Abstract:Resumo Estudos sobre a biologia reprodutiva e crescimento de Pistia stratiotes L. foram desenvolvidos com plantas crescendo em lagos de várzea, componentes do sistema de lagos denominados Janauacá e no rio Solimões. Também foram feitas algumas observações sobre o ataque de herbívoros nessas plantas. Os resultados mostraram que: essa planta investe mais energia para produção de folhas, quando jovem e para a produção de estolões, quando adultas; fatores abióticos parecem ser mais importantes para o controle de P… Show more
“…Daughter plants detach from parent plants and get dispersed either by water currents or by animals. "It was originally thought that water lettuce did not produce viable seeds", but seed production has now been confirmed in Africa [111], India [122], South America [123], USA [124], South-East Asia [125], and central Europe [126]. In South Africa, one fruit per plant with 4-6 seeds per fruit, 4-11 seeds per fruit in Australia [127], 4-9 seeds per fruit in Brazil [123], 6-10 seeds per fruit in India [122], and 2 fruits in a rosette with a range of 1-17 seeds per fruit averaging 4 seeds per fruit in the USA [124] have been recorded.…”
Aquatic ecosystems in Botswana have been under threat by the aquatic alien invasive plant species viz., salvinia Salvinia molesta Mitchell, water lettuce Pistia stratiotes L., and water hyacinth Eichhornia crassipes (Mart.) Solms-Laub. While salvinia has been termed the major threat to the Botswana wetlands, water lettuce and water hyacinth are considered to be of minor importance. This review presents the species biology, distribution, historical spread, negative impacts, control achieved right from their discovery in the country by referring to their control and management in the world.Having infested the Kwando-Linyanti-Chobe Rivers in the 1970s, salvinia was initially tried by the use of herbicides, paraquat and glyphosate, between 1972 and 1976. With the discovery of the host specific biological control weevil Cyrtobagous salviniae Calder and Sands in 1981, the weevil was introduced by Namibians on Kwando and Chobe Rivers in 1983 and by Botswana in 1986 in the Okavango Delta. While the control was slowly establishing in Kwando-Linyanti-Chobe Rivers, it became apparent that lakes and perennial swamps within and outside Moremi Game Reserve of the Okavango Delta were infested with salvinia from 1992 onwards.With continuous and sustained liberation of the weevil in the Kwando-Linyanti-Chobe Rivers and in the Okavango Delta between 1999 and 2000, salvinia control was achieved by 2003, and since then the weevil constantly keeps the weed at low levels. The success is mainly due to sustainable monitoring through the application of physical and biological control methods. However, salvinia is still threatening the Okavango Delta due to factors such as tourism activities, boat navigation fishing and transporttion by wild animals.The first occurrence of water lettuce was recorded on Kwando and Chobe Rivers in 1986. Its biocontrol weevil Neohydronomous affinis Hustache was released in the year 1987. The weevil became extinct in Selinda Canal and Zibadianja Lake on Kwando River due to dry and wet events for over 10 years and the weed had been under control biologically on Chobe River. Having surface covered the Selinda and a part of the Zibadianja in high flood and rainfall in 1999/2000 season, research was undertaken to contain water lettuce, which led to its eradication by 2005. Regular physical removal of the water lettuce prior to fruit maturity is an effective method of control or eradicating the weed in seasonal water bodies.The Limpopo Basin (shared by Botswana, South Africa, Zimbabwe and Mozambique) has become vulnerable to water hyacinth infestation. Water hyacinth infested the trans-boundary Limpopo River in 2010 sourced from Hartbeesport Dam on Crocodile River in South Africa. Botswana and South Africa have been consulting each other to implement integrated control of the weed jointly in the Limpopo River. Water hyacinth could be a continuous threat to the dams and the rivers in the Limpopo basin if its control is not taken seriously.These three species are found growing in Botswana in a range of pH...
