CROP AND WEED RESPONSES TO INCREASING ATMOSPHERIC CARBON DIOXIDE
Title: Empirical selection of cultivated oat in response to rising atmospheric carbon dioxide
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 1, 2007
Publication Date: July 1, 2007
Citation: Ziska, L.H., Blumenthal, D.M. 2007. Empirical selection of cultivated oat in response to rising atmospheric carbon dioxide. Crop Science. 47(4)1547-1552.
Interpretive Summary: All plants rely on four resources in order to grow: light, nutrients, water, and carbon dioxide. Any change in the availability of these resources will alter plant growth. Since 1960 the amount of carbon dioxide in the atmosphere has increased by 21%. Given this change, has any effort been made to select for crop varieties that can use this additional carbon dioxide to make more seed? Is such an effort even needed, if breeders have already, by default, selected these varieties? To answer these questions, we examined 14 different varieties of oat from seven locations in Europe and N. America. For each location a variety of oat from the 1920s was compared to one from the 1990s to see if the modern varieties were more CO2 responsive. We did not find any evidence that modern oat varieties were more responsive to carbon dioxide. In fact, we saw that the older oat lines were more responsive. This suggests that a more active effort is needed on the part of agronomists, physiologists, and breeders to select for carbon dioxide responsive varieties in order to utilize the additional carbon dioxide in the atmosphere as a means to positive increase seed yield. These data and conclusions will be of interest to plant scientists, extension specialists, plant breeders, and the general public.
Carbon dioxide (CO2) is a principle resource for plant growth; as such, the ongoing increase in its concentration may allow breeders to begin selecting for optimal varieties among current crop lines. However, such a selection program may not be necessary if breeders have, by empirical selection, already chosen the most CO2 responsive cultivars. To test this hypothesis, we examined the growth and vegetative characteristics of individual plants of cultivated oat (Avena sativa) from seven geographical locations in the United States and Europe. For each location we examined responses of lines that had been released early and late in the 20th century to [CO2] increases that corresponded roughly to the [CO2] from the 1920s, the current [CO2], and the [CO2] projected for the middle of this century, (300, 400 and 500 µmol mol-1, respectively). In contrast to our predictions, newer lines were less responsive than older lines to rising [CO2] in terms of both leaf area and tiller number. Biomass and growth characteristics, such as relative growth rate or leaf area ratio, showed no differences in CO2 responsiveness as a function of when the cultivar was released. A comparison of phenotypic variability indicated that for almost all measured parameters, older lines had a greater degree of intraspecific variability (i.e. newer lines were more uniform). Our results suggest that for oat: (a) newer lines are not intrinsically more responsive to rising CO2 levels than older lines; and (b) phenotypic homogenization among modern lines could hamper efforts to identify desirable characteristics associated with CO2 responsiveness.