Date of Award:

5-1971

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Plant Nutrition and Biochemistry

Committee Chair(s)

D. K. Salunkhe

Committee

D. K. Salunkhe

Committee

James T. Bowman

Committee

Bruce F. Burnham

Committee

George W. Cochran

Committee

John O. Evans

Abstract

The study was conducted to investigate the influence of eight s-triazine compounds--simazine, atrazine, terbutryne, GS-14254, propazine, prometryne, prometone, and ametryne--on the composition of seeds of peas and sweet corn through soil and foliar application. In order to understand the mechanism of the effects of these a-triazines on protein accumulation, the responses of the metabolic systems of pea and sweet corn seedlings to s-triazine treatment was studied with emphasis on the stimulation of certain enzymes, and the changes in the rates of incorporation of 14C-L-leucine (U) into soluble protein. In addition, the effect of simazine on the ultrastructure of the developing pea cotyledon was studied by electron microscopy.

Soil treatment with simazine and terbutryne at 0.5 pounds per acre, propazine at 2 and 0.5 pounds per acre, prometone at all three rates, and ametryne at 0.125 pounds per acre significantly increased the total nitrogen (8 percent to 22 percent) and soluble protein (10 percent to 20 percent), whereas the starch (6 percent to 9 percent) and sugars (9 percent to 20 percent) content of pea seeds was decreased. Simazine at 4 and 1 pound per acre and prometone, atrazine, terbutryne, and ametryne at 4 pounds per acre also increased the total nitrogen (5 per-cent to 10 percent) and soluble protein (5 percent to 9 percent) and decreased the starch (6 percent to 7 percent) content of sweet corn seeds.

Foliar applications of most of these s-triazines to peas 45 days after sowing and to sweet corn 60 days after sowing caused the highest increases in the total nitrogen (11 percent to 20 percent) and soluble protein (9 percent to 21 percent). Treatment at other times had less effect. In most cases, increases in soluble protein (9 percent to 21 percent) were accompanied by decreases in starch (6 percent to 9 percent) and sugar (9 percent to 18 percent) content.

Studies of amino acid patterns reveal ed that there were not only quantitative differences, but also qualitative differences, between s-triazine-treated plants and controls. However, in every instance, total amino acids of the treated plants exceeded those of the controls.

The field responses of the pea and sweet corn plants to s-triazines suggested that the rate of accumulation of protein in seeds may be enhanced considerably by the application of certain s-triazines. Such treatments may be of great nutritional significance in those countries which are plagued by a deficiency of proteins.

Experiments conducted in the greenhouse showed that all eight s-triazines at concentrations of either 5 parts per million or 2 parts per million increased the total nitrogen (9 percent to 51 percent) and soluble protein (17 percent to 50 percent) and decreased the starch (20 percent to 42 percent) and sugar {10 percent to 59 percent) content of peas and sweet corn seedlings 5 days after treatment. The intensity of the effects decreased 10 and 15 days after treatment. Foliar applications of s-triazines had no influence on nitrate and ammonium ion content in the leaves of peas and sweet corn.

Enzymatic studies indicated that foliar applications of simazine, terbutryne, and GS-14254 increase the activity of starch phosphorylase, pyruvate kinase, glutamate dehydrogenase, nitrate reductase, glutamic- pyruvic transaminase, and cytochrome oxidase in the leaves of pea and sweet corn seedlings and o-aminolevulinic acid dehydratase in the leaves of pea seedlings.

Leaf discs from the pea plants treated with any one of eight s-triazines had a higher rate of incorporation of 14C-L-leucine(U) into soluble protein than the control.

Foliar application of 2 parts per million of simazine increased the size and altered the shape of protein bodies in the developing pea cotyledons.

The increase in protein content which followed the applications of s-triazines may result from the following:

1. The increased activity of nitrate reductase, glutamate dehydrogenase, and transaminase may produce a greater supply of amino acids for protein synthesis.

2. Stimulation of starch phosphorylase and a-amylase may increase starch degradation which, coupled with stimulated pyruvatekinase, may provide more substrate for amino acid synthesis.

3. Increases in the activities of o-aminolevulinic acid dehydratase and cytochrome oxidase may accelerate the electron transport system and consequently produce a greater supply of ATP for synthesis of protein.

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