Auxin action on proton influx in corn roots and its correlation with growth

At concentrations inhibitory to the elongation of corn (Zea mays L.) roots, the auxins, indole-3-acetic acid (IAA) and α-naphthaleneacetic acid (α-NAA), cause an increase in the pH of the bathing medium; this increase occurs with an average latent period shorter than the latent period for the inhibitory effect of these auxins on elongation. Indole-2-carboxylic acid, an inactive structural analogue of IAA, and β-naphthaleneacetic acid, an inactive analogue of α-NAA, affect neither growth nor the pH of the medium. Since acid pH is known to promote and basic pH to inhibit root elongation, the data are consistent with the hypothesis that hormone-induced modification of cell-wall pH plays a role in the control of elongation of roots, as has been proposed for elongation of stems and coleoptiles.     

Trypanosoma brucei: Maintenance of concentrated suspensions of bloodstream trypomastigotes in vitro using continuous dialysis for measurement of endocytosis

A continuous dialysis technique capable of maintaining concentrated suspensions of bloodstream Trypanosoma brucei (up to 4 × 10⁸/ml) at 25 C for 2 hr without loss of viability has been developed in order to measure endocytosis under controlled conditions in vitro. Using this technique, the kinetics and mechanism of uptake of the metabolically inert macromolecule, ¹²⁵I-labelled polyvinylpyrrolidone (¹²⁵I-PVP), have been investigated. Binding to the plasma membrane and the rate of uptake of ¹²⁵I-PVP from the extracellular medium by the trypanosome are both decreased by the addition of unlabelled PVP and human serum albumin. A mechanism for uptake of ¹²⁵I-PVP by a combination of fluid-phase and adsorptive endocytosis from the flagellar pocket of the trypanosome is proposed. In the presence of serum albumin and unlabelled PVP, endocytosis of ¹²⁵I-PVP occurs in the fluid phase only, with endocytic indices of 14.5 ± 0.9 and 54.1 ± 11.3 nl/hr/mg protein in vitro at 25 C and in vivo at 37 C, respectively.     

Melovinone,an open chain analogue of melochinone from Melochia tomentosa

Melovinone, a new alkaloid isolated from the roots of Melochia tomentosa has been characterized as 3,7,8-trimethoxy-2-methyl-5(5′-phenylpentyl)-4-quinolinone.     

新兴垸低湖田莲藕引种栽培研究

本文报道了作者在湖北省监利县新兴垸低湖田进行的莲藕优良品种引种栽培试验结果,从低湖田试验莲藕的生长发育、产量、经济效益及生态适应性等方面说明了低湖田植藕是该区涝渍地开发利用的有效途径,同时简要提及了低湖田植藕应注意的若干技术问题。     

Non-light-dependent Shikimate Pathway in Plastids from Pea Roots

Non-green plastids (leucoplasts) isolated from pea roots are shown to be considerably active in forming aromatic amino acids by the shikimate pathway which, in contrast to the chloroplast pathway, is independent of light. Supply of phosphoenolpyruvate and 3-dehydroquinate, 3-dehydroshikimate, shikimate and quinate effectively enhances the formation of aromatic amino acids suggesting an intra- or/and intercellular intermediate transport.     

The effect of phosphate deficiency on mitochondrial activity and adenylate levels in bean roots

Bean plants ( Phaseolus vulgaris ) were grown for 16–20 days with or without phosphate in Knop nutrient medium. It was found in previous experiments that for roots grown on a P_i-deficient medium respiration is mainly carried out by the cyanide-insensitive pathway. Mitochondria isolated from—P_i, roots had poor respiratory control and their respiration exhibited 62% inhibition by cyanide and was inhibited (30%) by salicylhydroxamic acid (SHAM). In contrast, mitochondria obtained with control (+P_i) roots had respiratory control and ADP/O ratios typical for succinate as the substrate; their respiration was inhibited to 95% by cyanide and insensitive to SHAM. The integrity of mitochondrial membranes was similar in both types of mitochondria. Cytochrome oxidase activity, however, was about 20% lower in -P_i mitochondria, but the cytochrome composition was the same in both types of mitochondria. The cytochrorae pathway was not operating at full capacity in mitochondria isolated from—P_i roots but the alternative oxidation pathway participated in a great part in mitochondrial respiration, similar to in vivo whole roots. The participation of the non-phosphorylating., alternative pathway decreased the respiratory control ratio in mitochondria and had an effect on the total adenine nucleotide pool and energy charge values which were lower (16 and 13% respectively) in -P_i roots. About 50% lower ADP and 20% lower ATP levels were observed whereas AMP levels were several times higher.     

