Boosting underwater germination in Echinochloa colona seeds: the impact of high amplitude alternating temperatures and potassium nitrate osmopriming

JULIANA ECHEVERRY HOLGUÍN; MARÍA CREPY; GUSTAVO STRIKER; FEDERICO MOLLARD

Functional plant biology : FPB

CSIRO

Año: 2023 vol. 51

Underwater germination could risk seedling survival, suggesting the need for control through seedperception of environmental cues. These cues include diurnally alternating temperatures tied todrained soils or shallow water tables. We examined high-amplitude alternating temperatures impacton underwater germination. Besides, the conditions experimented by seeds in the soil (e.g.hydration/dehydration phases) change their germinability so we tested if osmopriming could affectunderwater germination. We worked with Echinochloa colona seedlots from extensive crop fields,exposing seeds to sequential submergence and drained treatments in combination with cues thatpromote germination. While a 10°C difference between maximum and minimum daily temperaturesmaximised germination in drained conditions, higher amplitudes (>15°C) alternating temperaturespromoted E. colona underwater germination under hypoxic water (pO2 < 4.1 kPa). KNO3osmopriming in drained conditions promoted later underwater germination even under hypoxicwater; however, PEG 6000 osmopriming induced seeds to enter secondary dormancy inhibitingunderwater germination. KNO3 improved E. colona underwater germination under air-equilibratedfloodwater (pO2: 16.5–17.4 kPa) yet not under hypoxic conditions. This suggests that germinationcan proceed in flooded nitrate-fertile soils as long as it remains aerobic. Hypoxic submergence didnot inhibit the induction of hypersensitivity to light in E. colona seeds. This research expands ourunderstanding of wetland seed germination ecophysiology, shedding light on the inducible natureof underwater germination in hydrophyte weeds.