ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604877

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Nitellopsiscells grown in fresh water have a relatively low cytoplasmic Na+(11 mol m−3) and high cytoplasmic K+(90 mol m−3) content. A 30‐min treatment with 100 mol m−3external NaCl resulted in a high [Na+]c(90 mol m−3) and a low [K+]c(33 mol m−3), Subsequent addition of external Ca2+(10 mol m−3) prevented Na+influx and then [Na+]cdecreased slowly. Changes in [K+]cwere opposite to [Na+]c. During the recovery time vacuolar Na+increased, while vacuolar K+decreased. Since all these processes proceeded also under ice‐cold conditions, the restoration of original cytoplasmic ion compositions is suggested to be a passive nature. The notion that the passive movement of ions across the tonoplast can act as an effective and economic mechanism of salt tolerance under transient or under mild salt stress conditio

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604878

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.The division rate ofMicrasterias torreyicells grown under continuous illumination first accelerated but soon slowed down, and the cells lost their ability to divide after about 1 month. During the treatment the cells became pale green, the pyrenoids became fewer in number and defects appeared in the chloroplasts. After 1 month, the cells also soon died, even when subjected to intermittent illumination. The most striking structural alterations were found in the chloroplasts: the starch granules lost their typical structure, the lamellae were damaged and numerous electron dense precipitates appeared in the chloroplasts. The precipitates were similar to those formed in cells treated with supraoptimal external calcium concentrations and X‐ray microanalysis showed that the precipitates were rich in calcium in both cases. The results suggest that light controls and activates the Ca2+uptake in the plasma membrane as well as in the chloroplast envelope, that the large sized chloroplasts ofMicrasteriasare effective in regulation of cytoplasmic Ca2+concentration, and that the injuries caused by continuous illumination may be largely due to the accumulation of Ca2+in the chloroplast

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604880

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.The sensitivity of stomata ofCommelina communisL. to abscisic acid (ABA) was evaluated by analysing the initial rates of response to the compound at different hormone concentrations. This was carried out at pH 6.8 and pH 5.5. The data were modelled and statistically analyzed by means of a computer program employing non‐linear regression techniques and step‐down analysis of variance. The response kinetics as quantified in terms of three sensitivity parameters were found to differ significantly between the two pH values. This finding is discussed in relation to previous research on purified ABA‐binding pro

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604886

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Seedlings ofPinus radiataD. Don were grown in growth chambers for 22 weeks with two levels of phosphorus, under either well‐watered or water‐stressed conditions at CO2concentrations of either 330 or 660mm3dm−3. Plant growth, water use efficiency and conductance were measured and the relationship between these and needle photosynthetic capacity, water use efficiency and conductance was determined by gas exchange at week 22. Phosphorus deficiency decreased growth and foliar surface area at both CO2concentrations; however, it only reduced the maximum photosynthetic rates of the needles at 660 mm3CO2dm−3(plants grown and measured at the same CO2concentration). Water stress reduced growth and foliar surface area at both CO2concentrations. Increases in needle photosynthetic rates appeared to be partly responsible for the increased growth at high CO2where phosphorus was adequate. This effect was amplified by accompanying increases in needle production. Phosphorus deficiency inhibited these responses because it severely impaired needle photosynthetic function. The relative increase in growth in response to high CO2was higher in the periodically water‐stressed plants. This was not due to the maintenance of cell volume during drought. Plant water use efficiency was increased by CO2enrichment due to an increase in dry weight rather than a decrease in shoot conductance and, therefore, transpirational water loss. Changes in needle conductance and water use efficiency in response to high CO2were generally in the same direction as those at the whole plant level. If the atmospheric CO2level reaches the predicted concentration of 660 mm3dm−3by the end of next Century, then the growth ofP. radiatawill only be increased in areas where phosphorus nutrition is adequate. Growth will be increased in drought‐affected regions but total water use is unlikely

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604890

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.The ultrastructure of chloroplasts from palisade and spongy tissue was studied in order to analyse the adaptation of chloroplasts to the light gradient within the bifacial leaves of pea. Chloroplasts of two nuclear gene mutants ofPisum sativum(chlorotica‐29 and chlorophyll b‐less 130A), grown under normal light conditions, were compared with the wild type (WT) garden‐pea cv. ‘Dippes Gelbe Viktoria’. The differentiation of the thylakoid membrane system of plastids from normal pea leaves exhibited nearly the same degree of grana formation in palisade and in spongy tissue. Using morphometrical measurements, only a slight increase in grana stacking capacity was found in chloroplasts of spongy tissue. In contrast, chloroplasts of mutant leaves differed in grana development in palisade and spongy tissue, respectively. Their thylakoid systems appeared to be disorganized and not developed as much as in chloroplasts from normal pea leaves. Grana contained fewer lamellae per granum, the number of grana per chloroplast section was reduced and the length of appressed thylakoid regions was decreased. Nevertheless, chloroplasts of the mutants were always differentiated into grana and stroma thylakoids. The structural changes observed and the reduction of the total chlorophyll content correlated with alterations in the polypeptide composition of thylakoid membrane preparations from mutant chloroplasts. In sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS‐PAGE), polypeptide bands with a relative molecular mass of 27 and 26 kilodalton (kD) were markedly reduced in mutant chloroplasts. These two polypeptides represented the major apoproteins of the light harvesting chlorophyll a/b complex from photosystem II (LHC‐II) as inferred from a comparison with the electrophoretic mobility of polypeptides isolated fr

