Dynamic stomatal behavior and its role in carbon gain during lightflecks of a gap phase and an understory Piper species acclimated to high and low light

Summary Steady-state and dynamic stomatal and assimilation responses to light transients were characterized in sun- and shade-acclimated plants of Piper auritum, a pioneer tree, and Piper aequale a shade-tolerant shrub from a tropical forest at Los Tuxtlas, Veracruz, México. Despite essentially identical steady-state responses of stomatal conductance to PFD of P. aequale and P. auritum shade plants, the dynamic responses to lightflecks were markedly different and depended on the growth regime. For both species from both growth environments, the increase in stomatal conductance occurring in response to a lightfleck continued long after the lightfleck itself so that the maximum stomatal conductance was not reached until 20–40 min after the lightfleck. Closing then occurred until stomatal conductance returned to near its original value before the lightfleck. Plants that were grown under light regimes similar to those of their natural habitat (high light for P. auritum and shade for P. aequale) had large maximum excursions of stomatal conductance and slower closing than opening responses. Plants grown under the opposite conditions had smaller excursions of stomatal conductance, especially in P. auritum, and more symmetrical opening and closing. The large and hysteretic response of stomatal conductance of P. aequale shade plants to a lightfleck was shown to improve carbon gain during subsequent lightflecks by 30–200%, depending on lightfleck duration. In contrast the very small stomatal response to lightflecks in P. auritum shade plants, resulted in no significant improvement in use of subsequent lightflecks.     

Removal of dissolved metals by plant tissue

Various types of microbial biomass have been shown to adsorb metals dissolved in aqueous media. It has now been demonstrated that certain plant tissues are also effective for this type of adsorption process. In particular, tomato and tobacco roots harvested from field-grown plants were shown to adsorb Sr from an aqueous solution of SrCl(2). Distribution coefficients in excess of 550 were measured and the adsorption isotherms at 25 degrees C could be fitted to Langmuir-type expressions. The bioadsorbent could be regenerated and metals recovered by either a reduction in the pH to less than 2.0 or by use of a concentrated chloride salt solution.     

Influence of oxygen adsorption on the dynamic K(L)a measurement in three-phase slurry reactors

To check for possible mass transfer limitations of oxygen and/or carbon dioxide in kinetic experiments on microbial desulphurization of coal, it is important to properly measure the volumetric mass transfer coefficient (k(L)a) especially at high slurry densities. Volumetric mass transfer coefficients of oxygen, at different solid hold-up values (epsilon(s) = 0 to 0.28) of coal slurries (d(par) < 100 * 10(-6) m), were measured in a lab scale fermentor and in a lab scale pachuca tank, using the dynamic gas-liquid absorption method. It was shown that serious errors could occur due to oxygen adsorption at the coal surface. Using the data of an independently measured adsorption isotherm, the real k(L)a could be calculated from the measured apparent k(L)a. The results show a k(L)a decrease of 40% to 50% at a volumetric solid hold-up of 28%. Estimation of the oxygen and carbon dioxide transfer rates, from the measured mass transfer coefficients, indicates that the stirred fermentor is suitable for kinetic experiments at high slurry densities, whereas the pachuca tank and shake flask are not. (c) 1992 John Wiley & Sons, Inc.     

Measurement of free space and sorption of large molecules by cereal roots

Abstract. Large molecular weight solutes that do not penetrate the root have been used to correct for the surface film in measurements with mannitol of the volume of the Apparent Free Space (FS) in bailey roots. The results are compared with those obtained using other correction techniques for elimination of the surface film. Large molecules seem to be adsorbed on the root surface and the kinetics of adsorption differ between the polyhydric alcohol mannitol or the polysaccharide dextran on the one hand, and the polyether polyethylene glycol (PEG-4000) on the other. The significance of this difference in kinetics is discussed in relation to the use of PEG as an osmoticum in studies on root water relations and its effect on ion uptake. Although smaller molecular weight PEG's penetrate the FS and diminish sodium uptake from 10 mol m⁻³ NaCl, more dilute solutions of mannitol and larger PEG polymers are unlikely to affect ion uptake from dilute nutrient solutions. Use of these substances along with labelled nutrients in kinetic studies of the compartmentation of ions in roots can help to distinguish between ions associated with the surface film, those in the FS and those that have crossed the cell membranes into the protoplast.     

