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 O2 present as a reactant‐carrier gas, and then absent and replaced with N2 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.

Emission of NO from several higher plant species

“…The principal result of these experiments is that NO emissions from plants growing in soil are similar to those from plants growing in nutrient solution. and Weiland and Stutte [1979] are somewhat higher than those found in the experiments presented here. Klepper [1979Klepper [ , 1990Klepper [ , 1991, Harper [1981], and Dean and Harper [1986,1988] With regard to the nitrogen balance of plants, the loss of N through the emission of NO is negligible.…”

“…Although the N compounds were not identified, a correlation between the rate of transpiration and the emitted nitrogen was found . Weiland and Stutte [1979] differentiated between nitrogeneous compounds in reduced and in oxidized forms. The majority of nitrogen emitted by the plants was in reduced form; only about 5% was in an oxidized form.…”

Concomitant Determination of Folar Nitrogen Loss, Net Carbon Dioxide Uptake, and Transpiration

“…This loss was greater in senescing or stressed tissue (8,24) In order to characterize the relationships of these separate processes, an apparatus for concomitant measurement of net CO2 uptake, transpiration, and foliar N loss from field, growth chamber, or greenhouse plants has been prepared. With this apparatus, correlated N loss, CO2 uptake, and transpiration in soybean To simulate a solar day, a noninductive 13-h photoperiod started at 0630 with 1.5 h of one-third maximum irradiance, progressed through 1.5 h of two-thirds maximum to maximum, and then ended with 1.25 h of two-thirds and 1.0 h of one-third maximum irradiance.…”

“…Plant foliage has been found to be a site for significant losses of N (6,8,21,22,24). This loss was greater in senescing or stressed tissue (8,24) correlated directly with temperature and transpiration (21,22), and most of the N evolved as a reduced form (8,24), although oxidized forms could be detected (24).…”

“…This loss was greater in senescing or stressed tissue (8,24) correlated directly with temperature and transpiration (21,22), and most of the N evolved as a reduced form (8,24), although oxidized forms could be detected (24). Data (20) were germinated in horticultural Vermiculite moistened daily with tap water in a controlled environment.…”