The Rise of Sap in Tall Grapevines.

Scholander, P. F.; Love, Warner E.; Kanwisher, John

doi:10.1104/pp.30.2.93

Cited by 113 publications

(67 citation statements)

References 19 publications

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“…This happens whether wvater freezes in bulk or in glass capillaries (27). It has been shown that the sap of the grapevine is fully saturated with dissolved atmiiosplheric nitrogen (28), and the same very likely holds also for other species. One must, therefore, assume that gas bubbles are formed whelnever freezing takes place in sap-filledl vessels and tracheids, andl a great many of these wvould henice becolme emptie(d aild eliminiatedl for the transl)ort system, wrere the sap under tension at the time of thawing.…”

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confidence: 87%

“…The only mechanism which might conceivably repair suich breaks, would be a sap pressure higlh enough to redlissolve the gas. In the case of the grapevine, which empties its vessels during the winter, the root pressuire in the sprinlgtime is so high that it nmay readily refill the conducting system (28). But such pressures are at present known only in a few hardwood species (3,8,13,17,32).…”

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confidence: 99%

“…XVith exception of the grapevine, an(l probably some other species which have air-filled vessels in the winter (28), it is known that the water content at all levels in the xylem of several species of trees remains as high or nearly as lhigh in winter as in sumimer (7,9,15,16,30).…”

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Winter Freezing in Relation to the Rise of Sap in Tall Trees.

Lybeck

1959

Plant Physiol.

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Winter Freezing in Relation to the Rise of Sap in Tall Trees.

Lybeck

1959

Plant Physiol.

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“…Scholander et al (7) showed this to be true in a leafless grapevine. In a plant with leaves, the water column is usually under tension, but nevertheless a static column should still show a hydrostatic gradient if the tube model is applicable.…”

Section: Iamentioning

confidence: 99%

Water Potential Gradient in a Tall Sequoiadendron

1971

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With an elevator installed in a 90-meter tall Sequoiadendron to collect the samples, xylem pressure potential measurements were made approximately every 15 meters along 60 meters of the tree's height. The measured gradient was about -0.8 bar per 10 meters of height, i.e., less than the hydrostatic gradient. Correction of the xylem pressure potential data by calibration against a thermocouple psychrometer confirmed this result. Similar gradients are described in the literature in tall conifers at times of low transpiration, although a different sampling teehnique was used. If the data in the present study and those supporting it are typical, they imply a re-evaluation of either the use of the pressure chamber to estimate water potential or the present theories describing water transport in tail trees. measurements at each sample position, with maxima and minima bracketed, are represented in Figure 1A. Along with these data is a line indicating the hydrostatic gradient.The observed gradient in xylem pressure potential (about -0.8 bars per 10 m) is not as steep as the hydrostatic gradient. However, errors involved in the pressure chamber method of .r . B IAIf the vascular system of a vertical plant stem acts like a series of long tubes, one might expect the water in it to show a hydrostatic gradient in its water potential (about 1.0 bar decrease per 10 m of height). Scholander et al. (7) showed this to be true in a leafless grapevine. In a plant with leaves, the water column is usually under tension, but nevertheless a static column should still show a hydrostatic gradient if the tube model is applicable. The existence of resistance to water flow through the xylem suggests that a gradient greater than hydrostatic should exist in an actively transpiring plant. However, in Sequoia sempervirens (D. Don) Endl. and Pseudotsuga menziesii (Mirb.) Franco., Scholander (6) found indications that water potential gradients approximated a pure hydrostatic gradient, even at midday.The rigging of an elevator in a 90-m Sequoiadendron giganteum (Lindl.) Buchh. in Kings Canyon National Park, California, allowed for the first time the rapid and replicate measurement of water potentials at known heights to the top of a tall tree. A Scholander-type pressure chamber (8) was carried aloft and readings of xylem pressure potential were taken on small, shaded twigs growing not more than 2 m from the bole of the tree. All samples were collected between 1300 and 1500 hr when Sequoiadendron was found to have a plateau in its diurnal cycle of xylem pressure potential. Not more than 1 min elapsed between the time of cutting the twig and sealing it inside the pressure chamber for any sample. The measurements were made on an overcast day with a relative humidity of about 70% and temperatures of 11 to 13 C at different sampling elevations. The means of three or four replicate

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“…This has been a result of the creation of new techniques based on the detection of sounds (Milburn, 1973) or, more reliably, ultrasounds (Tyree and Dixon, 1983) (Scholander et al, 1955;Hammel, 1967;Sucoff, 1969) using an instrument similar to the one described by Sandford and Grace (1985), slightly modified. Freezing of stem tissues was monitored with thermocouple sensors (type T) connected to a strip chart recorder.…”

Section: Introductionmentioning

confidence: 99%