Reproductive and vegetative biology ofCirsium vulgare(Savi) Ten. (Compositae: Cynareae)

Abstract

Botany, 1989, Vol. 27" 401-414 Abstract Achenes of Cirsium vulgare germinated at constant temperatures between 7~ and 32~ Fresh achenes had a higher optimum temperature of gerlnination (23.5~ than older achenes which had been stored for 10 months (20~ Fresh achenes also germinated more slowly and had a lower maximum level of germination. Achenes that were buried in the soil showed a decrease in viability over time. At depths of 2 cm achenes either germinated or were destroyed. At greater depths the achenes showed an exponential decay rate in viability with time. The slope of this exponential curve decreased with increasing depth of burial. Germination in the field was synchronous with rainfall pattern over the summer, although subsequent germination may occur ifachenes are brought to the surface. Young seedlings were not damaged by frosts of-2~ After germination a major root system developed rapidly, whilst a rosette more slowly formed above ground. Rosettes increased in diameter until the winter when growth ceased, although horizontal growth was reinitiated if the rosette became damaged. In late winter or early spring vertical growth is initiated, leading to the formation of a bushy plant with subsequent flowering and production ofachenes. C. vulgare flowers throughout the spring and summer with the maximum number of plants flowering in the late spring or early summer. Each capitulum holds approximately 200 achenes and a large plant may produce in excess of 50,000 fertile achenes. Apart from fertile achenes, "shrunken" and "hollow" Received 23 May 1988; accepted 31 January 1989achenes are also produced by non-pollination and self-pollination respectively. After the capitulum has matured the achenes are wind dispersed. However, despite the presence of a pappus the majority of achenes fall within a circle of radius 1.5 times the height of the parent plant. In conjunction with the production of non-viable achenes through self-fertilisation, this is expected to result in marginal spread of this species from existing infestations.

Comparing the reproductive success and pollination biology of an invasive plant to its rare and common native congeners: a case study in the genus Cirsium (Asteraceae)

“…He concluded that C. vulgare likely had a mixed mating system based on tradeoffs in offspring performance; self-pollinated seeds had higher germination, but cross-pollinated seeds were light-weight and had greater chances for long-distance dispersal. Michaux (1989) conducted a similar experiment and found that a New Zealand population was largely infertile, with the highest number of viable seeds produced by C. vulgare heads that had been crosspollinated by Apis mellifera and Bombus species.…”

Alien seedling recruitment as a response to altitude and soil disturbance in the mountain grasslands of central Argentina

“…Cirsium vulgare has a very widespread distribution in lowlands, particularly in disturbed or abandoned fields, and has been reported to be naturalized in highland sites that are similar to the study area, 200 km to the south (Petryna et al 2002). Seeds bear a pappus that enables wind dispersal, although most fall within a few meters of the parent plant (Michaux 1989). Although the seeds have no innate dormancy, this can be induced by wet and dry cycles (Downs and Cavers 2000).…”

“…Although the seeds have no innate dormancy, this can be induced by wet and dry cycles (Downs and Cavers 2000). Seed germination mainly occurs in spring and autumn (Michaux 1989;Randall 2000), in response to adequate soil moisture (Randall 2000). Cirsium vulgare seeds germinate at constant temperatures between 7°C and 32°C, with an optimum of 20°C (Michaux 1989).…”

“…(Fabaceae) because these alien species are both present on roadsides along the entire altitudinal gradient of the study area (unpublished data), but they are still rare in natural grasslands. Both species are biennial herbs of Eurasian origin (Klemow and Raynal 1981;Michaux 1989;Klinkhamer and De Jong 1993), and form persistent seed banks (Turkington et al 1978;Doucet and Cavers 1997), but differ in life history traits and germination requirements. Cirsium vulgare has a very widespread distribution in lowlands, particularly in disturbed or abandoned fields, and has been reported to be naturalized in highland sites that are similar to the study area, 200 km to the south (Petryna et al 2002).…”

“…Seed germination mainly occurs in spring and autumn (Michaux 1989;Randall 2000), in response to adequate soil moisture (Randall 2000). Cirsium vulgare seeds germinate at constant temperatures between 7°C and 32°C, with an optimum of 20°C (Michaux 1989). Germination rate tends to decrease as light decreases (Michaux 1989;Klinkhamer and De Jong 1993), although seeds are capable of germinating in dark conditions under favourable diurnal temperatures (Doucet and Cavers 1997).…”