Germinability and enforced dormancy in seeds of species of indigenous grassland

Abstract

SUMMARYGermination of seeds of a range of species from indigenous grassland was tested at an alternating temperature regime in incubators, soon after they were shed in 1978 and also after various intervals of dry storage at outdoor ambient temperatures. Concomitant investigations were made of seedling emergence from and seed survival at different depths of soil in pots; Poa annua and Poa trivialis were investigated separately in 1979.Almost all seeds of Lolium perenne, Cynosurus cristatus, Festuca rubra and Holcus lanatus germinated readily, but c. 30% of Deschampsia caespitosa seeds and c. 15% of fresh, early‐shed Agrostis capillaris did not germinate until they were also given gibberellic acid. However, more late‐ than early‐shed seed of the latter two species germinated and their seeds became more germinable with increasing length of storage. Of the dicotyledonous species tested, germination of Cerastium fontanum ssp. glabrescens was rapid and complete, but that of Ranunculus spp. was particularly protracted. All Ranunculus repens seeds and a large proportion of Ranunculus acris seeds were highly dormant.Species differed greatly in their ability to emerge from and persist at different depths in pots. The most persistent species after 15 months were R. repens (69%), A. capillaris (39%), Luzula campestris (37%), C. fontanum ssp. glabrescens (30%), P. trivialis (8%), D. caespitosa (7%) and H. lanatus (3%). A mean of 42% of P. annua and 16% of P. trivialis seeds persisted from autumn 1979 until late spring 1980, but pre‐imbibing the seeds decreased seed persistence to 12% and 4% respectively.The results are discussed in relation to previously published information on the germination biology of the species and to the different abilities of the species to become part of the soil seed population.