Hypoxic floodwaters can seriously damage seedlings. Seed dormancy could be aneffective trait to avoid lethal underwater germination. This research aimed to discovernovel adaptive dormancy responses to hypoxic floodwaters in seeds ofEchinochloacrus-galli, a noxious weed from rice fields and lowland croplands.
•Echinochloa crus-gallidormant seeds were subjected to a series of sequential treat-ments. Seeds were: (i) submerged under hypoxic floodwater (simulated with hypoxicflasks) at different temperatures for 15 or 30 days, and germination tested underdrained conditions while exposing seeds to dormancy-breaking signals (alternatingtemperatures, nitrate (KNO3), light); or (ii) exposed to dormancy-breaking signalsduring hypoxic submergence, and germination monitored during incubation and aftertransfer to drained conditions.
•Echinochloa crus-galliseed primary dormancy was attenuated under hypoxic submer-gence but to a lesser extent than under drained conditions. Hypoxic floodwater didnot reinforced dormancy but hindered secondary dormancy induction in warm tem-peratures. Seeds did not germinate under hypoxic submergence even when subjectedto dormancy-breaking signals; however, these signals broke dormancy in seeds sub-merged under normoxic water. Seeds submerged in hypoxic water could sense lightthrough phytochrome signals and germinated when normoxic conditions wereregained.
•Hypoxic floodwaters interfere withE. crus-galliseed seasonal dormancy changes. Dor-mancy-breaking signals are overridden during hypoxic floods, drastically decreasingunderwater germination. In addition, results indicate that a fraction ofE. crus-galliseeds perceive dormancy-breaking signals under hypoxic water and germinate imme-diately after aerobic conditions are regained, a hazardous yet less competitive environ-ment for establishment.