Pyro‐Chemiluminescent Differentiation of Oxidized and Reduced N Forms Evolved from Plant Foliage¹

Abstract

Evaluations were made to differentiate the forms of water soluble, non‐elemental nitrogen lost with the trans. piration water vapors from plant foliage. Chemiluminescent detection of chemically bound N, with O 2 present as a reactant‐carrier gas, and then absent and replaced with N 2 during the pyrolysis of transpiration samples, distinguished the oxidized from the reduced N forms in the transpirate. The majority of the N in several crop and weed species was in the reduced state; however, at least 5% of the N in all species tested was in an oxidized form. The percent of loss of oxidized N was fairly constant in cotton ( Gossypium hirsutum L.), ‘Forrest’ beans [ Glycine max (L) Merr.], and palmer amaranth [ Amaranthus palmeri (S.) Wats.] over the solar day. Older soybean leaf tissue lost a higher percentage of oxidized forms than did younger tissue. Both younger and older soybean tissue evolved greater total amounts of N than foliage in the middle of the plant canopy; yet the rate of transpiration was maximal in the middle foliage. Water‐stressed soybeans evolved greater quantities of oxidized N forms than did irrigated soybeans. The N loss increased in ‘Davis’ soybeans and transpiration decreased in the cultivar ‘Forrest’ as a result of water stress.