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Influence of Intensity, Quality, and Duration of Light on Nitrogen Reduction and Assimilation in Wheat¹

'Pawnee' wheat (Triticutn aestivum L.) seedlings were grown under lighting of low (7,500 lux) or high (15,600 lux) intensities, blue (380-470 mu) or red (680-740 mu) qualities, and short (8-hr) or long (16-hr) nhotoperiods. A single level of N was supplied in graded ratios of nitrate and ammonium in solution cultures.

In leaf blades, high light intensity had no consistent effect on nitrate reductase (NR) activity, increased soluble protein, and decreased nitrate. Blue light increased NR activity and soluble protein but decreased nitrate as compared with red light. The long photoperiod increased NR activity and decreased nitrate and soluble protein as compared with the short photoperiod. The light treatments had little effect on roots except for an accumulation of nitrate under the short photoperiod. NR activity and nitrate content in leaf blades and roots increased under all light treatments as the nitrate-to-ammonium ratio in the nutrient solution increased, and soluble protein content decreased slightly.

Key Words: nitrate reductase • nitrate • protein • ammonium

² Graduate Research Assistant and Associate Professor, Department of Agronomy, Kansas State University, Manhattan 66502.

Received for publication December 4, 1967.