摘要:

AbstractThe exchange of CO2, H+and O2between seawater and the intertidal brown macroalgaAscophyllum nodosum(L.) Le Jolis were measured in a flowthrough system. While the algae were kept in darkness, seawater with artificially increased alkalinity and pH at 9.85, was alternated with ‘normal’ seawater at pH 8.0. A proton buffering system, with capacity to release and reabsorb about 20 μmol protons per gram alga (fresh weight) was revealed. As the algae were returned to the ‘normal’ seawater, the kinetics of proton reabsorbtion indicated that a proton uptake was gradually induced. This proton uptake, which was not connected to ion exchange in the cell wall, reached its maximum after 12 h. If subjected to high alkalinity seawater in the light,A. Nodosumfor a certain period of time was capable of carrying out O, evolution in excess of the import of inorganic carbon. This ‘photosynthetic buffering capacity’ amounted to about 17 μmol O; per gram alga. Besides depending on a buffer of photorcducible substances, this ‘photosynthetic buffering capacity’ appeared to be functionally connected with the proton buffer. The time course for the discharge of the ‘photosynthetic buffer system’ and for the reabsorbtion of protons into the proton buffer (about 6h for 90× of the capacity at a temperature of 6°C) suggests that the ‘photosynthetic buffer system’ has a functional importance in the adaptation ofA. nodosumto intertidal regions. The function of the buffer system is discussed in relation to the crassulacean acid metabolism (CAM)‐like characteristics recently shown for the intertida

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1989.tb01637.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractAmong the brown algae, species of the Fucaceae (Pelvetia, FucusandAscophyllum) were found to have a ‘photosynthetic buffering’ system, allowing the algae to carry out oxygen production without a concomitant uptake of inorganic carbon. This system was not found in other brown algae examined (e.g.Halidrys, LaminariaandDesmarestia) nor in 16 examined species of red and green algae.Pelvetia, FucusandAscophyllumbelong to the littoral algae which are periodically emersed. In the Fucaceae, the meristodermal cells were found to have a special organization of organelles. Towards the outer cell wall there was a prominent layer of mitochondria while the chloroplasts were concentrated towards the inner and side walls. Between the mitochondria and the chloroplasts there was a large number of physodes. This arrangement of organelles was not found in the other brown algae examined nor in red or green algae. The significance of this organization of the mitochondria is discussed in connection with the function of the ‘photosynthetic buffering’

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1989.tb01638.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe relations between growth and internal nitrogen concentrations were investigated in nonnodulatedPisum sativumL. cv. Marma andLemna gibbaL. grown at relative rates of nitrate‐N additions (RA) varying from 0.03 to 0.27 d1(Pisum) and 0.05 to 0.40 d1(Lemna). At RA≤0.21 d1(Pisum) and ≤0.30 d1(Lemna), the relative growth rate (RGR) correlated well with RAwhereas higher RAwas not met by any further increawse in growth rate. The tissue nitrogen concentrations at growth‐limiting RAincreased linearly with RGR. The slope of these lines indicate a maximum nitrogen productivity (amount of biomass formed per unit nitrogen and time) of 14.4 g DW g1Nd1forPisumand 15.9 g DW g1N d1forLemna.Extrapolation of the plots to RGR=0 yielded intercepts of 10–15 mg N g−1DW forPisumtissue, whereas forLemnathe intercepts were closer to the origin than forPisum.These intercepts formally define a fraction of the total plant nitrogen that appears not to be active in production of new biomass, her termed ‘non‐growth nitrogen’. The partitioning of nitrogen as well as biomass to the roots increased at low RA, and is discussed in relation to activity of shoots and ro

