PHOTOSYNTHETIC LIMITATIONS - USE IN GUIDING EFFORT IN CROP IMPROVEMENT

Methods for identifying the important processes limiting crop producti on and especially photosynthesis are discussed with special reference to the use of transgenic plants with altered expression of the small s ubunit of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco), R ecent advances in the use of metabolic control analysis are reviewed a nd some restrictions in their application to crop improvement are disc ussed. Metabolic control and other sensitivity approaches are compared with the opportunities offered by 'elimination' analyses where the co ntribution of one component is estimated from the change in assimilati on rate when any limitation by that component is removed. It is conclu ded that although control or sensitivity analyses provide effective to ols for describing the importance of component processes, especially w hen using transgenic approaches to generation of isogenic material, ou r present limited knowledge of the complex interactions between variou s metabolic pathways restricts the value of these approaches in guidin g breeding effort.