Echinochloa crus‐galli seed physiological dormancy and germination responses to hypoxic floodwaters

Abstract

Hypoxic floodwaters can seriously damage seedlings. Seed dormancy could be an effective trait to avoid lethal underwater germination. This research aimed to discover novel adaptive dormancy responses to hypoxic floodwaters in seeds of Echinochloa crus-galli, a noxious weed from rice fields and lowland croplands.• Hypoxic floodwaters interfere with E. crus-galli seed seasonal dormancy changes. Dormancy-breaking signals are overridden during hypoxic floods, drastically decreasing underwater germination. In addition, results indicate that a fraction of E. crus-galli seeds perceive dormancy-breaking signals under hypoxic water and germinate immediately after aerobic conditions are regained, a hazardous yet less competitive environment for establishment.

Dormancy breakage and germination are tightly controlled by hypoxic submergence water on Echinochloa crus-galli seeds from an accession resistant to anaerobic germination

“…Nevertheless, the functional mechanisms by which submersion underwater may lead to such an inhibition are still not clear. It was previously demonstrated that a major fraction of E. crus-galli seeds is able to track dormancybreaking cues even under hypoxic submergence (Peralta Ogorek et al, 2019); however, downward physiological processes that lead to dormancy breakage and germination may be blocked by Shallow dormant seeds either H 2 SO 4 scarified or whole were incubated submerged under hypoxic (dissolved oxygen < 1.5 mg l −1 ) or normoxic (dissolved oxygen > 7 mg l −1 ) distilled water or imbibed on wet drained filter paper and exposed to dormancy-breaking signals [alternating temperature regime (20/30°C, 9/15 h) + red light pulses] or without signals (no dormancy-breaking signals). Germination percentages are presented as means ± SE (n = 4).…”

“…In this way, conditionally dormant seeds, which had their dormancy alleviated through after-ripening or stratification, may still require environmental signals like diurnally alternating temperatures and light to become non-dormant and get the capacity to germinate (Benech-Arnold et al, 2000;Finch-Savage and Leubner-Metzger, 2006). Seed dormancy is a key control point of the emergence process that might avoid lethal underwater germination in facultative wetland weeds Insausti, 2009, 2011;Peralta Ogorek et al, 2019); however, we still do not know the specific states in where hypoxic conditions could affect dormancy and seeds ability to germinate.…”

“…It is assumed that the perception of signals that break seed dormancy and promote germination is essential to avoid underwater germination in wetland species (Thompson and Grime, 1983;Pons and Schroder, 1986;Ekstam and Forseby, 1999;Mollard and Insausti, 2011;Peralta Ogorek et al, 2019). It was shown that Echinochloa crus-galli seeds can continuously monitor environmental cues under hypoxic floodwaters, thereby perceiving dormancy-breaking signals when submerged (Peralta Ogorek et al, 2019). Seed dormancy breaking occurs due to the coordinated action of several signalling pathways, jointly acting both on embryos and the structures surrounding them (Finch-Savage and Leubner-Metzger, 2006).…”

Snorkeling Strategy: Tolerance to Flooding in Rice and Potential Application for Weed Management

“…In flooded rice, correct management of water depth is the most efficient tool for the management of non-aquatic weeds. Flooding is effective in controlling major weeds, such as Echinochloa colona, E. crus-galli, Fimbristylis miliacea, Cyperus iria, and weedy rice, and has been used for this purpose since rice domestication [7,37]. Flooding during the germination and emergence stages is more effective in controlling E. crus-galli, Cyperus difformis, F. miliacea, and weedy rice than late flooding [37].…”

“…and Cyperus spp. (major weeds in rice), have also been investigated to gain an understanding of genes and genetic mechanisms for flood tolerance [5][6][7]. However, the majority of knowledge about flooding tolerance came from cultivated rice.…”