Seed dormancy in red rice. X. A 13C‐NMR study of the metabolism of dormancy‐breaking chemicals

Abstract

The metabolism of organic dormancy‐breaking chemicals is poorly defined and may provide clues to their mode of action. Therefore, hydrated, dormant seeds of red rice (Oryza sativa L.) were exposed to dormancy‐breaking treatments of propionate‐2‐13C (22 mW) or propanol‐1‐13C (75 mM) for 24 h at 30°C. Embryo extracts were analyzed by 13C‐nuclear magnetic resonance spectroscopy. Metabolism of propionate and propanol to 3‐hydroxypropionate, an intermediate of the modified β‐oxidation pathway, was detected after 2 and 4 h, respectively. This occurred prior to the onset of dormancy‐breaking which required 12 h of chemical exposure. Accumulation of 3‐hydroxypropionate was rapid and linear in the embryos of propionate‐treated seeds. In the embryos of propanol‐treated seeds, the level of 3‐hydroxypropionate reached a plateau at 4 h. Following 24 h of contact with propionate, labeled citrate was detected in the embryos. The decrease in tissue pH associated with the dormancy‐breaking process was fully accounted for by direct acid uptake and metabolic production of 3‐hydroxypropionate.