The assimilation of nitrate in plants involves the reduction of nitrate to ammonia in two steps. The first step requires nitrate reductase, a nitrate-inducible enzyme. When seedlings of squash (Cucurbita maxima L.) were treated with nitrate, both nitrate reductase activity and protein were induced in the cotyledons. Poly(A)(+) RNA was prepared from cotyledons of nitrate-treated seedlings and wa...

Two maize hybrids were grown under growth chamber conditions on solution or vermiculite medium that contained 2.5, 7.5, or 15 millimolar nitrate. The objectives were to determine: (a) the effect of nitrate supply on N metabolism and growth and (b) the interrelationship between nitrate uptake, flux, and reduction on the accumulation of reduced N and nitrate by the various plant parts and for the...

An enzymatic assay system for nitrate employing the membrane-bound nitrate reductase (EC 1.7.99.4) of E. coli is described. Contrary to previous enzymatic assay systems, the present method is a kinetic one, i.e. the substrate, nitrate, is assayed by measuring the reaction rate of the nitrate reductase-catalyzed reaction. Based on the observation that the nitrate reductase-catalyzed reaction obe...

The effect of tungsten on the development of endogenous and nitrate-induced NADH- and FMNH(2)-linked nitrate reductase activities in primary leaves of 10-day-old soybean (Glycine max [L.] Merr.) seedlings was studied. The seedlings were grown with or without exogenous nitrate. High levels of endogenous nitrate reductase activities developed in leaves of seedlings grown without nitrate. However,...

This study of the Arabidopsis thaliana nitrate transporter NRT1.9 reveals an important function for a NRT1 family member in phloem nitrate transport. Functional analysis in Xenopus laevis oocytes showed that NRT1.9 is a low-affinity nitrate transporter. Green fluorescent protein and β-glucuronidase reporter analyses indicated that NRT1.9 is a plasma membrane transporter expressed in the compani...

The electrical response of nitrate-grown maize (Zea mays L.) roots to 0.1 millimolar nitrate was comprised of two sequential parts: a rapid and transient depolarization of the membrane potential, followed by a slower, net hyperpolarization to a value more negative than the original resting potential. The magnitude of the response was smaller in roots of seedlings grown in the absence of nitrate...

The role of phytochrome in the induction of nitrate reductase of etiolated field peas (Pisum arvense L.) was examined. Terminal bud nitrate concentration increased in darkness, and the increase correlated with induction of nitrate reductase following brief exposure of intact plants to red, blue, far red, and white lights. Brief light exposure of intact plants stimulated nitrate uptake and induc...

Nitrate releases seed dormancy in Arabidopsis (Arabidopsis thaliana) Columbia accession seeds in part by reducing abscisic acid (ABA) levels. Nitrate led to lower levels of ABA in imbibed seeds when included in the germination medium (exogenous nitrate). Nitrate also reduced ABA levels in dry seeds when provided to the mother plant during seed development (endogenous nitrate). Transcript profil...