Minggu, 13 Juni 2010

About the Ecology of the Asiatic Dayflower

The Asiatic dayflower is considered an invasive weed in many areas where it has been introduced. The Virginia Department of Conservation and Recreation, for example, categorises the species as "occasionally invasive" in its Invasive Plant Species of Virginia. This means that the plant will "not affect ecosystem processes, but may alter plant community composition by outcompeting one or more native plant species". The species is typically limited to disturbed sites, whence it spreads relatively slowly. Within its native range in China it is also sometimes considered a pest, especially in the northeast of the country where it has caused economically significant agricultural damage in orchards.

The Asiatic dayflower has been used in pollination studies concerning the behaviour of plants in relation to their pollinators. One important experiment tested the hypotheses that floral guides (i.e. various patterns and colours on anthers and petals) simultaneously promote pollinator visitation and prevent visits where the pollinator fails to come into contact with the stigma or anthers, termed pollen theft. As the flowers of the Asiatic dayflower lack nectar, they offer only pollen as a reward to their visitors. To attract pollinators, the plant has three types of brightly colored floral organs: the large blue petals, fertile yellow anthers, and infertile yellow antherodes that lack pollen. When the infertile antherodes were experimentally removed in natural populations, the number of total floral visitor landings was reduced, supporting the hypothesis that these infertile anthers essentially trick their pollinators into believing they offer more than they actually do. When the central, bright yellow fertile anther was removed, leaving only two brown fertile anthers, the frequency of legitimate flower landings decreased, meaning that the visitors were not pollinating the flowers, suggesting that floral signals also prevent "theft", or visits where the pollinators take pollen, but do not place any on the stigma. Thus both the fertile anthers and the infertile antherodes were shown to play an important role in both increasing visitor landings and orienting floral visitors toward a landing point appropriate for pollination.

Recent studies have shown that wild Asiatic dayflower populations found growing on copper mine spoils in eastern China exhibited very high concentrations of copper within the plants, more so than the 48 species tested. Commelina communis had sequestered some 361 mg/kg−1 of copper, while the plant with the next highest concentration, Polygonum macrathum, had 286 mg/kg−1. Five of the species examined, including the Asiatic dayflower, also showed high concentrations of other metals such as zinc, lead, and cadmium. The results suggest that the Asiatic dayflower is a good candidate for copper mine spoil revegetation and phytoremediation.

Ten species of fungi have been found on the Asiatic dayflower, four of which can infect the plant, while 12 species of insects are known to be associated with it. Two of the fungi, Kordyana commelinae and Phyllosticta commelinicola, are thought to be host specific with the Asiatic dayflower. Of the ten fungi seven are Basidiomycota and three are Ascomycota. Nine of the 12 insects associated with the plant are beetles, seven of which are in the genus Lema, while the other two are in the families Hispidae and Pentatomidae. The remaining three insects include one species of moth, Pergesa acteus, and two true bugs, namely Aphis commilinae and Aeschrocoris ceylonicus. Important pollinators include the Asian honeybee, Apis cerana, syrphid fly, Episyrphus balteatus, and the bumble bee species Bombus diversus.




Source: http://en.wikipedia.org/wiki/Commelina_communis

See also: Florist Melbourne, Florist Sydney, Floral

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