ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11571159

出版商:Blackwell Publishing    

年代:1982

数据来源: WILEY

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11571386

出版商:Blackwell Publishing    

年代:1982

数据来源: WILEY

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11571398

出版商:Blackwell Publishing    

年代:1982

数据来源: WILEY

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11571409

出版商:Blackwell Publishing    

年代:1982

数据来源: WILEY

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11571463

出版商:Blackwell Publishing    

年代:1982

数据来源: WILEY

摘要:

Abstract.The role of ‘slippage’ reactions, in the form of passive H+uniport through CF0‐CF1, ATP synthetase and breakdown of the S2and S3intermediates of O2evolution, is considered in relation to the growth of phototrophic organisms at low photon fluence rates. Analysis of the limited data available suggests that adaptation (phenotypic or genotypic) to low photon fluence rates is accompanied by an increase in the ratio of light‐absorbing pigments to the (potentially slippage‐inducing) photosystem two units and CF0‐CF1ATP synthetases. Furthermore, organisms which are genotypically adapted to high photon fluence rates do not, when grown at low photon fluence rates, achieve the same low ratio of reaction centres to total light‐harvesting pigments as is found in phototrophs genotypically adapted to low photon fluence rates. The limits to, and energy costs of, such a mechanism of adaptation to low photon fluence rates are a

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11571479

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract.The measurements of Yes'kov&Sapozhnikov (1976) suggest that electrostatic potentials on foraging honeybees can reach hundreds of volts. Pollen grains of oilseed rape,Brassica napusL., subjected experimentally to potentials of this order, jumped a distance that increased approximately as the square of the voltage, between two pin electrodes on which, in some experiments, were impaled an anther or stigma of oilseed rape or a freshly‐killed honeybee. Most floral surfaces were insulated, but there was a low‐impedance path to earth via the stigma, and the electrostatic field due to an approaching charged bee must therefore concentrate there. Thus, if electrostatic potentials of this magnitude occur in nature they may increase the chance that pollen from bees will reach the stigma rather than other floral surfaces, as well as enabling pollen to jump from anther to bee and from bee to stigma across an air gap of the order of 0.5

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11571488

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract.Application of an acid aerosol generated from an aqueous HC1 or HNO3solution (pH 1‐2) to the hypocotyl segment ofVigna sesquipedalis, excised from the elongation zone and abraded with alumina gel, induced rapid elongation growth comparable with that induced by aerosol generated from neutral 1 mol m−31AA aqueous solution. The activity of the first electrogenic ion pump, whose activity is known to be stimulated by IAA aerosol in advance of the increase in growth rate, was little affected by acids. The latent period of the growth response to acids was only 1 min shorter than that to IAA (mean value: 12min), or than the period from the stimulation of the electrogenic ion pump activity by IAA to the beginning of growth acceleration (mean value: 4 min). The growth rate, together with the activities of the first and the second ion pump, was reduced by anoxia in the presence of acid. The acid N2‐sol was ineffective to stimulate the elongation under anoxia. The acid aerosol was ineffective to stimulate the elongation of a non‐abraded segment with intact cuticle layer on its

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11571517

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract.Responses to red light irradiation of discrete areas along the intact, etiolated oat seedling indicate that illumination of the region around the coleoptilar node results in maximal coleoptile growth stimulation and mesocotyl growth suppression. Quantitation of the fibre optic properties of these etiolated tissues shows that the amount of axially transmitted light is log linear as a function of distance for both the mesocotyl and coleoptile (plus primary leaf). Using the fibre optic properties of the tissues to predict the response of the etiolated seedling to defined illumination fields allows one to localize two sites of photoperception: although the mesocotyl response pattern can be explained by the action of a single site found near the top of the mesocotyl itself, the coleoptile response depends on irradiation of both the mesocotyl site and an additional site located just above the node. The very low‐ and the low‐fluence responses of etiolated oats independently predict similar regions of the seedling as sites of photo‐perception. The fibre optic properties of the seedling could allow the seedling to increase the effective light signal received by the photosensitive area signific

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11571543

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract.Osmotic adjustment, a mechanism whereby plants maintain positive turgor despite low water potential (ψ), was investigated in pearl millet (Pennisetum americanum[L.] Leeke) in three types of field experiment at Hyderabad, India:1Osmotic adjustment during the growing season was evaluated by comparing solute potential (ψs) of leaves taken at midday from irrigated and droughted plots and allowed to rehydrate in the laboratory. The degree of seasonal adjustment was also estimated by comparing observed values of ψsin the field with those expected if ψsdecreased solely in proportion to water loss. Both types of assessment indicated the maximum seasonal adjustment to be about 0.2 MPa. The cultivars BJ 104 and Serere 39 differed in their capacity to adjust osmotically over the season; Serere 39 was least able to osmoregulate.2Measurements of diurnal variations in ψ and ψsinBJ104 revealed osmotic adjustment during the afternoon hours. At a given value of ψ, turgor (ψp) was about 0.1 MPa higher in irrigated, and over 0.2 MPa higher in droughted plants, in the afternoon, than in the morning.3Osmotic adjustment of different leaves within the canopy was investigated. Upper leaves had lower ψ than basal leaves. Differences in ψ were matched by gradients in ψs, so that turgor was similar for all l

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11571559

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY