Awns play a dominant role in carbohydrate production during the grain‐filling stages in wheat (Triticum aestivum)

Abstract

In wheat (Triticum aestivum L), the leaves particularly flag leaves have been considered to be the key organs contributing to higher yields, whereas awns have been considered subsidiary organs. Compared with extensive investigations on the assimilation contribution of leaves, the photosynthetic characteristics of awns have not been well studied. In this study, we investigated the ultrastructure of chloroplasts, oxygen evolution, and phosphoenolpyruvate carboxylase [phosphoenolpyruvate carboxylase (PEPCase) EC 4.1.1.31)] activity in both flag leaves and awns during the ontogenesis of wheat. Transmission electron microscope observations showed initial increases in the sizes of grana and the degree of granum stacks from the florescenceemergence stage both in flag leaves and in awns, followed by the breakdown of membrane systems after the milk-development stage. The results of oxygen evolution assays revealed that in both organs, the rate of photosynthesis increased in the first few stages and then decreased, but the decrease occurred much earlier in flag leaves than in awns. A PEPCase activity assay demonstrated that the activity of PEPCase was much higher in awns than in flag leaves throughout ontogeny; the value was particularly high at the late stages of grain filling. Our results suggest that awns play a dominant role in contributing to large grains and a high grain yield in awned wheat cultivars, particularly during the grain-filling stages.

Genetic Yield Potential Improvement of Semidwarf Winter Wheat in the Great Plains

“…The rate of genetic gain is significant but significantly lower than that of the awned semidwarf cultivars if awnless cultivars are analyzed separately for genetic yield increase over time (data not shown). This increase in performance from awnless to awned cultivars may be due to lack of awn photosynthesis that occurs during maturation (Li et al, 2006); however, Table 4. Site years for wheat genetic yield potential trial with coefficient of variation, mean yields with and without fungicide treatment (kg ha -1 ), change in yield due to fungicide treatment, and significance of fungicide treatment.…”

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

“…in barley, Biscoe et al, 1973;Bort et al, 1994; in wheat, Li et al, 2006). The contribution of awns to total ear net photosynthesis is high, reaching 50% or more in some cases (see Tambussi et al, 2007 and references cited therein).…”

Important photosynthetic contribution from the non-foliar green organs in cotton at the late growth stage

“…Consideration and modeling of photosynthesis are usually restricted to leaves, but many parts of the plant besides leaves contain chlorophyll and, therefore, capture light energy to perform photosynthesis. Evidence of photosynthetic activity of non-foliar organs has been found in, for example, the panicles of rice (Ishihara et al 1991), the ear of wheat (Singal et al 1986;Araus et al 1993;Li et al 2006), the spikes of barley (Duffus and Cochrane 1993), and the fruit in tomato (Xu et al 1997). It is now accepted that photosynthesis of non-foliar green organs is an important, additional contribution to carbon acquisition and yield (Aschan and Pfanz 2003).…”

“…Although the photosynthetic capacity of non-foliar organs of cotton has been analyzed by the gas exchange technique or in an anatomical investigation (Wullschleger and Oosterhuis 1990;Bondada et al 1994;Bondada and Oosterhuis 2000), there is little information about the activities of carbon fixation enzymes in cotton, as has been studied in the ear of wheat (Singal et al 1986;Li et al 2006).…”