Date of Award:

5-1970

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Botany

Committee Chair(s)

Herman H. Wiebe

Committee

Herman H. Wiebe

Committee

R. L. Smith

Committee

H. P. Stanley

Committee

G. W. Miller

Committee

M. C. Williams

Committee

F. B. Salisbury

Committee

L. L. Hoeffert

Abstract

The effect of fluoride fumigation on water relations and several enzymes of Glycine max and Pelargonium zonale plants were studied.

Glycine Max leaves absorbed 600 parts per million fluoride from an atmosphere of 15 parts per billion fluoride during 96 hours fumigation. Lower, fully expanded leaves were always more severely damaged than the upper younger leaves. In day versus night fumigation experiments, although daytime fumigated plants absorbed less fluoride than continuously fumigated plants, they had two to three times more fluoride than the nighttime fumigated ones and also exhibited more severe damage.

Transpiration of fumigated plants decreased markedly, presumably due to the closing of stomata. Peak transpiration of nighttime fumigated plants definitely occurred in the afternoon, as in the controls, while in daytime fumigated plants, afternoon transpiration was depressed.

Leaf resistance of soybean plants was low during the day and increased at night. Leaf resistance values doubled within 90 minutes after the start of fumigation, indicating a prompt stomatal response.

Leaf temperatures of fumigated plants increased significantly. In continuously fumigated plants, the leaf temperature during the daytime was about 1 centigrade higher than the air temperature, while the control leaf temperature was about 3 centigrades below the air temperature during the same period. Leaf temperatures of day and night fumigated plants were intermediate between the control and the continuously fumigated plants.

Fumigated plants showed greater 32Phosphorus uptake by roots, followed by greater deposition at the site of injury. 32Phosphorus applied to the fumigated leaves showed a marked decrease in downward translocation.

Water and osmotic potentials decreased sharply after the appearance of fluoride damage. A slight, temporary increase in the water potential was associated with increased leaf resistance during the early stages of fumigation.

Decreased soil and solution moisture availability during fumigation decreased the fluoride damage in both soil and solution grown plants, presumably due to stomate closure and reduced fluoride uptake. Stress induced after the fumigation increased the amount of fluoride damage significantly.

Procedures for the quantitative estimation of histochemical reactions were developed for dehydrogenases and phosphates in plant tissues. In microscopic histochemical studies, greatest enzyme activity was observed in phloem. Fumigation greatly decreased the activity of dehydrogenases, excepting for an increased reduction of 2-(p-idophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride in the chloroplasts of fumigated pelargonium leave before the appearance of visible injury. Acid phosphatase and alkaline phosphatase activities increased significantly after the appearance of visible injury.

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