RUBISCO CAPACITY AND THE PHOTOSYNTHETIC PERFORMANCE OF C_4 PHOTOSYNTHESIS AT SUB-OPTIMAL TEMPERATURES

摘要

An apparently universal difference between C_3 and C_4 plants is the relative lack of Rubisco in the latter (Long 1999, Sage & Kubien 2003). By increasing the concentration of CO_2 in the bundle sheath tissues to which the enzyme is localised, C_4 plants are able to reduce the rate of RuBP oxygenation, thereby utilising Rubisco much more efficiently than is the case in C_3 species. The fundamental efficiency of Rubisco is inversely related to temperature, because both the CO2/O_2 specificity of the enzyme and the relative solubility of CO_2 to O_2 decline as temperatures increase (Berry & Raison 1981). This is a greater benefit to C_3 plants, however, because this increased efficiency is realised as a reduced rate of photorespiration.