On the hormonal nature of the stimulatory effect of high incubation temperatures on germination of dormant sorghum (S. bicolor) caryopses
2003
Benech‐Arnold, Roberto L. | Enciso, Silvina | Sanchez, Rodolfo A. | Rodríguez, M Verónica
• High incubation temperatures (i.e. 30°C) stimulate the germination of dormant sorghum grains. To test the hormonal nature of this response, experiments were carried out with two varieties with contrasting dormancy at harvest: Redland B2 (low dormancy, high germination percentages attained under a wide incubation thermal range) and IS 9530 (high dormancy, high germination percentages attained only at 30°C). • Redland B2 grains with reduced GA content (paclobutrazol‐treated) reached high germination temperatures (c. 100%) only when incubated at 30°C. By contrast, IS 9530 grains with reduced ABA content (fluridone‐treated) reached 100% germination at 30, 25, 20 and 15°C. • Incubation temperatures did not alter embryo responsiveness to ABA, nor did it modify the pattern of changes in embryo ABA content throughout incubation. Low GA₃ concentrations (0.1 µm) were required to totally overcome the inhibition imposed by ABA in embryos incubated at 30°C; by contrast, even the highest GA₃ concentrations used (1000 µm) were not able to revert ABA inhibition in embryos incubated at 15°C. • These results show the hormonal nature of the stimulatory effect of high incubation temperatures, and suggest that this effect is mediated by an increase in tissue responsiveness to GAs.
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