The Responses of Rubisco Protein to Long-Term Exposure to Elevated CO₂ in Rice and Bean Leaves

Abstract

For a number of C₃ species, a photosynthetic acclimation to elevated CO₂ involves a decline in the Rubisco activity/content in leaves (see 1, 2). Stitt (1) has suggested that this phenomenon may be one of the photosynthetic regulatory mechanisms mediated through an accumulation of carbohydrate(s) under the sink-source imbalance. In addition, many studies have also shown that CO₂ enrichment induces a decrease in the total leaf N content (3, 4). The change in total leaf N is directly related to changes in the amounts of photosynthetic proteins including Rubisco, because 70–80% of total leaf N is allocated into chloroplasts in C, plants (5, 6). Furthermore, the ratio of Rubisco to total leaf N is also altered with changing total leaf N content in several C₃ species (7, 8). Nevertheless, there are few studies discussing an elevated-CO₂-induced decline in the Rubisco activity/content in relation to a change in the total leaf N (2, 9). The nature of the response of Rubisco to elevated CO₂, and its species-dependent difference are still unclear.