Germination behaviour of the seeds of four New Zealand species ofCoriaria(Coriariaceae)

Abstract

Abstract Experiments were conducted to determine the germination rates, percentage germination success, and phenomena related to germination delay for two provenances each of freshly collected achenes of Coriaria arborea, C. sarmentosa, C. angustissima, and C. sp. cf. plumosa. These studies, carried out in an unheated, partially shaded glasshouse in Christchurch, involved treatments to simulate natural conditions that the seeds might experience after dispersal (well-lit; in the dark; in the fleshy false fruit tissues; after dry storage; on soil). In the standard (cleaned, moist, well-lit) treatment, all seeds of C. arborea germinated rapidly, in summer. Some C. sarmentosa seeds also germinated rapidly in summer, but in one provenance a few seeds remained dormant until autumn or the following spring, and the success was slightly lower. Germination of C. angustissima and C. sp. cf. plumosa seeds was usually slow in late summer and autumn, halted in winter, and was completed in spring, with 90 %–100% success in all except one of the C. sp. cf. plumosa provenances. A few seeds of this set germinated in late summer, but many remained dormant until spring. The specific differences in germination pattern are consistent with the habitat conditions in which the respective species live. For C. arborea the dark, in-fruit, dry, and soil treatment seeds each germinated more slowly than for the standard treatment; total germination was more than 90%. Seeds of the other three species in these three treatments also germinated more slowly than those in the standard treatment, usually with much lower total success. Overwinter delay of germination of some seeds of C. sarmentosa, C. angustissima, and C. sp. cf. plumosa appears to be determined by biochemical blocking (true dormancy). In all cases but two, the tetrazolium test indicated that seed viability was less than 90%. This was substantially lower than the actual germination success in the standard treatment.