Temperature and dormancy-breaking treatments: germination of endemic and geographically restricted herbaceous perennials

This paper describes the effects of temperature and simple or multiple dormancy-breaking treatments (potassium nitrate, surgical treatment, gibberellic acid (GA(3)), after-ripening at 45 degrees C and nitrogen dioxide gas) on germination of five endemic and geographically restricted herbaceous perennials (Apium prostratum Vent. subsp. phillipii Keighery ms, Goodenia stenophylla F. Muell., Marianthus granulatus (Turcz.) Benth, Myriocephalus suffruticosus Benth. and Velleia foliosa (Benth.) K. Krause) from the species-rich south-west of Western Australia. Except for seeds of A. prostratum that were non-dormant, seeds were partially dormant or fully dormant when incubated without pre-treatment at three temperatures (15, 20 and 25/10 degrees C). Low germination (<= 52%) was detected in M. granulatus under the best identified conditions, and seeds of G. stenophylla showed little to no response to any germination cue. In M. granulatus, M. suffruticosus and V. foliosa combinations of treatments were found that led to enhanced germination and in the case of V. foliosa, germination was not significantly different from a tetrazolium test of viability when seeds were surgically treated and then incubated with KNO3. Although none of the species studied exhibited physical dormancy, surgical excision of the seed coat in the vicinity of the embryo featured in the most successful combination of treatments in every case. Whilst seeds of M. granulatus responded positively to surgical treatment, after-ripening of seeds at 45 degrees C for 2, 4 or 6 weeks did not increase either speed or final germination compared with other treatments. The mean time to germinate (MTG) ranged from 12.6 days (A. prostratum ssp. phillipii) to 46.5 days (G. stenophylla) under the best treatment conditions for each species.