Martin Erbs

Effects of elevated atmospheric CO2 concentrations on the quantitative protein composition of wheat grain.

The continuing increase in atmospheric CO 2 concentration is predicted to enhance biomass production and to alter biochemical composition of plant tissues. In the present study, winter wheat ( Triticum aestivum L. cv. Batis) was grown under ambient air (BLOW, CO 2 concentration: 385 muL L (-1)) and free-air CO 2 enrichment (FACE, CO 2 concentration: 550 muL l (-1)) and two different nitrogen (N) fertilization levels (normal N supply: N100, 50% of normal N supply: N50). Mature kernels were milled into white flour and analyzed for the contents of crude protein, Osborne fractions, single gluten protein types and glutenin macropolymer. Elevated CO 2 caused significant reductions in crude protein and all protein fractions and types ( p < 0.001) except albumins and globulins. Effects were more pronounced in wheat samples supplied with normal amounts of N fertilizer. Crude protein was reduced by 14% (N100) and 9% (N50), gliadins by 20% and 13%, glutenins by 15% and 15% and glutenin macropolymer by 19% and 16%, respectively. Within gliadins, omega5-gliadins (-35/-22%) and omega1,2-gliadins (-27/-14%) were more affected than alpha-gliadins (-21/-13%) and gamma-gliadins (-16/-12%). Within glutenins, HMW subunits (-23/-18%) were more affected than LMW subunits (-12/-15%). According to these results, flour from high CO 2 grown grain will have a diminished baking quality. To our knowledge, these are the first results of elevated CO 2 concentrations impacts on wheat grain protein composition gained under relevant growing conditions at least for Central Europe.

Atmospheric carbon dioxide enrichment effects on ecosystems — experiments and the real world

The beneficial effect of atmospheric CO2 on the growth of plants has been known since 1804 (De Sassure 1804; cited in Kimball et al. 1993), and its role as a C source for vegetation was proven by Justus von Liebig 125 years ago. Atmospheric CO2 enrichment has been used to promote the growth of legumes in greenhouse cultures for >50 years. As early as 1961, greenhouses covering >1,600 ha were under enriched CO2 in the Netherlands alone. However, only after atmospheric CO2 concentrations had been recorded from continuous monitoring sites such as the Mauna Loa Observatory at Hawaii, where [CO2] has been recorded since 1958, was there a growing awareness that CO2 enrichment occurs on a global scale and that it affects ecosystems throughout the world. In 2005, the concentration of atmospheric CO2 will be around 380 μmol mol −1; thus already exceeding by ca. 35% the background concentration of ca. 280 μmol mol−1 before the beginning of industrialization. A further increase to at least 550 μmol mol−1 will have occurred by the end of this century (IPCC 2001). Consequently, numerous studies have been performed to test the response of vegetation and ecosystems to CO2 enrichment, and great progress has been made in developing experimental facilities and in our understanding of biosphere–atmosphere interactions with respect to CO2 by means of both experimentation and modelling. CO2 enrichment effects on crops were reviewed as early as the mid 1980s by Cure and Acock (1986) who reported an average increase in C3 crop yield due to CO2 doubling of approximately 41%. A mechanistic understanding of the physiological background for this CO2 fertilization effect in C3 plants that has been widely accepted was provided by von Caemmerer and Farquhar (1981). This CO2 gas exchange model for C3 plants was later extended and modified by Sage (1994) and other authors to explain photosynthetic acclimation to CO2 enrichment. Down-regulation of photosynthesis in C3 plants

Effects of free air carbon dioxide enrichment and drought stress on the feed value of maize silage fed to sheep at different thermal regimes

Information about the effects of rising atmospheric CO2 concentration and drought on the feed value of maize silage and interactions with the thermal environment during feeding is limited. A free air carbon dioxide enrichment facility was operated in a maize field to generate an elevated CO2 concentration of 550 ppm. Drought was induced by the exclusion of precipitation in one half of all experimental plots. Plants were harvested, chopped and ensiled. In a balance experiment on sheep, the nutrient digestibility was determined for three climatic treatments (temperate, temperature humidity index (THI) 57–63; mild heat, THI 68–71; severe heat, THI 75–80). The CO2 concentration and drought did not alter the crude nutrient content of silage dry matter (DM) or nutrient and organic matter (OM) digestibility. Drought increased the concentration of deoxynivalenol (DON, p < 0.001). The drought-associated increase of DON was reduced by CO2 enrichment (p = 0.003). The lowest digestibility of acid detergent fibre (p = 0.024) and neutral detergent fibre (p = 0.005) was observed during the coldest climate. OM digestibility increased during mild heat (p = 0.023). This study did not indicate considerable alterations of the feed value of maize silage due to increased atmospheric CO2 and drought. Enriched CO2 may decrease DON contaminations during drought. The thermal environment during the balance experiment did not interact with feeding maize silage grown under elevated CO2, but may affect cell wall and OM digestibility.

Free-air CO2 enrichment modifies maize quality only under drought stress

Climate scenarios show that atmospheric CO2 concentrations will continue to increase. As a consequence, more frequent and severe drought periods are expected. Drought will thus modify plant growth. Although maize is a major crop globally, little information is available on how atmospheric and climatic changes will change maize quality. Here, in a field experiment, maize was grown in 2007 and 2008 under ambient (380xa0ppm) and elevated CO2 (550xa0ppm) using free-air CO2 enrichment. In 2007, maize was grown under well-watered conditions only. In 2008, we applied a drought stress treatment in which the plants received only half the amount of water of the well-watered treatment. We measured the concentrations of minerals and quality-related traits in aboveground biomass and kernels at the end of each growing season. Results show first the absence of effect of elevated CO2 under well-watered conditions. By contrast, drought stress modified several traits and interactions under elevated CO2. These results support the hypothesis that the C4 plant maize does not react to an increase in atmospheric CO2 as long as no drought stress is prominent. This finding contrasts with the impact of elevated CO2 on C3 plants. Several drought stress effects found in our study will have important implications for food and feed use. However, the effects of drought stress on the traits were less pronounced under elevated CO2 than under ambient CO2 level. Hence, an elevated CO2 concentration mitigates the drought stress impacts on elemental composition and quality traits of maize.

Effects of the thermal environment on metabolism of deoxynivalenol and thermoregulatory response of sheep fed on corn silage grown at enriched atmospheric carbon dioxide and drought

Future livestock production is likely to be affected by both rising ambient temperatures and indirect effects mediated by modified growth conditions of feed plants such as increased atmospheric CO2 concentrations and drought. Corn was grown at elevated CO2 concentrations of 550xa0ppm and drought stress using free air carbon dioxide enrichment technology. Whole plant silages were generated and fed to sheep kept at three climatic treatments. Differential blood count was performed. Plasma DON and de-epoxy-DON concentration were measured. Warmer environment increased rectal and skin temperatures and respiration rates (pu2009<u20090.001 each) but did not affect blood parameters and the almost complete metabolization of DON into de-epoxy-DON. Altered growth conditions of the corn fed did not have single effects on sheep body temperature measures and differential blood count. Though the thermoregulatory activity of sheep was influenced by the thermal environment, the investigated cultivation factors did not indicate considerable impacts on the analysed parameters.