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Subject: Crop Physiology × Author: Khwairakpam, Rowndel × End date: 2017 × Start date: 2015 × Type: Thesis × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    TAPPING OF CARBON DIOXIDE IN RICE ECOSYSTEM THROUGH AZOLLA CULTIVATION
    (AAU, Jorhat, 2017-07) Khwairakpam, Rowndel; Das, Ranjan
    The present investigation was carried out in the stress physiology laboratory under fully automated bioreactor where tapping of CO2 and external injection regulation CO2 facility were available. To understand the assimilation and N accumulation in Azolla-Rice ecosystem in response elevated CO2 possible interactions of CO2 and Azolla on the growth and yield of rice investigation was conducted during the kharif season of 2014 and 2015.The studies revealed that there was variable response of photosynthetic parameters which lead to impact on carbon sequestration potential as well as change in O2 evolution under varying levels of CO2 environment under rice-Azolla ecosystem. In case of fluorescence and related parameters, there was deviation from the normal range as the CO2 concentration increased, however these deviations were minimized in presence of Azolla. These were also same in case of ETR, NPQ, PQ, ф PSII etc. Photosynthetic and its related parameters viz. gs, Ci, T, etc. were found to be related to stomatal density and size. These factors ultimately affected plant growth which was translated as yield. Elevated (500 ppm) CO2 with Azolla has a greater potential for C sequestration, while soil organic carbon enhancement helped increase crop productivity and sustainability which was evident from higher yield and yield attributing parameters. Soil microbial population with higher C: N ratio was recorded under elevated CO2 with rice-Azolla ecosystem. There have been increasing concerns regarding the role of soil microbial population in biological stabilization of SOC in agricultural soils because change in the soil microbial population within rhizo-spheres with changes in organic matter input. Significant reduction of NPK was recorded due to elevated CO2, however; reduction rate was variable with Azolla when compared with without Azolla and ambient. Conversion of inorganic nitrogen was significantly reduced in elevated CO2 however there was amelioration affect under 500 ppm CO2 with Azolla due to significant increase in key enzymes such NR, NiR and GS syntheses activity. CO2 enrichment decreased the N concentration in rice without any change in the C content, leading to an increase in C:N ratio However variability among systems also recorded. This study: (1) depicts the changes in microbial population and fungal predominance; (2) infers a biological stabilizing mechanism behind the C sequestration which includes physical-chemical stabilization as the major controlling processes leading to variation of yield. Azolla has enormous potential to sequester of atmospheric CO2 due to its rapid growth in freshwater without the need for a soil-based nitrogen source. Azolla is a novel opportunity to expand and diversify the supply of fertilizers and production of rice fields vis a vis tapping the CO2 and enhancing the O2 evolution system under changed environmental conditions.