Papers by Keyword: Elevated CO2

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Authors: Oh Hyun Kyung, Yeonsook Choung
Abstract: The response of Quercus mongolica, one of the major tree species in Northeast Asia and the most dominant deciduous tree in Korea, was studied in relation to elevated CO2 and the addition of nitrogen to soil in terms of its physiology and growth over two years. Plants were grown from seed at two CO2 conditions (ambient and 700 µL L-1) and with two levels of soil nitrogen supply (1.5 mM and 6.5 mM). Elevated CO2 was found to significantly enhance the photosynthesis rate and water use efficiency by 2.3-2.7 times and by 1.3-1.8 times, respectively. Over time within a growing season, there was a decreasing trend in the photosynthesis rate. However, the decrease was slower especially in two-year-old seedlings grown in elevated CO2 and high nitrogen conditions, suggesting that their physiological activity lasted relatively longer. Improved photosynthesis and water use efficiency as well as prolonged physiological activity under high CO2 condition resulted in an increase in biomass accumulation. That is, in elevated CO2, total biomass increased by 1.7 and 1.2 times, respectively, for one- and two-year-old seedlings with low nitrogen conditions, and by 1.8 and 2.6 times with high nitrogen conditions. This result indicates that the effect of CO2 on biomass is more marked in high nitrogen conditions. This, therefore, shows that the effect of CO2 is accelerated by the addition of nitrogen. With the increase in total biomass, the number of leaves and stem diameter increased significantly, and more biomass was allocated in roots, resulting in structural change. Overall, the elevated CO2 markedly stimulated the physiology and growth of Q. mongolica. This demonstrates that Q. mongolica is capable of exploiting an elevated CO2 environment. Therefore, it will remain a dominant species and continue to be a major CO2 sink in the future, even though other resources such as nitrogen can modify the CO2 effect.
Authors: Wei Huang, Xing Yuan He, Chang Bing Liu, De Wen Li
Abstract: To investigate the effect of elevated CO2 and O3 on the accumulation of flavonoids in Ginkgo Biloba leaves, four-year-old trees were exposed in open-top chambers with ambient and twice ambient CO2 and O3 concentrations singly and in combination in 2006. The results show that elevated CO2 reduce the concentrations of keampferol aglycon (-10%), isorhamnetin aglycon (-15%). Elevated O3 reduce the concentrations of the isorhamnetin aglycon (-7%), but increase the concentration of quercetin aglycon (+6%). Under elevated CO2 and O3 in combination, O3-derived effects on flavonoids concentrations are changed by elevated CO2, which are similar to that under the elevated CO2 alone. In conclusion, the concentrations of flavonoids are influenced by the changes in leaf dry mass induced by elevated CO2 and elevated O3. Furthermore, some flavonoids may not respond as antioxidant under ozone stress in ginkgo leaves.
Authors: Xia Jia, Chun Juan Zhou
Abstract: The effect of long-term elevated CO2 (as open top chambers) on rhizosphere and bulk bacterial community structure in Pinus sylvestriformis seedlings field was investigated in July, August, and September. The bacterial communities were processed by Denaturing Gradient Gel Electrophoresis (DGGE) analysis of bacterial 16S rDNA fragments amplified by PCR (Polymerase Chain Reaction) from DNA extracted directly from soil. DGGE profiles from rhizosphere samples showed large changes in rhizosphere bacterial community under elevated CO2 compared to ambient except for that in September. For bulk samples, bacterial community structure changed when exposed to elevated CO2 in three months. With the exception of bulk samples in August, a similitude of bacterial communities structures existed between different elevated CO2 concentrations by analyzing UPGMA dendrogram based on Jaccard’s coefficient.
Authors: Jiang Yan Gao, Sheng Xu, Wei Chen, Xing Yuan He
Abstract: Changes of oxidative stress and antioxidant system were studied in leaves of Ginkgo biloba exposed to elevated CO2 and O3 fumigation (2006-2008), and released the gases fumigation for the natural recovery in open-top chambers (OTCs) during the growing season in 2009. Elevated CO2 had no significant effect on hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents, and the activities of antioxidant enzymes in leaves of G. biloba during the gas fumigation in 2008. Elevated O3 increased significantly H2O2 and MDA contents, especially after 90 days of gas fumigation. The adverse effect or damage of elevated O3 on trees during the gas fumigation was also alleviated by the released-O3 exposure during the natural recovery. The antioxidative enzyme including superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities showed higher levels under the natural recovery than under the gas fumigation, which may be a helpful response to scavenging reactive oxygen species (ROS). The results also indicated that future alleviating the emissions of CO2 and O3 would differentially affect the antioxidant system in plants.
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