Plant Water Potential Gradients Measured in the Field by Freezing Point

Cary, J.W. and Fisher, H.D. (1971) Plant Water Potential Gradients Measured in the Field by Freezing Point. Physiologia Plantarum (Sweden). 24(3):397-402.

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Abstract

A portable freezing point meter was used in the field to
measure the water potential gradients in sunflower (Helianthus
annuus), beans (Phaseolus vulgaris), corn (Zea mays),
wheat (Tritium aestivum), pumpkin (Cucurbita pepo), potato
(Solanam tuberosum), alfalfa (Medicago sativa), and sugarbeets
(Beta vulgaris). The measurements were made between
daybreak and sunrise, and again during the middle of the
afternoon on days when the potential evapotranspiration
varied between 6.5 and 8.0 mm of water.
The gradients varied from a maximum of 0.2 bar per cm
in a wheat, down to an undetectable value for pumpkin. Although
most of the soil in the root zone was kept at potentials
above –1 bar, the bulk of the root tissue had water
potentials of –5 to –10 bars. Differences in water potential
between shaded and unshaded leaves, and between leaf tissue
and guttation fluid suggested a similar drop of several bars
between xylem elements and the surrounding leaf tissue in
some plant species. The implications of such drops are discussed
with respect to plant water transport equations and
pressure cell potential measurements.

Item Type:	Article
NWISRL Publication Number:	0202
Subjects:	Mass Import - unclassified
Depositing User:	Dan Stieneke
Date Deposited:	20 Nov 2010 21:51
Last Modified:	24 Feb 2017 21:01
Item ID:	211
URI:	https://eprints.nwisrl.ars.usda.gov/id/eprint/211