Elevated CO2 influences photosynthetic characteristics of Avena sativa L cultivars.

The impact of elevated CO2 concentration on the growth, photosynthesis and biomass production was investigated in three oat (Avena sativa L) cultivars viz. Kent, JHO-822 and JHO-851 by growing under three environmental conditions i.e. elevated CO2 at 600 ± 50 μ mol mol-1 (C600), OTC with ambient CO2 (COTC) and under open field condition (Ca). Plant height and leaf area increased in the elevated CO2 grown plants. JHO-822 attained maximum height under C600 followed by Kent and JHO-851. The specific leaf mass (SLM) and specific leaf area (SLA) were also influenced significantly when the plants were grown under C600. Kent showed highest SLM under C600 corresponding lower value of SLA. The accumulation of soluble protein in the oat leaves decreased under C600 except JHO-822 where marginal increase in soluble protein was recorded under C600. JHO-822 showed an increase in Chl orophyll a, b and total in C600 over Ca, whereas other two cultivars did not follow any specific trend in the pigment accumulation. Our results confirmed that the net phosynthetic rate (PN) increased by 37% in Kent followed by JHO 822 under elevated CO2 over the control. This strong association of PN with gs was evidenced by a positive significant correlation (r=0.885**). A clear stimulatory effect at elevated CO2 was detected in all the cultivars in term of green and dry matter production than at ambient CO2 and COTC. A large increase in PN in the present investigation was accompanied by relatively small decrease in gs, which limits the water loss through transpiration rate. The elevated CO2 induced changes in gs and reduction in transpiration.

Growth, yield and photosynthesis of Panicum maximum and Stylosanthes hamata under elevated CO2.

Plant height, biomass production, assimilatory functions and chlorophyll accumulation of Panicum maximum and Stylosanthes hamata in intercropping systems was influenced significantly under elevated CO2 (600 ±50 ppm) in open top chambers (OTCs). The plant height increased by 32.0 and 49.0% over the control in P. maximum and S. hamata respectively in intercropping system under elevated CO2 over open field grown crops (Ca). P. maximum and S. hamata produced 67 and 85% higher fresh and dry biomass respectively under elevated CO2. Rates of photosynthesis and stomatal conductance increased in both the crop species in intercropping systems under elevated CO2. The canopy photosynthesis (photosynthesis x leaf area index) of these crop species increased significantly under elevated CO2 over the open grown crops. The chlorophyll a and b accumulation were also higher in the leaves of both the crop species as grown in OTC with elevated CO2. The increased chlorophyll content, leaf area index and canopy photosynthesis led to higher growth and biomass production in these crop species under elevated CO2. The total carbon sequestration in crop biomass and soils during the three years was 21.53 Mg C/ha under elevated CO2. The data revealed that P. maximum and S. hamata intercropping system is the potential as a sink for the increasing level of CO2 in the atmosphere in the semi-arid tropics.

Drought stress induced changes in lipid peroxidation and antioxidant system in genus Avena.

Seven species of genus Avena viz., Avena sativa, Avena strigosa, Avena brevis, Avena vaviloviana, Avena abyssinica, Avena marocana and Avena sterilis were used to study the impact of drought stress on lipid peroxidation and other antioxidant enzymes. Maximum increase in the catalase activity was recorded in A. vaviloviana (129.97%) followed by A. sativa (122.82%) and A. brevis (83.38%) at vegetative stage; however at flowering stage the maximum increase was reported in A. sativa (25.62%) followed by A. sterilis (20.46%) and A. brevis (18.53%). At vegetative stage drought, maximum increase in peroxidase activity was recorded in A. sativa (122.82%) followed by A. brevis (83.38%) and A. sterilis (49.78%). Flowering stage drought, showed maximum increase in A. sativa (27.09%) followed by A. marocana (23.50%) and A. sterilis (20.46%). A. sativa and A. sterilis showed stress tolerance at both the stages by accumulating higher percentage of peroxidase followed by A. brevis at vegetative and A. marocana at flowering stage. Level of lipid peroxidation in terms of Malondialdehyde (MDA) content was increased in the leaves when plants were subjected to moisture stress. The rate of increase in lipid peroxidation occurs irrespective of stage however; maximum increase was recorded in A. strigosa at both the stages. Avena species which showed high level of MDA content, indicates more lipid peroxidation and more membrane permeability and are comparatively more susceptible for water stress than those which produce less Malondialdehyde (MDA) content at higher magnitude of water stress such species have better capability for moisture stress tolerance.