Zur Keimungsbiologie von zehn ausgewählten xerothermen Grasarten

Abstract

Partzsch, M.: Germination biology of ten xerothermic grass species – Hercynia N. F. 43 (2010): 299 –317.The germination process generally determines the chance of survival of any plant species; and thediversity of germination strategies among plants is wide. Dry and semi-dry grasslands are characterisedby the dominant occurrence of species from the Poaceae family. In order to determine the germinationsuccess in different Poaceae taxa, seeds from ten species were collected in the vicinity of Halle (Saale):Agrostis capillaris, A. vinealis, Brachypodium pinnatum, Bromus erectus, Danthonia decumbens,Festuca brevipila, F. glaucina, F. rupicola, Poa angustifolia and Sesleria varia. The region of the townHalle is located in Central Germany (Saxony-Anhalt) and characterised by climatic dryness.In order to identify optimal germination conditions, experiments were carried out under three differenttemperature-light regimes (8/4 °C, 20/10 °C, 32/20 °C; 12 h light : 12 h darkness; 45 days). After thefirst germination experiment, the remaining diaspores were buried in soil, to ensure hibernation until thenext experimental phase in following spring. Seed viability was tested before and after the experiments.Results indicate that the species are generally characterised by an asynchronistic germination, meaningthat, even under favourable conditions, only a proportion of seeds germinates in a certain time. Suchwas the case in particular for Brachypodium pinnatum, Bromus erectus, Danthonia decumbens, Festucabrevipila, F. glaucina, Poa angustifolia and Sesleria albicans. The optimal germination temperaturefor most species was 20/10 °C (light/dark). An increase in temperature induced a higher germinationpercentage and velocity in Agrostis vinealis, Bromus erectus and Poa angustifolia. With the exception ofPoa angustifolia, the natural cold stratification (over-wintering) did not lead to an enhanced germination.Results regarding the germination behaviour and seed viability allow to range Poaceae species in threediaspore bank types: (1) the more transient type: Agrostis capillaris, A. vinealis, Festuca rupicola; (2)the short-term persistent type: Festuca brevipila, F. glaucina, Poa angustifolia, Sesleria albicans; (3) thelong-term persistent type: Brachypodium pinnatum, Bromus erectus, Danthonia decumbens.Key words: germination, dormancy, natural stratification, seed bank type, viability