Showing papers by "Alexander Lux published in 2007"

Zinc in plants

Abstract: Zinc (Zn) is an essential component of thousands of proteins in plants, although it is toxic in excess. In this review, the dominant fluxes of Zn in the soil-root-shoot continuum are described, including Zn inputs to soils, the plant availability of soluble Zn(2+) at the root surface, and plant uptake and accumulation of Zn. Knowledge of these fluxes can inform agronomic and genetic strategies to address the widespread problem of Zn-limited crop growth. Substantial within-species genetic variation in Zn composition is being used to alleviate human dietary Zn deficiencies through biofortification. Intriguingly, a meta-analysis of data from an extensive literature survey indicates that a small proportion of the genetic variation in shoot Zn concentration can be attributed to evolutionary processes whose effects manifest above the family level. Remarkable insights into the evolutionary potential of plants to respond to elevated soil Zn have recently been made through detailed anatomical, physiological, chemical, genetic and molecular characterizations of the brassicaceous Zn hyperaccumulators Thlaspi caerulescens and Arabidopsis halleri.

Nitrogen-Fixing Activity of Root Nodules in Relation to Their Size in Peanut (Arachis hypogaea L.)

Abstract: The nitrogen-fixing activity of root nodules was examined with reference to the nodule size in peanut. Root nodules of field-grown peanut were collected at flowering through harvesting stages and classified into five groups of size using a circle template. Then acetylene reduction activity was measured to evaluate nitrogen-fixing activity for respective size groups. In addition, the diameter of the cross-section of each root nodule and rhizobium-infected areas on the cross-section were measured. The results showed that the nitrogen-fixing activity of root nodules is closely related with their size. In the root nodules in the medium size group (1.5-2.0 mm in diameter), nitrogen-fixing activity per unit fresh weight of nodule was highest at the flowering stage and rapidly decreased thereafter. The nitrogen-fixing activity of root nodules larger than 2.0 mm in diameter did not vary significantly with their size. Colors of rhizobium-infected zones varied with their size: white in small nodules; red in medium-sized nodules; and greenish in larger nodules, which suggests that the concentration of leghemoglobin is highest in the medium-sized nodules. Nitrogen-fixing activities of the medium-sized nodules might determine the amount of nitrogen fixation in the whole root system during pod-filling because medium-sized nodules had high activity and were large in number. Classification of root-nodule size based on the circle template is a simple, rapid, and useful method to evaluate nitrogen-fixing activity of root nodules.

Influence of galactoglucomannan oligosaccharides on root culture of Karwinskia humboldtiana

Abstract: Galactoglucomannan oligosaccharides (GGMOs) activity in K. humboldtiana root culture has been determined. GGMOs inhibited adventitious root growth and lateral root induction in contrast to IAA, IBA, and NAA stimulating effect in these processes. Similarly, the combination of GGMOs with natural auxins (IAA, IBA) evoked an inhibition of adventitious root growth and lateral root induction that depended on the oligosaccharides concentration and the type of auxin. The growth stimulating effect of the synthetic auxin, NAA, in adventitious roots was negatively affected by GGMOs, but they were without influence on lateral root induction. The presence of oligosaccharides triggered lateral root position on adventitious roots and the anatomy of adventitious roots (diameter, proportion of primary cortex to the central cylinder, number and size of primary cortical cells, intercellular spaces, and the number of starch grains in cells of primary cortex) in dependence on their coactions with auxin.