Does ear C sink strength contribute to overcoming photosynthetic acclimation of wheat plants exposed to elevated CO2?

13 p., 3 tables, 6 figures and bibliography

Wheat plants (Triticum durum Desf., cv. Regallo) were grown in the field to study the effects of contrasting [CO 2] conditions (700 versus 370 μmol mol -1) on growth, photosynthetic performance, and C management during the post-anthesis period. The aim was to test whether a restricted capacity of sink organs to utilize photosynthates drives a loss of photosynthetic capacity in elevated CO 2. The ambient 13C/ 12C isotopic composition (δ 13C) of air CO 2 was changed from-10.2‰ in ambient [CO 2] to-23.6‰ under elevated [CO 2] between the 7th and the 14th days after anthesis in order to study C assimilation and partitioning between leaves and ears. Elevated [CO 2] had no significant effect on biomass production and grain filling, and caused an accumulation of C compounds in leaves. This was accompanied by up-regulation of phosphoglycerate mutase and ATP synthase protein content, together with down-regulation of adenosine diphosphate glucose pyrophosphatase protein. Growth in elevated [CO 2] negatively affected Rubisco and Rubisco activase protein content and induced photosynthetic down-regulation. CO 2 enrichment caused a specific decrease in Rubisco content, together with decreases in the amino acid and total N content of leaves. The C labelling revealed that in flag leaves, part of the C fixed during grain filling was stored as starch and structural C compounds whereas the rest of the labelled C (mainly in the form of soluble sugars) was completely respired 48 h after the end of labelling. Although labelled C was not detected in the δ 13C of ear total organic matter and respired CO 2, soluble sugar δ 13C revealed that a small amount of labelled C reached the ear. The 12CO 2 labelling suggests that during the beginning of post-anthesis the ear did not contribute towards overcoming flag leaf carbohydrate accumulation, and this had a consequent effect on protein expression and photosynthetic acclimation.

This work has been funded by the Spanish National Research and Development Programme–European Regional Development Fund ERDF (Projects AGL2009-13539-C02-01, AGL2006- 13541-C02–02, and CGL2009-13079-C02-02).

Peer reviewed