Tropical Plant Research

C. Buvaneswaran*, K. Arivoli, T. Sivaranjani, E. Menason, K. Vinothkumar, S. Padmini and S. Senthilkumar

DOI: https://doi.org/10.22271/tpr.2016.v3.i3.072

Abstract:
Global climate change the looming environmental threat is mainly due to the increase in atmospheric CO₂ levels, which was increasing earlier by about 1.55 ppm per year and currently by 2.76 ppm per year. Thus, CO₂ concentration has reached 400.16 ppm in 2015. To understand the response of various tropical tree species to such an elevated CO₂, experiments were conducted in Automated Open Top Chambers (AOTC) facility at Institute of Forest Genetics and Tree Breeding (IFGTB), Coimbatore (India). The results of initial studies indicated the scope for exploring intra-specific variation in response of tropical trees to elevated CO₂. Subsequently, experiments were carried out to assess intra-specific variation in Neem (Azadirachta indica). The selected phenotypes of Neem (varieties or clones) were exposed to four treatments viz., i) CO₂ of 600 ppm, ii) CO₂ of 900 ppm, iii) chamber control- without any CO₂ enrichment and iv) ambient conditions. The parameters studied were shoot length, root length, dry matter accumulation in shoot and root. The results of the study showed that there existed significant variation among different treatments of CO₂ as well as among various phenotypes or clones in terms of growth characteristics. This intra-specific variation in biomass accumulation under elevated CO₂ levels could be exploited for future breeding programmes in developing climate ready genotypes having greater potential to sequester more carbon and produce greater biomass under forecasted elevated levels of atmospheric CO₂. Another objective in this study was to analyze intra-specific variation in selected biometrical and biochemical characteristics of leaf samples of neem trees in relation to their differential response to elevated CO₂. Among parameters of leaf, Fumaric acid, Malic acid and Oxalic acid, leaf Nitrogen and Specific Leaf Weight may be considered as a biochemical and biometrical marker to categorize the plants adapted to elevated CO₂ environments.