Interactions of detrital particulates and plankton

Detrital particulates, i.e. inorganic and non-living organic material of colloidal size and larger, span ten orders of magnitude in size and are ubiquitous in inland waters. Interactions between plankton and detrital particulates are reciprocal. Release of dissolved organics by living organisms enter the particulate size fraction by flocculation on bubbles or adsorption to inorganic particles. Bacteria benefit from attachment to particles and are agents in the aggregation of particulates. Nutrients released by decaying plankton can support phytoplankton growth. Potentially toxic compounds adsorb to particulates and then can enter pelagic food webs or sediment. Material egested by zooplankton contributes to the detrital pool which in turn is a food source for zooplankton.     

Aminopeptidase activity associated with alpha1-conarachin (peanut protein)

Aminopeptidases were investigated in protein extracts of dormant and germinated peanut cotyledons by electrophoretic immunochemical techniques. Considerable activity was observed in protein zones that migrated toward the anode after simple electrophoresis. Of the immunogenic proteins in dormant seed, aminopeptidase activity was associated only with the immunocomplex of α₁-conarachin, a globular protein in peanuts. The specific aminopeptidase activity of total extracts was marginally higher than that of purified α-conarachin. Specific iso-enzyme(s) adsorption on the antigen-antibody complex of α₁-conarachin might be attributed in part, to these phenomena. Reactions of protein extracts from germinated cotyledons with immune sera made against protein in germinated tissues—roots and cotyledons—showed the identical associative interaction. Some of the determinant groups on α₁-conarachin in the germ and cotyledon were apparently maintained during early phases of germination.     

Electron microscopic visualization of restriction sites on DNA molecules.

DNA molecules were adsorbed to a polylysine-treated carbon film and digested directly on the film by restriction enzymes. After washing the film with 1 M NaCl, 0.4% Kodak Photo-Flo and 9% formamide, each cleavage site introduced was visualized as a gap under the electron microscope. By measuring the gapped positions on linear DNA molecules induced by other enzymes, a single EcoRI site on a lambda dv1 molecule and three HinHI sites on an fd1RF molecule were mapped at the positions expected from the cleavage maps, respectively. This electron-microscopic procedure may be useful for the construction of a cleavage map.     

Interactions of Pseudomonas Aeruginosa Hemagglutinins With Euglena Gracilis, Chlamydomonas Reinhardi, and Tetrahymena Pyriformis

SYNOPSIS The galactosephilic and mannosephilic hemagglutinins of Pseudomonas aeruginosa adsorbed onto Euglena gracilis, Chlamydomonas reinhardi , and Tetrahymena pyriformis . Furthermore, peroxidase binding to the 3 protozoan species was shown to be mediated by these lectins. Binding of Pseudomonas lectins to E. gracilis and C. reinhardi caused their specific agglutination, whereas no agglutination was observed with T. pyriformis , even after treatment by papain or by NaF. Added to the culture medium, the Pseudomonas hemagglutinins stimulated growth of E. gracilis and T. pyriformis due to their binding to these protozoa: this effect was partly inhibited by the specific sugar.     

Flying honey bees adsorb airborne viruses

Tethered honey bees (Apidea Apis melifera) coaxed to fly in a miniature wind tunnel for a specific time interval, adsorb a virus (i.e., bacteriophage MS2) aerosol at a linear rate of 1% of the aerosol concentration for every 6.73 pC of electrostatic charge on the bee.