An mRNA that specifically accumulates in maize roots delineates a novel subset of developing cortical cells

A near full-length cDNA clone (pZRP3) corresponding to an mRNA that accumulates specifically in roots of maize was isolated. The ZRP3 mRNA is ca. 600 nucleotides in length. The amino acid sequence of the predicted polypeptide is rich in leucine (16%), proline (11%), and cysteine (8.5%). The zrp3 gene appears to be expressed exclusively in roots, whereas other ZRP3-related genes are expressed in additional organs of the maize plant. In situ hybridization shows that ZRP3 mRNA accumulation is largely confined to the cells of the cortical ground meristem. Furthermore, accumulation of this mRNA occurs within a distinct subset of cortical cells, the inner three to four cell layers.Journal paper number J-14572 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa Project Number 2997.     

Seasonal and spatial patterns of S,Ca, and N dynamics of a Northern Hardwood forest ecosystem

Seasonal dynamics of S, Ca and N were examined at the Huntington Forest, a northern hardwood ecosystem in the central Adirondacks of New York for a period of 34 months (1985–1988). Solute concentrations and fluxes in bulk precipitation, throughfall (TF) and leachates from the forest floor, E horizon and B horizon were quantified. Both above and below-ground elemental fluxes mediated by vegetation (e.g. uptake, litter inputs, and fine roots production) were also determined. The roles of abiotic and biotic processes were ascertained based on both changes in solute concentrations through the strata of the ecosystem as well as differences between dormant and growing seasons. Concentrations of SO₄ ²⁻, NO₃ ⁻, NH₄ ⁺ and Ca²⁺ were greater in TF than precipitation. Forest floor leachates had greater concentrations of SO₄ ²⁻, NO₃ ⁻ + NH₄ ⁺ and Ca²⁺ (9, 6 and 77 μeq L⁻¹, respectively) than TF. There were differences in concentrations of ions in leachates from the forest floor between the dormant and growing seasons presumably due to vegetation uptake and microbial immobilization. Concentrations and fluxes of NO₃ ⁻ and NH; were greatest in early spring followed by a rapid decline which coincided with a demand for N by vegetation in late spring. Vegetation uptake (44.7 kg N ha⁻¹ yr⁻¹ ) could account for the low leaching rates of N0₃ ⁻. Within the mineral soil, changes with soil depth and the absence of seasonal patterns suggest that cation exchange (Ca⁺) or anion sorption (SO₄ ²⁻) are primarily responsible for regulating solute concentrations. The increase in SO₄ ²⁻ concentration after leachates passed through the mineral soil may be attributed to desorption of sulfate that was adsorbed during an earlier period when SO₄ ²⁻ concentrations would have been greater due to elevated S inputs.     

Hernandulcin in hairy root cultures of Lippia dulcis

The hairy root culture of Lippia dulcis Trev., Verbenaceae, was established by transformation with Agrobacterium rhizogenes A4. The transformed roots grew well in Murashige and Skoog medium containing 2% sucrose. The roots turned light green when they were cultured under 16 h/day light. The green hairy roots produced the sweet sesquiterpene hernandulcin (ca. 0.25 mg/g dry wt) together with 20 other mono- and sesquiterpenes, while no terpenes were detected in the nontransformed root cultures. The growth and hernandulcin production in the hairy root cultures were influenced by the addition of auxins to the medium. The addition of a low concentration of chitosan (0.2 – 10.0 mg / l) enhanced the production of hernandulcin 5-fold.Abbreviations Cht chitosan - IAA indole-3-acetic acid - NAA 1-naphthaleneacetic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - MS Murashige and Skoog(1962)     

Monitoring hairy-root growth by image analysis

Hairy roots, incited byAgrobacterium rhizogenes, form a useful system for analysing the expression and phenotypic effects of foreign genes in plant root tissue. Image analysis offers a non-invasive method of describing their growth in culture. Images of pea (coarse) andBrassica (fine) hairy roots were captured, processed and analysed without difficulty using a commercially available image analysis system. The value of this method in monitoring intermediate changes in growth pattern was illustrated by following the changes in five putatively chlorsulfuron-resistantBrassicc hairy-root lines cultured with and without a selective level of chlorsulfuron. Areas of hairy-root research where this technique will be particularly useful are discussed.