Respiration and Dry Matter Accumulation Around the Time of Anthesis in Field Stands of Winter Wheat (Triticum aestivum)

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Abstract
Rates of CO2 efflux from the aerial parts of eight winter wheat (Triticum aestivum L. em Thell) genotypes were determined during spike emergence, anthesis and early grain filling over two seasons. Dry weight data were also recorded at flag leaf full expansion and anthesis Respiration rates on a ground area basis did not differ (P > 0–05) among the times of day when measurements were made. In contrast, highly significant day-to-day effects (P > 0–001) were evident. Daily respiratory efflux was consistently high during spike emergence, declining to lower values before and after anthesis in each year. Changes in daily respiration were analysed in terms of a two-parameter respiration model. Model predictions suggested that changes in chemical composition of the dry matter formed during ontogeny could explain the day-to-day effect Although no genotypic differences in respiration (ground area basis) and crop growth rate were found, significant negative correlations between crop d. wt and respiration rate per unit d. wt were evident. Genotypic differences in crop d. wt also became more distinct from the first harvest to the second. These observations are discussed in terms of genotypic variation in maintenance respiration