摘要:

Abstract.It is suggested that increased levels of free cytosolic calcium ([Ca2+]cyt) may serve as the primary physiological transducer of chilling injury in plants. Numerous similarities between the effects of [Ca2+]cyt‐raising treatments on plants and the effects of chilling temperatures on chilling‐sensitive (CS) plants are noted. It is proposed that chilling temperatures may lead to increases in [Ca2+]cytin CS plant cells by reducing the rate at which they exclude Ca2+from their cytosol and that rapid cooling (coldshock) may cause rapid increases in [Ca2+]cytdue to the activation of voltage‐dependent cation channels. Chill‐induced increases in [Ca2+]cytin the cells of CS plants may reflect either an inherent inability of such plants to maintain homeostatic levels of Ca2+at low temperatures or a stress‐induced reaction which has evolved to enable such cells to cope more effectively with the short‐term hardships imposed by cold. Previous proposals concerning the physiological transduction of chilling injury are also discussed. It is argued that there is little evidence to suggest that the immediate effects of low temperatures on CS cells include either decreases in ATP levels, general increases in the passive permeability of membranes, or increased rates of f

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01226.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.Plant scientists concerned both with crop improvement and with understanding the control mechanisms of complex processes such as photosynthesis need to identify those processes that are most important in restricting the overall rate and to quantify the relative importance of different components. The techniques that have been used for quantifying the relative importance of component processes in limiting net assimilation rate are reviewed and related to a fundamental definition based on sensitivity analysis. It is concluded that many methods currently in use, including standard resistance analysis, frequently give very misleading answers.In addition, possible methods for apportioning the contributions of different component processes to observed changes in net photosynthetic rate (for example after stress) are also reviewed and compared against a fundamental approach based on sensitivity analysis. Unfortunately, the detailed time course of changes in mesophyll and stomatal properties that is required for application of the basic sensitivity analysis is seldom likely to be available, so that it is usually necessary to adopt an approximate method. The standard approximation that is recommended for calculating the contributions of different component processes to a change in assimilation rate, involves measurements at the initial and final states only. The various methods discussed in this paper are compared using published photosynthetic data for a range of species.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01227.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.Net NO3uptake by NO−3deficientCharacells was used to calculate [NO−3]cassuming that the cytoplasm occupies 10% total volume and that nitrate reduction and storage are negligible (i.e. maximum [NO−3]cwas calculated). A linear relationship was found between NO−3efflux and [NO−3]c. There was an initial burst of NO−3efflux when NH+4was added, followed by a slower efflux rate which matched influx rate such that net NO−3uptake was zero. Over 50% of NO−3that had been taken up in 2 h was lost within the first 5 min of NH+4addition. The Nernst equation was used to predict the direction of the electrochemical driving force for NO−3entry. Under the experimental conditions used NO−3efflux is actively transported. The differential involvement of both NO−3influx and NO−3efflux in the regulation of NO−3uptake is discussed and a model is proposed to account for these results which envisages discrete NO−3inf

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01216.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.In controlled environments, the interactive effects of warm (16: 8°C, day: night) and cool (12: 4°C, day: night) temperatures and long (13.5 h) and short (10 h) photoperiods on the dehardening of seedlings ofPinus radiataD. Don were investigated. In another experiment, the effect of four photoperiods from 9 to 14 h was examined. In a third, dehardening at constant temperatures from 5 to 17°C was followed. There was no evidence for an interaction between photoperiod and temperature. Dehardening was temporarily delayed by photoperiods below about 10 h, but there was no other quantitative effect of photoperiod. At constant temperatures, the rate of dehardening was initially constant but declined as the minimum summer frost hardiness was reached. In the initial phase the rate of dehardening was a linear function of temperature, increasing from 0.05°C day−1at 8°C to 0.30 °C day−1at 17°C. Temperature controlled the loss of frost hardiness by regulating the rate of d

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01217.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.Oxygen plays a dual role in affecting the rate of respiration of avocado fruit (Persea americanaMill, cv. Hass). The respiration ratev.oxygen concentration curve for steady state avocado fruit respiration is biphasic. The curve becomes monophasic, however, when measured under conditions of rapidly changing oxygen concentration in a closed circulating system. The results are interpreted as indicating that oxygen at relatively high concentrations modulates respiration independent of its interaction with the terminal oxidase—presumably cytochrome oxidase.A computer model is presented which takes into account the effect of diffusion barriers on the kinetics of oxygen utilization as a function of concentration in avocado fruit. The model is used to make predictions concerning the apparentKmof the terminal oxidase or oxidases in avocado fruit. It is concluded that the apparentKmof the terminal oxidase of uninhibited avocado fruit is that of cytochrome oxidase, and that the alternative, cyanide‐resistant oxidase of avocado fruit does not contribute appreciably to the uninhibited respiration of preclimacteric or climacteric avocado fr

