ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01796.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01797.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01798.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractEnvironmental stresses can decrease photosynthesis by a direct effect on photosynthetic capacity of the mesophyll or by a CO2limitation resulting from stomatal closure. In the present study, a ‘path‐dependent method’ (Jones, 1985) for the partitioning of a stress‐related decline in assimilation rate between non‐stomatal and stomatal factors was evaluated, using light quality as a ‘stress’. Kinetic data on assimilation rate and conductance ofPhragmipedium longifoliumfollowing a change in light quality from 95 μmol m−2s−1white light to 95 μmol m−2s−1red light failed to generate a smooth response curve for conductance. Partitioning of limitations on assimilation by a path‐dependent method that utilizes the actual trajectories of conductance and assimilation was therefore not feasible. A simplified path‐dependent method (Jones, 1985) which assumes that either mesophyll cells or guard cells respond first to a stress was applied to steady‐state measurements of assimilation and conductance under red and white illumination. Either 5% or 23% of the observed reduction in assimilation rate under white light was attributable to stomatal factors, depending on whether the ‘stomatal first’ or the ‘mesophyll first’ path was assumed. In the absence of additional information indicating the appropriate choice of path, arbitrary choice may therefore lead to widely divergent estimates, and potentially erroneous conclusions. An alternative approach to the evaluation of the importance to carbon assimilation of stomatal

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01799.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractCO2gas exchange, transpiration and water uptake of the succulentSenecio medley‐woodiiwere monitored simultaneously during a 10 day period of increasing drought. The measurements were performed with a combination of a CO2gas exchange chamber and a potometer system. Further, leaf water relations and CO2gas exchange of a branched potted plant were measured during 15 days of water shortage. The enhancement of CO2dark fixation at the beginning of drought modifies the leaf water relations according to the increased malate accumulation during the dark period. The enhancement of water uptake from dusk to dawn corresponds to the increase of Ψleafduring the same period. Therefore at the beginning of drought a short time improvement of plant water status through the increased CO2dark fixation and malate accumulation can be maintain

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01800.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractPhotosynthetic responses to light, temperature and leaf‐to‐air water vapour concentration deficit forStrophostyles helvola(L.) Ell. in an open beach site, andAmphicarpa bracteata(L.) Ell. in two deciduous forest sites were quantified. Photosaturated rates of net CO2assimilation were 52.1 ± 4.6, 11.0 ± 1.6 and 4.1 ± 0.3 μmol m−2s−2for plants in beach, roadside and closed canopy sites, respectively. In terms of photosynthesis, plants in the beach site were more tolerant of higher leaf temperatures and water vapour concentration deficits than were plants in forested sites. Heliotropic leaf movements in the beach site reduced calculated total daily transpiration by 2%, increased total daily carbon gain by 8% and reduced the transpiration ratio by 9% relative to an horizontal leaf. During long‐term sunflecks in forested sites, heliotropism reduced transpiration by 15%, increased carbon gain by 71% and reduced the transpiration ratio by 50% relative to an horizontal leaf. We hypothesize that heliotropic leaf movements in mesic, high‐light, low‐nitrogen habitats may increase carbon return on nitrogen investment in photosynthesis, while heliotropism in canopy gaps may represent a morphological mechanism to reduce damage to low‐light acclimated photosynthetic systems during

