PLANT CALORIMETRY - HOW TO QUANTITATIVELY COMPARE APPLES AND ORANGES

Methods for the study of living plants or tissues by calorimetry have developed to the point that increasingly complex questions about plant physiology can be examined. Equipment now available or being developed for plant studies includes simple isothermal calorimeters with sample volumes from 1 ml to several liters, isothermal perfusion calorimeters, photocalorimeters, differential temperature scanning calorimeters, and calorimeters with multiple sample and CO2 and O2 sensing capabilities. Isothermal calorimetry, both with and without perfusion attachments, can be used to examine total metabolic rates of plant samples and to study effects of a wide variety of naturally occurring or artificially added factors on those rates. Moderately large numbers of plants can be examined for properties such as growth rates and tolerance limits to selected stimuli. Short term predictors of long term plant response can aid in selection of desired growth or tolerance characteristics and should prove of value in both classical plant breeding and future uses of biotechnology. Plant metabolism may be modeled with two inputs (photosynthate and oxygen) and three outputs (CO2, biomass, and heat). Understanding the transform function between input and output requires measuring at least four of the five parameters. Calorimetric measurements in conjunction with measurement of the other input-output parameters provides a quantitative understanding of metabolism in apples and oranges.