|KIMBALL B A|
|IDSO S B|
|PINTER P J JR|
|WALL G W|
|GARCIA R L|
|HUNSAKER D J|
|LAMORTE R L|
|HENDRIX D L|
Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/1996
Publication Date: N/A
Interpretive Summary: The CO2 concentration of the atmosphere is increasing and is expected to double sometime during the next century. Such an increase in CO2 concentration is expected to stimulate the growth of plants, although different species may respond differently or in varying degrees to the elevated CO2. The elevated CO2 may also affect the production of various biochemical compounds within the plants, and in this study, the effects on phenolics were determined. Phenolics are bad-tasting secondary compounds that plants make to help defend themselves from herbivores such as leaf- eating insects. We found that elevated CO2 increased the phenolic content of wheat leaves slightly, had little effect in sour orange leaves, and decreased the phenolic content of pine tree needles. The changes in phenolic contents were in inverse proportion to the amount of growth stimulation of the CO2. Thus, the greater the growth stimulation, the relatively less the plants made phenolics for herbivore protection. Information such as this is needed to help predict the consequences of the future high CO2 concentrations on agricultural productivity and on natural ecosystems.
Technical Abstract: A wide range of responses to elevated CO2 was found for leaf total phenolic content of one grass species (wheat) growing in a Free-Air CO2 Enrichment system and two woody species (orange and pine trees) growing in Open-Top chambers. The total phenolic content of wheat flag leaves from elevated CO2 was increased for most of the grain-filling stages; there was no significant change in phenolic content of CO2 enriched orange tree leaves; and CO2 enriched pine tree needles had reduced total phenolic content. There was an inverse relationship between the changes in leaf total phenolic content and increases in biomass. The same trend has been found recalculating data reported in the literature. When and where increases in biomass were larger, plants accumulated less phenolics. These data suggest that a change in the priority of partitioning occurs, rather than a simple dilution by carbohydrates. The data fit better to the more general growth-differentiation balance theory than to the more particular carbon-nutrient balance theory.