March 1996
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Publications (33)
March 1996
March 1995
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7 Reads
Aquatic Botany
March 1995
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4 Reads
Aquatic Botany
March 1995
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5 Reads
Aquatic Botany
March 1995
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14 Reads
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2 Citations
Aquatic Botany
December 1990
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45 Reads
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26 Citations
Aquatic Botany
The pollination ecology of Zannichellia palustris L. was studied in natural and aquarium populations in Utah, U.S.A. and Zürich, Switzerland. This monoecious plant was found to be self- and cross-pollinated. The pollen grains are somewhat sticky as they are released from the anther thecae, and are initially dispersed in a non-random manner in many small threads or ‘clouds’. The adhesive in transient and within minutes the individual grains are set free and sink. The primary effect is for the pollen to be dispersed in small clouds or threads of grains instead of as one large cloud of grains randomly spaced apart. This type of dispersal may increase the frequency of collision with the stigma. By experiment it was found that the presence of stigmas stimulated pollen germination; this can lead to the presence of some precociously germinated pollen grains in the water surrounding flowers; these thread-like grains are rare in natural conditions and are not considered to be important in pollination. Emasculated isolated plants failed to set seed, indicating agamospermy to be unlikely. Although underwater pollination has been previously considered to be highly inefficient the fruit-set efficiency varied from 55.6 to 91%, which must be considered high. Most seed develops from self-pollination, but some outbreeding was demonstrated in artificial and natural populations.
November 1990
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45 Reads
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18 Citations
Aquatic Botany
Althenia filiformis Petit is a habitual colonizer of brackish water. In Sardinia, at least, it is annual and dependent on sexual reproduction. Seeds remain in the fruit and germinate underwater. Some seeds germinate while still on the mother plant, others after a period of desiccation; low temperatures or periods in darkness induce germination of dormant seeds. Althenia is not able to utilize HCO3− and is dependent on CO2 as a carbon source. The leaves reach the water surface where they not only get CO2, but are exposed to considerable wave action. They thus have relatively large marginal bundles of fibres. Althenia is monoecious, but some male and female flowers develop close together and form a bisexual floral unit. Pollination takes place either on the upper surface of the water (epihydrophily) or inside gas bubbles underwater (bubble autogamy) - which accounted for about half the seed set in cultivated populations. The pollen does not form stable rafts or “search vehicles”, but spreads as individual grains over the water surface. Pollination at the water surface probably leads to a high degree of outbreeding.
November 1990
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50 Reads
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22 Citations
Aquatic Botany
The floral biology of the obligately aquatic plant species Groenlandia densa (L.) Fourreau was studied. It is effectively pollinated (1) in air above the water surface (anemophily), (2) at the water surface where the stigmas can pick up pollen grains directly from the surface of the water (epihydrophily), or (3) underwater with wet stigmas (hypohydrophily). Underwater, the pollen grains are associated with the air-water interface of bubbles, but they may be positioned on both sides of this interface. The breeding system is almost entirely autogamous with self-fertilization; a slight degree of proterogyny may permit some outbreeding.
September 1990
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34 Reads
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35 Citations
Aquatic Botany
Nymphoides peltata (S.G. Gmelin) O. Kuntze is a common and relatively widespread aquatic plant; for efficient dispersal seeds must be transported over land from one body of water to another. The seeds are thin-walled and digested by fish and waterfowl and thus unsuitable for endozoochory. The seeds are disc-like with rigid marginal trichomes, they are heavier than water and are kept floating by a relatively weakly hydrophobic coating. They occupy the air-water interface and aggregate into chainlike rafts thus offering vectors moving through the water large targets. The seeds are picked up by some parts of waterfowl, such as the flanks, the region between bill and eyes and the webs of the feet of the mallard, and the bill and shield of the coot; perhaps some amphibious mammals also play a role. The marginal trichomes ensure that the seeds stick to the vector in a dry atmosphere. When the marginal trichomes are removed the seeds sink with the slightest disturbance, but if they do stick to a vector they fall off as they become dry. The weakly hydrophobic coating guarantees that the seeds will be discarded in water where they need to be for germination. Seeds made highly hydrophobic by being coated with silicon or teflon would not stick to vectors, neither would they sink; if made hydrophilic they would not float nor would they stick to vectors in water but if deliberately placed on a vector in air they were not discarded when the vector was put into water.
Citations (23)
... Brazil, South America, Bangladesh, China, Colombia, Borneo, Ecuador, Africa, Malaya, India, Indonesia, Nepal, Papua New Guinea, Peru, Solomon Islands, Sri Lanka, Taiwan, Thailand, and Vietnam are its native regions. In India, it is widely distributed to Andhra Pradesh, Assam, Chhattisgarh, Goa, Gujarat, Himachal Pradesh, Kerala, Karnataka, Meghalaya, Maharashtra, Madhya Pradesh, Odisha, Rajasthan, and Tamil Nadu (11). ...
