Effects Inoculation With Two strain of Rhizobium on Anatomical Indexes of Persian Clover (Trifolium resupinatum) Under SO2 Pollution

Aim: The aim of this study was to evaluate the effects of rhizobial inoculation on the anatomical
parameters of clover under SO2 pollution.
Material and methods: 31 day-old plants (no-inoculated and inoculated with two strains of
Rhizobium) exposed to the different concentrations of SO2 (0 as a control, 0.5, 1, 1.5 and 2 ppm) for 5
consecutive days for 2 hours per day. The anatomical parameters of 40 day-old plants were Then
investigated.
Results: Under high SO2 concentrations (1, 1.5, and 2ppm), the length of the palisade cells and diameter of
the spongy cells decreased in both leaf surfaces. Stomatal density decreased in the adaxial epidermis and
increased in the abaxial epidermis. Also, stomatal opening increased in the adaxial epidermis and decreased in
the abaxial epidermis. Trichome density in both leaf surfaces significantly increased in 1.5 and 2ppm SO2
compared with the control plants. Under 2 ppm, trichome length increased significantly in both leaf
surfaces. Inoculation of clover with two strains of Rhizobium significantly reduced the negative effects
of high SO2 concentration.
Conclusion: The results indicate the negative effects of high concentrations of SO2 air pollution on the
some anatomical parameters and the positive effects of bacterial inoculation on resistance to air SO2
pollution stress.