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01801.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe regulation of crassulacean acid metabolism (CAM) under controlled environmental conditions has been investigated for two tropical epiphytes, relating plant water and carbon balance to growth form and habitat preference under natural conditions.Aechmea fendleriis restricted to wet, upper montane regions of Trinidad, whileA. nudicaulishas a wider distribution extending into more arid regions of the island. Morphological characteristics of these plants are related to habitat preference in terms of leaf succulence (0.44 and 0.94 kg m−2for the two species respectively) and a distinct layer of water storage parenchyma inA. nudicaulisIn contrast, the thinner leaves ofA. fendlericontain little water‐storage parenchyma and less chlorenchyma per unit area, but the plants have a more open leaf rosette. The two species differ in expression of CAM, since the proportion of respiratory CO2recycled as part of CAM had been found to be much lower inA. fendleriThis study compared the efficiency of water use and role of respiratory CO2recycling under two PAR regimes (300 and 120 μnol m−2s−1) and three night temperatures (12, 18 and 25 °C). Dark CO2uptake rates for both species were comparable to plants in the field (maximum of 2.3 ± 0.2 μmol m−2s−1± SD,n= 3). Total net CO2uptake at night increased on leaf area basis with temperature for both species under higher PAR, although under the low PAR regime CO2uptake was maximal at 18 °C. Water‐use efficiency (WUE) increased at 18 °C and 25 °C during dark CO2uptake (Phase I) and also during late afternoon photosynthesis (Phase IV) in both species. ForA. fendleri, dawn to dusk changes in titrable acidity (ΔH+) were similar under high and low PAR, although ΔH+was correlated to night temperature and PAR inA. nudicaulis.The proportion of ΔH+derived from respiratory CO2also varied with experimental conditions. Thus percentage recycling was lower inA. fendleriunder high PAR (0–10%), but was only reduced at 18 °C under low PAR. Recycling byA. nudicaulisranged from 32–42% under high PAR, but was also reduced to 6% under low PAR at 18 °C; at 12 °C and 25 °C, recycling was 37% and 52% respectively. Previous studies have suggested a relationship between the proportion of recycling and degree of water stress. This study indicated that CAM as a CO2concentrating mechanism regulates both water‐use efficiency and plant carbon balance in these epiphytes, in response to PAR and night temperature. However, the precise relationship between respiratory processes and the balance between external and internal

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01802.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractI propose that one single formulation can be applied to relate growth and content of several nutrients, including the most important macronutrients, of most plant species. The plant growth rate is proportional to the nutrient content minus a given minimal concentration of the nutrient in minimum. The proportionality factor, the nutrient productivity, and the minimum concentration are species specific properties. The nutrient productivity formulation is shown to apply for very different plant species and for different nutrients.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01803.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractInLolium multiflorumnodal segments, bending responses both to geostimulation and unilateral indole‐3‐acetic acid (IAA) application exhibited much variability in their lag times and speeds of early bending. Despite this variability, mean response curves to gravity and auxin stimulus were markedly similar with each having a phase of immediate, negative bending followed by phases of slow, positive bending and eventually more rapid, positive bending within 40 min of initial treatment. Comparison of lag times for response to geostimulation and unilateral IAA application, whether derived from the mean of individual replicates, or from mean curve data, showed that at least 4 min is available in this geotropic system for establishment of asymmetric auxin levels that could lead to differential growth. The hypothesis that variability in georesponse inLoliumnodal segments is linked to variable sensitivity of geosensitive tissue to auxin was tested using matching longitudinally‐halved nodal segments and evidence was obtained in support of the hypothesis from lag time but not from early bending speed data. The implications of the findings for an involvement of endogenous IAA in shoot geotropism together with the necessity to understand better the complex behaviour of bending response in individual replicates are disc

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01804.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractAn artificial osmotic cell has been constructed using reverse osmosis membranes. The cell consisted of a thin film of an osmotic solution (thickness: 100 to 200 μm) containing a non‐permeating solute and was bounded between the membrane and the front plate of a pressure transducer which continuously recorded cell turgor. The membrane was supported by metal grids to withstand positive and negative pressures (P). At maximum, negative pressures of up to –0.7 MPa (absolute) could be created within the film on short‐term and pressures of up to –0.3 MPa could be maintained without cavitation for several hours. As with living plant cells, the application of osmotic solutions of a non‐permeating solute resulted in monophasic relaxations of turgor pressure from which the hydraulic conductivity of the membrane (Lp) and the elastic modulus of the cell (ɛ) could be estimated. The application of solutions with permeating solutes resulted in biphasic pressure relaxation curves (as for living cells) from which the permeability (Ps) and reflection (σs) coefficients could be evaluated for the given membrane.Lp, Ps, andσswere independent ofPand did not change upon transition from the positive to the negative range of pressure. It is concluded that the artificial cell could be used to simulate certain transport properties of living cells and to study phenomena of negative pressure as they occur in the xylem and, perhaps, also in living cells of

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1988.tb01805.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY