Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Plants, Soils, and Climate

Department name when degree awarded

Plant Science

Committee Chair(s)

Frank B. Salisbury


Frank B. Salisbury


Wheat (Triticum aestivum L.) grown in controlled environments with a 24-hour photoperiod was analyzed for phenylpropanoid and amino acid metabolites. Discrete spectral environments, including a metal halide, high-pressure sodium and low-pressure sodium lamps, provided both photosynthetically active radiation and phenylpropanoid inducing fluences of light. A greenhouse spectral environment supplemented with fluorescent lamps was also used to culture wheat. All four spectral environments were used to culture wheat to maturity separately. The activities of phenylalanine and tyrosine ammonia-lyase were photoinduced in wheat tissue obtained from plants grown in the metal halide, high-pressure sodium and greenhouse spectral environments. These enzyme activities are the committed catalytic step in phenylpropanoid biosynthesis and were induced in wheat tissue by fluences of light in the ultraviolet and blue regions of the spectrum. The low-pressure sodium lamp, which does not provide strong irradiance in these wavelengths, produced significantly lower ammonia-lyase activities than were observed in wheat grown within the metal halide, high-pressure sodium, or greenhouse spectral environments. These effects were not caused by phytochrome, since calculation of Pfr/Ptotal for the low-pressure sodium lamp was higher than the ratio obtained from metal halide or high-pressure sodium lamps. Lignin was also significantly reduced in wheat grown with low-pressure sodium lamps. Several essentialamino acids were in lower molar concentration in protein from wheat grown under low-pressure sodium lamps. However, phenylalanine and tyrosine were in significantly higher concentration in wheat grain produced in this spectral environment, and amino acid concentrations of wheat cultured with the low-pressure sodium lamp are regarded as a direct result of the spectral properties of this light source.