Acclimation to irradiance of leaf photosynthesis and associated nitrogen reallocation in photosynthetic apparatus in the year following thinning of a young stand of Chamaecyparis obtusa

In order to quantify the effects of thinning on photosynthetic parameters and associated change in leaf nitrogen (N) contents, half of the trees in a 10-year-old Chamaecyparis obtusa (Sieb. et Zucc.) Endl. stand (36° 3′N, 140°7′E) were removed, giving a final density of 1 500 trees ha⁻¹, in May 2004. Photosynthetic photon flux density (PPFD) and leaf N and carbon (C) contents in the lower (L), middle (M), and upper (U) crowns were monitored one, three, and five months after thinning in both the thinned stand and a non-thinned control stand. In addition, leaves’ photosynthetic responses to CO₂ concentration were simultaneously measured in situ to estimate the maximum rates of carboxylation (V_cmax) and electron transport (J_max). Thinning increased PPFD in the L and M crowns but not in the U crown. V_cmax in both the L and M crowns of the thinned stand increased significantly in comparison with the same crown position of the control stand in the three and five months following thinning. In addition, the thinned stand exhibited an increase in N partitioned to ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) in the L and M crowns relative to the control stand three and five months after thinning, indicating that N had been redistributed within the photosynthetic machinery. Thinning did not affect N per unit area at any of the crown positions, but significantly increased the content of N as a fraction of the total leaf dry mass in the L and M crowns three and five months after thinning. This was a consequence of a decrease in leaf dry mass due to rapid shoot growth. Thus thinning did not cause a redistribution of N between leaves. Thinning improved irradiance in the L and M crowns of C. obtusa, leading to photosynthetic acclimation. Photosynthetic acclimation in the first year mainly occurred via redistribution of N within but not between leaves.     

Mode of Action of the Antibacterial Compound Ar26 Produced by Agrobacterium vitis Strain E26 with Activity against A. tumefaciens, A. rhizogenes and A. vitis

The biological control bacterium Agrobacterium vitis strain E26 was previously shown to produce an antibacterial compound, Ar26. This compound was involved in the biocontrol process and inhibited grapevine crown gall-causing A. vitis strains in vitro by an unknown mechanism. This work was undertaken to determine the antibacterial properties and mode of action of Ar26. In a well agar plate diffusion assay against 29 tumorigenic isolates of Agrobacterium spp., Ar26 displayed broad inhibitory activity against 27. All of the 10 A. vitis , 8 of 9 A. tumefaciens and 9 of 10 A. rhizogenes strains were sensitive to this compound. Agrobacterium vitis strains were more sensitive to Ar26 than A. tumefaciens or A. rhizogenes strains, with larger inhibition zones and lower minimal inhibitory concentration (MIC). Ar26 exhibited a bactericidal effect against A. vitis. This compound did not cause bacterial cell lysis, as determined by morphological observation with an electronic microscope. Also, no leakage of cytoplasmic materials from cells of A. vitis occurred after treatment with Ar26 at concentrations equivalent to the MIC. However, an inhibition of the incorporation of radiolabelled precursors into DNA, RNA and protein was observed after treatment with Ar26. Results obtained suggest that Ar26 inhibited DNA, RNA and protein syntheses in tumorigenic A. vitis .     

Liquid chromatographic direct resolution of flecainide and its analogs on a chiral stationary phase based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid

Flecainide, an antiarrythmic agent, and its analogs were resolved on a high performance liquid chromatographic chiral stationary phase (CSP) based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid with the use of a mobile phase consisting of methanol‐acetonitrile‐trifluoroacetic acid‐triethylamine (80/20/0.1/0.3, v/v/v/v). The chiral resolution was quite successful, the separation factors (α) and the resolutions (R_S) for 20 analytes including flecainide being in the range of 1.19–1.82 and 1.73–6.80, respectively. The ortho‐substituent of the benzoyl group of analytes was found to cause decrease in the retention times of analytes probably because of the conformational deformation of analytes originated from the steric hindrance exerted by the ortho‐substituent. Chirality, 2010. © 2009 Wiley‐Liss, Inc.     

Synthesis of heteroaromatic N-β-glycosides of N-acetylglucosamine under the conditions of phase transfer catalysis: I. Glucosaminides of 2-oxobenzazoles

Glycosylation of benzothiazolone-2, 5-methylbenzoxazolone-2, and benzothiazolone-2 with the full acetate of α-D-glucosaminyl chloride in the phase transfer systems investigated (solid-organic solvent and aqueous alkali-organic solvent) regioselectively leads to the corresponding N-β-D-glucosaminides, which is proved by ¹H NMR spectroscopy and X-ray analysis.     

