K+(Rb+) and Ca2+ fluxes in young winter wheat plants exposed to sub-zero temperatures

Ice crystal formation temperature was determined in the region of the crown in one group of 7-day-old intact unhardened high-salt plants of winter wheat (Triticum aestivum L. cv. Weibulls Starke II) with TA (Thermal Analysis) and DTA (Differential Thermal Analysis) methods. After exposure of another group of plants, grown for the first 7 days in the same way as the first group, to various sub-zero temperatures (-1 to 5°C), influx in roots of Rb⁺(⁸⁶Rb⁺) and Ca²⁺(⁴⁵Ca²⁺) and contents of K⁺ and Ca²⁺ were determined at intervals during 7 days of recovery. Ice crystal formation in the crown tissue was probably extracellular and took place at about -4°C. There was a large loss of K⁺ from the roots after treatment at sub-zero temperatures. This loss increased as the temperature of the sub-zero treatment decreased. During recovery, roots of plants exposed to -1, -2 and -3°C gradually reabsorbed K⁺. Reabsorption of K⁺ in roots of plants exposed to -4°C was greatly impaired. Rb⁺ influx decreased and Ca²⁺ influx increased after sub-zero temperature treatments of the plants. Active Rb⁺ influx mechanisms and active extrusion of Ca²⁺ were impaired or irreversibly damaged by the exposure. While Rb⁺ influx mechanisms were apparently repaired during recovery in plants exposed to temperatures down to -3°C, Ca²⁺ extrusion mechanisms were not. The temperature for ice crystal formation in the region of the crown tissue coincides with the temperature at which the plants lost the ability to reabsorb K⁺ and to repair Rb⁺ influx mechanisms during the recovery period. Plants were lethally damaged at temperatures below ?4°C.     

An approach to chemotaxonomy of the Asarum subgenus

A survey of chemical composition of 23 species of Asarum subgenus Heterotropa showed that the five groups could be distinguished on the basis of the presence or absence of asatone, phenol ethers and terpenes.     

Types of sesquiterpene-coumarin ethers from Achillea ochroleuca and Artemisia tripartita

In addition to known derivatives, four new sesquiterpene-coumarin ethers were isolated from the roots of Achillea ochroleuca and Artemisia tripartita and identified by ¹H and ¹³C NMR spectroscopy, including lanthanide induced shifts. The new compounds are isofraxidin derived ethers which differ from the previously described derivatives by ring cleavage and methyl migration within the terpenoid unit. The chemosystematic importance of sesquiterpene-coumarin ether accumulation within the two genera is briefly discussed.     

Integration of Agrobacterium T-DNA into a tobacco chromosome: Possible involvement of DNA homology between T-DNA and plant DNA

Summary We established tobacco tumour cell lines from crown galls induced by Agrobacterium. Restriction fragments containing T-DNA/plant DNA junctions were cloned from one of the cell lines, which has a single copy of the T-DNA in a unique region of its genome. We also isolated a DNA fragment that contained the integration target site from nontransformed tobacco cells. Nucleotide sequence analyses showed that the right and left breakpoints of the T-DNA mapped ca. 7.3 kb internal to the right 25 by border and ca. 350 by internal to the left border respectively. When the nucleotide sequences around these breakpoints were compared with the sequence of the target, significant homology was seen between the region adjacent to the integration target site and both external regions of the T-DNA breakpoints. In addition, a short stretch of plant DNA in the vicinity of the integration site was deleted. This deletion seems to have been promoted by homologous recombination between short repeated sequences that were present on both sides of the deleted stretch. Minor rearrangements, which included base substitutions, insertions and deletions, also took place around the integration site in the plant DNA. These results, together with previously reported results showing that in some cases sequences homologous to those in T-DNA are present in plant DNA regions adjacent to left recombinational junctions, indicate that sequence homology between the incoming T-DNA and the plant chromosomal DNA has an important function in T-DNA integration. The homology may promote close association of both termini of a T-DNA molecule on a target sequence; then TDNA may in some cases be integrated by a mechanism at least in part analogous to homologous recombination.Shogo Matsumoto is on leave from Biochemical Research Institute, Nippon Menard Cosmetic Co., Ltd, Ogaki, Gifu-ken 503, Japan     

