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Influence of temperature gradients on leaf water potential.

Plant physiology (1977-02-01)
H H Wiebe, R J Prosser
ABSTRACT

Water potential was monitored at nine locations along single maize (Zea mays L.) leaf blades with aluminum block in situ thermocouple hygrometers. Water potential showed a continuous decrease toward the tip, with a 2- to 4-bar difference between leaf base and tip under both moist and dry soil conditions. The water potential difference between the soil and the leaf base was about 4 bars. Water potentials decreased during the day and during a drying cycle, and increased at night and after irrigation. Heating a band of a leaf to 40 C or cooling it to 7 C had no influence on the water potential of the affected portion when this was corrected for hygrometer output over standard calibrating solutions at the respective temperatures. Heating or cooling a portion of a leaf had neither short nor long term effects on water potential of more distal leaf portions continuously monitored by hygrometers in dew point readout. Water potential fluctuated with an amplitude of about 1.5 bars and an irregular period of 10 to 30 minutes. Measurements with silver foil in situ psychrometers gave similar results.

MATERIALS
Product Number
Brand
Product Description

Silver, foil, 15mm disks, thickness 1.0mm, as rolled, 99.95+%
Silver, foil, 15mm disks, thickness 0.009mm, 99.97%
Silver, foil, 4mm disks, thickness 0.5mm, as rolled, 99.99+%
Silver, foil, 25mm disks, thickness 0.25mm, as rolled, 99.99+%
Silver, foil, 4mm disks, thickness 0.0125mm, 99.95+%
Silver, foil, not light tested, 100x100mm, thickness 0.0125mm, 99.95+%
Silver, foil, light tested, 50x50mm, thickness 0.0125mm, 99.95+%
Silver, foil, not light tested, 100x100mm, thickness 0.0025mm, 99.97%
Silver, foil, not light tested, 300x300mm, thickness 0.025mm, as rolled, 99.95+%
Silver, foil, 50mm disks, thickness 0.008mm, 99.95+%
Silver, foil, 25mm disks, thickness 0.025mm, as rolled, 99.99+%
Silver, foil, 2m coil, thickness 0.0125mm, coil width 9mm, 99.95+%
Silver, foil, 8mm disks, thickness 1.0mm, as rolled, 99.95+%
Silver, foil, 6mm disks, thickness 0.008mm, 99.95+%
Silver, foil, light tested, 150x150mm, thickness 0.025mm, as rolled, 99.95+%
Silver, foil, 8mm disks, thickness 0.1mm, annealed, 99.95+%
Silver, foil, light tested, 100x100mm, thickness 0.025mm, annealed, 99.95+%
Silver, foil, 8mm disks, thickness 0.025mm, as rolled, 99.99+%
Silver, foil, 8mm disks, thickness 0.1mm, as rolled, 99.95+%
Silver, foil, 4mm disks, thickness 0.1mm, as rolled, 99.95+%
Silver, foil, 8mm disks, thickness 0.0025mm, 99.97%
Silver, foil, 8mm disks, thickness 0.007mm, 99.97%
Silver, foil, light tested, 100x100mm, thickness 0.025mm, as rolled, 99.99+%
Silver, foil, light tested, 150x150mm, thickness 0.05mm, annealed, 99.95+%
Silver, foil, 8mm disks, thickness 0.008mm, 99.95+%
Silver, foil, light tested, 100x100mm, thickness 0.02mm, 99.97%
Silver, foil, 8mm disks, thickness 0.05mm, as rolled, 99.95+%
Silver, foil, 6mm disks, thickness 0.5mm, as rolled, 99.99+%
Silver, foil, light tested, 150x150mm, thickness 0.035mm, as rolled, 99.95+%
Silver, foil, 8mm disks, thickness 0.035mm, as rolled, 99.95+%