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604894

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Dynamic responses of stomatal conductance to lightflecks (15 s to 5 min) were observed in the tropical understory plantAlocasia macrorrhiza.Brief observations were also made on step changes in light, flashing light and short low‐light periods (darkflecks) after stomata had reached steady state conductances in high light. Stomata opened substantially even in response to very short lightflecks, with maximal opening being reached about 20 min after the end of the lightfleck. These responses are compared to those of a semi‐mechanistic stomatal model consisting of three steps in series: a biochemical signal which responds directly to light, producing osmotic changes within the guard cells which, in turn, drive the movement of water into the guard cells. The rate of change of each component was assumed to be given by the difference between the current state of that component and the state of the previous component in the series divided by a characteristic time constant for each step. This model allowed excellent description of observed responses to lightflecks, including the fleck‐length dependence of stomatal opening, the lag between the end of the lightfleck and the time of maximal stomatal conductance and the response to multiple flecks. However, agreement with predicted responses to flashing light and darkflecks was poor. Good agreement could be restored by using different time constants for the initial biochemical step, suggesting that the speed of the initial biochemical response is not constant but dependent on the current physiological state of the stomata. For leaves experiencing predominantly low light, punctuated by relatively short and infrequent periods of high light, this model allows good description of the dynamic changes in stomatal conduc

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604898

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Rhodamine 123 (Rh 123), a relatively new mitochondrial marker, little used in the study of plant cells, was tested on excized leaves ofElodea canadensisMichx. and on suspension‐cultured cells ofRanunculus serbicusVis. In both preparations, the dye accumulated rapidly and selectively in the mitochondria whose number, morphology and cell distribution could be easily observed. In the presence of Rh 123, cytoplasmic movements could also be perceived and the spatial arrangement of the mitochondria with respect to that of the auto‐fluorescent chloroplasts was studied in connection with a normal or altered cytoskeletal framework. The specific uptake of Rh 123 by the organdies seemed to be potential‐dependent since it was influenced by cations, ionophores and inhibitors of electron transport. Short exposures to the stain were practically non‐toxic, whereas prolonged treatments (6–20 h) provoked specific alterations in structure of the mitochondria. The data reported here indicate that Rh 123 may be an excellent vital stain to study the morphology, function and dynamics of the mitochondria in living pl

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604901

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.Cuticular resistance to water vapour diffusion is an important aspect of thermocouple psychrometry and may introduce significant error in the measurement of leaf water potential (Ψ). The effect of the citrus (Citrus mitisBlanco) leaf cuticle on water vapour movement was studied using the times required for vapour pressure equilibration during thermocouple psychrometric measurement of Ψ. Cuticular abrasion with various carborundum powders was used to reduce the diffusive resistance of both the adaxial and abaxial leaf surfaces, and the extent of the disruption to the leaf was investigated with light and electron microscopy.Cuticular abrasion resulted in reduced equilibration times due to decreased cuticular resistance and greater water vapour movement between the leaf and the psychrometer chamber. Equilibration times were reduced from over 5 h in the unabraded control leaves to 1 h with cuticle abrasion. This was associated with the decrease in diffusive resistance with cuticular abrasion from over 55 s cm−1to less than 8 s cm−1for both the adaxial and abaxial leaf surfaces.Scanning electron micrographs of the abraded leaf tissue revealed considerable disruption of the stomatal ledge and of the guard cells, surface smoothing and displacement of waxes into the stomatal aperture, and damage to veins. Observations with the transmission electron microscope revealed frequent disruption of epidermal cell walls, and damage to both the cytoplasmic and vacuolar memb

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604905

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract.The solutes accumulated by cyanobacteria in response to hyper‐osmotic stress include Na+, K+, sucrose, trehalose, glucosyl‐glycerol, glyeine betaine and glutamate betaine. The compatibility of several of these solutes with glutamine synthetase activity has been examined using cell‐free extracts from a range of freshwater, marine and halotolerant cyanobacteria. All of the solutes tested were compatible with (i.e. non‐inhibitory to) enzymic activity at physiological concentrations and the results demonstrate a rank order of compatibility which correlates with the concentrations at which the organic solutes occur in cyanobacteria, i.e. glycine betaine>polyol‐derivatives>disaccharides and with the upper salinity limit for growth. The protection against inhibition by NaCl (halo‐protection) afforded by these solutes to enzymic activity was also examined. Only glycine betaine was found to exert a significant halo‐protective effect and this may be explained by differences in the mechanism of compatible solute function between small charged molecules and s

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604910

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY