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Abstract. Immunocytochemical localization of the (1-3)--glucan, callose, in developing barley (Hordeum vulgare L.) grain was investigated using a specific monoclonal antibody and observed by means of confocal laser-scanning microscopy. The nucellar projection (NP) and vascular tissue (VT) of the crease cells were specifically labelled by this antibody at all stages of grain development. Maximum intensity...
Abstract. Excision of the apical bud (decapitation) of tobacco (Nicotiana tabacum L.) plants reduced the endogenous levels of indole-3-acetic acid (IAA), gibberellinA20 (GA20), and GA1 (the bioactive GA), in internode tissue below the excision site. Application of IAA to the stump of decapitated plants dramatically increased GA20 content, to a level 3-fold greater than in intact plants. GibberellinA1...
Abstract. Psilotum nudum Griseb is a pteridophyte and belongs to the single family (Psilotaceae) of the division, Psilophyta. Being the only living species of a once populated division, P. nudum is the most primitive vascular plant. Chalcone synthase (CHS; EC2.3.1.74) superfamily enzymes are responsible for biosyntheses of diverse secondary metabolites, including flavonoids and stilbenes. Using a...
Abstract. We describe the properties of npq4-9, a new mutant of Arabidopsis thaliana (L.) Heynh. with reduced nonphotochemical quenching (NPQ) capacity that possesses a single amino acid substitution in the PsbS gene encoding PSII-S, a ubiquitous pigment-binding protein associated with photosystem II (PSII) of higher plants. Growth, photosynthetic pigment contents, and levels of the major PSII antenna...
Abstract. Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC4.1.1.39) activase mRNA and protein synthesis were measured in the leaves of cotton (Gossypium hirsutum L.) plants under control (28C) or heat-stress (41C) conditions. A decline in activase transcript abundance occurred rapidly during the photoperiod and was unaffected by heat stress. In response to high temperature, de novo protein...
Abstract. The first morphogenetic events of lateral root primordium (LRP) formation in the Arabidopsis thaliana (L.) Heynh. pericycle occur soon after cells of the primary root complete elongation. Pericycle cells in direct contact with underlying protoxylem cells participate in LRP formation. Two types of LRP initiation were found, longitudinal uni- and bi-cellular. These occur when a single or two...
Abstract. Mutation of the Arabidopsis thaliana (L.) Heynh. gene MUR1, which encodes an isoform of GDP-D-mannose-4,6-dehydratase, affects the biosynthetic conversion of GDP-mannose to GDP-fucose. Cell walls in the aerial tissues of mur1 plants are almost devoid of -L-fucosyl residues, which are partially replaced by closely related -L-galactosyl residues. A line of suspension-cultured A. thaliana cells...
Abstract. An endo--1,4-glucanase (EG) was purified from ripe strawberry (Fragaria ananassa Duch.) fruit using cellulose affinity chromatography. The purified enzyme gave a single protein band of 54kDa on sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The N-terminal amino acid sequence of this protein showed strong homology with the proteins encoded by recently identified EG genes from...
Abstract. We have investigated both the kinetics and regulation of 15NH4+ influx in roots of 3-month-old hydroponically grown Citrus (Citrus sinensis L. Osbeck Poncirus trifoliata Blanco) seedlings. The 15NH4+ influx is saturable below an external ammonium concentration of 1mM, indicating the action of a high-affinity transport system (HATS). The HATS is under feedback repression by the N status of...
Abstract. A mathematical model of the diffusive transport of abscisic acid (ABA) and gibberellins (GAs) through the aleurone layer of barley (Hordeum vulgare L.) grain is presented. The model consists of two partial differential equations describing the accumulation of phytohormone in the apoplastic and symplasmic compartments of the aleurone layer, both spatially and temporally. The mathematical...
Abstract. The source of Ca2+ involved in transducing an oxidative-burst defense signal was examined in aequorin-transformed tobacco (Nicotiana tabacum L.) cells using modulators of Ca2+ entry. Treatments that either increased or decreased the influx of Ca2+ from external stores were found to have little effect on the magnitude or kinetics of an osmotically stimulated oxidative burst. In contrast,...
Abstract.Regulation of the concentration of Ca2+ in the apoplast of plants is essential in order to allow Ca2+-dependent processes, such as Ca2+-mediated signal transduction in stomatal guard cells, to function correctly. This is particularly important for plants growing with high levels of Ca2+ in the rhizosphere. Recently, we have shown that in two calcicoles, Leontodon hispidus L. and Centaurea...
Abstract. Non-linear excitation of fluorophores by contemporaneous absorption of two or more near-infrared (NIR) photons following diffraction-limited focusing with high-numerical-aperture objectives circumvents out-of-focus fluorescence (without a confocal pinhole) and spatially limits photobleaching and photodamage to the minute sub-femtoliter focal volume. This is in contrast to optical events...
Abstract. Lobaria pulmonaria (L.) Hoffm. is an epiphytic lichen common to temperate deciduous forests where it copes with large changes in temperature and light levels through repeated annual cycles. Samples of L. pulmonaria were taken from a deciduous forest in southeastern Canada at 35-day intervals from February 1999 to February 2000 and also from a rare population in an evergreen forest in March...
Abstract. Copper-containing amine oxidase (CuAO) has been proposed to play a role in H2O2 production in plant cell walls during cell development and in response to pathogen attack. We have compared the localisation of CuAO in pea (Pisum sativum L.), lentil (Lens culinaris M.) and chick pea (Cicer arietinum L.) grown under different light conditions, using both immuno- and histochemical techniques...
Abstract. The role of pyrophosphate:fructose-6-phosphate 1-phosphotransferase (PFP) in developing leaves was studied using wild-type tobacco (Nicotiana tabacum L.) and transformants with decreased expression of PFP. (i) The leaf base, which is the youngest and most actively growing area of the leaf, had 2.5-fold higher PFP activity than the leaf tip. T3 transformants, with a 5695% decrease in PFP...
Abstract. Cyclic electron transport around photosystem (PS) I is believed to play a role in generation of ATP required for adaptation to stress in cyanobacteria and plants. However, elucidation of the pathway(s) of cyclic electron flow is difficult because of low rates of this electron flow relative to those of linear photosynthetic and respiratory electron transport. We have constructed a strain...
Abstract. From photosynthetic studies on a range of monocotyledonous (C-3 and C-4) and dicotyledonous (C-3) plants using a leaf oxygen electrode, we conclude the following. (i) A non-linear model [J.H.M.Thornley (1976) Mathematical models in plant physiology, Academic Press, London; B. Marshall and P.V. Biscoe (1980) J Exp Bot 31:2939] significantly better describes the photosynthetic light response...
Abstract. Plant development depends upon the control of growth, organization and differentiation of cells derived from shoot and root meristems. Among the genes involved in flower organ determination, the cadastral gene SUPERMAN controls the boundary between whorls 3 and 4 and the growth of the adaxial outer ovule integument by down-regulating cell divisions. To determine the precise function of this...
Abstract. An acid phosphatase (APase, EC3.1.3.2) from ripened banana (Musa cavendishii L. cv. Cavendish) fruit has been purified 1,876-fold to electrophoretic homogeneity and a final p-nitrophenylphosphate (pNPP)-hydrolyzing specific activity of 745mol Pi produced (mg protein)1 min1. Non-denaturing PAGE of the final preparation resolved a single protein-staining band that co-migrated with APase activity...
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