- Citing Article
March 1996
... Samples of emergent plants and algae were collected and their morphological features were analyzed for identification. The identification of aquatic plants was carried out with the help of Cook and Rutishauser (2001), and Gamble (2008). The abundance is usually measured by counting the plant species in the sampling quadrate. ...
- Citing Article
November 2001
Taxon
... Posteriormente, las mejores secciones fueron montadas en miel Karo natural diluida en agua al 70% y selladas con barniz transparente. Todas las ilustraciones de estructuras internas fueron elaboradas usando un accesorio de camara lucida o siguiendo los procedimientos recomendados por Cook (1998). Para ilustrar las plantas prensadas (caracteres externos) se hicieron dibujos calcados, en papel albanene, de fotografías B & N. La razón para ésto es sencilla, los dibujos constituyen la mejor manera de hacer evidentes y claros los caracteres (Cook 1998); las fotografías, por el contrario, dificultan la interpretación taxonómica de los mismos dada la nula profundidad de campo permitida por las preparaciones. ...
- Citing Article
May 1998
Taxon
... Such habitats have a long history of human uses, as many have been transformed to extract salt in the past (De Wit et al., 2019). Their vegetation is composed of macrophytes and Characeae with narrow ecological niches (Cook & Guo, 1990;Verhoeven, 1975), including several species of high conservation issues, mainly associated with this habitat. This is notably the case for Althenia filiformis Petit, Riella helicophylla (Bory & Mont.) ...
- Citing Article
November 1990
Aquatic Botany
... Hydroautogamy have been reported in three hermaphroditic genera of Potamogetonaceae [4,17,18]. In these genera, another uncommon pollination phenomenon was reported. ...
- Citing Article
August 1989
Aquatic Botany
... Some families of Diptera (Chironomidae) have a positive ecological role both in the larval and in the aquatic environment the adult state (Dejoux, 1981). ...
- Citing Article
December 1981
Aquatic Botany
... In Sarawak, a species of Baccaurea (Euphorbiaceae) flowering in the forest understorey was visited only by muscid flies (Nagamitsu & Inoue, 1994). In India, the dioecious aquatic herb, Blyxa octandra (Hydrocharitaceae) was visited mostly by calliphorids and muscids (Cook, Luond & Nair, 1981) and, in Hong Kong, calliphorids were the commonest visitors to two species of Lithocarpus (Corlett, 2001). A calliphorid fly, Stomorhina obsoleta, was the commonest flower-visiting insect on the Amami Islands (28.30x ...
- Citing Article
December 1981
Aquatic Botany
... They are known to become dominant in many freshwater environments (Langeland, 1996;Murphy, 1988), forming dense semi-floating mats with intertwined vegetation (Gordon-Bradley et al., 2014;Madigan et al., 1975). Hydrilla verticillata exhibits a highly branched structure, with narrowly serrate leaves arranged in whorls (Cook and Lüönd, 1982). Mayaca fluviatilis possesses simple needle-shaped leaves arranged spirally (Su et al., 2020). ...
- Citing Article
December 1982
Aquatic Botany
... (Haynes and Holm-Nielsen, 1999 Geographical distribution and ecology: Venezuela, Colombia, Guyana, Suriname, Brazil and Bolivia. It is found mainly in low altitude areas, however it is recorded up to 1500 m in Colombia (Cook, 1985). In Brazil, the species is found in the North (Amazonas, Pará, Roraima and Tocantins), Northeast (Bahia, Ceará, Maranhão, Paraíba, Pernambuco, Piauí, Rio Grande do Norte and Sergipe), Central-West (Goiás, Mato Grosso do Sul and Mato Grosso) and Southeast (Minas Gerais, Rio de Janeiro and São Paulo) regions (Lourenço and Bove, 2019). ...
- Citing Article
February 1985
Aquatic Botany
... The relatively recent self-establishment of O. ovalifolia in New Zealand (McCullough, 1997) suggests that the species can disperse long distances and is capable of colonising isolated freshwater bodies opportunistically. Furthermore, O. ovalifolia is cleistogamous in the deeper rock-holes and generally only produces open flowers when the water is shallow (usually at draw-down when the rock-holes are nearly dry; a feature seen in several members of the genus), with an estimated 90-95% of O. ovalifolia seeds the result of cleistogamous self-pollination (Cook et al., 1984;Ernst-Schwarzenbach, 1956). These flexible reproductive strategies are possibly an adaptation for the establishment and persistence of O. ovalifolia in ephemeral waterbodies from arid and semi-arid regions, where populations are small, widely separated, and where pollinators may be limiting. ...
- Citing Article
April 1984
Aquatic Botany