Jacques Berner
North-West University, South Africa
Title: Changes in the photosynthetic efficiency of sugarcane (Saccharum sp.) when fumigated with CO2 and O3
Biography
Biography: Jacques Berner
Abstract
Global CO2 concentrations have been rising during the past few decades and it is expected that these levels will reach 550 ppm by next century. Together with rise in global CO2 levels is the increase in in surface O3 due to increases in anthropogenic sources. Surface O3 is regarded as a very serious air pollutant, causing damage to all forms of live. Crops are especially vulnerable to O3 stress and significant loss to yields have been reported. In this study we investigated the effect of elevated CO2, O3 and a combination of elevated CO2 and O3 on the light dependent photosynthetic reactions of sugarcane. Two sugarcane varieties, N31 and NCo376 were exposed to 750 ppm CO2, 80 ppm O3 and a combination of 750 ppm CO2 and 80 ppb O3 in open-top chambers. Chlorophyll a fluorescence analysis was used to investigate the effects on the light dependent photosynthetic reactions. Elevated CO2, O3 and the combination treatment all effected the photosynthetic efficiency, but the two varieties responded differently to these conditions. Analysis of the OJIP kinetics indicated that elevated CO2 resulted in an early decline in the ability of the plant to create a charge separation in the photosynthetic reaction centers of PSII of NCo376. Electron transport between PSII and PSI of NCo376 was also reduced, whereas these reactions of N31 reduced much later. The effect of O3 was less dramatic, but the results did indicate that N31 had a higher tolerance level to O3 compared to NCo376. A combination of 80 ppb O3 and 750 ppb CO2 does indicate that elevated levels of CO2 can ameliorate the negative impacts of O3 on the photosynthetic efficiency.
