Comparative Germination Responses of 28 Temperate Grassland Species

Abstract

The comparative germination biology of 28 perennial species native to the temperate grasslands of southern Victoria was tested using a single temperature regime (20/10˚C) in either constant darkness or 12 h diurnal white-light conditions. This temperature regime was chosen because it corresponds to the temperature found to produce substantial or optimal germination in other germination studies of grassland plants. Four germination attributes—time to the beginning of germination (germination lag), time taken to achieve 50% of final germination (germination speed –t₅₀), percentage germination in diurnal light conditions and percentage germination in continuous darkness—were calculated for each species and correlated to three plant attributes: plant family, life form and seed weight. Germination lag was short for many species: 50% had a lag of less than 7 days, whilst 96% of species had begun germinating within 28 days. Germination speed was moderately fast for most species: 75% of species had a t₅₀ of less than 28 days. Total percentage germination in diurnal light or continuous darkness was variable (0–98%), but many species (64%) germinated readily (> 50%) in at least one treatment. Twenty-four percent of species had germination substantially inhibited by darkness (i.e. Acaena echinata, Bulbine bulbosa, Eryngium ovinum, Podolepis sp. aff. jaceoides, Velleia paradoxa and Wahlenbergia luteola). No species had its germination promoted by darkness. Few correlations between plant and germination attributes were detected. Seed weight was not correlated with any of the three germination attributes, nor was life form or plant family correlated with germination speed or percentage germination in the light or dark. Germination lag, however, was significantly associated with plant family and, in a related way, with life form: species from the Liliaceae (geophytes) took longer to begin germination than species from the Asteraceae (hemicryptophytes). The ecological implications of the observed germination biology on the potential formation of persistent soil seed banks and seedling recruitment dynamics are discussed.