Date of Award:

5-1968

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Plant Physiology

Committee Chair(s)

H. H. Wiebe

Committee

H. H. Wiebe

Committee

P. J. Carter

Committee

R. T. Sanders

Committee

G. W. Welkie

Committee

M. C. Williams

Committee

S. A. Taylor

Abstract

Experiments involving pressure, temperature, salt solutions, decenylsuccinic acid, a surfactant, and respiration inhibitors including azide, dinitrophenol, malonate, and iodoacetic acid were conducted to determine the extent to which the cytoplasm of the parenchymatous cells of the potato tuber influenced the tissue's water filterability.

The amount of water or solution moved through the potato tissue was measured by applying a pressure differential to the solution, forcing it across a 1.0 mm thick disc of tissue which was supported in a pressure filtration apparatus. The solution moved was collected and measured directly. In certain experiments the conductivity of dialysis membrane material was compared with that of the potato tissue under the same conditions.

On the basis of conductivity measurements, cm3/min/atm, potato tissue resistance to water movement decreased with pressure in a manner somewhat similar to that observed when water is forced through root systems. The resistance of dialysis membrane increased under the same conditions. Concentrated solutions (10-4 to 10-2 M) of calcium and sodium chlorides increased the conductivity of potato tissue in all treatments. However, some degree of antagonism was exhibited by the presence of additional monovalent cations. Calcium chloride plus o.1 N Hoagland's solution was less effective than when calcium chloride was the only salt in solution, but sodium chloride caused a greater increase in conductivity when it was in the presence of the additional salts in the 0.1 N Hoagland's solution.

In those experiments involving the effects of the respiratory inhibitors, the surfactant, and decenylsuccinic acid on the tissue's conductivity and respiration, indicated that the two properties were not directly linked. Except for malonate, neither agent influenced conduction and respiration in the same manner; conductivity appeared to follow a course that was independent of that of respiration. Conductivity was increased by all except malonate, whereas respiration was decreased except by 10-5 and 10-4 M concentrations of dinitrophenol and 10-5 M azide. The dissimilar effect of the various chemical agents on respiration and conduction suggest that an independent status exists for them.

Although prolonged physiologically high temperature treatments disrupted the normal conductivity pattern while having relatively little effect on respiration, respiration responded to sequential temperature treatments to a much greater extent and with a different pattern than did conductivity. Also, the activation energy measurements for respiration were considerably higher than those for conductivity. But the range of activation energy values for conductivity of potato discs was generally higher than those for dialysis membrane conductivity. Therefore, as with the effects of the chemical agents, the effects of the temperature treatments also indicated that no direct link between conductivity and respiration exists.

The average of 32 permeability calculations, 16 x 10-4 cm/min/atm, was from 2 to 1000 times greater than the values generally reported for the high and low permeabilities, respectively, for various types of plant cells. These high values for permeability and the absence of a direct connection between conduction and respiration indicate that a non-protoplasmic pathway exists in the potato tuber tissue as the major avenue of water movement.

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