SUMMARY In the laboratory flat forms of the Lemna gibba/Lemna minor complex which are potentially... more SUMMARY In the laboratory flat forms of the Lemna gibba/Lemna minor complex which are potentially gibbous, swell up in the presence of extremely low concentrations of ethylene (from 24 nl/l air upwards). In control cultures, where the ethylene concentration is 16 nl/l air or lower, the plants remain flat. In ditches in the Netherlands ethylene concentrations occur which are in the same range as the concentrations which induce gibbosity in the laboratory. These are further indications that ethylene is the gibbosity regulator of the Lemna gibba/Lemna minor complex in natural waters.
SUMMARY In the laboratory flat forms of the Lemna gibba/Lemna minor complex which are potentially... more SUMMARY In the laboratory flat forms of the Lemna gibba/Lemna minor complex which are potentially gibbous, swell up in the presence of extremely low concentrations of ethylene (from 24 nl/l air upwards). In control cultures, where the ethylene concentration is 16 nl/l air or lower, the plants remain flat. In ditches in the Netherlands ethylene concentrations occur which are in the same range as the concentrations which induce gibbosity in the laboratory. These are further indications that ethylene is the gibbosity regulator of the Lemna gibba/Lemna minor complex in natural waters.
International Journal of Agronomy and Plant Production, 2013
Anion transporting proteins belonging to the chloride cnannel (CLC) family are involved in anion ... more Anion transporting proteins belonging to the chloride cnannel (CLC) family are involved in anion homeostasisin variety of organisms. They seem to play a role in different processes (osmo-regulation, detoxification, cell expansion, and maybe more). Roles those are so important in plant cells that several protein systems exist which can fulfill these roles next to the CLC proteins. Functional studies on these proteins require, next to creativity of the researcher, very specific conditions in the experiments (for instance Ca 2+ alleviation of Cd 2+ effects) to observe phenotypes. Several important issues remain to be studied: the role of the two CBS domains and the role of ATP binding in the functioning of CLC proteins as shunts and osmo-regulators. Also important for plants is the strictness of the duality of CLC proteins as specific Cl or specific NO3 transporters and the strictness of the duality as channels or H + -cotransporters. The study of the CLC protein family will remain a challenge for researchers in the coming years.
Leaves from the submerged angiosperm P. lucens are able to assimilate bicarbonate. These leaves b... more Leaves from the submerged angiosperm P. lucens are able to assimilate bicarbonate. These leaves behave polarly: during bicarbonate utilization protons (H/sup +/) are excreted by the cells of the lower epidermis, while hydroxyl (OH/sup -/) ions are excreted by the upper epidermal cells. It has been proposed that acidification of the apoplast is a prerequisite for bicarbonate utilization. To test this hypothesis /sup 14/C fixation by protoplasts was determined at different pH values. Also experiments, using the isotopic disequilibrium technique were performed. They showed that at pH values > 8, bicarbonate is a major carbon source for photosynthesis in protoplasts, despite the absence of cell walls and polarity. At pH values around 6, the rate of /sup 14/C-fixation in protoplasts equals that of intact leaves. At pH values > 8, however, intact leaves show a higher rate. From this, and other experiments, the authors conclude that at least 2 processes contribute to bicarbonate utilization in P. lucens leaves: active transport (H/sup +/-HCO/sub 3//sup -/ symport.) and acidification of the apoplast resulting in the conversion of bicarbonate into CO/sub 2/. Polarity may increase the efficiency of both.
Volgens berekeningen die worden gebruikt voor verkeersvliegtuigen kunnen bijen en hommels niet vl... more Volgens berekeningen die worden gebruikt voor verkeersvliegtuigen kunnen bijen en hommels niet vliegen. Toch zie je het ze doen, hoe kan dat? Vogels, vleermuizen en insecten gebruiken anders dan vliegtuigen meer dan een principe om in de lucht te blijven. Door metingen aan de luchtstroom rond insectenvleugels tijdens de vlucht, heeft men een goed beeld gekregen van de manier waarop ze in de lucht blijven. Studies aan vliegende bijen zelf leveren nog geen compleet beeld op van het ontstaan van de krachten tussen slaande vleugels en lucht bij die soort. We spelen daarom leentjebuur bij kennis over fruitvliegjes, hommels en zweefvliegen om in te zien hoe bijen vliegen.
