摘要:

SUMMARYOperation of the pollination mechanisms ofRhinanthus serotinus(Schönh.) Oborny,R. minorL.,Pedicularis palustrisL.,P. sylvaticaL., andMelampyrum pratenseL. by nectar and pollen‐collecting bumblebees (BombusLatr.) was studied. Pollination by bumblebees may be achieved in two ways:Head‐thorax pollination by nototribic long‐tongued bumblebees. Long‐tongued bumblebees forage upright for nectar, while the stigma nototribically contacts residual pollen in the head‐thorax crevice; pollen not retained in this crevice is groomed from the body by a forward movement of the middle legs crossed over the dorsum and deposited in the corbiculae.Venter pollination by sternotribic, short‐tongued bumblebees (incl. nectar thieves). Nectar thieves obtain nectar by biting a hole in the long corolla tube close to the nectary. These short‐tongued bumblebees usually collect pollen in an inverted position. They grasp the edge of the galea with their mandibles and tear it asunder. Their abdomen is curved under the pollen chamber formed by the galea enclosing the anthers. Pollen is vibrated loose by means of wing movements, which produce a hissing sound; pollen is deposited on the ventral side of the body of the bumblebee, particularly on the sternites and transported to the corbiculae. Both ways of pollen collecting result in deposit of large amounts of pollen on the bodies and in the corbiculae of the pollinat

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1977.tb01103.x

年代:1977

数据来源: WILEY

摘要:

SUMMARYThe internal atmosphere of gibbous as well as flat modifications ofLemna gibbaG3v, as determined by gas chromatography after cultivation in vitro under conditions of continuous light. A similar analysis was done on a gibbous strain ofL. gibbacollected in the field. The gaseous constituents of the air chambers were found to be N2, O2and CO2. The CO2concentration was approx. 1% in gibbous forms of strain G3 as well as the field strain and approx. 3% in flat forms of strain G3. The O2concentrations tended to be slightly higher in the gibbous forms than in the flat. The CO2to O2ratio of the flat modification was much higher than in the gibbous forms. The remaining part of the internal atmosphere consisted of nitrogen. Methane and ethylene could not be detected.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1977.tb01104.x

年代:1977

数据来源: WILEY

摘要:

SUMMARYUptake of glycine, L‐alanine, L‐leucine, L‐isoleucine, L‐valine, and D‐valine by intact fronds of the duckweedSpirodela polyrhizawas investigated.The time‐course of amino acid uptake showed that the uptake rate (= net influx) was apparently not affected by accumulation of amino acid in the fronds, suggesting that there was no trans‐inhibition of the influx, and that the efflux was negligible.Efflux was measured from fronds preloaded with L‐(14C)leucine. When the external and internal concentration were both about 2.5 mM the efflux was ≤ 1% of the influx.Uptake rates were measured over a wide concentration range, 1 μM to 10 mM. For each amino acid the relation between uptake rate and external concentration could be described as the sum of two Michaelis‐Menten processes. It is suggested that the duckweed possesses two transport systems common to the neutral amino acids tested: a low Km, low capacity system (system 1), and a high Km, high capaci

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1977.tb01105.x

年代:1977

数据来源: WILEY

摘要:

SUMMARYMeasurements of leaf temperature, air temperature, stomatal resistance and the net radiation of leaves are presented for coffee leaves exposed to the sun and shaded. Sunlit leaves were generally between 10°C and 15°C above air temperature (which was approximately 29°C) and shaded leaves were 1°C or 2°C below air temperature. Leaf temperatures are analysed in terms of the leaf energy balance equation and transpiration rates are calculated. Stomatal resistance of sunlit leaves was often higher than that of shaded leaves in continuous sunshine, however on days following substantial rain the stomata of sunlit leaves remained open. The affect of leaf temperatures on the dry matter production of coffee is briefly discu

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1977.tb01106.x

年代:1977

数据来源: WILEY

摘要:

SUMMARYSequel to a paper in Acta Bot. Neerl. 24(2) April 1975, p. 139–154. Twelve new species ofTaraxacumare described:T. argillicola, belonging to sect.SpectabiliaDahlst.,T. dissectiforme, belonging to sect,Dissectav.S.;T. limnophilum, of which the systematical situation is not yet clear;T. eminens, T. exsanguineum, T. exsurgens, T. Fabrei, T. glandonense, T. providens, T. pubicaule, T. tristiceps, T. varense, all belonging to sect.VulgariaDahls

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1977.tb01107.x

年代:1977

数据来源: WILEY

摘要:

SUMMARYPavlova ennoreasp. nov. is described at both the light and electron microscope level with emphasis on the palmelloid stage. Characteristic features of the genusPavlovaobserved in our material include the reserve material paramylon, the system of flagellar roots, and the pit entering the cell at the flagellar pole. The flagellar apparatus and the pit are not continually present in the encapsulated condition. An investment of minute dense particles on the plasmalemma, as known from otherPavlovaspecies, is completely absent. InPavlova ennorea, ecdysis of the periplast is a natural phenomenon, in which the plasmalemma is replaced by a membrane of the endoplasmic reticulum. The original plasmalemma and the substituting E.R. membrane have dissimilar garnitures of internal particles, which suggest that periplast ecdysis effectuates a change in the protoplast's boundary conditions. The mucilage envelope is composed of long microfibrils. Staining experiments indicate an anionic nature of the mucilage. However, the permeability for anions seems not impaired to a biologically signifidegree.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1977.tb01108.x

年代:1977

数据来源: WILEY

摘要:

SUMMARYMitotic activity, cytokinesis and arrangement of daughter cells within the parental wall are studied in synchronized cultures ofScenedesmus quadricauda, which yield either unicells or coenobia. Irrespective of the formation of either unicells or coenobia, no essential differences occur in the nuclear patterns and the positions of the cleavage planes. Only the stages of daughter cell arrangement differ significantly in these two cycles. Daughter unicells are arranged within the parental wall more or less radially, whereas daughter coenobia become arranged with their axis parallel to the axis of the mother cell.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1977.tb01109.x

年代:1977

数据来源: WILEY

摘要:

SUMMARYWhen combined with GA, phenylalanine produced marked enhancement of red colouration of rose (cvBaccara) petals, this effect significantly exceeding that of GA applied alone, while phenylalanine when administered alone was virtually ineffective in this respect. Parallel assays of phenyl‐ammonialyase (PAL) activity indicated essentially similar endogenous levels of enzyme irrespective of treatment. These results are interpreted as indicating that mode of GA action in this system is probably not by direct PAL activation but rather via GA‐induced enhancement of membrane permeability thus providing more phenylalanine precursor for anthocyanidin pigment synthesis. This hypothesis is substantiated by the results of plasmolysis studies executed on rose petal epidermal strips in hypertonic solutions where GA significantly cut down time required to achieve a given degree of plasymoly

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1977.tb01110.x

年代:1977

数据来源: WILEY

摘要:

Growing, cutting, and handlingAvenacoleoptiles in total darkness is a prerequisite for studies on the influence of small quantities of light on the production of auxin by isolated coleoptile tips. A technique is described for putting coleoptile tips on agar without exposing them to any light before and during handling.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1977.tb01111.x

年代:1977

数据来源: WILEY

摘要:

Strasburger's Textbook of Botany. Rewritten by D.vonDenffer, W. Schumacher, K. Mägdefrau, F. Ehrendorfer. New English Edition, translated by P. R. Belland D. E. Coombe. XVIII/877 p., 759 figs. Fischer, Stuttgart 1976. Price DM 6

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1977.tb01113.x

年代:1977

数据来源: WILEY