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Water Relations of Leaf Epidermal Cells of Tradescantia virginiana    

Water Relations of Leaf Epidermal Cells of Tradescantia virginiana     Abstract Water-relation parameters (cell turgor pressure [P], volumetric elastic modulus [ε] and hydraulic conductivity [Lp]) of individual leaf epidermal cells of Tradescantia virginiana have been determined with the pressure-probe technique. Turgor was 4.5 ± 2.1 [41] bar (mean ± sd; in brackets the number of cells) and ranged from 0.9 to 9.6 bar. By vacuum infiltration with nutrient solution, it was raised to 7.5 ± 1.5 [5] bar (range: 5.3-8.8 bar). There was a large variability in the absolute value of ε of individual cells. ε ranged from 40 to 360 bar; mean ± sd: 135 ± 83 bar; n = 50 cells. ε values of individual cells seemed to be rather independent of changes in cell turgor. A critical assessment of the errors incurred in determining ε by the technique is included. The half-times of water exchange of individual cells ranged from 1 to 35 seconds, which gave values of 0.2 to 11 × 10−6 centimeters per second per bar for Lp (mean ± sd: 3.1 ± 2.3 × 10−6 centimeters per second per bar; n = 39 cells). The large range in Lp and ε is believed to be due to the difficulties in determining the effective surface area of water exchange of the cells. Lp is not influenced by active salt pumping driven by respiration energy inasmuch as it was not altered by 0.1 millimolar KCN. The temperature dependence of Lp (T½) was measured for the first time in individual higher-plant cells. Lp increased by a factor of 2 to 4, when the temperature was increased by 10 C. The activation energy of water exchange was found to be between 50 and 186 kilojoules per mole. Within the large range of variation it was found that T½, Lp, and ε did not change under various experimental conditions (intact and excised tissue, water content and turgidity, age, etc.). Similar results were obtained for the epidermal cells of Tradescantia andersoniana. The measurements suggest that the entire epidermis would respond very rapidly (i.e. with a half-time of 1 to 30 s) to a demand for water from the stomata. 1 Supported by a grant from the Deutsche Forschungsgemeinschaft, Zi 99/7, and by a research fellowship to A. D. T. from the Royal Society (U.K.). 2 Dedicated to the memory of Noë Higinbotham. This content is only available as a PDF. © 1981 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Plant Physiology Oxford University Press

Water Relations of Leaf Epidermal Cells of Tradescantia virginiana    

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References (21)

Publisher
Oxford University Press
Copyright
Copyright © 2021 American Society of Plant Biologists
ISSN
0032-0889
eISSN
1532-2548
DOI
10.1104/pp.68.5.1135
Publisher site
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Abstract

Abstract Water-relation parameters (cell turgor pressure [P], volumetric elastic modulus [ε] and hydraulic conductivity [Lp]) of individual leaf epidermal cells of Tradescantia virginiana have been determined with the pressure-probe technique. Turgor was 4.5 ± 2.1 [41] bar (mean ± sd; in brackets the number of cells) and ranged from 0.9 to 9.6 bar. By vacuum infiltration with nutrient solution, it was raised to 7.5 ± 1.5 [5] bar (range: 5.3-8.8 bar). There was a large variability in the absolute value of ε of individual cells. ε ranged from 40 to 360 bar; mean ± sd: 135 ± 83 bar; n = 50 cells. ε values of individual cells seemed to be rather independent of changes in cell turgor. A critical assessment of the errors incurred in determining ε by the technique is included. The half-times of water exchange of individual cells ranged from 1 to 35 seconds, which gave values of 0.2 to 11 × 10−6 centimeters per second per bar for Lp (mean ± sd: 3.1 ± 2.3 × 10−6 centimeters per second per bar; n = 39 cells). The large range in Lp and ε is believed to be due to the difficulties in determining the effective surface area of water exchange of the cells. Lp is not influenced by active salt pumping driven by respiration energy inasmuch as it was not altered by 0.1 millimolar KCN. The temperature dependence of Lp (T½) was measured for the first time in individual higher-plant cells. Lp increased by a factor of 2 to 4, when the temperature was increased by 10 C. The activation energy of water exchange was found to be between 50 and 186 kilojoules per mole. Within the large range of variation it was found that T½, Lp, and ε did not change under various experimental conditions (intact and excised tissue, water content and turgidity, age, etc.). Similar results were obtained for the epidermal cells of Tradescantia andersoniana. The measurements suggest that the entire epidermis would respond very rapidly (i.e. with a half-time of 1 to 30 s) to a demand for water from the stomata. 1 Supported by a grant from the Deutsche Forschungsgemeinschaft, Zi 99/7, and by a research fellowship to A. D. T. from the Royal Society (U.K.). 2 Dedicated to the memory of Noë Higinbotham. This content is only available as a PDF. © 1981 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Journal

Plant Physiology – Oxford University Press

Published: Nov 1, 1981

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