Correlative inhibition of lateral bud growth in Phaseolus vulgaris L. timing of bud growth following decapitation

Summary On intact, 3-week-old plants of Phaseolus the larger bud in the axils of the primary leaves shows slow, continuous elongation growth. Release from correlative inhibition can be detected within 30 min following decapitation. When 0.1% indoleacetic acid in lanolin is applied to the decapitated stem stump, the lateral bud shows slow growth during the first 7 h, then stops completely for a further 15 h but after 2 days a further gradual increase in length is observed.The movement of ¹⁴C-labelled assimilates from the subtending primary leaf into the lateral bud increases following removal of the shoot apex. When indole acetic acid is applied to decapitated plants the ability of the buds to import ¹⁴C increases for 5–7 h and then declines to a negligible amount. Little or no radioactivity from tritiated indoleacetic acid is transported into the lateral buds of decapitated plants during the first 48 h following removal of the apex and it appears that rapid metabolism of the compound occurs in the stem tissues.     

Xylem changes in the correlative inhibition of lateral bud growth in flax (Linum usitatissimum L.)

Xylem or tracheary changes at the base of the cotyledonary buds of flax seedlings (Linum usitatissimum L.), released from inhibition by decapitation of the main apex were studied. The differentiation of xylem strands and/or tracheary elements was correlated with the growth in length of the lateral buds, especially 48–72 hr after the removal of the main apex. The xylem strands, connected to the hypocotylary stele or not, and the tracheary elements increased with age within and outside the strands of both non-decapitated and decapitated seedlings. In the latter, the differentiation of these structures, however, occurred much earlier and in greater abundance in the same regions. The early growth in length of lateral buds, 1 or 2 hr after decapitation, was correlated with the early development of tracheary perforations in the xylem strands. The xylary strands with perforated elements are known to be more efficient than those without them. Therefore, it is suggested that the inhibition of lateral-bud growth was due, in fact, to a lack of appropriate tracheary perforations in the bud xylem strands that were connected with the hypocotylary stele of flax seedlings.     

Electron transport inhibitor in Cyperus javanicus

The natural quinone, hydroxydietrichequinone (3-heptadec-8-enyl-2-hydroxy-5-methoxy-[1,4]benzoquinone) is a secondary metabolite of Cyperus javanicus. We found that this quinone inhibited both mitochondrial respiration and photosynthesis in their electron transportation systems. The quinone was found to have a mode of action against the ubiquinone reductase site from the results of different electron donor experiments on intact mitochondria from rat liver. The electron transport system, photosystem-II (PS-II), in chroloplast from spinach leaves was inhibited by the quinone in a similar way to that of the triazin sires herbicide, atrazin, with its mode of action against PS II. This natural quinone has a long aliphatic chain (C17) including an unsaturated bond at its midpoint. We recognized 8-9 unsaturated bonds in the aliphatic chain from an MS analysis of the methylthio-addact, and spectral data presumed a configuration of cis. form.     

Ethylene formation in pea seedlings; its relation to the inhibition of bud growth caused by indole-3-acetic Acid

Indole-3-acetic acid stimulates ethylene production in the nodal region of pea stems, and the gas inhibits bud growth. At all concentrations of IAA there is a close correlation between the intensity and duration of ethylene production and the bud inhibition which results. Kinetin reverses the inhibitory actions of ethylene and IAA on bud growth. It is concluded that auxins suppress bud development by stimulating ethylene formation. The possibility that auxin induced ethylene formation controls apical dominance is considered.     

Quantitative trait loci and candidate gene mapping of bud set and bud flush in populus

The genetic control of bud phenology in hybrid poplar was studied by mapping quantitative trait loci (QTL) affecting the timing of autumn bud set and spring bud flush. The founders of the mapping pedigree were collected from widely separated latitudes to maximize segregating variation for dormancy-related traits in the F(2) generation-the female Populus trichocarpa parent is from Washington State (48 degrees N) and the male P. deltoides parent is from Texas (31 degrees N). Bud set and bud flush timing were measured on the F(2) generation in a replicated clonal field trial. Using a linkage map constructed of AFLP and microsatellite markers, three QTL controlling bud set and six QTL controlling bud flush were detected. Additionally, five candidate genes believed to be involved in perception of photoperiod (PHYB1, PHYB2) or transduction of abscisic acid response signals (ABI1B, ABI1D, and ABI3) were placed on the QTL map. PHYB2 and ABI1B were found to be coincident with QTL affecting bud set and bud flush.     

