Photosynthetic Acclimation in Pea and Soybean to High Atmospheric CO2 Partial Pressure

Abstract

Nonnodulated pea (Pisum safivum 1. cv Frosty) and soybean (C/ycine max [L.] Merr. cv Wye) plants were grown under artificial lights from germination with ample nutrients, 600 pmol photons m-2 s-', and either 34 to 36 (control) or 64 to 68 Pa (enriched) CO,. For soybean, pod removal and whole-plant shading treatments were used to alter the source-sink balance and carbohydrate status of the plants. Crowth of both species was substantially increased by CO, enrichment despite some down-regulation of photosynthesis rate per unit leaf area ("acclimation"). Acclimation was observed in young pea leaves but not old and in old soybean leaves but not young. Acclimation was neither evident in quantum yield nor was it related to triose phosphate limitation of net photosynthesis. A correlation between levels of starch and sugars i n the leaf and the amount of acclimation was apparent but was loose and only weakly related to the source-sink balance of the plant. A consistent feature of acclimation was reduced ribulose bisphosphate carboxylase (RuBPCase) content, although i n vivo RuBPCase activity was not necessarily diminished by elevated growth COz owing to increased percentage of activation of the enzyme. A proposal is discussed that the complexity of photosynthetic acclimation responses to elevated CO, is as an expression of re-optimization of deployment of within-plant resources at three levels of competition.

The Effect of Elevated Partial Pressures of CO2 on the Relationship between Photosynthetic Capacity and N Content in Rice Leaves

“…In addition, Sage et al (1989) found that the deactivated Rubisco immediately after exposure to elevated CO, levels does not recover during the subsequent prolonged exposure, and they pointed out that this indicates an incomplete acclimation to elevated CO, levels. On the other hand, there have been some reports that the activation state of Rubisco at elevated CO, partial pressures is unchanged in soybean (Campbell et al, 1988;Sicher et al, 1995), loblolly pine (Tissue et al, 1993), tobacco (Sicher and Kremer, 1994), and pea (Xu et al, 1994). In rice Rowland-Bamford et al (1991) observed that Rubisco activation declined in the plants grown at 90 Pa CO,, whereas it was not affected in the plants grown at CO, levels up to 60 Pa.…”

“…Growth under high CO, partial pressures leads to carbohydrate accumulation. Since an apparent correlation between carbohydrate accumulation and the suppression of photosynthesis has often been reported (Sasek et al, 1985;Peet et al, 1986;Yelle et al, 1989;Wong, 1990;Xu et al, 1994), much attention has been paid to the causal relationship(s) between the two phenomena. Stitt (1991) proposed the existence of a feedback mechanism(s) by which the accumulation of carbohydrate indirectly leads to a decrease in the amounts of key components of the photosynthetic apparatus.…”

“…Stitt (1991) proposed the existence of a feedback mechanism(s) by which the accumulation of carbohydrate indirectly leads to a decrease in the amounts of key components of the photosynthetic apparatus. In fact, many studies of long-term acclimation to elevated CO, partial pressures have shown a decrease in Rubisco (Peet et al, 1986;Sage et al, 1989;RowlandBamford et al, 1991;Xu et al, 1994;Jacob et al, 1995;Rogers et al, 1996). In addition, a decrease in the transcript levels of rbcS and rbcL mRNA was recently found in the plants grown at elevated CO, partial pressures (Nie et al, 1995;van Oosten and Besford, 1995).…”

Acquisition and allocation of carbon and nitrogen by Danthonia richardsonii in response to restricted nitrogen supply and CO2 enrichment

“…Total soluble protein and Rubisco contents (g m -2 ) have been observed to decline in response to CO 2 enrichment in D. richardsonii (Lutze & Gifford, unpublished). Rubisco (Sage, Sharkey & Seemann 1989;Besford 1990;RowlandBamford et al 1991) and chlorophyll contents (g m -2 ; Sage et al 1989;Xu, Gifford & Chow 1994) have often decreased in a range of plant species in response to CO 2 enrichment.…”

Regulation of Leaf Photosynthesis Through Photosynthetic Source-Sink Balance in Soybean Plants

“…However, there is also evidence from high CO 2 treatment experiments using various C 3 plants that decreased Rubisco activity in leaf rather than changes in leaf Rubisco content is likely to be a main cause (Sage et al, 1989). Data from experiments conducting excisions of sink organs (pods or flower buds and flowers) or petiole girdling suggest that a decrease of stomatal conductance or Rubisco activity or Rubisco content in leaf, or both decreases of Rubisco activity and Rubisco content in leaf can be responsible for the decrease in leaf photosynthetic rate under excessive photosynthetic source capacity (Mondal et al, 1978;Wittenbach, 1982Wittenbach, , 1983Xu et al, 1994;Crafts-Brandner & Egli, 1987;Cheng et al, 2008). As described in the Introduction, excising sink organs or high CO 2 treatment can have side effect(s) other than inducing excessive photosynthetic source capacity.…”