Photosynthetic acclimation to CO₂ enrichment related to ribulose-1,5-bisphosphate carboxylation limitation in wheat

Abstract

Net photosynthetic rate (P N ) measured at the same CO 2 concentration, the maximum in vivo carboxylation rate, and contents of ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (RuBPCO) and RuBPCO activase were significantly decreased, but the maximum in vivo electron transport rate and RuBP content had no significant change in CO 2 -enriched [EC, about 200 μmol mol −1 above the ambient CO 2 concentration (AC)] wheat leaves compared with those in AC grown wheat leaves. Hence photosynthetic acclimation in wheat leaves to EC is largely due to RuBP carboxylation limitation.Additional key words: maximum in vivo electron transport rate; net photosynthetic rate; ribulose-1,5-bisphosphate carboxylase/oxygenase activase; RuBP regeneration limitation; sucrose-phosphate synthase; Triticum. --After long-term exposure to elevated CO 2 concentration (EC) leaf net photosynthetic rate (P N ) is often significantly lower in the plants grown at EC than that in plants grown in ambient air (AC) when measured at a same CO 2 concentration. This phenomenon is so called photosynthetic acclimation to EC (Xu et al. 1994). Usually, this acclimation has been almost entirely attributed to the decrease in active ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) (Jacob et al. 1995, Rogers and Humphries 2000, Pérez et al. 2007). Nevertheless, Chen et al. (2005 reported that the photosynthetic acclimation in rice leaves is related to both RuBP carboxylation limitation and RuBP regeneration limitation. The similar result was also observed in Norway spruce (Urban et al. 2003). Furthermore, Zhang et al. (2008) has demonstrated that RuBP regeneration limitation is predominant within the two limitations. However, it is not known whether such mechanism of photosynthetic acclimation operating in rice is speciesspecific or universal. In order to answer the question the photosynthetic acclimation was investigated further in wheat.The Chinese CO 2 enrichment facilities were located at Xiaoji village (119°42'0"E, 32°35'5"N), Yangzhou city in Jiangsu Province, East China. In the experimental field, there were six rings of 15 m diameter. Among them, three rings were sprayed with pure CO 2 as EC treatment, and the others were in the normal atmosphere as AC control. The distances between EC and AC rings were more than 90 m. Target CO 2 concentration in the centre of EC rings was about 200 μmol mol -1 above the AC. The EC treatment was made from emergence of wheat seedlings to harvesting. Seeds of wheat (Triticum aestivum L.cv. Ningmai 9) were sown in mid November. The cultivation of wheat was performed with typical agronomic management techniques for this region.---Abbreviations: C i -internal CO 2 concentration; Cyt -cytochrome; J max -maximum in vivo electron transport rate; P N − net photosynthetic rate; RuBP -ribulose-1,5-bisphosphate; RuBPCO -ribulose-1,5-bisphosphate carboxylase/oxygenase; SPS -sucrosephosphate synthase; V cmax -maximum in vivo carboxylation rate. Acknowledgements: The Chinese Rice/Wheat free-air CO 2 enrichment project ...

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

“…However, when photosynthetic activity was determined in all plant treatments at 370 μmol mol −1 and 700 μmol mol −1 [CO 2 ] ( Table 1 ) it was found that plants grown in elevated [CO 2 ] had lower photosynthetic capacity than plants grown in ambient [CO 2 ]. Similar results were described by Zhang et al (2009) . Photosynthetic acclimation has been previously described in wheat plants exposed to elevated [CO 2 ] in greenhouses located in the field ( Martínez-Carrasco et al , 2005 ; Alonso et al , 2009 ; Gutiérrez et al , 2009 ).…”

Elevated CO2 has concurrent effects on leaf and grain metabolism but minimal effects on yield in wheat

“…In wheat, cultivation under free-air atmospheric CO 2 enrichment (FACE) leads, on average, to a yield enhancement of only 10% ( Kimball, 2010 , 2016 ). Photosynthesis acclimates to elevated CO 2 via lower average stomatal conductance ( g c ), lower photosynthetic capacity (maximum carboxylation rate V cmax ), and/or lower ribulose 1,5-bisphosphate regeneration ability ( Miglietta et al , 1996 ; Adam et al , 2000 ; Rogers and Humphries, 2000 ; Wechsung et al , 2000 ; Zhang et al , 2009 ). Of course, wheat response to elevated CO 2 also depends on water and N supply.…”

“…In addition to such quantitative changes in crop production and photosynthesis, elevated CO 2 leads to modifications in leaf biochemical composition and grain quality. Under elevated CO 2 , wheat leaves invest more C in cellulose and flavonoids ( Akin et al , 1995 ; Peñuelas et al , 2000 ) and are generally less N-rich, with a higher C/N ratio ( Zhu et al , 2009 ; Aranjuelo et al , 2015 ) and lower amounts of proteins (or transcripts encoding them) involved in photosynthesis (Calvin cycle enzymes) ( Nie et al , 1995 ; Adam et al , 2000 ; Zhang et al , 2009 ; Pandey et al , 2017 ). Proteomics conducted on leaves sampled during anthesis in wheat cultivated in a CO 2 -enriched greenhouse (at 700 µmol mol −1 CO 2 ) have shown that the Rubisco content did not increase, while there was a slightly higher content of Rubisco activase ( Aranjuelo et al , 2015 ).…”

Influence of irradiance on photosynthesis and PSII photochemical efficiency in maize during short-term exposure at high CO₂ concentration

“…It has been observed that in C 3 plants the P N reduction at elevated CO 2 is due to RuBP carboxylation limitation and/or RuBP regeneration limitation (Jacob et al 1995, Rogers and Humphries 2000, Chen et al 2005, Urban et al 2003, Pérez et al 2007). Zhang et al (2009) showed that Fig. 2.…”