Technical Abstract: The relative contribution of individual heat shock proteins to acquired thermotolerance was evaluated through analysis of chromosomal deletions in a ditelosomic series of the hexaploid wheat cultivar 'Chinese Spring'. This study describes the identification of a line within this ditelosomic series that exhibited a reduced level of acquired thermotolerance. Changes in the temperature sensitivity of chlorophyll accumulation were used as an indicator of acquired thermotolerance. The temperature providing maximum chlorophyll accumulation was 30 deg C in leaves under continuous light. A 30 min challenge temperature of 47 deg C prior to the light exposure was shown to inhibit subsequent chlorophyll accumulation. Preincubation at 40 deg C for 4 hr before the 30 min 47 deg C challenge triggered acquired thermotolerance system of the plant resulting in chlorophyll accumulation upon exposure to light. Evaluation of the ditelosomic series revealed reductions in acquired thermotolerance levels in the DT7DS line relative to controls. Two dimensional SDS polyacrylamide gel analysis was used to identify reduction in the level of 2 low molecular weight heat shock proteins in DT7DS.