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Variations in the Total, Nonprotein, and Amide Nitrogen Fractions of Agrostis palustris Huds. Leaves in Relation to Certain Environmental Factors¹

The influence of certain environmental factors on the seasonal variation in the total, nonprotein, glutamine, asparagine and total amide nitrogen fractions of Agrostis palustris Huds. leaf tissue were investigated. Five linear multiple correlation-regression analyses indicated temperature to be the major environmental factor influencing seasonal variations in the five nitrogen fractions measured. Temperature accounted for three-fourths of the predicted variation in total nitrogen. Daily maximum soil temperature at 15 cm was most highly correlated of the measured air and soil temperatures with the five nitrogen fractions.

The coefficient of determination for the non-protein nitrogen fraction was quite low, indicating a minimum response to soil and air temperatures, light intensity, and soil moisture.

The total nitrogen content measurements throughout the season showed total nitrogen levels above 5% to be closely related to soil temperatures which exceeded 18 C. When soil temperatures exceeded 24 C a decrease in the total nitrogen content was noted.

The nonprotein nitrogen fraction increased slightly during the higher temperature periods of late July and August, but decreased when soil temperatures exceeded 27 C.

Glutamine showed the greatest response to temperature of the five nitrogen fractions, with quite low levels occurring at soil temperatures above 24 C. Asparagine responded much less than glutamine to seasonal variation related to temperature. The total amide content responded decidedly to increases in temperature with the major response being attributed to the glutamine fraction.

² National Science Foundation Cooperative Fellow (now Assistant Professor, Department of Crop Science, Michigan State University) and Professor, Department of Agronomy, Purdue University.

Received for publication May 14, 1969.