Responses of Photosynthesis and Dark Respiration to Temperature

This analysis suggests that a model of the temperature dependenceof carbon exchange by a plant can be developed based upon absolutereaction rate theory. Component temperature-dependent physiologicalprocesses necessary to describe net photosynthesis over thebiological temperature range include the light reaction, darkreaction (carboxylase CO₂ uptake, oxygenase photorespiration)and mitochondrial dark respiration. An essential assumptionof the model is the reversibility of thermal inhibition. Supportingevidence for this assumption is provided within the biologicalrange. Thermodynamic constants were found to be strongly correlatedwith the thermal environment to which they were adapted. Therewas little difference in non-photorespiration thermodynamicconstants between C₂ andC₄species within thermal habitat types.The model shows the observed shift in temperature optima withlight intensity as a natural consequence of enzyme kineticsand absolute reaction rate theory. photosynthesis, photorespiration, dark respiration, temperature response, carbon exchange, mathematical model     

Sink Metabolism: A Conceptual Framework for Analysis

The basic objective of this study was to build a model thatdescribes the physiology of sinks and the process of unloadingassimilates from the phloem. The metabolic steps necessary todescribe a typical sink were obtained from the literature. Severalmethods to describe mathematically these metabolic steps areavailable but they were either too cumbersome and slow or toosimple. This necessitated the development of a new method todescribe multiple enzyme systems. This paper describes the developmentof that method. The method involves a rather simple enzyme analysisof coupled biochemical processes common to most types of sinks.A conceptual framework is presented to provide a basis for furtherquantification of the metabolism of various types of sinks throughtheir development sequence. sink metabolism, model-enzyme kinetics, King-Altman analysis, phloem unloading