Induction of heat shock proteins and acquisition of thermotolerance in barley (Hordeum vulgare L.). Variations associated with growth habit and plant development.

Co-electrophoresis of extracts from barley (Hordeumvulgare) seedlings of two different genotypes labeled under heatshock revealed that the cultivars, Onice and Georgie, had both common and genotype-specific heatshockproteins (hsps). The differences were evident in both the aerial and the soil-born parts of the plant. In roots the hsps of 107, 90 and 43 kD were present only in «Georgie», whereas the 49, 31 and 27 kD hsps were induced only in «Onice». In coleoptiles the differences concerned the hsps of 107, 49 and 37 kD, specific for «Onice», and the hsp of MW 31 kD, found only in «Georgie». Further variations in the heatshock response were found in both genotypes during development from seedling to plant. At the stage of late tillering, the major hsps had MWs of 21, 22, 24, 69, 81, 90 and 107 kD in «Onice» and 21, 22, 24, 37, 69, 81, 90 and 107 kD in «Georgie». At the stage of flag leaf emergence the major hsps had MWs of 17, 69, 81, 90 and 107 kD in «Onice» and 17, 31,51, 69, 81, 90 and 107 kD in «Georgie». The two genotypes, different in growthhabit, exhibited similar tolerance to heat stress at 45 °C. The pre-treatment at 34 °C, which induced hsps and did not affect the ability for regrowth, potentiated the tolerance to heat stress in both seedlings and adult plants. Significant differences between the two cultivars at the level of thermoprotection achieved after pretreatment were not observed at the seedling stage, while a somewhat different response was obtained with adult plants.