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01218.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.When isobutyric acid (IBA) or abscisic acid (ABA) are supplied to leaf sections a similar rapid and marked decrease in the intracellular pH is observed. This acidification is accompanied by an increase in proline level which is about the same for both 3 mol m−3IBA and 1 mol m−3ABA treatments.Fusicoccin (FC), known to act at the proton pump level, almost completely suppresses the ABA‐induced acidification of the cell sap, whereas it only partially counteracts the acidifying effect of IBA, in particular during short periods of treatment. This effect of FC is paralleled by a similar inhibition of the induced proline accumulation: in fact, FC completely suppresses the ABA‐induced increase in proline during short treatment periods, whereas it is only effective in inhibiting the IBA‐induced proline accumulation after long treatment periods.These data seem to suggest that the ABA‐ and IBA‐induced changes in proline level might be mediated by changes in the int

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01219.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.Coleus blumeiBenth. (PI No. 354190), a green‐leafed cultivar, was exposed to 5°C for 48 or 72 h after pretreatment for 48 h at two levels of photosynthetically active radiation (PAR) (8 and 320 μmol s−1m−2), two temperatures (13 and 20°C), and two abscisic acid (ABA) levels (0 and 200 g m−3of the racemic mixture). Plants given low PAR for only 48 h prior to chilling treatment (48 or 72 h at 5°C) showed increased protection against chilling injury while those given high PAR were severely injured. The former plants were darker green, contained greater concentrations of chlorophyll‐a, chlorophyll‐b, total chlorophyll and anthocyanin and generally had a lower abscission rate than the latter plants. There were no differences, however, in chlorophyll‐a/bratio among plants grown at the two PAR levels, two temperatures or two ABA concentrations. Temperature and ABA pretreatment and number of hours at 5°C had no significant effect on chilling injury as measured by leaf chlorosis, but generally had a significant effect on leaf abcission, especially at 3 and 7 d after returning the plants to the greenhouse. Enclosing intact plants or excised shoots in plastic bags to maintain 100% relative humidity during 72 h chilling treatment failed to provide protection against chilling injury. These findings indicate that the protective effects of low PAR applied prior to chilling treatment may be as important or more important than that applied during chilling. They also indicate the importance of making careful measurements of PAR levels when conducting studies

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01220.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.Vegetative plants of soybean [Glycine max(L.) Merr. cv. Wells II] grown in a greenhouse and agitated periodically on a gyratory shaker had shorter stems, less leaf area, and lower leaf and plant dry weight than did undisturbed greenhouse‐grown (GG) plants after 16 d of treatment. Outdoor‐grown (OG) plants, which were subjected to additional environmental stresses including ultraviolet radiation, wind loading, and uncontrolled temperature and humidity fluctuations, were smaller and had less dry weight than GG controls, but growth was not inhibited further by gyratory shaking. Periodic shaking of GG soybeans resulted in the same plant and leaf dry weight as for OG soybeans. Response of GG plants to mechanical stress depended on light intensity, with minimum growth reduction occurring under full light (FL) level, and maximum growth reduction occurring under lower light levels (24–45% FL). Reduction in dry weight gain due to mechanical stress corresponded to a decrease in relative growth rate (RGR). Decreases in net assimilation rate and leaf area ratio contributed equally to the lower RGR of shaken plants, indicating that seismic stress inhibits dry weight accumulation by decreasing both the photosynthetic efficiency and the assimilatory surface of so

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01221.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.A method is described here for isolating protoplasts and vacuoles from leaves of the halophyteSuacda maritima.Integrity of the protoplasts and vacuoles was tested by staining and shown to be more than 75%, while use of biochemical markers, staining and light microscopy suggested a high degree of purity of the vacuoles. Phosphatase and NADH cytochrome‐c‐reductase were associated with vacuoles; phosphatase showed an eight‐fold enrichment and NADH cytochrome‐c‐reductase a 3.5‐fold enrichment relative to protoplasts. The vacuoles contained only 15% of the protein in

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01222.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.The effects of NaCl salinity on germination and early seedling growth of cotton were studied. Germination was both delayed and reduced by 200 mol m−3NaCl in the presence of a complete nutrient medium. Seedlings, 7–9 d old, were greatly reduced in fresh weight by salinity. The addition of supplemental Ca2+(10 mol m−3as SO42−or Cl−) to the medium did not improve germination but, to a large degree, offset the reduction in root growth caused by NaCl. Roots growing in the high salt medium without supplemental Ca2+appeared infected by microbes. The cation specificity of the beneficial Ca2+effect on growth was ascertained by testing additions of MgSO4or KCl to the NaCl treatments. The contents of K4and Ca2+were reduced in both roots and shoots by the NaCl treatments. Supplemental Ca2+partially offset this effect for K4in the roots and for Ca2+in both roots and shoots. Sodium contents were not affected by the supplemental Ca2+. It is concluded that the beneficial effect of high Ca2+concentrations on root growth of cotton seedlings in a saline environment may be due to maintenance of K/Na‐selectivity and adequate Ca status

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1985.tb01223.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY