The structural and photosynthetic characteristics of the exposed peduncle of wheat (Triticum aestivumL.): an important photosynthate source for grain-filling

Abstract

BackgroundIn wheat (Triticum aestivum L), the flag leaf has been thought of as the main source of assimilates for grain growth, whereas the peduncle has commonly been thought of as a transporting organ. The photosynthetic characteristics of the exposed peduncle have therefore been neglected. In this study, we investigated the anatomical traits of the exposed peduncle during wheat grain ontogenesis, and we compared the exposed peduncle to the flag leaf with respect to chloroplast ultrastructure, photosystem II (PSII) quantum yield, and phosphoenolpyruvate carboxylase (PEPCase; EC 4.1.1.31) activity.ResultsTransmission electron microscope observations showed well-developed chloroplasts with numerous granum stacks at grain-filling stages 1, 2 and 3 in both the flag leaf and the exposed peduncle. In the exposed peduncle, the membranes constituting the thylakoids were very distinct and plentiful, but in the flag leaf, there was a sharp breakdown at stage 4 and complete disintegration of the thylakoid membranes at stage 5. PSII quantum yield assays revealed that the photosynthetic efficiency remained constant at stages 1, 2 and 3 and then declined in both organs. However, the decline occurred more dramatically in the flag leaf than in the exposed peduncle. An enzyme assay showed that at stages 1 and 2 the PEPCase activity was lower in the exposed peduncle than in the flag leaf; but at stages 3, 4 and 5 the value was higher in the exposed peduncle, with a particularly significant difference observed at stage 5. Subjecting the exposed part of the peduncle to darkness following anthesis reduced the rate of grain growth.ConclusionOur results suggest that the exposed peduncle is a photosynthetically active organ that produces photosynthates and thereby makes a crucial contribution to grain growth, particularly during the late stages of grain-filling.

Influence of water deficit on photosynthetic activity, dry matter partitioning and grain yield of different durum and bread wheat genotypes

“…It is consistent with the findings of other authors (Siddique et al 1999;Dulai et al 2006;Olsovska et al 2016). Green leaves of plants are the main source of products derived from photosynthesis (Kong et al 2010). In general, durum wheat genotypes formed relatively large area of leaves per stem and accumulated more assimilates.…”

Response of wheat ear photosynthesis and photosynthate carbon distribution to water deficit

“…Wheat spike possesses several ---advantages, which include vast space for receiving light and CO 2 , strong ability of osmotic adjustment, and higher water potential and maintenance of a relatively high photosynthetic rate under drought conditions (Tambussi et al 2007). Existing studies show that nonleaf organs are resistant to water deficit, and are important sources of photosynthetic carbon assimilation under drought condition during the grain filling phase (Bort and Febrero 1994, Sánchez-Díaz et al 2002, Kong et al 2010. After flowering, the contribution of ear photosynthesis to grain yields begins to rise (Araus et al 1993, Zhang et al 2003, Maydup et al 2010.…”

Vandenyje tirpių angliavandenių kaupimasis kviečio žiedynkotyje ir jų ryšys su morfoanatominiais bei produktyvumo požymiais

“…Water-soluble carbohydrates accumulation in peduncle of wheat and its relationship to morpho-anatomical and productive traits as carbohydrate metabolism or in maintaining higher water potential than the flag leaf under drought stress or high temperatures (Kong et al, 2010). The morphology of peduncle has been related to grain yield and drought tolerance in wheat (Villegas et al, 2007;Li et al, 2011).…”