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1989.tb01639.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractNet nitrate uptake rates were measured and the kinetics calculated in non‐nodulatedPisum sativumL. cv. Marma andLemna gibbaL. adapted to constant relative rates of nitrate‐N additions (RA), ranging from 0.03 to 0.27 d−1forPisumand from 0.05 to 0.40 d−1forLemna, Vmaxof net nitrate uptake (measured in the range 10 to 100 mmol m−3nitrate, i.e. ‘system I’) increased with RAin the growth limiting range but decreased when RAexceeded the relative growth rate (RGR), Kmwas not significantly related to changes in RA. On the basis of previous13N‐flux experiments, it is concluded that the differences in Vmaxat growth limiting RAare attributable to differences in influx rates. Linear relationships between Vmaxand tissue nitrogen concentrations were obtained in the growth limiting range for both species, and extrapolated intercepts relate well with the previously defined minimal nitrogen concentrations for plant growth (Oscarson, Ingemarsson&Larsson, 1989). Analysis of Vmaxfor net nitrate uptake on intact plant basis in relation to nitrogen demand during stable, nitrogen limited, growth shows an increased overcapacity at lower RAvalues in both species, which is largely explained by the increased relative root size at low RA. A balancing nitrate concentration, defined as the steady state concentration needed to sustain the relative rate of increase in plant nitrogen (RN), predicted by RA, was calculated for both species. In the growth limiting range, this value ranges from 3.5 mmol m−3(RA0.03 d−1) to 44 mmol m−3(RA0.21 d−1) forPisumand from 0.2 mmol m−3(RA0.05 d−1) to 5.4 mmol m−3(RA0.03 d−1) forLemna.It is suggested that this value can be used as a unifying measure of the affinity for nitrate, integrating the performance of the nitrate uptake system with nitrate flux and long term

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1989.tb01640.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA negative correlation between water‐use efficiency (W), defined as the ratio of moles of carbon in the plant to moles of water transpired, and carbon isotope discrimination (Δ) was established for barley in pot experiments using 12 cultivars. The correlation was strong in two independent experiments in four different controlled environment where ambient temperature and vapour pressure deficit were varied and plants were either well‐watered or given limited amounts of water. Variation among cultivars was found in both Δ andWand rankings of both parameters, according to cultivar, were similar in different environments. Limiting water usually increased water‐use efficiency of plants. Total dry matter can be substituted for moles of carbon when calculating water‐use efficiency but the correlation betweenWand Δ were calculated using the carbon content of dry matter. There were differences varied significantly among cultivars. Despite these differences, correlations were also large between whole plantWand Δ of any of the plant parts. The amount of dry matter partitioned into reproductive growth varied genetically, as did the effect of stress on the partitioning. Growth,Wand Δ of barley were compared with theory derived from gas exchange properties and with other literature. The effect onWof variation in vapour pressure deficit in these experiments was removed by multiplyingWby vapour pressure deficit to derive the parameter,k(Pa mol C/mol H2O). This allowed comparisons among experiments with different vapour pressure deficits. The meankfor these barley cultivars was similar to that calculated by others for grasses. However, variation was found, and, in contrast with previous work which treatskas a species constant, we conclude that there is promise in selecting fo

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1989.tb01641.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe CO2compensation concentrations (points) of leaves of the submerged vascular aquatic plantMyriophyllum spicatumL. were determined in a closed aqueous system at pH 7.0 by a gas chromatographic technique and over the range 10–30deg;C were found to range from 36 to 46 cm3m−3in medium equilibrated with 21% O2(0.03 kgm−3), and 25 to 35 cm3m−3in medium equilibrated with 2% O2(0.03 kgm−3). The rates of true (TPS) and apparent (APS) photosynthesis of leaves were measured in medium equilibrated with 21% O2and buffered at pH 7.0, at subsaturating concentrations (12.8–18.8 mmol m−3) of dissolved inorganic carbor. (DIC) containing H14CO3, by determining the initial rates of uptake by the leaves of DIC and14C‐activity from the medium. The rate of photorespiration, the difference between TPS and APS, was 7.0–13.3% of TPS over the range of 10–25°C and rose to 29% of TPS at 35°C. The magnitude of the compensation point of this plant is therefore similar to, but is much less O2‐sensitive than, those of C3plants, and the photorespiratory rate, at DIC concentrations near the CO2compensation point, is very low compa

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1989.tb01642.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractSix genotypes of tomato (Lycopersicon esculentumMill.) that differ in their salt‐tolerance, were exposed to 200 mol m−3NaCl for 4 weeks. Seedlings exhibited a marked decline in shoot dry weight accumulation and increased petiolar epinasty after exposure to salinity stress. Ranking accessions on the basis of their relative growth reduction in response to salinity, provided good agreement with the level of epinasty promoted during the salinity treatment. In the absence of salt‐stress, leaf epinasty promoted by exogenous ethylene treatment was found to be a positive indicator of the genotypes incipient salt‐sensitivity. Endogenous ethylene levels in untreated plants were negatively correlated with ethephon‐induced epinasty. Genotypes with normally high endogenous C2H4levels were less responsive to ethephon treatment and also exhibited greater salt‐tolerance than genotypes with low endogenous C2H4levels. These observations are consistent with the suggestion that a main feature of adaptation in the genotypes examined may involve modulation of their cellular sensitivity to C2H4. The results indicate that leaf epinasty, whether salt‐ or ethylene‐induced, is a sensitive indicator of salt‐sensitivity. Ethylene‐induced epinasty may, therefore, provide a simple basis upon which to identify and select s

