On the hormonal nature of the stimulatory effect of high incubation temperatures on germination of dormant sorghum (S. bicolor (L.) Moench) caryopses

ROBERTO L. BENECH-ARNOLD, SILVINA ENCISO, RODOLFO A. SÁNCHEZ, AND M. VERÓNICA RODRÍGUEZ.

NEW PHYTOLOGIST

Año: 2003 vol. 160 p. 371 - 377

0028-646X

Pre-harvest sprouting in sorghum is related to the lack of a sufficient dormancy level during late seed development. As in other species, expression of dormancy depends on the incubation temperature; incubation at 30ºC stimulates germination of dormant sorghum grains, while dormancy is expressed strongly at 15ºC. Two sorghum varieties were tested: RedlandB2 (sprouting-susceptible, low dormancy) and IS9530 (sprouting-resistant, high dormancy). Results obtained after treatment of developing panicles with paclobutrazol and addition of GA3 during incubation of dormant grains suggest that the stimulatory effect of high incubation temperatures is hormonally mediated. Incubation temperature did not alter embryo responsiveness to ABA, nor did it modify the evolution of embryonic ABA throughout incubation. Gibberellin A1+3 content prior to radicle emergence did not increase significantly at 30ºC. Low GA3 concentrations (0.1 uM) reverted the inhibition imposed by 50uM ABA in embryos incubated at 30ºC, while 1000 uM was not able to revert ABA inhibition at 15ºC, suggesting that the stimulation of germination of dormant grains by high temperatures is mediated by an increased responsiveness to gibberellins.