Crown ether mediated cadmium halide dimers and polymers

The reactions of cadmium halides with the 15-membered macrocyclic crown ethers, 15-crown-5 and benzo-15-crown-5, have been carried out and six new complexes have been isolated and structurally characterized. Metal to ligand stoichiometries of 1:1, 2:1, 3:1 and 3:2 have been observed with a variety of different formulations. Examples of charge separated ion pairs ([(NH₄)(benzo-15-crown-5)₂]₂[Cd₂I₆]), halogen bridged monomers, dimers or polymers ([Cd(15-crown-5)(OHMe)(μ-Br)CdBr₃], [Cd(15-crown-5)(μ-Br)₂CdBr(μ-Br)]₂(isolated from the same reaction mixture) and [(CdCl₂)₂CdCl₂(15-crown-5)]_n), and hydrogen bonded finite chains or polymers ([(Cd(OH₂)₂(15-crown-5)][CdI₃(OH₂)]₂·2(15-crown-5)·2CH₃CN and [CdI₂(OH₂)₂(THF)]·benzo-15-crown-5) have been isolated. Three different types of 15-crown-5 coordination modes have been observed in these complexes. In-cavity coordination resulting in pentagonal bipyramidal geometries about Cd²⁺ was observed in [(CdCl₂)₂CdCl₂(15-crown-5)]_n, [Cd(15-crown-5)(OHMe)(μ-Br)CdBr₃], and [Cd(OH₂)₂(15-crown-5)][CdI₃(OH₂)]₂·2(15-crown-5)·2CH₃CN, [Cd(15-crown-5)(μ-Br)₂CdBr(μ-Br)]₂ displays out-of-cavity coordination with one etheric donor distorted into an axial position of a distorted pentagonal bipyramid. The third coordination mode is secondary sphere coordination via hydrogen bonding which is observed for [Cd(OH₂)₂(15-crown-5)][CdI₃(OH₂)]₂·2(15-crown-5)·2CH₃CN. The good fit of Cd²⁺ within the cavity of 15-crown-5 results in shorter bonding contacts and a more narrow distribution in Cd---O values (2.273(7)-2.344(6) Å) than observed for cadmium halide complexes of 18-crown-6 (Cd---O = 2.69(1)–2.81(1) Å).     

Synthesis of methyl

In Lemna pausicostata Hegelm. 6746, light is required for sufficient acifluorfenmethyl (AFM) stimulation of protoporphyrin IX (Proto IX) accumulation to cause significant herbicidal action. In darkness, AFM causes Proto IX levels to increase for about 2 h, after which Proto IX content is stable at levels significantly lower than those accumulated in light. In darkness, sucrose cannot increase levels of AFM-induced Proto IX. However, addition of δ-aminolevulinic acid (ALA) increases Proto IX levels in AFM-treated plants in darkness, demonstrating that the herbicide blocks the porphyrin pathway in darkness as it does in the light. Thus, Proto IX accumulation in darkness appears to be limited by ALA availability. This is supported by the finding that dioxoheptanoic acid caused more ALA to accumulate in light than in darkness. Heme is a feedback inhibitor of ALA synthesis, and heme synthesis is inhibited by AFM. However, total extractable heme levels were reduced by AFM by about the same amount in both light and darkness. Exogenously supplied hemin reduced AFM-caused Proto IX accumulation and herbicidal damage in the light and also reduced Proto IX accumulation caused by AFM or AFM plus ALA in darkness. AFM-stimulated Proto IX accumulation was inversely proportional to the log of the photon flux density between 5 and 500 μmol in m⁻² s⁻¹. Reduced effects of higher photon fluxes on AFM-stimulated Proto IX accumulation are probably due to both increased photobleaching of Proto IX and reduced porphyrin synthesis because of herbicidal damage. AFM-stimulated Proto IX accumulation in darkness could not be demonstrated to be under phytochrome control, but it appeared to be under the negative influence of protochlorophyllide levels.     

Light control of porphyrin accumulation in acifluorfen-methyl-treated Lemna pausicostata

In Lemna pausicostata Hegelm. 6746, light is required for sufficient acifluorfenmethyl (AFM) stimulation of protoporphyrin IX (Proto IX) accumulation to cause significant herbicidal action. In darkness, AFM causes Proto IX levels to increase for about 2 h, after which Proto IX content is stable at levels significantly lower than those accumulated in light. In darkness, sucrose cannot increase levels of AFM-induced Proto IX. However, addition of δ-aminolevulinic acid (ALA) increases Proto IX levels in AFM-treated plants in darkness, demonstrating that the herbicide blocks the porphyrin pathway in darkness as it does in the light. Thus, Proto IX accumulation in darkness appears to be limited by ALA availability. This is supported by the finding that dioxoheptanoic acid caused more ALA to accumulate in light than in darkness. Heme is a feedback inhibitor of ALA synthesis, and heme synthesis is inhibited by AFM. However, total extractable heme levels were reduced by AFM by about the same amount in both light and darkness. Exogenously supplied hemin reduced AFM-caused Proto IX accumulation and herbicidal damage in the light and also reduced Proto IX accumulation caused by AFM or AFM plus ALA in darkness. AFM-stimulated Proto IX accumulation was inversely proportional to the log of the photon flux density between 5 and 500 μmol in m⁻² s⁻¹. Reduced effects of higher photon fluxes on AFM-stimulated Proto IX accumulation are probably due to both increased photobleaching of Proto IX and reduced porphyrin synthesis because of herbicidal damage. AFM-stimulated Proto IX accumulation in darkness could not be demonstrated to be under phytochrome control, but it appeared to be under the negative influence of protochlorophyllide levels.     

The three-dimensional structure of vascular tissues in Agrobacterium tumefaciens-induced crown galls and in the host stems of Ricinus communis L.