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1989.tb01643.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractModerately frost‐hardy leaves of the wintergreen broadleaf woody shrubsPyracantha coccineaandLigustrum ovalifoliumand the winter annual herbSpinacia oleraceawere subjected to extended freezing stress up to 15 d at temperatures 2–8°C above the mean lethal temperature (LT50). After thawing, the fast kinetics ofin vivochlorophyll fluorescence of photosystemII (PSII)and the potential of linear photosynthetic electron transport of isolated thylakoid membranes was measured at room temperature. The lower the minimum freezing temperature and the longer the time of exposure, the greater was the suppression of the fluorescence signals of the leaves and decrease of the electron transport capacity of the thylakoid membranes. The pattern of inactivation ofPSII‐mediated electron flow, i.e. inhibition of photoreaction to photochemistry and/or electron donation to the photochemical reaction, during long‐term freezing at temperatures somewhat above the LT50of the leaves was similar to that observed earlier after relatively brief exposure of leaves and isolated thylakoid membranes to more severe freezing stress. As injury occurred during freezing in complete darkness, it is likely that prolonged winter stress under natural environmental conditions causes changes in the photosynthetic apparatus of moderately hardy leaves which are not due to photoin

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1989.tb01644.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractModification of the ‘intracellular concentration of reduced glutathione’ (IC‐GSH) affected the response of cultured rose cells (Rosa damascena) to ultraviolet radiation (UV)‐induced leakage of K+. High IC‐GSH induced by incubation of cells in 10 mol m−3GSH (IC‐GSH increased linearly with time from 20 to about 600 μmol g−1in 61.2 ks) caused cells to become significantly less sensitive to UV. Low IC‐GSH induced by treatment with 1 mol m−3buthionine sulphoximine (BSO) plus 1 mol m−3diethylmaleate (DEM) (IC‐GSH decreased from 20 to about 3 μg g−1in 61.2 ks) reduced, rather than increased, the UV‐sensitivity of the cells. However, treatment with DEM also induced a large transient K+leakage; and treatment with BSO induced a slight leakage. The K+leaked was recovered by 3.24 ks. Following K+recovery, the DEM‐treated cells showed almost complete insensitivity to UV, and BSO‐treated cells showed a slightly reduced sensitivity to UV. These results are in agreement with our previous findings that other treatments (heat, cycloheximide, UV), which also cause a transient leakage of K+, also reduce the induction of K+leakage by a subsequent UV treatment. We conclude that high IC‐GSH may play a role in protecting plant cells from UV‐induced K+leakage. Increased UV‐sensitivity with low ICGSH was not observed, we believe, because of the transient K+leakage, though the mechanism of reduced sensitivity to UV induced by transient leakage of K+is not known at this time. Treatment with UV did not reduce the IC‐GSH, showing that this is not th

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1989.tb01645.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractWater storage and nocturnal increases in osmotic pressure affect the water relations of the desert succulentFerocactus acanthodes, which was studied using an electrical circuit analog based on the anatomy and morphology of a representative individual. Transpiration rates and osmotic pressures over a 24‐h period were used as input variables. The model predicted water potential, turgor pressure and water flow for various tissues. Plant capacitances, storage resistances and nocturnal increases in osmotic pressure were varied to determine their role in the water relations of this dicotyledonous succulent. Water coming from storage tissues contributed about one‐third of the water transpired at night: the majority of this water came from the nonphotosynthetic, water storage parenchyma of the stem. Time lags of 4 h were predicted between maximum transpiration and maximum water uptake from the soil. Varying the capacitance of the plant caused proportional changes in osmotically driven water movement but changes in storage resistance had only minor effects. Turgor pressure in the chlorenchyma depended on osmotic pressure, but was fairly insensitive to doubling or halving of the capacitance or storage resistance of the plant. Water uptake from the soil was only slightly affected by osmotic pressure changes in the chlorenchyma. For this stem succulent, the movement of water from the chlorenchyma to the xylem and the internal redistribution of water among stem tissues were dominated by nocturnal changes in chlorenchyma osmotic pressure, not by transpirat

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1989.tb01646.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY