Date of Award:

5-1959

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Soil Chemistry

Committee Chair(s)

R. L. Smith

Committee

R. L. Smith

Committee

Raymond W. Miller

Abstract

Iron chlorosis has been a srious problem for many years. This physiological disease has occurred so frequently on calcareous soils that it has been called lime-induced chlorosis by many of the workers. Because the western United States has so many soils of this type, the chlorosis problem has been of primary concern. Untold economic losses have been the result of this physiological disease.

Interveinal yellowing of the leaves along with loss of plant vigor and retarded growth characterize the disease. In severe cases die-back of the terminal growth and eventual death of the plant result. No single factor has been established as being the cause of this condition. Consequently, no permanent cures have been recommended.

Of the many theories that have been advanced as to the cause of this chlorotic condition, much emphasis has been placed upon the effect of the bicarbonate ion (HCO3).a In past years many experiments have been conducted concerning plant growth in relation to HCO3 and the results have been varied. Although the results of most of the early workers have been variable, generally a toxic effect of HCO3 was reported. This was particularly true with high concentrations of HCO3 in the nutrient solution. Kearney and Cameron (1902) compared the effects of bicarbonate salts with that of poisons and observed that very dilute solutions of HCO3 stimulated growth whereas greater concentrations inhibited growth. Harley and Lindner (1945) found that irrigating with water high in HCO3 caused a chlorotic condition in certain varieties of pear and apple.

This chlorotic condition has brought about closer investigation of the effects of HCO3 in its effects on plant growth. It has been noted by Wadleigh and Brown (1952), Miller (1954), and Goss (1957) that high concentrations of HCO3 inhibited respiratory processes and cation uptake of many plants. It has also been reported by Ulrich (1941) that HCO3 caused an increase in sap pH, a greater change in individual organic acids, and a decrease in the respiratory quotient of some plants in comparison to other salts.

Baxter and Belcher (1955) indicated that the internal environment of chlorotic citrus roots was disturbed by an accumulation of HCO3. This seemed to effect the hydrogen ion concentration and the buffer capacity of the plant sap. Goss (1957) postulated that the HCO3 inhibits the translocation of minerals more than it does their absorption. Honda (1955) also indicated that the internal pH increased as a result of HCO3 influences. This resulted in decreased iron solubility and an upset of the cytochrome oxidase system which initiated chlorosis in chlorotic-resistant varieties. Carlson (1957) observed that the translocation of iron tended to decrease with an increased pH and HCO3 of the plant sap.

These observations suggest that the build up of HCO3 concentration internally enhances chlorotic conditions in plants. The objective of this study is to compare the internal HCO3 concentration of plants, both those susceptible and those resistant to chlorosis.

Checksum

aca2c923eb810659c206416f8859f440

Download

Included in

Soil Science Commons

Share

COinS

Copyright for this work is retained by the student. If you have any questions regarding the inclusion of this work in the Digital Commons, please email us at .