摘要:

Abstract.Factors affecting stomatal conductance (g1) of pearl millet (Pennisetum americanum[L.] Leeke), cultivar BJ 104, were examined in the field in India during the dry season.Diurnal changes in g1were evaluated for upper expanded leaves at flowering on two occasions using plants subjected to varying degrees of water stress. Except for the most severely stressed treatment, diurnal changes in g1closely matched changes in irradiance (I), the promotive effect of which largely overcame opposing influences on g1of increasing atmospheric vapour pressure deficit, and decreasing leaf water and turgor potentials (Ψ, Ψp).Two main effects of water stress on g1were evident: (i) a decrease in the amplitude of the mid‐day peak in g1, and (ii) a decrease in the time over which high g1was maintained, resulting in early (mid‐day) closure and hysteresis in the relationship between g1andI.Leaf conductance was greatest for upper leaves and decreased down the canopy. At equivalent depths in the canopy g1was higher in flowering than in photoperiodically‐retarded plants of the same age. The magnitude of water stress‐induced stomatal closure increased down the plant, and was more marked in retarded than in flowering plants.Within individual stress treatments Ψ of upper leaves decreased linearly as transpiration flux increased. It is concluded that stomatal behaviour of upper leaves of pearl millet at flowering largely operates to maximize assimilation rather than to minimize

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11587603

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract.Net fluxes of gaseous sulphur compounds, water vapour and carbon dioxide to current‐ and one‐year‐old shoots of Scots pine were simultaneously measured in the field. The shoots were fumigated in temperature‐controlled assimilation chambers with sulphur dioxide at concentrations ranging from 40 to 250 μg m−3(15–95 ppb). The hypothesis that stomatal opening regulates the uptake of sulphur dioxide was tested. The following conclusions were reached concerning the dry deposition of sulphur dioxide to a dry coniferous shoot.There was a marked diurnal variation in the uptake rate of sulphur dioxide. The net deposition velocity of sulphur was about three times higher during the day than during the night during July‐October. Stomatal opening was not the primary factor controlling the dry deposition rate of sulphur dioxide. The net dry deposition rate was significantly smaller than the calculated rate based on stomatal conductances for water vapour.Part of this deviation could be explained by re‐emission of reduced sulphur compound(s) from the needles. The re‐emission of sulphur was a light‐dependent process and might be of great significance for the sulphur balance calculations.A variable deposition velocity should be used in atmospheric transport models to account for the diurnal and seasonal variation in the surface resist

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11587612

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract.Factors underlying the process of photosynthetic acclimation to temperature were investigated for the shrubNerium oleanderL. Ramets of a single clone were grown under day/night temperature regimes of 20°C/15°C or 45°C/32°C. Plants grown at the lower temperature regime possessed rates of photosynthesis twice that of the high‐temperature grown plants when CO2fixation was measured at 20°C. In contrast, the plants grown at the high‐temperature regime had twice the rate of CO2fixation of the 20°C/l 5°C‐grown plants at a measurement temperature of 45° C. It was determined that the ability to acclimate to changes in temperature regime was present in fully mature leaves. A reciprocal transfer of plants between the two growth regimes resulted in the appearance of the CO2fixation characteristics appropriate to the new growth temperature after 12–14d. The response of CO2fixation to light, temperature, and CO2partial pressure and the temperature responses of soluble and membrane‐bound photosynthetic enzyme systems were analysed to determine which components might be responsible for the superior photosynthetic performance of the 20°C/I5°C‐grown plants at 20°C, and the enhanced high‐temperature stability of the 45°C/32°C plants. The measured photosynthetic capacity of the 20°C/15°C plants could not be attributed to gross morphological, stomatal, or other physical changes, or to a general increase in the concentration of components of the photosynthetic process. Only a single enzyme, Fru‐P2phosphatase, was affected to an extent similar to that of photosynthesis. The enhanced thermal stability of the 45°C/32°C plants may be attributed primarily to an enhanced stability of the chloroplast membrane‐bound enzymatic activities and the stability of the photosynthetic carbon metabolism enzymes

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11587620

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract.Studies on the subcellular location of ethylene binding activity from developing cotyledons ofPhaseolus vulgarisL. are described. Binding activity has been shown to be predominantly membrane bound. When separated by rate‐zonal centrifugation more than 70% of this activity was of low sedimentation rate. The slowly sedimenting band of activity was further fractionated into three bands by isopycnic density gradient centrifugation. The three bands occur at sucrose densities of 1.125 g cm−3, 1.155 g cm−3and 1.175 g cm−3, corresponding to the distribution of putative marker enzymes for the cell endomembrane system and to protein body membranes. Further circumstantial evidence was obtained by electron microscopy and sucrose step gradient centrif

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11588010

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY