One of the questions arising from experiments dealing with CO2 and temperature is whether crop responses are strongly positive or weakly positive to the combined effects of elevated CO2 and high temperature. Due to temporal and spatial differences in crop responses to elevated CO2 and high temperature, it is currently impossible to clearly state the stimulatory effects of elevated CO2 at high temperature. Therefore, it seems appropriate that we suggest a possible range for crop performance under these environmental conditions (Fig. 1.2).
In order to investigate in-depth the effects of climate change on crops, future studies should consider plant performance under simulated future climate, using all available techniques and tools, including ecological, physiological, biochemical and molecular, in large scale multi-factorial experiments.
It has been predicted that global warming leads to many changes in the environment that may affect the interactive effects of CO2 and temperature (Tables 1.2 and 1.3). Hence, it is better to design experiments, which include other important factors
Fig. 1.2 Crop responses to the combined effects of CO2 and temperature
Ambient Carbon Dioxide
Elevated Carbon Dioxide
besides CO2 and temperature. Such experiments can be conducted in the field, using free-air CO2 enrichment (FACE) and free-air temperature increase (FATI) (Nijs et al. 1997), which closely represent future high-CO2 and high-temperature world. Results from the multi-factorial experiments should allow plant biologists to create models, which can predict the effects of global climate change on crops more realistically.
Relatively recent studies that demonstrate the protective aspects of biogenic volatile organic compounds (BVOCs) from plants against global warming are encouraging. For example, Pefluelas and Llusia (2003) have suggested that some of the assimilated carbon that is returned to the atmosphere as BVOCs could protect plants from the negative effects of high temperature.
Although crop yields will inevitably be influenced by climate change in the future, it is possible that through enhanced technology, improved agronomic and management practices, and development and use of stress-tolerant varieties, crop production may remain stable and retain its sustainability under conditions of increased atmospheric CO2, despite the adverse effects of global warming.
Acknowledgments We thank the Natural Sciences and Engineering Research Council (NSERC) of Canada for financial support through a Discovery grant to D. M. Reid.
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