Kinetics of efflux of K+ from cultured rose cells treated with ultraviolet light

Irradiation of cultured rose ( Rosa damascena Mill. cv. Gloire de Guilan) cells with ultraviolet light caused of loss of K⁺, which occurred with sigmoid kinetics. The kinetics of loss of K⁺ were not changed when the extracellular concentration of K⁺ was held constant during the period of efflux. Furthermore, the rate of loss of K⁺ was approximately the same even though the K⁺ concentration in the medium was increased from 0.1 to 10 m M . The kinetics of uptake of the lipophilic methyltriphenylphosphonium cation, an indicator of the plasma membrane potential, were linear throughout the period of K⁺ efflux, suggesting that the starting and stopping of K⁺ efflux do not reflect a passive response to changes in the membrane potential of the cells. The results are interpreted in terms of activation and inactivation of an efflux channel or pump for K⁺.     

Rose leaf elasticity changes in response to mycorrhizal colonization and drought acclimation

Tissue elasticity can affect plant response to drought, in terms of turgor maintenance and water uptake from drying soils. The purpose of this study was to determine the effect of mycorrhizal colonization and drought acclimation on rose ( Rosa hybrida L. cv. Samantha) leaf elasticity. Bulk elasticity was characterized by the pressurevolume method using plots of the elastic modulus as a function of leaf turgor pressure, total water potential and relative water content. The treatments, arranged in a 2 × 3 factorial design, included acclimated and unacclimated plants, and either Glomus irararadices Schenck and Smith, Glomus deserticola Trappe, Bloss and Menge, or a non-mycorrhizal control. Plants with root mycorrhizal colonization showed reduced leaf elasticity (i.e. higher elastic moduli) over a broad range of leaf waler potential and water content. Both mycorrbizal colonization and acclimation facilitated the maintenance of positive values of turgor and elasticity at lower leaf water potential and water content than in controls. Mycorrhizal infections may aid plants in acclimating to water deficits through effects on leaf tissue elasticity.     

Plant Cuticle Staining with Bismarck Brown Y and Azure B or Toluidine Blue O before Paraffin Extraction

Transverse paraffin sections of mature greenwood stems of rose (Rosa x hybrida) and flowering dogwood (Cornus florida L.) were stained with Bismarck brown followed by azure B or tolnidine blue O. The Bismarck brown was replaced by thiazin dye metachromasia in all structures except the cuticle which remained brown or yellow. The interface between the cuticle and exterior cell walls of the epidermis was delineated clearly.     

Transpiration of detached leaves from mycorrhizal and nonmycorrhizal cowpea and rose plants given varying abscisic acid, pH, calcium, and phosphorus

 Vesicular-arbuscular mycorrhizal (VAM) colonization can alter transpiration of host leaves, but scientists remain unclear about the mechanisms involved. We tested whether intact root systems were required to observe effects of root colonization by Glomus intraradices on leaf transpiration, or whether some VAM influence resided in leaves even after they were detached from root systems. We measured the transpiration of detached leaves of VAM and nonmycorrhizal plants exposed to different levels of several substances known to influence stomata locally or act in whole-plant regulation of transpiration: abscisic acid, calcium, phosphorus, and hydrogen ions. In rose, some VAM influence on transpiration resided in leaves, even after they had been separated from their root systems. However, removing leaves from their root systems eliminated the VAM influence on stomatal behavior of cowpeas. Accepted: 22 June 1998     

Taxonomic review of the genus Macrosiphum (Sternorrhyncha: Aphididae) for the Korean Peninsula, with description of a new species

Eight species of the genus Macrosiphum Passerini 1860 (Sternorrhyncha: Aphididae) are recognized from the Korean Peninsula. A new species, Macrosiphum ( Macrosiphum ) paektusani n. sp., is described herein for apterous and alate viviparous females on Rosa marretii Lev. (Rosaceae). The taxonomic position of Macrosiphum ( Macrosiphum ) cornifoliae Shinji 1924, com. rev., is transferred from the genus Sitobion Mordvilko 1914 to its original position. Host plants of the Korean Macrosiphum are reviewed and the identification key to subgenera and species is also presented.