Size structure of current-year shoots in mature crowns

Characteristics of current-year shoot populations were examined for three mature trees of each of three deciduous broad-leaved species. For first-order branches (branches emerging from the vertical trunk) of the trees examined, lengths or diameters of all current-year shoots were measured. Total leaf mass and total current-year stem mass of first-order branches were estimated using an allometric relationship between leaf or stem mass and length or diameter of current-year stems. For each tree, the number of current-year shoots on a first-order branch was proportional to the basal stem cross-sectional area of the branch. On the other hand, first-order branches had shoot populations with size structures similar to each other. As a result, the leaf mass of a first-order branch was proportional to the basal stem cross-sectional area of the branch, being compatible with the pipe-model relationship. All current-year shoot populations had positively skewed size structures. Because small shoots have a larger ratio of leaf mass to stem mass than large shoots, first-order branches had an extremely large ratio of leaf mass to current-year stem mass. This biased mass allocation will reduce costs for current stem production, respiration and future radial growth, and is beneficial to mature trees with a huge accumulation of non- photosynthetic organs. The allometric relationships between leaf mass and basal stem diameter and that between leaf mass and current-year stem mass of first-order branches were each similar across the trees examined. Characteristics of shoot populations tended to offset inter-species diversity of shoot allometry so that branch allometry shows inter-species convergence.     

Enantioselective transport and liquid-liquid extraction of amino acids as their potassium and sodium salts by optically active diaza-18-crown-6 ethers

Complexation of amino acids as their sodium and potassium salts by optically active diaza crown ethers has been investigated in transport across bulk liquid membranes containing the carriers and in extraction experiments. The observed enantioselectivity was achieved by (noncovalent) steric and repulsive interactions between the side arm of the crown ether and functional group(s) of the amino acids. The highest enantioselectivity was observed in the case of tryptophan.     

Spatial arrangement of branches in relation to slope and neighbourhood competition

To gain a better understanding of the effects of spatial structure on patterns of neighbourhood competition among hardwood trees, the three-dimensional extension of primary branches was surveyed for ten community-grown Castanea crenata (Fagaceae) trees with respect to the positioning of neighbouring branches and the slope of the forest floor. There were significantly more branches extending towards the lower side of the slope than towards the upper side, but structural properties such as branch length and vertical angle were not affected by slope. When horizontal extension of a branch towards its neighbour was compared for a C. crenata branch and a neighbouring heterospecific, the former was significantly narrower than the latter when the inter-branch distance (horizontal distance between the base positions of two neighbouring branches) was short (< approx. 5 m). Castanea crenata branches tended to extend in a direction avoiding neighbouring branches of heterospecifics when the inter-branch distance was short. Furthermore, for an inter-branch distance <3 m, the horizontal extension of a C. crenata branch was less when it was neighbouring a heterospecific branch than when neighbouring a conspecific branch. These results suggest that horizontal extension of C. crenata branches is more prone to spatial invasion by nearby neighbouring branches of heterospecifics, and that the invasion can be lessened when C. crenata trees are spatially aggregated. The reason why such an arrangement occurs is discussed in relation to the later leaf-flush of C. crenata compared with that of other species in the forest.     

The functional morphology of light capture and carbon gain in the Redwood forest understorey plant Adenocaulon bicolor Hook

1. A three-dimensional geometric simulation model of crown architecture was utilized to investigate the efficiency of light capture and its relationship to whole-plant CO₂ assimilation of Adenocaulon bicolor .
2. Positioning of the leaves by the combined effects of ontogenetic variations in petiole length and angle and leaf size, and the leaf divergence angles were shown to be effective in minimizing self shading. The efficiency of light absorption varied from 0·64 to 0·70 among individual plants that were sampled.
3. Plant to plant variation in simulated daily carbon gain was strongly influenced by variations in the direct and diffuse PFD received by the individual plants. When simulations were run for all plants under a single common light environment, the carbon gain was strongly dependent on the efficiencies of light absorption of the different plants.
4. Simulations in which petiole length was varied showed a non-linear dependence of light absorption efficiency on petiole length. When both petiole length and leaf size were varied in a way that maintained a constant biomass then an optimal petiole length that corresponded to the observed petiole length was apparent. The observed divergence angle between successive leaves also maximized light absorption efficiency as compared to greater or lesser angles, but increases in internode length had no significant effect.
5. The results of this study provide evidence for selection for an 'optimal design' of crown architecture in Adenocaulon bicolor that maximizes light capture.     

Allometry and Shade Tolerance in Pole‐Sized Trees of Two Contrasting Dipterocarp Species in Sabah,Malaysia1

We compared the allometry of two contrasting late‐successional dipterocarp species to test whether a monolayer (shade‐tolerant)–multilayer (shade‐intolerant) model applies to pole‐sized trees. Crown traits of the more shade‐tolerant species (Vatica micrantha) did not conform to either of the familiar monolayer or multilayer models for pole‐sized trees, but instead were consistent with a “persistent multilayer” model. Species differences in crown traits may be influenced more by future rather than present light environments.     

The lysopinedehydrogenase gene used as a marker for the selection of octopine crown gall cells

Plant cells transformed into octopine-synthesizing tumour cells by the bacterium Agrobacterium tumefaciens survive when cultured in the presence of homo-arginine (HA), whereas both normal plant cells and nopaline producing plant tumour cells do not. Survival of octopine crown gall cells is due to the activity of the enzyme lysopinedehydrogenase (LpDH) in these cells, which converts toxic homo-arginine into non-toxic homo-octopine. The selective toxicity of homo-arginine for normal cells can be applied for the enrichment of octopine Ti plasmid transformed plant cells vs normal plant cells in mixed cultures.