Gaseous Nitrogen Loss from Soybean Foliage¹

Abstract

The loss of non‐elemental N from plant foliage was verified, and the significance of this loss was investigated. Soybean (Glycine max (L.) Merr.) leaf vapors were condensed (–50 C) using a calibrated test tube tra in a closed system. Subsequent N analysis of this condensate revealed water soluble N forms. Since the pyrochemiluminescent technique that was used for N analysis does not detect elemental N, the N present must be in chemically bound forms; preliminary research indicates the N in both oxidized and reduced forms. Significant losses of N from the determinate cultivar ‘Davis’ were positively correlated to temperature and to transpiration rate under field conditions. These losses, which like transpiration followed a diurnal trend, were greater in early vegetative growth stages than during flowering and pod‐fill. The amount of N lost is significant under the high temperatures of field Conditions and may account for much of the reduction in potential seed yields under this stress condition.

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

“…2). Although CO2 uptake and transpiration were also high at 1200, when the chamber air temperature had just increased to 30 C, total N loss was near minimum during this time; a similar trend had been noted during an earlier field study with soybeans (22). This decrease in N loss with corresponding increases in CO2 uptake and transpiration indicates that N loss is a separate process.…”

“…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.…”

“…The condensate was then analyzed for soluble N with a pyrochemiluminescent technique which was sensitive to 10 jig N/liter. The technique allowed determination of total N (21,22) and oxidized N (24) concentrations, and reduced N was estimated by difference.…”

Nitrogen supply to corn from sunn hemp and velvet bean green manures

“…*Significant at (p < 0.05). for the total nitrogen and it is likely due to the loss of nitrogenous compounds from the mature or pre-senescent leaves, which can happen next to the transpiratory strem (Stutte et al, 1979;Silva & Stutte, 1981). The occurrence of the nitrogen decline accumulation in the above ground part of the corn plant, at the end of the cycle (Table 5) was also reported by other authors (Flores, 1986;Villas Bôas, 1990), as well as for sugarcane (Ng Kee Kwong & Deville, 1994).…”