THE RELATION BETWEEN PLANT-GROWTH AND RESPIRATION - APPLICATIONS TO ECOLOGY AND CROP CULTIVAR SELECTION

Respiratory rates of plants have frequently been considered as possibl e determinants of growth rates. However, correlations between growth a nd respiration rates that could establish this relation are often weak and do not explicitly include the effects of environmental variables. A respiration model that avoids these difficulties is presented and g rowth rate-respiration rate relations are illustrated with data on mai ze seedlings. Simultaneous determination of metabolic heat rate (q) an d CO2 rate (R(CO2)) as functions of temperature lead to a mathematical description of the temperature dependence of growth rate and substrat e carbon conversion efficiency (epsilon). Results show that (a) differ ent genotypes may have different temperature dependencies for both q a nd R(CO2), (b) a given genotype may have different temperature depende ncies of q and R(CO2), and (c) epsilon may increase or decrease as tem perature increases. This model can be used for rapid selection of crop plants for increased productivity in a specified climate and leads to better understanding of interactions between genotype and environment . We propose that respiratory properties are the characteristics of pl ants most closely adapted to the environment so as to optimize surviva l and reproduction. Further, relative values of the temperature coeffi cients of q and R(CO2) may be used to place a genotype into one of two major categories, i.e., plants that grow best in cool, variable tempe rature climates and plants that grow best in warm, constant temperatur e climates.