The influence of atmospheric CO2 concentration on the protein, starch and mixing properties of wheat flour

Abstract

Wheat (Triticum aestivum L.) cultivars Hartog and Rosella were grown at CO2 concentrations of 280 µL L-1 (representing the pre-industrial CO2 concentration), 350 µL L-1 (ambient) and 900 µL L-1 (an extreme projection of atmospheric CO2 concentration). The plants were grown in naturally lit glasshouses in 7 L pots containing soil to which basal nutrients had been added and the pH adjusted to 6.5. Hartog yielded 2.4 g of grain per plant when grown at 280 µL CO2 L-1. This yield was increased by 38% and 75% at CO2 concentrations of 350 µL L-1 and 900 µL L-1 respectively. These changes were due to increases in both grain number and individual grain weight as the level of CO2 was raised. The yield of Rosella was unaffected by altering the CO2 concentration. Increasing the CO2 concentration reduced grain protein concentration of cv. Hartog from 17.4% at 280 µL CO2 L-1 to 16.5% and 16% at CO2 concentrations of 350 µL L-1 and 900 µL L-1 respectively. The grain protein concentration of cv. Rosella was reduced from 10.7% to 10.2% by increasing the CO2 concentration from 280 µL L-1 to 350 µL L-1; however, an additional increase in the CO2 concentration to 900 µL L-1 had no effect on grain protein concentration. In Hartog flour, the highest proportion of polymeric protein in the flour (7.7%) occurred at 280 µL CO2 L-1. This was reduced to 6.3% at 350 µL CO2 L-1 but then increased again to 7.0% at 900 µL CO2 L-1. These changes in concentration of polymeric protein were correlated (r2=0.58) with changes in mixing properties. The mixing time required to produce optimum dough strength was greatest at 900 µL CO2 L-1 (181 s), then 141 s and 151 s at 350 µL CO2 L-1 and 280 µL CO2 L-1 respectively. These changes in mixing time could not be explained by changes in grain protein concentration. The proportion of ‘B’ starch granules (<10 m diameter) increased from 25% of total weight of starch at 280 L CO2 L-1 to 30% at CO2 concentrations 350 and 900 µL L-1. There were generally no effects of CO2 concentration on dough mixing properties or starch granule size distribution for Rosella.

Exposure to preindustrial, current and future atmospheric CO2 and temperature differentially affects growth and photosynthesis in Eucalyptus

“…This contrasts with an average 25% reduction in plant dry mass production at subambient [CO 2 ] for a range of species grown at various temperatures (Sage & Coleman, 2001). Nevertheless, our results are supported by a number of studies which reported no growth inhibition in response to decreasing [CO 2 ] from current ambient to preindustrial levels in C 3 plants such as winter wheat (Rogers et al , 1998) and barley (Cunniff et al , 2008). Particularly significant to our study was the report by Rogers et al (1998) that the growth responsiveness to subambient [CO 2 ] depended on the wheat cultivar.…”

Quantitative and qualitative evaluation of selected wheat varieties released since 1903 to increasing atmospheric carbon dioxide: can yield sensitivity to carbon dioxide be a factor in wheat performance?

“…From the current study, and others (e.g. Mandersheid & Weigel, 1997; Hakala, 1998; Rogers et al , 1998; Kimball et al , 2001) it is clear that rising [CO 2 ] is an environmental parameter that results in additional wheat productivity at the whole‐plant level. Preliminary studies for a number of crop species have indicated significant variation in yield among cultivars in response to elevated [CO 2 ] (reviewed in Hall & Ziska, 2000).…”

Effects of environmental factors on cereal starch biosynthesis and composition

“…(1995) observed a higher proportion of the large A-granules, while Rogers et al (1998) found a higher proportion of the small Bgranules in response to higher CO 2 (Table 2).…”

“…In general, changes in starch morphology and composition were unpredictable (Table 2). It appears that the mode of introducing CO 2 , the concentration and the genotype studied probably influence the data (Rogers et al, 1998). For example, Blumenthal et al…”

“…Abscisic acid (ABA) modulates whole suites of genes in response to stress often in cross-talk with sugar signaling (Rook et al, 2006), and changes in starch biosynthetic enzyme activity would be an expected downstream response to an ABA-dependent stress-signaling cascade (Zheng et al, 2010). Such networks may be essential in wheat (Yang et al, 2003), rice (Zhang et al, 2012a) and barley (Seiler et al, 2011) during grain filling because endogenous ABA accumulates and correlates positively with higher grain starch in the moderately water-stressed grain; and, in the rice and wheat studies, these changes were accompanied by increases in SuSy, SBE and SS activity (Yang et al, 2003;Zhang et al, 2012a).…”