“…Daughter plants detach from parent plants and get dispersed either by water currents or by animals. "It was originally thought that water lettuce did not produce viable seeds", but seed production has now been confirmed in Africa [111], India [122], South America [123], USA [124], South-East Asia [125], and central Europe [126]. In South Africa, one fruit per plant with 4-6 seeds per fruit, 4-11 seeds per fruit in Australia [127], 4-9 seeds per fruit in Brazil [123], 6-10 seeds per fruit in India [122], and 2 fruits in a rosette with a range of 1-17 seeds per fruit averaging 4 seeds per fruit in the USA [124] have been recorded.…”
Aquatic ecosystems in Botswana have been under threat by the aquatic alien invasive plant species viz., salvinia Salvinia molesta Mitchell, water lettuce Pistia stratiotes L., and water hyacinth Eichhornia crassipes (Mart.) Solms-Laub. While salvinia has been termed the major threat to the Botswana wetlands, water lettuce and water hyacinth are considered to be of minor importance. This review presents the species biology, distribution, historical spread, negative impacts, control achieved right from their discovery in the country by referring to their control and management in the world.Having infested the Kwando-Linyanti-Chobe Rivers in the 1970s, salvinia was initially tried by the use of herbicides, paraquat and glyphosate, between 1972 and 1976. With the discovery of the host specific biological control weevil Cyrtobagous salviniae Calder and Sands in 1981, the weevil was introduced by Namibians on Kwando and Chobe Rivers in 1983 and by Botswana in 1986 in the Okavango Delta. While the control was slowly establishing in Kwando-Linyanti-Chobe Rivers, it became apparent that lakes and perennial swamps within and outside Moremi Game Reserve of the Okavango Delta were infested with salvinia from 1992 onwards.With continuous and sustained liberation of the weevil in the Kwando-Linyanti-Chobe Rivers and in the Okavango Delta between 1999 and 2000, salvinia control was achieved by 2003, and since then the weevil constantly keeps the weed at low levels. The success is mainly due to sustainable monitoring through the application of physical and biological control methods. However, salvinia is still threatening the Okavango Delta due to factors such as tourism activities, boat navigation fishing and transporttion by wild animals.The first occurrence of water lettuce was recorded on Kwando and Chobe Rivers in 1986. Its biocontrol weevil Neohydronomous affinis Hustache was released in the year 1987. The weevil became extinct in Selinda Canal and Zibadianja Lake on Kwando River due to dry and wet events for over 10 years and the weed had been under control biologically on Chobe River. Having surface covered the Selinda and a part of the Zibadianja in high flood and rainfall in 1999/2000 season, research was undertaken to contain water lettuce, which led to its eradication by 2005. Regular physical removal of the water lettuce prior to fruit maturity is an effective method of control or eradicating the weed in seasonal water bodies.The Limpopo Basin (shared by Botswana, South Africa, Zimbabwe and Mozambique) has become vulnerable to water hyacinth infestation. Water hyacinth infested the trans-boundary Limpopo River in 2010 sourced from Hartbeesport Dam on Crocodile River in South Africa. Botswana and South Africa have been consulting each other to implement integrated control of the weed jointly in the Limpopo River. Water hyacinth could be a continuous threat to the dams and the rivers in the Limpopo basin if its control is not taken seriously.These three species are found growing in Botswana in a range of pH...
“…Fruto não visto. Pistia stratiotes é uma espécie cosmopolita, ocorrendo nas margens de rios e em lagoas, estando amplamente distribuída nas regiões tropicais e subtropicais (Silva 1981). Encontrada com flores em outubro.…”
A Área de Proteção Ambiental (APA) do Cariri está localizada entre os municípios de Boa Vista e Cabaceiras, estado da Paraíba, Nordeste do Brasil. Esta APA apresenta microhabitats variados, dentre os quais se destacam os corpos aquáticos. O presente estudo compreende o levantamento das angiospermas aquáticas na APA do Cariri, onde foram registradas 29 espécies distribuídas em 22 gêneros e 14 famílias, sendo Cyperaceae a que apresentou maior riqueza específica (nove spp.). Nesse trabalho são apresentadas descrições, ilustrações, dados de distribuição, floração e/ou frutificação, além de uma chave de identificação para as espécies registradas na APA.
“…Esses ambientes podem ser eutrofizados, se comportando como daninhas, ou não, e a disponibilidade de nutrientes local influencia o tamanho da planta (SILVA, 1981) e a multiplicação assexuada com separação dos brotos em torno da planta mãe. Assim, estudos tem demonstrado que P. stratiotes apresenta diversas adaptações morfológicas e fisiológicas, para poder sobreviver em ambiente adverso (LEMON;POSLUSZNY, 2000) e controle e erradicação da espécie (SILVA, 1981).…”
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