PLANT PHYSIOLOGY , Vol 107, Issue 4 1365-1370, Copyright © 1995 by American Society of Plant Biologists
|
DEVELOPMENT AND GROWTH REGULATION |
Seed Dormancy in Red Rice (Oryza sativa) (IX. Embryo Fructose-2,6-Bisphosphate during Dormancy Breaking and Subsequent Germination)
S. Footitt and M. A. Cohn
Department of Plant Pathology and Crop Physiology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge, Louisiana 70803
Fructose-2,6-bisphosphate (Fru-2,6-bisP) was evaluated as a potential
marker for the dormancy-breaking phase or the germination phase before
pericarp splitting in red rice (Oryza sativa). During 4 h of imbibition at
30[deg]C, Fru-2,6-bisP of dehulled dormant and nondormant seeds increased
to 0.26 and 0.38 pmol embryo-1, respectively. In nondormant seeds, embryo
Fru-2,6-bisP content remained stable until the onset of pericarp splitting
(12 h) and increased rapidly thereafter. In dormant seeds, Fru-2,6-bisP
declined to 0.09 pmol embryo-1 at 24 h. Embryo Fru-2,6-bisP was correlated
with O2 uptake of dormant and nondormant seeds. A 24-h exposure of
dehulled, water-imbibed, dormant seeds to treatments yielding >90%
germination (sodium nitrite [4 mM], propionic acid [22 mM], methyl
propionate [32 mM], propanol [75 mM], and propionaldehyde [40 mM]) led to
changes in embryo Fru-2,6-bisP that were unrelated to the final germination
percentages. Furthermore, a 2-h pulse of propionaldehyde increased
Fru-2,6-bisP 4-fold but did not break dormancy. Whereas nitrite and
propionaldehyde increased Fru-2,6-bisP to 0.33 pmol embryo-1 after 2 h of
contact, propionic acid and methyl propionate did not increase Fru-2,6-bisP
above the untreated control. In all cases, further increases in
Fru-2,6-bisP occurred after pericarp splitting. However, the plateau
Fru-2,6-bisP attained during chemical contact was inversely correlated with
elapsed time to 30% germination (r = -0.978). Therefore, although
Fru-2,6-bisP is not a universal marker for dormancy release, its rapid
increase during nitrite and propionaldehyde treatments suggests that events
associated with dormancy breaking can occur within 2 h of chemical
treatment.