SUMMARY In the laboratory flat forms of the Lemna gibba/Lemna minor complex which are potentially... more SUMMARY In the laboratory flat forms of the Lemna gibba/Lemna minor complex which are potentially gibbous, swell up in the presence of extremely low concentrations of ethylene (from 24 nl/l air upwards). In control cultures, where the ethylene concentration is 16 nl/l air or lower, the plants remain flat. In ditches in the Netherlands ethylene concentrations occur which are in the same range as the concentrations which induce gibbosity in the laboratory. These are further indications that ethylene is the gibbosity regulator of the Lemna gibba/Lemna minor complex in natural waters.
SUMMARY In the laboratory flat forms of the Lemna gibba/Lemna minor complex which are potentially... more SUMMARY In the laboratory flat forms of the Lemna gibba/Lemna minor complex which are potentially gibbous, swell up in the presence of extremely low concentrations of ethylene (from 24 nl/l air upwards). In control cultures, where the ethylene concentration is 16 nl/l air or lower, the plants remain flat. In ditches in the Netherlands ethylene concentrations occur which are in the same range as the concentrations which induce gibbosity in the laboratory. These are further indications that ethylene is the gibbosity regulator of the Lemna gibba/Lemna minor complex in natural waters.
International Journal of Agronomy and Plant Production, 2013
Anion transporting proteins belonging to the chloride cnannel (CLC) family are involved in anion ... more Anion transporting proteins belonging to the chloride cnannel (CLC) family are involved in anion homeostasisin variety of organisms. They seem to play a role in different processes (osmo-regulation, detoxification, cell expansion, and maybe more). Roles those are so important in plant cells that several protein systems exist which can fulfill these roles next to the CLC proteins. Functional studies on these proteins require, next to creativity of the researcher, very specific conditions in the experiments (for instance Ca 2+ alleviation of Cd 2+ effects) to observe phenotypes. Several important issues remain to be studied: the role of the two CBS domains and the role of ATP binding in the functioning of CLC proteins as shunts and osmo-regulators. Also important for plants is the strictness of the duality of CLC proteins as specific Cl or specific NO3 transporters and the strictness of the duality as channels or H + -cotransporters. The study of the CLC protein family will remain a challenge for researchers in the coming years.
Leaves from the submerged angiosperm P. lucens are able to assimilate bicarbonate. These leaves b... more Leaves from the submerged angiosperm P. lucens are able to assimilate bicarbonate. These leaves behave polarly: during bicarbonate utilization protons (H/sup +/) are excreted by the cells of the lower epidermis, while hydroxyl (OH/sup -/) ions are excreted by the upper epidermal cells. It has been proposed that acidification of the apoplast is a prerequisite for bicarbonate utilization. To test this hypothesis /sup 14/C fixation by protoplasts was determined at different pH values. Also experiments, using the isotopic disequilibrium technique were performed. They showed that at pH values > 8, bicarbonate is a major carbon source for photosynthesis in protoplasts, despite the absence of cell walls and polarity. At pH values around 6, the rate of /sup 14/C-fixation in protoplasts equals that of intact leaves. At pH values > 8, however, intact leaves show a higher rate. From this, and other experiments, the authors conclude that at least 2 processes contribute to bicarbonate utilization in P. lucens leaves: active transport (H/sup +/-HCO/sub 3//sup -/ symport.) and acidification of the apoplast resulting in the conversion of bicarbonate into CO/sub 2/. Polarity may increase the efficiency of both.
Volgens berekeningen die worden gebruikt voor verkeersvliegtuigen kunnen bijen en hommels niet vl... more Volgens berekeningen die worden gebruikt voor verkeersvliegtuigen kunnen bijen en hommels niet vliegen. Toch zie je het ze doen, hoe kan dat? Vogels, vleermuizen en insecten gebruiken anders dan vliegtuigen meer dan een principe om in de lucht te blijven. Door metingen aan de luchtstroom rond insectenvleugels tijdens de vlucht, heeft men een goed beeld gekregen van de manier waarop ze in de lucht blijven. Studies aan vliegende bijen zelf leveren nog geen compleet beeld op van het ontstaan van de krachten tussen slaande vleugels en lucht bij die soort. We spelen daarom leentjebuur bij kennis over fruitvliegjes, hommels en zweefvliegen om in te zien hoe bijen vliegen.
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