Date of Award:

5-1977

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Committee Chair(s)

Neal K. Van Alfen

Committee

Neal K. Van Alfen

Committee

Marion W. Pedersen

Committee

Herman H. Wiebe

Committee

Orson S. Cannon

Abstract

The effect of Corynebacterium insidiosum (McCull) H. L. Jensen on the water relations of its host, alfalfa, was studied by field measurements made on a 6-year-old stand of Ranger alfalfa. Periodic measurements of stomatal conductance, xylem pressure potential Ψ, and root, stem, and leaf conductance were made in relation to soil moisture conditions. Water regain and electrolyte leakage studies were also made to test membrane integrity in diseased plant leaves.

At all times the xylem pressure potential Ψ was found to be much more negative in diseased plants than in healthy plants. Stomatal conductance was found to respond to the Ψ values in both diseased and healthy plants, indicating no impairment of stomatal function in diseased plants. Liquid flow conductance was found to be adversely affected in diseased plants. Flow of water through leaflet veins was found to be 60 times less in diseased than in healthy leaflets. No evidence was found in water regain or electrolyte leakage studies to suggest cellular membrane damage. Counts of bacterial colonies as related to liquid flow conductance studies indicated that location of impairment of water movement was not correlated with the location of the greatest numbers of bacteria.

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