Some Applications of the Thermoelectric Method for Measuring Water Flow Rates in Plants<sup>1</sup>

Bloodworth, M. E.; Page, J. Bryan; Cowley, W. R.

doi:10.2134/agronj1956.00021962004800050008x

Cited by 33 publications

(11 citation statements)

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“…This conclusion is also supported by measurements of flow velocity in herbs and shrubs using the heat pulse technique Schmidt, 1936,1937). Zimmermann and Brown (1980) reported that the L-value determined experimentally was one magnitude smaller than the value calculated theoretically (see also Bloodworth, 1956;Wendt et al, 1965). Interestingly, the average flow velocity of 2.8 * m -s-l measured by the heat pulse technique (Huber, 1932) agrees very well with the value of 2.5 -m -s-l reported here.…”

Section: Discussionsupporting

confidence: 82%

Direct Measurements of the Pressure and Flow in the Xylem Vessels of Nicotiana tabacum and their Dependence on Flow Resistance and Transpiration Rate

1991

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The relationships between xylem tension, velocity of water ascending and transpiration in tobacco plants were measured by means of the "xylem pressure probe technique" (Balling, A. and Zimmermann, U., Planta 182,325-338.19901. The flow velocity was determined by suction or injection of fluorescein (or FITC-labelled dextrans of various molecular weights) from the microcapillary of the pressure probe into the punctured xylem vessel, followed by serial-sectioning of the stem after a given propagation time. The distance travelled was defined as the distance from the injection point to the uppermost xylem section in which the dye could be detected.For a transpiration rate of 0.52 f 0.121111 -h-', a linear dependence between the flow velocity and the tension gradients was found as expected from the Hagen-Poiseuille law. The slope of the straight lines decreased with increasing molecular weight of the fluorescent labelled compound, presumably because of (partial) plugging of the pit membranes. The average value of the flow velocity (2.5 -m -s-') was one magnitude smaller than the value estimated from the geometric dimensions of the xylem vessels, but agreed well with the literature value of 2.8 -m

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Section: Discussionsupporting

confidence: 82%

Direct Measurements of the Pressure and Flow in the Xylem Vessels of Nicotiana tabacum and their Dependence on Flow Resistance and Transpiration Rate

1991

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“…This is mainly because it is simple and accurate compared with other methods, as described by Slavik (1974). For example, Kuniya(1950), Bloodworth(1955;1956), Closs(1958), Ledefoged (1960), Kobayashi(1963), Decker and Skau (1964), Skidmore and Stone (1964), Wendt et al (1965), Swanson (1972), Morikawa (1972;, Shaw and Gifford (1975), Stone and Shirazi (1975), and Schurer et al (1979) have used the heat pulse method to study the water velocity in the trunk of arbores or in the stem of herbaceous plants in relation to environmental conditions. However, as pointed out by Marshall (1958), the heat pulse method has a fundamental disadvantage in that the measured pulse velocity is different from the stream velocity of water in a trunk or stem of plants.…”

Section: Introductionmentioning

confidence: 99%

A Heat Balance Method for Measuring Water Flux in the Stem of Intact Plants

Sakuratani

1981

J. Agric. Meteorol.

446

259

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This paper describes the method and apparatus for measuring the flow rate of water in intact plant stems, on the basis of heat balance of a stem segment. Under stationary conditions, the heat energy supplied continuously to a segment of plant stem is partitioned into three components such as conduction, mass flow and convection [see Eq. (1)]. By predetermining both heat losses due to conduction in the stem and convection from the segment surface into ambient air, it is possible to evaluate the heat loss due to mass flow of water in the stem, that is, the water flow rate equivalent to the transpiration stream. The water flow rate evaluated by this method is compared with the transpiration loss of water determined directly by weighing potted soybean and sunflower plants and measured by using a chamber method. The comparison shows there is a good agreement between them. This indicates that the newly developed method can be applied for determining transpiration rates of intact plants under laboratory and field conditions.

