The effect of environmental factors on field and laboratory germination in a population of Zostera marina L. from southern England

The effects of temperature, oxygen availability and salinity on seed germination in a population of Zostera marina L. from the Fleet, a tidal lagoon in southern England, were investigated in the laboratory. The fate of seeds under natural conditions was also monitored throughout the year from core s...

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Bibliographic Details
Published in:Seed science research 1999-04, Vol.9 (4), p.331-339
Main Authors: Probert, Robin J., Brenchley, Jennie L.
Format: Article
Language:English
Subjects:
aerobic conditions
air temperature
anaerobic conditions
field experimentation
oxygen
oxygen availability
salinity
seasonal variation
seed dispersal
Seed germination
temperature
tidal lagoon
water temperature
Zostera
Zostera marina
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Summary:The effects of temperature, oxygen availability and salinity on seed germination in a population of Zostera marina L. from the Fleet, a tidal lagoon in southern England, were investigated in the laboratory. The fate of seeds under natural conditions was also monitored throughout the year from core samples and from seed samples buried in the sediment layer in nylon sachets. Supported with temperature, salinity and oxygen level measurements at the study site, field data confirmed that following seed dispersal in September/October, the majority of seeds germinated in the Fleet during the winter and early spring. In the laboratory, seeds germinated more rapidly and to a higher final percentage under anaerobic conditions compared to aerobic conditions. Under anaerobic conditions, rapid, near complete germination was possible at full salinity (30 g l-1) or when the salinity was reduced by 50%(15 g l-1). Under aerobic conditions, seeds germinated more rapidly at lower salinity. The effects of temperature were strongly dependent on the presence or absence of oxygen. Under anaerobic conditions, there was a pronounced optimum constant temperature for germination around 6°C, corresponding closely to the average water temperature recorded during the period mid-October to the end of March. On the other hand, under aerobic conditions, very low levels of germination were recorded at low temperatures. These findings support previously published evidence that seeds of Z. marina are well adapted to germinate in anaerobic sediments and that water temperature is the key environmental variable that determines the timing of germination under natural conditions. Previous misuse of dormancy terms to describe seed populations of Z. marina is discussed.
ISSN:0960-2585
1475-2735
DOI:10.1017/S0960258599000343