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

Abstract

Wheat plants (Triticum durum Desf., cv. Regallo) were grown in the field to study the effects of contrasting [CO2] 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 CO2. The ambient 13C/12C isotopic composition (δ13C) of air CO2 was changed from –10.2‰ in ambient [CO2] to –23.6‰ under elevated [CO2] between the 7th and the 14th days after anthesis in order to study C assimilation and partitioning between leaves and ears. Elevated [CO2] 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 [CO2] negatively affected Rubisco and Rubisco activase protein content and induced photosynthetic down-regulation. CO2 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 δ13C of ear total organic matter and respired CO2, soluble sugar δ13C revealed that a small amount of labelled C reached the ear. The 12CO2 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.

Impact of Elevated CO<sub>2</sub> on Wheat Growth and Yield under Free Air CO<sub>2</sub> Enrichment

“…However, RuBisCO (spot nos 176, 185, 187, 189) which accounts for around 50% of leaf protein was found downergulated under eCO 2 condition. N reallocation within plants or non-selective decrease in leaf N content resulted in decrease of RuBisCO [27]. Our PCA analysis also showed inverse relation of leaf nitrogen with photosynthetic rate (Figure 3 and carbonic anhydrase (CA) regulates mesophyll conductance [27].…”

“…N reallocation within plants or non-selective decrease in leaf N content resulted in decrease of RuBisCO [27]. Our PCA analysis also showed inverse relation of leaf nitrogen with photosynthetic rate (Figure 3 and carbonic anhydrase (CA) regulates mesophyll conductance [27]. Similarly ATP synthase and photorespiratory enzyme like phosphoglycolate phosphatase (PGLP) (spot no 88) were also increased in abundance.…”

“…A/Ci curve showed that continued high CO 2 supply resulted in photosynthetic acclimation ( Figure 4). Photosynthetic acclimation has been previously described in wheat plants exposed to eCO 2 [27]. It has been reported that in C 3 plants downward photosynthetic acclimation occurs after prolonged eCO 2 exposure.…”

Advances in understanding CO2 responsive plant metabolomes in the era of climate change

“…Rising atmospheric CO 2 is also associated with increasing atmospheric temperature. Although current research suggests that several crops such as wheat (Levine et al 2008;Aranjuelo et al 2011), maize (Prins et al 2011), and barley (Robredo et al 2011) respond positively to increased atmospheric CO 2 with respect to yield (Long et al 2004), the associated effects of high temperature and altered precipitation patterns would likely reduce yields (Easterling et al 2007). …”

Relationships of Leaf Net Photosynthesis, Stomatal Conductance, and Mesophyll Conductance to Primary Metabolism: A Multispecies Meta-Analysis Approach

“…Despite these advances, there are only few studies that have examined the relationships between metabolic profiles and plant in vivo photosynthetic rates and conductances (Aranjuelo et al, 2011;Warren, 2011;Warren et al, 2011Warren et al, , 2012. Elucidating relations between metabolites and conductances is particularly relevant, since conductances are the diffusive physiological determinants that mainly drive the final plant productivity and plant's relation with the environment.…”