摘要:

AbstractPlant growth is the balance of photosynthetic gains and respiratory losses, and it is therefore essential to consider respiration in analyses of plant productivity. The partitioning of dark respiratory losses into twofunctionalcomponents, a growth component and a maintenance component, has proved useful. The growth loss is that associated with synthesis of new biomass while the maintenance loss is that associated with maintenance of existing biomass.Experimental evidence indicates that the respiratory cost of maintenance in herbaceous plants is about equal to the cost of growth over a growing season, with daily maintenace expenditures less important in the small, rapidly growing plant but increasing in significance as plant size increases and the relative growth rate decreases. Because it is such a large fraction of the total carbon budget of a plant, any variations in maintenance requirements may result in significant alterations in productivity. In the present work the theoretical and empirical bases of maintenance respiration are described: magnitudes of maintenance expenditures are summarized; and applications to models of plant growth and productivity are discussed. It is concluded that the costs of maintenance should be included in analyses of plant growth.

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11591833

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractPolysomes and ribosomes recovered from a number of plant species were tested for stability when incubated at 25°C in salt solutions in the absence of ATP and initiation factors. Stability was assessed by sucrose density gradient analysis. The stability was inversely proportional to salt concentrations above 125 mol m−3KCl. Polysomes were less stable in the presence of Na+than K+salts, and were much less stable in Cl−than in acetate salts. Polysomes fromTriticum aestivum. Hordeum vulgare, Capsicum annuum, Helianthus annuus.Pisum sativum, Atriplex nummularia, Beta vulgaris, Cladophorasp.,Enteromorphasp. andCorallina cuvieriwere similarly sensitive to KCl. Polysomes fromUlva lactucawere more sensitive than the other species. Cytoplasmic and plastid polysomes fromT. aestivumwere similarly unstable in 500 mol m−3KCl. Unprogrammed ribosomal subunit couples fromT. aestivum, B. vulgarisandU. lactucashowed Mg2+‐dependent conformational instability and dissociation in KCl. Slight differences in ribosomal stability were observed between species, but these were unrelated to the salt tolerances of the plants. The ‘compatible’ organic solutes, glycinebetaine and proline, failed to reduce ion‐induced instability. Ribosome yield and polysome profiles were similar in leaves ofB. vulgariscontaining significantly different levels of both Na+and Cl−after growth in media containing 50 or 200 mol m−3NaCl. The results are consistent with the hypothesis that plants maintain a cytoplasmic solute environment that is compatible with r

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11591840

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractMessenger RNA from salt‐sensitive and salt‐tolerant plantsTriticum aestivum.Beta vulgaris, Pisum sativum, Chenopodium albumandAtriplex nummulariawas translatedin vitroin a wheatgerm translation system. The optimal monovalent and divalent ion concentrations for translation were independent of the salt tolerance of the plants from which the m‐RNAs were derived. Translation was optimal in 100 120 mol m−3potassium acetate and 1.5–2.0 mol m−3Mg2+. Substitution of Na+for K+, or of Cl−for acetate, was inhibitory. The pattern of polypeptides synthesized from cytoplasmic m‐RNAs of salt‐sensitive and salt‐tolerant plants remained constant in all the conditions examined. The effects of adding the ‘compatible' organic solutes glycine‐betaine and mannitol were examined in the wheat‐germ system primed with RNA from the leaves ofTriticum aestivumorBeta vulgaris.The rate of translation, the optimum ionic concentrations and the distribution of polypeptide products were maintained in organic solute concentrations of up to 500 mol m−3. Proline above 300 mol m−3and surcose above 100 mol m−3did inhibit translation. The results indicate that translation in plants is unlikely in cytoplasmic K+concentrations exceeding 180 mol m−3, but would proceed in the presence of up to 500 mol m−3mannitol or glyinebeta

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11591845

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe growth, biomass δ13C values, and ability to accumulate titratable acidity at night were compared in eight environmental treatments forCremnophila linguifolia, Sedum greggii, and their F1hybrid. In the phytotron, differences in treatment daylength, day/night temperature and water availability were all found to have effects on total plant dry weight, nocturnal accumulation of titratable acidity and biomass δ13C value of at least some of the genotypes. However, there were differences between the genotypes both in the magnitude and direction of response of the phenotypic properties to the treatment variables. The phytotron δ13C values ranged from ‐12.9 to ‐19.2‰ forC. linguifolia, from ‐22.2 to ‐33.4‰ forS. greggii, and from ‐19.2 to ‐24.9‰ for the hybrid. After with‐holding water for 76 h bothC. linguifoliaand the hybrid had midday Ψleafvalues of ‐0.23 MPa; however,S. greggiihad a value of ‐1.05 MPa. In contrast to past observations of other species, the daily watered plants ofC. linguifoliahad less negative δ13C values than did th

