METHOD: Life Cycle CONDITIONS: Growth Chamber - 18h light at either 33/25C (hot) or 20/10C (cool) METHOD NARR: Ten days after start of temperature regimen, plants were removed, separated into component parts, measured for leaf arnt weight. Additional plants were measured for CO2 flux. Efflux rates were measured to represent maintainance respiration. CO2 influx rates were made only on plants in the hot chamber. Chlorophyll flourescence measurement hot chamber after 1h in darkness at 30C. Initial, peak and terminal values were recorded. RESULTS NARR: Accessions with significantly smaller relative growth rate (RGR) & net assimilation rate (NAR) values than the controlpossess heat tolerance. Only occasionally did accessions significantly exceed the photosynthetic rate of control clones. Accessions with greater dry weight had greater investment in stem than leaf tissue, except for non-tuberosum clonvestment in stem dry weight. The chc accession exceeded the contol clones' value for RGR. Acl498066 and crc498116 were found to be heat tolerant. AUTHOR EXPLANATION: Measurements based on the disruption of PSII couldtolerance.