The response of wheat to elevated carbon dioxide concentration (e[CO2]) is likely to be dependent on nitrogen supply. To investigate the underlying mechanism of growth response to e[CO2], two wheat cultivars were grown under different carbon dioxide concentration [CO2] in a chamber experimental facility. The changes in leaf photosynthesis, C and N concentration, and biomass were investigated under different [CO2] and N supply. The result showed an increase in photosynthesis under e[CO2] at all N level except the one with the lowest N supply. Furthermore, a significant decrease in g(s) and Tr for both the cultivars was also observed under e[CO2] at all N levels. A considerable increase in WUEi was observed for both the cultivars under e[CO2] at all N levels except for the lowest concentration one. Therefore, the study shows that a stimulation of plant growth under e[CO2] to be marginal at higher N supply.

Atmospheric carbon dioxide conditions predicted for future climates cause increases in wheat biomass, but also decreases wheat grain protein concentration. We investigated the response of grain protein concentration of wheat to elevated carbon dioxide in nineteen wheat genotypes, including five tetraploid, eleven hexaploid and three synthetic hexaploid genotypes to test whether decreased grain protein is genotype dependent and whether it is caused by biomass dilution. These were grown in ambient and elevated carbon dioxide conditions simultaneously. Shoot biomass and grain samples were taken at maturity. The grain protein concentration, grain biomass, shoot biomass and harvest index were analysed for each genotype. Despite most genotypes increasing in total grain protein (g), the majority of genotypes decreased in grain protein concentration (%) under elevated carbon dioxide. Elevated carbon dioxide caused an increase in grain biomass for all genotypes and total shoot biomass for most genotypes, with harvest index increasing for all genotypes except the two synthetic hexaploids CPI133814 and CPI133811. Most of the differences between wheat types were not statistically significant, suggesting that the individual genotype of wheat plants determines the response to elevated carbon dioxide rather than the wheat type.

Rising atmospheric carbon dioxide concentration ([CO2]) significantly influences plant growth, development, and biomass. Increased photosynthesis rate, together with lower stomatal conductance, has been identified as the key factors that stimulate plant growth at elevated [CO2] (e[CO2]). However, variations in photosynthesis and stomatal conductance alone cannot fully explain the dynamic changes in plant growth. Stimulation of photosynthesis at e[CO2] is always associated with post-photosynthetic secondary metabolic processes that include carbon and nitrogen metabolism, cell cycle functions, and hormonal regulation. Most studies have focused on photosynthesis and stomatal conductance in response to e[CO2], despite the emerging evidence of e[CO2]'s role in moderating secondary metabolism in plants. In this review, we briefly discuss the effects of e[CO2] on photosynthesis and stomatal conductance and then focus on the changes in other cellular mechanisms and growth processes at e[CO2] in relation to plant growth and development. Finally, knowledge gaps in understanding plant growth responses to e[CO2] have been identified with the aim of improving crop productivity under a CO2 rich atmosphere.

To elucidate the mechanism of plant growth we investigated chromosome region affecting traits (CRATs) using the chromosome segment substitution lines derived from a cross between japonica 'Koshihikari' and indica 'Kasalath' using rice (Oryza sativa L.). Four CRATs associated with increased plant growth rate were identified which were derived from 'Kasalath' alleles on chromosomes 1, 6, 8 and 12. This was achieved by evaluating the net dry weight gain from seed germination to 30 day-old seedlings. Physiological analysis of substitution lines containing a 'Kasalath' allele chromosome segment in the 'Koshihikari' background revealed that the CRAT on chromosome 1 (EGR1) increased the relative growth rate by increasing the net assimilation rate (NAR), and increased expression of the OsSPS1 gene that encodes the rate-limiting enzyme in sucrose synthesis. In contrast, CRATs on chromosomes 6, 8 and 12 (EGR6, EGR8 and EGR12) were associated with an increased uptake of NH4 (+), the major nitrogen source for rice. These results suggest that early growth of rice is controlled by multiple traits and sucrose biosynthesis and NH4 (+) uptake play key roles.