Pak. J. Bot., 37(4): 959-967, 2005. | Back to Contents | ||||
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Updated: 09-07-09 | ||||
MITIGATION OF SALINITY EFFECTS ON SESBANIA ACULEATA L., THROUGH ENHANCED AVAILABILITY OF CARBON DIOXIDE F. AZAM, F. AZIZ*, M.H. SIAL*, M. ASHRAF* AND S. FAROOQ
Abstract:
Experiments were conducted to assess the effect of CO2 on
growth and nitrogen fixation in Sesbania aculeata L., under different
salinity and water regimes. Salinization of soil led to decrease in
different growth attributes of the plants. The negative effect of salinity
was mitigated to a significant extent at elevated CO2. Growth
and N content of the plants was better when grown at 25 than 15% soil
moisture level. Roots of Sesbania were densely nodulated, the weight
of nodules being reduced with the increase in salinity but more at higher
moisture level. The analysis of shoot material for total N and 15N showed
significant amounts of N2 being fixed by the plants. The
shoot contained 23-67% of the N from fixation under different growth
conditions and 33-77% from the soil. Contribution of biological fixed
N to the total N content of shoots decreased with salinity but was more
at higher moisture in all the cases. Enclosure of plants in the polyethylene
chamber led to an increase in the contribution of biologically fixed
N to the total N of shoots irrespective of the soil conditions. Soil
salinity had in general a depressing effect on contribution of biologically
fixed N suggesting a decrease in the rhizobial activity vis-à-vis
decreased photosynthate supply to the root-zone. Significantly higher
amounts of N seemed to have been fixed at 25% than 15% soil moisture.
Elevated CO2 favoured N2 fixation leading to a
greater contribution of fixed N to the total plant N.
Nuclear Institute for Agriculture and Biology, Faisalabad, Pakistan. |
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