Breaking Setaria parviflora seed dormancy by nitrates and light is part of a mechanism that detects a drawdown period after flooding

MOLLARD FEDERICO; INSAUSTI PEDRO

AQUATIC BOTANY

Elsevier

Año: 2009 vol. 91 p. 57 - 60

0304-3770

We explored the hypothesis that, in flood-prone habitats, nitrates can signal to seeds that a drawdownperiod has begun. To investigate this issue, Setaria parviflora (Poir.) Kergue ´ len seeds were buried in anever-flooded upland and a nearby, flood-prone lowland grassland. Seeds were exhumed during theflooding period. Additionally, grassland mesocosms with buried S. parviflora seeds were flooded during20 d (controls drained). After both field and mesocosm pretreatments germination was assayed inlaboratory at 25 8C in a medium with or without nitrates, under red light pulses or in darkness. Seedsexhumed from the never-flooded upland showed no specific requirements to germinate. In contrast,seeds exhumed from the flooded lowland germinated ca. 65% when nitrates were combined with redlight pulses, significantly higher than in the rest of the treatments. Seeds exhumed from drainedmesocosms germinated equally in all treatments. However, in the seeds exhumed from the floodedmesocosms, nitrates increased germination by more than 20% compared with seeds imbibed in water.Seeds germinated ca. 85%when nitrateswere combinedwith red light pulses, significantly higher than inthe other treatments.We can conclude that after flooding, S. parviflora seeds require nitrate and light togerminate. Therefore, a large fraction of seeds do not germinate unless nitrates are combined with light,indicating a drawdown period after floods and vegetation gaps. 2009 Elsevier B.V. All rights reserved.