A fairly recent review on the role of nitrate in
terminating dormancy of seeds can be found in Karssen
and Hilhorst (1992). Consequently, we will refer to
it only brie¯y in this paper.
Nitrate is a requirement for dormancy termination
in a number of species. Because nitrate concentration
in the soil fluctuates seasonally (i.e. the higher the
temperature, the higher the mineralisation rate of soil
organic matter and consequently, the higher the actual
nitrate concentration), the possibility that the requirement
for nitrates could be an environmental signal
determining the seasonal emergence of some weeds
has been considered. No correlation was found
between the period of emergence of weeds requiring
nitrates to completely exit from dormancy, however,
and soil nitrate concentration at different times of the
year (Karssen and Hilhorst, 1992). Rather, this
requirement has been proposed as a gap-detection
mechanism, since mineralisation rates in open gaps
are higher than in the soil under a vegetation cover
(Pons, 1989).
A fairly recent review on the role of nitrate interminating dormancy of seeds can be found in Karssenand Hilhorst (1992). Consequently, we will refer toit only brie¯y in this paper.Nitrate is a requirement for dormancy terminationin a number of species. Because nitrate concentrationin the soil fluctuates seasonally (i.e. the higher thetemperature, the higher the mineralisation rate of soilorganic matter and consequently, the higher the actualnitrate concentration), the possibility that the requirementfor nitrates could be an environmental signaldetermining the seasonal emergence of some weedshas been considered. No correlation was foundbetween the period of emergence of weeds requiringnitrates to completely exit from dormancy, however,and soil nitrate concentration at different times of theyear (Karssen and Hilhorst, 1992). Rather, thisrequirement has been proposed as a gap-detectionmechanism, since mineralisation rates in open gapsare higher than in the soil under a vegetation cover(Pons, 1989).
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