|Rogers Jr, Hugo|
|Runion, G - AUBURN UNIVERSITY|
|Mitchell, R - JONES ECOLOGICAL RES CTR|
Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 23, 1996
Publication Date: N/A
Interpretive Summary: We examined the influence of atmospheric CO2 concentration on root to shoot allocation. It is clear that much remains to be done and evident from the highly variable data base that additional parameters will need to be controlled or recorded in future experiments. With regard to root-shoot allocation, we do know that it is highly dynamic in nature and its response to elevated atmospheric CO2 may well depend on prevailing environmental conditions. In this review elevated CO2 increased root to shoot ratio in 59.5% cases, decreased this ratio in 37.5% cases and did not change this measure in 3.0% of the cases. These variable results were probably related to such factors as either crop type and/or resource supply. To better understand how elevated CO2 will impact the biosphere, we need to amplify our understanding of the mechanisms that regulate partitioning, how they work, and how they are controlled (by genes and other exogenous factors, and by atmospheric and edaphic resources). The flow of carbon within the crop plant is key to our predictions of how global change will affect future agro-ecosystems. An understanding of carbon allocation in crops will be useful, not only in predicting agriculture's response to a high CO2 world, but also in helping to met our goals of increasing crop productivity and cultivating sustainable agro-ecosystems. Clarification of the root to shoot relationship in the context of high CO2 would be a good starting point. A greater knowledge of crop carbon dynamics will better enable us to feed ourselves and six billion fellow inhabitants.
Technical Abstract: Crops of tomorrow are likely to grow under higher levels of atmospheric CO2. Fundamental crop growth processes including yield will be affected. Among these processes is carbon allocation. Allocation is regulated by source-sink relationships. As dynamic functions within plants modulate inputs from the environment, the various plant organs receive photosynthetically derived products according to their various demands and the availability of these products. The plant must integrate incoming stimuli from both above and below the ground in order to optimize its functions either to survive if there are resource limitations, or to flourish if there are not. The root to shoot ratio (R:S) depends upon the partitioning of photosynthate which may be influenced by environmental stimuli. Exposure of plant canopies to high CO2 concentration often stimulates growth. The question here is whether elevated CO2 will affect root and shoot of crop plants proportionally. Since elevated CO2 can induce changes in plant structure and function, there may be differences in allocation between root and shoot. The effect of elevated CO2 on carbon allocations has yet to be fully elucidated, especially in the context of changing resource availability. Herein we provide a survey of the extant data (which are quite variable) on the response of root to shoot allocation in crops. In many cases (59.5%) R:S increased, in a very few (3.0%) remained unchanged, and in others (37.5%) decreased. The explanation for these differences probably resides in either crop type or resource supply. Efforts to understand allocation under CO2 enrichment will add substantially to the global change response data base.