Absorption of Atmospheric NO₂ by Spruce (Picea abies) Trees. III. Interaction with Nitrate Reductase Activity in the Needles and Phloem Transport

Abstract

In order to compare the effects of excess pedospheric and atmospheric nitrogen supply on nitrate reductase activity (NR, EC 1.6.6.1) excised spruce branches were exposed to nitrate solutions or were fumigated with N0 2 • Immersion of spruce branches in 6 mM nitrate caused an increase in NR activity by a factor of 14 or 19 in current-year and in one-year-old needles, respectively, as compared to controls incubated in tap water. Exposure to 65 nll-1 N0 2 increased NR activity by a factor of 1.5 in current-year needles and by a factor of 2.5 in one-year-old needles as compared to non-fumigated controls. Addition of cycloheximide (0.17 JlM) or puromycin (200 JlM) to the incubation solution prevented the induction of NR activity from both nitrate and N0 2 exposure. This finding indicates that induction of NR activity by both atmospheric N0 2 or increased nitrate supply of the needles is both caused by de-novo synthesis of NR protein. The increase in NR activity in needles of branches still attached to the tree as a consequence of exposure to 65 nl 1-1 N0 2 was found to be a transient phenomenon, The increase persisted for several days only and was no longer observed after one week of sustained N0 2 exposure. An interruption of phloem transport by girdling, applied subsequent to the induction of NR activity by atmospheric NOb prevented the decrease in NR activity. Apparently, export out of the exposed needles and phloem transport within the stem are involved in the regulation of NRactivity upon N0 2 exposure.

Stable isotope analysis reveals differential effects of soil nitrogen and nitrogen dioxide on the water use efficiency in hybrid poplar leaves

“…Eventually, the atmospheric N influx is metabolized, after passage through the plasmalemma, to ammonium as a result of an enzymatic pathway by nitrate and nitrite reductase in the cytosol and chloroplasts (Beevers & Hagemann, 1983; Wellburn, 1990; Amman et al. , 1995; Weber et al. , 1998).…”

“…, 1996); (2) nitrate reductase activity (NRA) (Von Ballmoos et al. , 1993; Weber et al. , 1998) and (3) incorporation of the airborne nitrogen into free amino acids (Nussbaum et al.…”

Measurement report: Leaf-scale gas exchange of atmospheric reactive trace species (NO<sub>2</sub>, NO, O<sub>3</sub>) at a northern hardwood forest in Michigan

“…The uptake efficiency varies across plants and is influenced by environmental conditions. Studies at leaf level and within leaves have found that after entering the stomata, NO2 is metabolized through dissolution and enzyme-catalyzed reactions (Hu et al, 2014;Nussbaum et al, 1993;Vallano and Sparks, 2008;Weber et al, 1998). Unlike NO2 and O3, foliar exchange of NO is small to insignificant (Hereid and Monson, 70 2001;Rondón et al, 1993), except for herbicide-treated soybeans (Klepper, 1979) and nutrient-fed sugar cane, sunflower, corn, spinach, and tobacco plants (Wildt et al, 1997), where NO emission was observed.…”

“…Across the stomata, the deposition is a diffusion-controlled process Weber et al, 1998), where the expected rate is the product of the stomatal conductance of water multiplied by the square root of the ratio of the molecular weight of water to the molecular weight of NO2:…”

Nitrate reductase and its role in legume-rhizobia symbiosis

“…Виявлено, що індукування НР світлом і нітратами забезпечує адитивні ефекти і стимулюється цитокінінами [11]. Показано, що NO 2 , який є основним компонентом газоподібних викидів автотранспортних засобів, може поглинатися рослинами після окиснення до нітрату і спричинювати підвищення нітратредуктазної активності чи білків НР у мезофілі листків [13][14][15]. Довготривала посуха призводить до інактивації та деградації НР [16], а короткотривалий водний стрес зумовлює зворотну інактивацію НР, що припиняється додаванням НАДН чи фериціаніду [17].…”