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11591864

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractTo determine the usefulness of the J‐14 Hydraulic Press (Campbell Scientific, Inc., Logan, Utah, U.S.A.) in estimating leaf water potential, we calibrated the J‐14 Press against a Scholander‐type pressure chamber for leaves of various tree species. The species tested were:Acer saccharum, Acer negundo, Acer rubrum. Populus tremuloides, Populus grandidentata, Quercus rubra, andBrassaia actinophylla(Schefflera). The regression calibrations were linear with standard errors about the regression less than 0.1 MPa. The regression equations for the four genera were significantly different, with they‐intercept increasing and the slope decreasing in order of decreasing specific leaf area (SLA). There were no significant differences between species of the calibration lines within the generaAcerandPopulus.These data may indicate that leaves with lower SLA resist mechanical compression by the hydraulic press, causing the J‐14 Press to be less sensitive to differences of leaf water potential. Therefore the J‐14 Press is only a relative measure of leaf water status and does not measure leaf wate

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11591871

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractFreeze‐fracture electron microscopy of the plasmalemma of dry cowpea radicle cells disclosed a normal‐appearing membrane with a high area density of intramembraneous particles (IMPs). Seeds imbibed in either water or salt solution exhibited decreased area density of IMPs, but water‐imbibed tissue showed the greatest decline. Mean particle size increased with hydration but not enough to suggest aggregation as the cause for this density decrease. Calculations of plasmalemma area expansion during imbibition show that such expansion can account for the decrease in IMPs per unit area in the cytoplasmic side (PF) of the membrane in water‐imbibed, but not in salt‐imbibed, tissue. During imbibition, there is a change in the ratio of IMPs per unit area of the PF versus EF (external) membrane faces, suggesting a relative increase in the number of EF particles. These changes in membrane structure are probably not related to any decrease in membrane permeability during the early phases of i

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11592139

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractSteady‐state labelling with11CO2was used to observe the blocking of phloem transport, induced by chilling short regions of stems or petioles of velvetleaf (Abutilon theophrastiMedic.) or cotton (Gossipium hirsutumL.). The abruptness of these blockages was evidenced by sharp decreases in11C activity below, and increases above a 2 to 3 cm region cooled from 28°C to 18 or 13°C for periods as short as 2 min. Abrupt unblocking of transport in velvetleaf occurred a few minutes after rewarming, as evidenced by a sharp rise and and overshoot in11C activity. Recovery of transport in cotton was more prolonged and was marked by occasional spontaneous blocking and unblocking of transport at various points along the petiole or stem, not necessarily in the cooled region. Similar spontaneous events were often observed in undisturbed cotton plants, but only rarely in velvetl

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11592141

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractConcurrent estimates of stem density, leaf and stem water potential, stomatal conductance and ultrasonic acoustic emissions (cavitations) in an excised sapling ofThuja occidentalisL. were made. As the sapling dehydrated in air, the decline in leaf water potential to about ‐ 2.0 MPa was followed by apparent rehydration of the foliage while the stem showed no sign of rehydration. The rate of acoustic emissions peaked prior to the onset of rehydration which coincided with virtual stomatal closure. There was a significant decline in stem density until maximum foliage rehydration level was reached. From this point, leaf water potential, stem water potential and stem density continued a relatively slow decline while acoustic emission rate and stomatal conductance remained low.Removal of the bark and majority of foliage from the sapling resulted in increased cavitation and more rapid deelines in leaf and stem water potential and stem densit

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11592146

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe CO2compensation point ofUlva lactucafrond sections has been measured in artificial seawater using a sensitive gas‐chromatographic method. Under nitrogen the compensation point remained relatively constant at 3–6 cm3m−3at temperatures from 10 to 30°C while in air‐saturated medium (0.3 kg m−3O2) the compensation point rose from 5 cm3m−3at 10°C to 11 cm3m−3at 30°C. These responses of the compensation point to temperature and oxygen concentration indicate that there is little photorespiratory CO2loss in this marine macroalga, and the low values of these compensation points indicate that inorganic carbon is actively accumula

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11592150

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractEquipment and methodology are described that allows the radial variation in axial xylem permeability (hydraulic conductivity) over a tree cross‐section to be measured and the flow paths to be identified by the strictly controlled flow of dye through a specimen. The apparatus can be calibrated so that the point‐to‐point variation of absolute permeability over a xylem cross‐section can be calculated from the dye‐flow patterns, which otherwise show only relative variations in permeability. The effect of using different dyes and dye concentrations on the penetration time and the shape of the dye patterns was investigated. The penetration time through the wood of identical end‐matched specimens is appreciably longer for fixing dyes than for non‐fixing dyes, and for the fixing dyes it depends strongly on the dye concentration. However, the dye patterns of the end‐matched specimens were indistinguishable with fixing and non‐fixing dyes, and independent of dye concentration. The fixing dye toluidine blue at 0.25% to 0.5% (w/w) was found most suitable as it yields a clear

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11592154

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY