摘要:

AbstractThe growth of young plants of the epigeal speciesPhaseolus vulgarisandGlycine maxis compared with that of the hypogeal speciesPisum sativumandVicia faba, with particular reference to synchronization between the exhuastion of seed reserves of N and the availability of fixed N. It is argued that the N stress symptoms which occur when these two processes are not synchronized are more common and obvious inPhaseolusorGlycinethan inPisumorVicia.This is primarily because in these species (a) the first fixed N is used for nodule growth rather than being exported to the shoot system and (b) the first foliage leaves have a much greater area and contain a larger proportion of N reserves from the seed.It is further suggested thatPhaseolusandGlycinemay show the greater response to nitrogen fertilizer applied at sowing since (a) most of the applied nitrate is passed directly to the shoots (rather than being reduced in the roots as inPisumorVicia) and (b) in addition to being used for growth (following reduction), it may also be usedpriorto reduction as part of the osmotic force driving cell expansion.

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11571523

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe path of [14C]photosynthate translocation into citrus fruit was examined to determine which anatomical and physiological features were involved in this process. Experiments were conducted during the final pre‐harvest months of 2 years grapefruit crops (Citrus paradisiMacf. cv. ‘Marsh’). A source leaf nearest the fruit was exposed to14CO2for 1 h + 5 h ambient air, followed by dissection of vascular and phloem‐free tissues in the fruit quarter directly aligned with the source. Radioactivity in each tissue was quantified after separation and extraction in boiling 80% ethanol. Peel (flavedo+albedo) contained an average 35% of the label in the quarter fruit, but an additional 20% was localized entirely in dorsal vascular bundles along exterior walls of juice segments. Less [14C]photosynthate was recovered from other vascular tissues and was nearly absent from adjacent mature seeds. Radioactivity in the single layer of segment epidermis, however, averaged 17% of that in the quarter fruit. Juice tissues interior to this accumulated only 17% of the total. No phloem tissue was evident in either the segment epidermis or juice tissues, but over 70% of the [14C]assimilates in the latter were localized in thread‐like stalks which attach juice vesicles to dorsal vascular bundles. In addition, labelled hexose/sucrose ratios in these structures increased with distance from the vascular bundle. The majority of photosynthates, therefore, entered citrus fruit via dorsal vascular bundles and were partially hydrolysed during slow transfer through non‐vascular segment epidermis and j

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11571540

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe germination responses of a nondormant fraction of a seed population ofTaraxacum officinaleWeber at constant temperatures in the range 7–34°C were analysed through a time‐course study. Maximal percentage germination (approximately 90%) was attained at temperatures 10–18°C, where simple linear relationships were observed between the temperature and the germination rates, i.e. the reciprocals of the time taken to germinate by subpopulations with 20–80% germination. There was a variation in the required ‘thermal times’ (θ) which characterized the linear relationships, the distribution of which could be approximated for the seed population by the following distribution function:wheremis the median of the distribution, andAis a shape parameter characterizing the pattern of the distribution. Final percentage germination decreased with increasing temperature from 20 to 32°C, where the final percentage germinationvs. temperature plotted on a normal probability scale yielded a straight line, indicating the normality of the distribution of the upper limit temperature in the seed population. The estimated mean and standard deviation were 27.25 ± 3.75°C. The rate of germination for the subpopulation with 20–80% germination also decreased with increases in the temperature from 22 to 30°C. If the relationships between the temperature within this range and the rate for the subpopulations with 20–80% germination were approximated by the regression lines, the negative ‘thermal time’ characterizing the yielded linear relationship would have a distribution which could be approximated by the same function with the required thermal time for the relationship of suboptimal range. The parametersmandAfor the negative ‘thermal time’ were determined to be

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11571610

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractYoung, amphistomatous hybrid poplar (Populus deltoides x trichocarpa) plants were exposed daily to either background (0.025 cm3m‐3) or elevated (0.125 cm3m‐3) concentrations of O3. Levels of abaxial and adaxial leaf conductance were affected interactively by pollutant treatment, leaf age, and photon fluence rate. Consequently, conductance in O3‐treated leaves was sometimes higher and sometimes lower than in comparable control leaves, depending on leaf age or level of photon fluence rate. For example, at low photon fluence rate or in the dark, conductance was greater in O3‐treated than in control plants, while at high photon fluence rate that relationship was reversed. Exposure to O3also reduced the water‐use efficiency and range of leaf conductance of individual leaves, and altered the relationship between the conductances of the two leaf surfaces (the ratio of abaxial to adaxial leaf conductance was increased). Furthermore, O3treatment resulted in diminished stomatal control of water loss; excised O3‐treated leaves had higher conductances and wilted sooner than excised control leaves of identical ages. Overall, the data indicate that exposure to O3resulted in impaired stomat