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“…Plant water deficits may induce both leaf and boll abscission from cotton under field conditions (5,6,18). In most instances, actual separation follows relief from the deficit and rehydration of the abscission zone.…”

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confidence: 99%

An Effect of Water Stress on Ethylene Production by Intact Cotton Petioles

1972

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The concept that ethylene is an endogenous growth regulator has evolved in the past few years (16). This concept has been strengthened by recent findings that internal concentrations of endogenous ethylene in vegetative tissues reach physiologically active levels (3,12,13). These internal concentrations have been directly related to the corresponding production rates of excised tissues (13), although parallel data on production rates of intact plant tissues are not available. Using excised abscission zones from primary bean leaves, Jackson and Osborne (9) presented evidence that the timing of abscission of explant petioles can be related to the extent of ethylene production adjacent to the separation zone. They suggest that the ethylene production is coupled to a particular stage of senescence. Further, they proposed that in natural leaf abscission ethylene initiates the biochemical sequences leading to separation, but the mechanism is not clear. Beyer and Morgan (4) have recently shown that ethylene production by and internal levels in detached cotton cotyledons increases as auxin transport declines. Amounts of exogenous ethylene necessary to induce abscission and inhibit auxin transport were similar. They propose that the rise in ethylene production and decline in auxin transport capacity are causally related and that reduced auxin transport is one of the ethylene mediated actions which precede induction of hydrolytic enzymes in the separation layer. Their measurement of ethylene involved whole cotyledons and was not restricted to the petiole. McAfee and Morgan (13) found internal ethylene levels and production rates were several times higher in petioles than leaf blades. Since auxin must be translocated through the petiole to the abscission zone, this observation strengthens the proposed role of ethylene in auxin transport inhibition preceding cotton leaf abscission (4). Alternatively, high rates of ethylene production by petiole tissue near the abscission zone may directly trigger the biochemical changes preceding separation independent from the proposed effect on auxin supply to the abscission zone.Aside from abscission related to senescence, little attention has been directed to other problems of natural abscission, particularly those involving environmental stresses. Plant water deficits may induce both leaf and boll abscission from cotton under field conditions (5, 6, 18). In most instances, actual separation follows relief from the deficit and rehydration of the abscission zone. This communication describes the effect of a brief period of water deficit on ethylene production by intact cotton petioles. MATERIALS AND METHODSCotton plants (Gossypium hirsutum L. var TM-1) used in this study were grown in pots containing sand in a greenhouse and were between 75 and 90 days of age. Each pot contained two plants of equal size, each with 15 to 17 leaves on the main stem. The use of paired plants made possible the determination of leaf water potential on one plant, while ethylene production was measured on the ...

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Some Applications of the Thermoelectric Method for Measuring Water Flow Rates in Plants¹

Cited by 33 publications

References 5 publications

Direct Measurements of the Pressure and Flow in the Xylem Vessels of Nicotiana tabacum and their Dependence on Flow Resistance and Transpiration Rate

Direct Measurements of the Pressure and Flow in the Xylem Vessels of Nicotiana tabacum and their Dependence on Flow Resistance and Transpiration Rate

A Heat Balance Method for Measuring Water Flux in the Stem of Intact Plants

An Effect of Water Stress on Ethylene Production by Intact Cotton Petioles

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Some Applications of the Thermoelectric Method for Measuring Water Flow Rates in Plants1

Cited by 33 publications

References 5 publications

Direct Measurements of the Pressure and Flow in the Xylem Vessels of Nicotiana tabacum and their Dependence on Flow Resistance and Transpiration Rate

Direct Measurements of the Pressure and Flow in the Xylem Vessels of Nicotiana tabacum and their Dependence on Flow Resistance and Transpiration Rate

A Heat Balance Method for Measuring Water Flux in the Stem of Intact Plants

An Effect of Water Stress on Ethylene Production by Intact Cotton Petioles

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Some Applications of the Thermoelectric Method for Measuring Water Flow Rates in Plants¹