Responses of Datura ferox seeds to a far-red-light pulse are inhibited by continuous Far-Red-Light radiation

BURGIN, MJ; ARANA, MV; DE MIGUEL, LC; SÁNCHEZ, RA

Salamanca, España

Workshop; 7 th International Workshop on Seeds; 2002

The International Society for Seed Science

Promotion of germination by phytochrome of Datura ferox seeds involves weakening of micropylar endosperm. Phytochrome activation promotes the hydrolysis of cell wall mannose polymers by endo-B-mannanase and B-mannosidase. Seeds sensibility to light can be greatly enhanced by incubation in water saturated atmosphere for ten days (sensibilization treatment) allowing promotion of germination by a FR pulse (FRp). A FRp, given after the sensibilization treatment is able to stimulate germination of almost 100 % of the seed population, while germination of the dark controls is 30%. In contrast, when these seeds are exposed to continuous FR (FRc) germination is lowered to 20 % germination. Endo-B-mannanase activity is greater in FRp-treated seeds than either in dark incubated or FRc-treated seeds. GA 3B-hydroxylase transcript accumulation follows a similar pattern. GA 20 oxidase mRNA levels change in the opposite fashion. mRNAs levels of expansins in the micropylar endosperm are reduced by FRc, while accumulation of mRNA for expansins in embryos, and mannanase in endosperm are not affected by the light treatments. These results suggest that the antagonism between the action of a FR pulse and a prolonged exposure to FR light involves both changes in gene transcription and in post-transcriptional events.