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11571645

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractStomatal responses to humidity as affected by both evaporation from the epidermis and the hydraulic conductance of the transpiration stream to evaporation sites on the epidermis are discussed.Recent estimates of evaporation from the inner walls of the epidermis are too high because the cell wall surfaces were assumed completely wet, and leaves have usually been considered isothermal.It is suggested that a fall in humidity increases evaporation from the epidermis, and that stomata respond to the consequent fall in water potential. Cuticular transiration is inversely related to stomatal conductance. Thus, evaporation from the epidermis is dependent on the stomatal, boundary layer, and cuticular conductances, and on evaporation from the inner walls of the epidermis. Stomatal responses to humidity will change as the boundary layer conductance changes.The conductance of the transpiration stream is a determinant of the water potential of the epidermis. Water potentials of adjacent cells will be more similar if flow is symplastic than if it is apoplastic. It is concluded that flow in living tissues is primarily symplastic over long distances, but over shorter distances it is increasingly apoplastic, and that stomatal responses to humidity are mediated by the water potential of the whole epidermis.

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11571796

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractChilling auxin‐depleted, etiolated stems ofPisum sativumL. to 4°C for 60 s enhanced the production of previously described voltage transients 20‐fold. It is postulated that plasmalemmal permeability to Ca2+is increased at low temperature, permitting influx of the ion from the apoplast to the cytosol and thereby promoting production of transients. Heating to 40°C or 45°C elicits no increase in transients, and heating to 50°C leads to loss of

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11571879

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractRates of uptake of14C‐labelled inorganic carbon were measured for wholeChara hispidaplants, detached parts of the shoot and isolated (split‐chamber technique) apices, lateral branchlets and rhizoid—node complexes.The rates of inorganic carbon uptake by the rhizoid—node complex expressed per gram fresh weight whole plant were three to four orders of magnitude less than the uptake for the whole plant. Up to 70% of the carbon taken up by the rhizoid—node complex was translocated to the shoot. After 12 h exposure to14C‐labelled inorganic carbon the concentration of14C was greater in apices than in uppermost or central internodal cells and in all lateral branchlets, regardless of whether label was supplied to the whole plant or isolated rhizoid—node complexes. Measurement of inorganic carbon uptake by detached internodal cells and detached and isolated apices and lateral branchlets showed that lateral branchlets had the greatest rates of inorganic carbon uptake. During 12 h exposure to14C, isolated lateral branchlets translocated to the attached shoot 55% of the labelled carbon taken up; for isolated apices this value was only 13%.It is concluded that it is highly unlikely that the rhizoid ofChara hispidacould acquire a significant fraction of the whole plant requirement for inorganic carbon and that apices are sink regions for photosynthate while lateral branchlets are s

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11572119

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractGermination and protein synthesis of lily pollen subjected to a short heat shock after imbibition are strongly inhibited. The proteins synthesized after the heat shock were analysed by polyacrylamide gel electrophoresis. The patterns obtained from heat‐treated pollen are strikingly different from those of control samples. The difference is nearly completely climinated by a high concentration of proline in the incubation medium. This proline effect correlates with the protection of pollen germination from high temperature by the amino aci

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11572397

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractA simple stem hygrometer for attachment to a bared section of sapwood or a cross‐sectional cut end of a shoot is described. Two welded chromelconstantan thermocouples inside the chamber, one touching the sample and the other in the chamber air, allowed measurement of and correction for the temperature gradient between the sample and the dewpoint measuring junction. The instrument was attached to the cut end of an apical shoot ofThuja occidentalisL. protuding from a Scholander‐Hammel pressure bomb. Cut‐end water potential (ψhyg), measured using the stem hygrometer, was compared to xylem pressure potential (ψxp) while the latter was manipulated in the pressure bomb. After an initial equilibration time of 3–4 h, hygrometer equilibrium values were achieved within 1.5–4.0 min of changing ψxpin the pressure bomb. The half‐time (ψ1/2) for vapour pressure equilibration was 15–40 s. Stable temperature gradients between the sample and dewpoint measuring junction of 0.01–0.1°C were measured. Correcting ψhygfor the temperature gradient resulted in excelle

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11572454

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

AbstractThe fluorochrome Auramine O has been evaluated as a fluorescent probe for components of the endomembrane system of living plant cells. At 0.001% w/v the compound did not inhibit seedling growth or cytoplasmic streaming but stained the nuclear envelope, endoplasmic reticulum and Golgi apparatus. The three‐dimensional, structural interrelationships of these organelles in living tissues could be resolved after minimal tissue preparation. The method is also a valuable control treatment for use in conjunction with electron microscope fixation procedures. It provides a rapid means of examining dynamic changes in the endomembrane system associated with cell development and differentiation and could have application in monitoring the effects of applied physiological or chemical stres

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11572462

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY