Date of Award:

5-1965

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Plant Nutrition and Biochemistry

Committee Chair(s)

Gene W. Miller

Committee

Gene W. Miller

Committee

David R. Walker

Abstract

There are many reports relating the effects of fluorides on plant respiration. Fluoride has been regarded as an inhibitor of respiration. Warburg et al. (1942) demonstrated that fluoride inhibited enolase activity, therefore, decreased the respiration rate of yeast. Miller (1958), found a similar inhibition of enolase from pea seed. Bonner (1948), Bonner and Wildman (1946), and Laties (1949) reported that the fluoride ion in culture solutions reduced the respiration rate in Avena Coleoptile, spinach leaves and barley roots. Since the inhibition was reversed by the addition of pyruvate, they concluded that the inhibition of respiration was due to the inactivation of fluoride sensitive enolase. Chung and Nickerson (1954) studied yeast cells grown in presence of fluoride and concluded that the inhibition of growth was due to the inhibition of polysaccharide synthesis, and the site of inhibition was the enzyme phosphoglucomutase. Yang and Miller (1963) found divergent sucrose, reducing sugar contents in fluoride fumigated soybean leaves and concluded that the enzyme phophoglucomutase was the site of fluoride inhibition in sucrose synthesis. Phosphorylase (Rapp and Sliwinski, 1956), phosphatase (Lammer and Hafer, 1953; Pierpoint, 1957) and hexokinase (Melchior and Melchior, 1956) have also been reported to be fluoride sensitive in vitro.

In spite of so many enzymes in the Emden-Meyerhof-Parnas pathway that are sensitive to fluoride, many investigators have reported accelerated oxygen uptake in fluoride treated plants. Weinstein (1961) found a 67 to 72 percent increase of respiration in hydrogen fluoride fumigated tomato and tendergreen bean leaves. Yu and Miller (unpublished data) also observed 30 to 80 percent increase in fluoride fumigated soybean leaves. Christiansen and Thimann (1950) grew pea stem sections and found that sodium fluoride at a concentration, which gave 50 percent depression in growth, stimulated oxygen uptake. Chung and Nickerson (1954) with yeast cells and Bonner and Thimann (1950) with oat coleoptile obtained similar results.

Applegate et al. (1960a, 1960b, 1960c) found that either sodium fluoride in solution culture or atmospheric fluoride fumigation at low concentrations stimulated oxygen uptake in bush bean seedlings.

Ross et al. (1962) applied glucose-1-C14 and glucose-6-C14 to control and fluoride treated Chenopodium murale L. and Polygonum orientale L. They found a decreased C6/C1 ration and concluded increased significance of the pentose phosphate shunt mechanism in fluoride sensitive plants, when subjected to fluoride treatment.

McNulty and Newman (1957) exposed bush beans and gladioli to atmospheric fluoride, and reported an increased oxygen uptake. They concluded that fluoride at low concentrations might cause an initial inhibition, followed by stimulation of respiration, with the appearance of damage. Hill et al. (1959) studied seven varieties of gladioli at low fluoride fumigation concentrations. Two varieties with necrotic injuries showed respiratory increases. The others remained uninjured and showed no respiratory response in spite of very high concentration of fluoride. Therefore, they concluded that the increased respiration was mainly caused by injury. The amount of fluoride accumulated in the tissue did not appear to be a significant factor.

McNulty and Lord (1960) studied Chlorella pyrenoidosa and found high concentrations of fluoride inhibited, while lower levels stimulated oxygen uptake. The increase of oxygen uptake seemed to be correlated with the concentration of undissociated hydrogen fluoride in the suspending media. They also found a significant increase in phosphorylated nucleotides associated with the stimulation of oxygen consumption.

= Our present knowledge of the effect of fluoride on plant respiration is mainly based on studies of overall gas exchange and in vitro tests of some individual respiratory enzymes. To a lesser extent studies have been made on individual enzymes in fluoride treated plant tissue. The comparison of enzyme activities of individual enzymes between fluoride treated and control plant tissues may provide a new approach to the understanding of the actual effect of fluoride on plant intermediary metabolism. In this paper the enzyme activities of five terminal oxidases namely: cytochrome oxidase, catalase, peroxidase, polyphenol oxidase and ascorbic acid oxidase, in addition to glucose-6-phosphate dehydrogenase were compared in hydrogen fluoride-fumigated and control soybean leaves, to determine whether any relationship existed between the change of enzyme activities and the accelerated oxygen uptake. Experiments were conducted with glucose-6-phosphate dehydrogenase, a connecting enzyme to the hexose monophosphate shunt, to measure changes in activity associated with fluoride injury.

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