The Hertz Corporation

About: The Hertz Corporation is a based out in . It is known for research contribution in the topics: Population & Soil water. The organization has 9562 authors who have published 11044 publications receiving 447929 citations. The organization is also known as: Hertz Rental Car & Hertz Rent-a-Car.

Physiological evidence for a high-affinity cadmium transporter highly expressed in a Thlaspi caerulescens ecotype

Abstract: • Uptake kinetics and translocation characteristics of cadmium and zinc are presented for two contrasting ecotypes of the Cd/Zn hyperaccumulator Thlaspi caerulescens, Ganges (southern France) and Prayon (Belgium). • Experiments using radioactive isotopes were designed to investigate the physiology of Cd and Zn uptake, and a pressure-chamber system was employed to collect xylem sap. • In contrast to similar Zn uptake and translocation, measurements of concentration-dependent influx of Cd revealed marked differences between ecotypes. Ganges alone showed a clear saturable component in the low Cd concentration range; maximum influx Vmax for Cd was fivefold higher in Ganges; and there was a fivefold difference in the Cd concentration in xylem sap. Addition of Zn to the uptake solution at equimolar concentration to Cd did not decrease Cd uptake by Ganges, but caused a 35% decrease in Prayon. • There is strong physiological evidence for a high-affinity, highly expressed Cd transporter in the root cell plasma membranes of the Ganges ecotype of T. caerulescens. This raises evolutionary questions about specific transporters for non-essential metals. The results also show the considerable scope for selecting hyperaccumulator ecotypes to achieve higher phytoextraction efficiencies.

A re-evaluation of the ATP :NADPH budget during C3 photosynthesis: a contribution from nitrate assimilation and its associated respiratory activity?

Abstract: The purpose of this review in reanalysing the ATP:reductant balance in illuminated leaf cells is to stress that photosynthesis in vivo does not involve CO 2 fixation alone, but embraces other processes, chief among which is N assimilation. Prior to the demonstration of CO 2 fixation and photophosphorylation by isolated chloroplasts, the mitochondria were thought likely to provide all the ATP required for CO 2 fixation (discussed in Arnon et al., 1954). During the 1960s, the development of techniques for the isolation of chloroplasts able to fix CO 2 at rates approaching those of the parent tissue induced a paradigm shift, leading to the establishment of a dominant (if not unanimous) view that chloroplasts in vivo must by themselves meet all their ATP requirements. More recent studies, however, indicate that the reality lies somewhere between these two extremes. The present work places emphasis on the integrated nature of photosynthesis and proposes that much of the respiratory ATP necessary for whole cell photosynthesis may be generated during the production of C skeletons for N assimilation. Rather than considering dissipative electron transport pathways as necessary to uncouple respiratory precursor synthesis from ATP production, the present analysis emphasizes the metabolic value of ATP produced during N-linked respiration, with cellular ATP supply being tailored to ATP demand.

Nitric oxide synthases

Abstract: Nitric oxide is a reactive free radical gas that can act as an intracellular or extracellular messenger. It may act locally as an autacoid, paracrine substance or neurotransmitter, and at a distant target if it is carried and delivered as a protected complex, or prodrug. It is therefore, a very unique signaling molecule. It is formed from L-arginine by a family of isoforms of nitric oxide synthases (NOS 1-3). These enzymes are separate gene products encoded on three different chromosomes. The three isoforms have about 50-60% homology and each isoform has considerable homology between species (about 90%). A variety of co-translational and posttranslational modifications of the different isoforms can take place, including phosphorylation, myristoylation and palmitoylation, each of which may influence their subcellular location and/or activity. This family of enzymes has considerable homology with cytochrome P450 and has both oxidase and reductase domains with complex cosubstrate and cofactor requirements that include heme, O2, NADPH, FAD, FMN, tetrahydrobiopterin and calmodulin. The enzyme isoforms are active as homodimers and catalyze the oxidation of the guanidino nitrogen of L-arginine to nitric oxide. The other product of the reaction is citrulline.

Vesicular-arbuscular mycorrhizal infections in root organ cultures

Abstract: Vesicular-arbuscular mycorrhizal infections, similar to those formed in plants with leaves, have been established for the first time in clover root organ cultures. These infections are most easily established in roots grown on a modified White's agar medium but they can also form in liquid culture. The pH of the medium is a critical factor determining the initiation and spread of infection. White's medium inhibited spore germination and growing roots did not relieve this inhibition. Pre-germinated spores were therefore used as inoculum. The possible value of root organ cultures for the study of root: endophyte interactions is discussed in relation to studies of some obligate fungi.