, ascorbate peroxidase,
superoxide dismutase and catalase were
significantly increased in the presence of
lead. An increase in total hydrogen peroxide
(H2O2) content was noticed under lead stress
in all cultivars, which was similar to
production of malondialdehyde (MDA).
However, promotion of growth was evident
in most cultivars as a consequence of
rhizobacterial inoculation, since plant
growth promoting rhizobacteria could
improve grain yield, proline content and
membrane integrity, while significantly
reduced the production of MDA and H2O2.
Total chlorophyll content considerably
declined with Pb stress. Between cultivars
the best performance under lead stress was
observed in Sardari, Shahriyar and Gaspard
which had the highest yield and antioxidants
activity. Obtained results showed that
inoculation with Azotobacter and Azospirillium possibly through
bioremediation strategy can stimulate plant
growth under adverse environmental
conditions, such as heavy metal
contamination.