Ecological studies on Cyperus difformis, Cyperus iria and Fimbristylis miliacea: three troublesome annual sedge weeds of rice

Cyperus difformis , Cyperus iria and Fimbristylis miliacea are troublesome annual sedges of rice grown in many countries. Laboratory and screenhouse experiments were conducted to determine the effects of temperature, light, salt and water stress, seed burial depth, and flooding time, duration and depth on germination, emergence and growth of these three species. Germination of all the three species was stimulated by light and warm fluctuating temperatures. Germination of C. difformis was influenced to a greater degree by increasing salt and water stress than C. iria and F. miliacea . In all three species, seeds sown on the soil surface gave the greatest percentage of seedling emergence, and no seedlings emerged from seeds buried in soil at depths of ≥1 cm. Flooding, although not continuous or deep, had a suppressive effect on emergence and growth of C. iria and F. miliacea . Intermittent flooding to shallow depths, however, was less effective in controlling C. difformis ; deep flooding was needed to suppress growth of C. difformis seedlings. When the flooding was delayed to 21 days after sowing, there was little growth reduction in all three species.     

Constituents of the essential oil of Cyperus alopecuroides

We have investigated the constituents of the essential oil of Cyperus alopecuroides. Three new compounds, the hydrocarbon, (-)-eudesma-2,4(15)-11-triene, the sesquiterpene alcohol (-)-eudesma-3,11-dien-5-ol and the diterpene hydrocarbon (-)-dolabella-3,7,18-triene were isolated and their structure elucidated.     

Typification of names in Cyperus section Arenarii (Cyperaceae)

The typification of names in the genus Cyperus was done as part of an ongoing study of the section Arenarii. The latest monograph on the genus by Kükenthal (1936), accepted eight species in the section Bobartia (= Arenarii ), and a number of lower level taxa, which are treated here either as distinct species or synonyms. The taxonomic treatment of the core species, C. conglomerates Rottb., turned out to be especially confusing, which is reflected in the past identifications of the material, and consequently, has created wrong interpretations on the distributions. C. jeminicus Rottb. has similarly caused a lot of confusion. Currently we recognize 26 species in the section, with two subspecies in C. conglomerate. Most names in the section have not earlier been typified. Here we designate lectotypes for 33 names, three epitypes, and one neotype. Cyperus sections Arenarii Kunth and Hymenolepides Nees are typified also.     

A biogenetically important hydrocarbon from Cyperus scariosus

A new hydrocarbon isopatchoul-3-ene has been isolated from the essential oil of Cyperus scariosus. The structure and stereochemistry was assigned on the basis of spectroscopic and chemical data. Its biomimetic conversion to isopatchoulenol has been achieved.     

AXR1 acts after lateral bud formation to inhibit lateral bud growth in Arabidopsis

The AXR1 gene of Arabidopsis is required for many auxin responses. The highly branched shoot phenotype of mature axr1 mutant plants has been taken as genetic evidence for a role of auxin in the control of shoot branching. We compared the development of lateral shoots in wild-type Columbia and axr1-12 plants. In the wild type, the pattern of lateral shoot development depends on the developmental stage of the plant. During prolonged vegetative growth, axillary shoots arise and develop in a basal-apical sequence. After floral transition, axillary shoots arise rapidly along the primary shoot axis and grow out to form lateral inflorescences in an apical-basal sequence. For both patterns, the axr1 mutation does not affect the timing of axillary meristem formation; however, subsequent lateral shoot development proceeds more rapidly in axr1 plants. The outgrowth of lateral inflorescences from excised cauline nodes of wild-type plants is inhibited by apical auxin. axr1-12 nodes are resistant to this inhibition. These results provide evidence for common control of axillary growth in both patterns, and suggest a role for auxin during the late stages of axillary shoot development following the formation of the axillary bud and several axillary leaf primordia.     

海南莎草属植物叶下表皮微形态的研究

利用光学显微镜对海南莎草属(Cyperus Linnaeus)15个种1个变种的叶下表皮微形态进行了研究。结果显示:(1)该属叶下表皮微形态基本特征如下:长细胞为长筒形、短筒形,少数为近方形,边缘波状、深波状;无短细胞的存在;副卫细胞为高圆屋顶形、圆屋顶形、圆屋顶至三角形或三角形;(2)根据保卫细胞的形态将海南莎草属分为两大类型即保卫细胞两端明显加厚型和保卫细胞两端不明显加厚型;(3)海南莎草属叶下表皮微形态一致,表明莎草属是一个自然类群,但在莎草属种间叶下表皮的长细胞形态、保卫细胞及副卫细胞形态、气孔长宽等存在一定的差异,可作为本属种间分类鉴别的参考依据。     

Zinc localization in taste bud membranes

Zinc was measured by flame aspiration atomic absorption spectrophotometry in homogenates and in enriched fractions and subfractions from bovine taste bud membranes and from surrounding control tissues that contained no taste buds. Zinc was found in significantly higher concentrations in tissues containing taste buds and increased in concentration as biochemical and electron microscopic purity increased. The role of zinc in taste bud membranes could relate to its role in membrane stabilization or to its activity in alkaline phosphatase, a zinc-dependent enzyme whose specific activity increased in taste bud membranes in the same manner as did zinc concentration.