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 at discovering novel adaptive dormancy responses to hypoxic floodwaters in seeds of Echinochloa crus-galli, a noxiuous weed from rice fields and lowland croplands. •Echinochloa crus-galli dormant seeds were subjected to a series of sequential treatments. Seeds were: 1) submerged under hypoxic floodwaters (simulated with hypoxic flasks) at different temperatures during 15 or 30 days and germination was tested under drained conditions while exposing seeds to dormancy-breaking signals (alternating temperatures, nitrates (KNO3 ), light) or 2) exposed to dormancy-breaking signals during hypoxic submergence and germination was monitored during incubation and after transfer to drained conditions . •Echinochloa crus-galli seeds primary dormancy was attenuated under hypoxic submergence but to a lesser extent than under drained conditions. Hypoxic floodwaters did not reinforced dormancy yet hindered secondary dormancy induction by warm temperatures. Seeds did not germinate under hypoxic submergence even when subjected to dormancy-breaking signals; however, these signals broke dormancy in seeds submerged under normoxic water. Seeds submerged in hypoxic water could sense light through phytochromes and germinated when normoxic conditions were regained. •In conclusion, hypoxic floodwaters interfere with E. crus-galli seed seasonal dormancy changes. Dormancy-breaking signals are overruled during hypoxic floods, drastically decreasing underwater germination. Additionally, 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. This article is protected by copyright. All rights reserved.