Ear and flag leaf photosynthesis of awned and awnless Triticum species

Abstract

The net photosynthetic rates of ears and flag leaves of awned and awnless wheats were measured by infra-red gas analysis in a controlled environment experiment. At 107 W m--2 the rates of net photosynthesis of the ears of two awned Triticum aestivum lines were two to three times greater than those of their isogenic awnless counterparts. The net rates of photosynthesis of the flag leaves of all four lines were, however, similar. Net photosynthetic rates of ears of T . durum and T . turgidum, which have much larger awns, were considerably higher than those of T . aestivum. Between 70 and 90% of carbon-14 assimilated by the flag leaves and by the ears of T . aestivum was translocated to the grains, with no effect of awns in this respect.In a glasshouse experiment with detached shoots the contributions of the component organs to gross photosynthesis were determined by carbon-14labelling. Ears of awnless lines of T . aestivum contributed about 10 yo to the photosynthesis of the organs above the node of the penultimate leaf and awns increased this to about 18%. Fixation by awned ears of T . durum and T . turgidum was 21~29% and of this 78-86% was contributed by the awns.In both experiments the contribution of the flag leaf to shoot photosynthesis was greater in T . aestivum than in the other species.

Comparison of flag leaf and ear photosynthesis with biomass and grain yield of durum wheat under various water conditions and genotypes

“…The contribution of awns to the total photosynthetic area of ears may be important. Thus differences in whole-ear area, as a consequence of differences in the total area of awns, accounts for the greater ear photosynthesis in barley than in bread wheat [15] and in tetraploid wheat than in hexaploid wheat [21]. Nevertheless, in Blum [5] net photosynthesis rates per unit area in the ear of the tetraploid wheat were only 25% of those of flag leaves.…”

The contribution of the awns of bread wheat (Triticum aestivum L.) to grain filling: Responses to water deficit and the effects of awns on ear temperature and hydraulic conductance

“…Jiang et al, 2006;Li et al, 2006;Olugbemi et al, 1976), their contribution to grain filling is not well known, and even controversial (e.g. McKenzie, 1972;see Tambussi et al, 2007 and references therein).…”

Wheat flour protein content and water absorption analysis in a doubled haploid population

“…Most of the previous studies have been focused on the awn phenotype ignoring the conferring locus. In general, research has centred on effects of the awn phenotype on grain yield and photosynthesis (Olugbemi et al, 1976;Weyhrich et al, 1994), largely ignoring potential effects on quality attributes. Two previous reports have indicated that awn phenotype is related to grain protein content (Ibrahim and Abo Elenein, 1977;Sharma et al, 1983).…”