In Australia, where both species co-exist, the plants readily hybridise. Both species are monoecious with flowers of both sexes forming near the apex of the stems as the plant grows. Due to the more erect morphology of E. Putievsky et al. They were, however, able to backcross with the parental species giving the possibility of gene flow between the species. There is very little genetic variability within E.
|Published (Last):||18 November 2016|
|PDF File Size:||18.87 Mb|
|ePub File Size:||8.1 Mb|
|Price:||Free* [*Free Regsitration Required]|
In Australia, where both species co-exist, the plants readily hybridise. Both species are monoecious with flowers of both sexes forming near the apex of the stems as the plant grows. Due to the more erect morphology of E. Putievsky et al. They were, however, able to backcross with the parental species giving the possibility of gene flow between the species. There is very little genetic variability within E. Panetta a states "E.
Indeed, 16 of the 21 surveyed South African populations could not be distinguished from Australian populations. Weiss found that up to six distinct cohorts may sometimes occur within a single year and attributed these to the earlier rains arriving before the majority of viable seed had completed their required period of innate dormancy. Although mid-season accessions may contain the most individuals, it was the first accessions of each year that contributed the most to seed production.
Flowers could be produced within 4 weeks of germination and seeds within 6 weeks; however, this was highly variable and in some years it took 18 weeks before flowers were even produced.
Seeds are produced continuously at the growing apex of the stems throughout the growing season. Regardless of when they germinate, all Emex plants die at the end of the winter rains when soil moisture disappears Weiss, The longevity of the growing season can vary immensely from site to site and from year to year with weeks after the first accession, reported in Weiss Within a Mediterranean climatic region, irrigation during the summer will permit some E.
In sub-tropical climates e. Under glasshouse conditions, for the first 8 weeks after emergence, growth rates are rapid and most energy is diverted towards foliage production. At weeks there is a slight decrease in growth with foliage production decreasing but with more stem elongation, branching and buds, flower and fruit formation and a corresponding increase in root biomass. From 15 weeks senescence occurs and whilst during this phase there is no net increase in plant weight, resources from the leaves, stems and roots are reabsorbed and translocated to the developing achene.
Embryo development begins in the seed 3 weeks after flowering and seeds are mature 6 weeks after flowering. Gilbey and Weiss report the average weight of achenes as being 20 mg, 50 mg and 60 mg at 3, 6 and 8 weeks respectively after flowering.
The weight of the achene remained stable after it was 8 weeks old. Weiss and Simmons found that the optimum temperature for production of seed, stems and leaves was A delayed flowering and necrosis of stems was shown at the lowest 6.
Above Within an annual pasture system of a Mediterranean climatic region, early cohorts of E. This is due to the ability for some E. In Australia, these result from events such as cyclonic activity which happens reasonably frequently within northern New South Wales and northern Western Australia.
Out of season rainfall events are locally referred to as a "false break". The long tap root of E. This can lead to dramatic increases in infestations of E.
Reproductive Biology E. The spiny female flowers are sessile and in axillary clusters which form first on the crown, in the centre of the rosette, but subsequently in leaf axil nodes along the stems. The male flowers form in short axillary racemes, often emerging between the female achenes Gilbey and Weiss, Weiss and Julien report mean achene lengths capsule base to the top of the inner lobes of the female perianth of 8.
The persistence of E. All seeds are dormant when freshly formed and require a month period of after-ripening before they can germinate Hagon and Simmons, ; Panetta and Randall, c. Panetta and Randall c , studying four populations of E.
Seeds that remain in the constant non-dormant state give the species the flexibility to recruit opportunistically after summer rainfall events within the Mediterranean climate Panetta and Randall, c.
Seeds that remain in the extended innate-dormant state ensure the continued recruitment of seedlings each year Scott, Despite most of the viable E. Cultivation is known to increase germination Gilbey and Weiss, ; Weiss, Another important factor is the ability of the seed to imbibe sufficient water for germination via its encapsulating, large, hard and spiny perianth Cheam, As a consequence, unburied seeds have in general a low rate of germination.
Within a particular season, seeds buried cm deep are most likely to become established Scott, ; Cheam, whereas those on the soil surface or buried deeper than 10 cm are more likely to remain viable in future years thus acting as seed reservoirs in the event of future soil disturbances. Cheam studied germination patterns from E.
After 4 years, Some E. Environmental Requirements A prerequisite to invading a new habitat is the ability to tolerate the new climatic conditions. Values estimated within the Climate table are derived from long-term climatic averages from sites known to be at the edge of the known distribution range for E.
Models for predicting the potential distribution of both species, based upon both climate and plant development requirements, are given in Pheloung et al. For E. A similar model based on climatic conditions for New Zealand Panetta and Mitchell, predicts a range that is considerably larger than the actual range even following over years of opportunity.
Associations E. It can be managed by the inclusion of non-host species grown in rotation with the susceptible crops therefore the presence of E. There is no known mycorrhiza associated with E. In Australia, both within pastures and crops, E.
Seed of E. In Australia, up to a quarter of the seeds on the soil surface are removed by mice Weiss, and in South Africa, a third are removed by gerbils Scott, In the northern grain-growing region of south-west Australia, the seeds of E. Air Temperature.
Rumex spinosus Linnaeus, Sp. Lectotypified by S. Chapter 5B, Florida Administrative Code. Endangered: A species of plants native to the state that are in imminent danger of extinction within the state, the survival of which is unlikely if the causes of a decline in the number of plants continue, and includes all species determined to be endangered or threatened pursuant to the Federal Endangered Species Act of , as amended. Defined as species of plants native to the state that are in rapid decline in the number of plants within the state, but which have not so decreased in such number as to cause them to be endangered. Endangered: Any species which is in danger of extinction throughout all or a significant portion of its range.
Stem: nodes swollen or not. Leaf: simple, basal or cauline, generally alternate; ocreae present or 0, generally scarious, persistent or not. Fruit: achenes, included in or exserted from perianth, generally 3-angled, ovoid or elliptic, generally glabrous. Note: Treatment of genera in Eriogonoideae based on monographic work of James L. Involucre number throughout is number many per ultimate grouping, at tips of ultimate branches; flower number is per flower cluster or involucre, unless otherwise stated. Rosatti, Bruce G. Staminate Inflorescence: axillary, terminal, raceme-like; flowers
Arkive Buy Seeds and Docs Seeds of wild plants for sale for studies, trials, research, or personal use. Availability depends on season. For these reasons you are kindly requested to first fill and submit a quotation form by which you will get confirmation of the purchase, availability and charges. Online Purchase Seeds Buy images found in this large collection of Maltese flora. Prices reasonable and rated differently according size and resolution. Please note that all images are copyright of the author.
Doublegee (Emex spinosa)