The three-dimensional pattern of phloem and xylem in 10-d-to two-month-old tumors induced by Agrobacterium tumefaciens (C58) and in adjacent Ricinus communis L. stem tissues was studied in thick sections by clearing with lactic acid and by staining with lacmoid. The crown galls contained two types of vascular strands: treelike branched bundles, which developed towards the tumor surface in fast-growing regions, and globular bundles in the slowly developing parts. Both types of vascular bundles contained xylem and phloem and were continuous with the vascular system of the host plant. The tumor bundles were interconnected by a dense net of phloem anastomoses, consisting of sieve tubes but no vessels. These vascular patterns reflect the apparent synthesis sites, concentration gradients and flow pathways of the plant hormones additionally produced in the tumors upon expression of the T-DNA-encoded genes. The A. tumefaciens-induced crown gall affected vascular differentiation in the host stem. In the basipetal direction, the tumor induced more xylem differentiation directly below it, where the crown-gall bundles joined the vascular system of the host. In the centripetal direction, the crown gall caused the development of pathologic xylem characterized by narrow vessels, giant rays and absence of fibers. On the other hand, most probably as a consequence of its gibberellic acid content, the host plant stimulated a local differentiation of regenerative phloem and xylem fibers with unique ramifications, only at the base of the tumor. However, fibers were absent from the main body of the crown gall. The study shows that A. tumefaciens-induced crown galls are characterized by a sophisticated network of vascular tissues in the tumor and are accompanied by a perturbated vessel system in the host. The hormonal mechanisms controlling vascular differentiation in the tumor and neighboring host tissues are discussed. In addition, the gall constriction hypothesis is proposed for explaining the mechanism which gives priority in water supply to the growing gall over the host shoot.We thank Dr. Zs. Koncz (Max-Planck-Institut für Züchtungsforschung, Köln, Germany) for Agrobacterium strains and the Deutsche Forschungsgemeinschaft (SFB 199) for financial support to C.I.U.     

Mixed anion lanthanide(III) crown ether complexes: crystal structures of [LaCl2(NO3)(12-crown-4)]2, [La(NO3)(OH2)4-(12-crown-4)]Cl2·CH3CN and [LaCl2(NO3)(18-crown-6)]

Reaction of LaCl₃·7H₂O containing small amounts of La(NO₃)₃·7H₂O as an impurity with 12-crown-4 or 18-crown-6 in 3:1 CH₃CN:CH₃OH resulted in the isolation of the mixed anion complexes [LaCl₂(NO₃)(12-crown-4)]₂, [La(NO₃)(OH₂)₄(12-crown-4)]Cl₂·CH₃CN and [LaCl₂(NO₃)(18-crown-6)]. The nine-coordinate dimer, [LaCl₂(NO₃)(12-crown-4)]₂, has all of the anions in the inner coordination sphere and La³⁺ has a capped square antiprismatic geometry. It crystallizes in the orthorhombic space group Pbca with (at −150 °C) a = 12.938(6), B = 15.704(3), C = 13.962(2) Å, and D_calc = 2.08 g cm⁻³ for Z = 4. The second complex isolated from the same reaction, [La(NO₃)(OH₂)₄(12-crown-4)]Cl₂·CH₃CN, has the bidentate nitrate anion in the inner coordination sphere but the two chloride anions are in a hydrogen bonded outer sphere. This complex is ten-coordinate 4A,6B-expanded dodecahedral and crystallizes in the monoclinic space group P2₁ with (at 20 °C) A = 7.651(2), B = 11.704(7), C = 11.608(4) Å, β = 95.11(2)°, and D_calc = 1.80 g cm⁻³ for Z = 2. The 18-crown-6 complex, [LaCl₂(NO₃)(18-crown-6)], has all inner sphere anions and has ten-coordinate 4A,6B-expanded dodecahedral La³⁺ centers. It crystallizes in the orthorhombic space group Pbca with (at 20 °C) a = 14.122(7), B = 13.563(5), C = 19.311(9) Å, and D_calc = 1.89 g cm⁻³ for Z = 8.     

Crown alterations induced by decline: a study of relationships between growth rate and crown morphology in beech (Fagus sylvatica L.)

One of the first symptoms expressed by declining trees is reduced growth in stem diameter and length increment. The possibility of a relationship between length increment and crown thinning in beech (Fagus sylvatica L.) was investigated by developing a computer model to simulate first order branching patterns of the apical 2 m of monopodially branching beech trees, 70–100 years old, for a range of length increment rates. The model was based on values for branching angle, main axis and branch length increment, number of branches produced per year and branch mortality rates for six healthy and declining trees. Shoot growth rates in the apical 2 m of the sample trees ranged from about 5 cm/year (decline class 3) to 43 cm/ year (healthy). Simulations of branching patterns in the apical 2 m of trees growing at different rates indicated that, when growth rate exceeded about 20 cm/year, total first order branch length and area explored were independent of growth rate. When growth rates fell below this value there was a reduction in total area explored and first order branch length due primarily to the formation of fewer branches. More acute branching angles contributed to a reduction in the area explored. Growth rate-related crown thinning could increase the risk of bark necrosis and secondary pathogen infection during dry and/or hot spells.