ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604598

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.The fluorescent probes 6–carboxyfluorescein and lucifer yellow CH which do not pass the plasmalemma have been used to examine cell‐to‐cell communication in the leaf ofCommelina cyanea.Dye movement from cell‐to‐cell occurs in epidermal, spongy and palisade mesophyll, and vascular cells. Dye movement between these tissues was also found. Hence, the epidermis, spongy and palisade mesophyll cells, and vascular tissue are all linked in a continuous symplast. However, dye injected into the epidermal cells rarely moves into guard cells, indicating that these cells are relatively isolated from the surrounding cells. In the same way, guard cells inVicia fabaand the C4grassAnthephora pubescensalso appeared to be isolated from epidermal cells. Thus guard cell isolation from cell‐to‐cell communication appears to be a common phenomenon. Hence, the ion fluxes required for guard cell function must occur via

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604602

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.Seedlings ofZea maysL. were grown in the dark at 27°C. Four‐day‐old seedlings were then exposed for 3 days to solutions equilibrated with gas mixtures to give O2concentrations between 0.02 and 0.25 mol m−3. Root growth was impaired just as severely at 0.06 as 0.02 mol O2m−3while growth at 0.16 mol O2m−3was about the same as in solutions in equilibrium with air (0.25 mol O2m−3).Growth of young seedlings at low O2concentrations was inhibited to the same extent in nutrient solution and 0.5 ml m−3CaCl2, showing that the adverse effect of O2deficits on growth was not due to less uptake of inorganic nutrients. Furthermore, at low O2concentrations neither exposure of the shoots to a relative humidity of 100% (26.0 g H2O m−3) nor excision of the entire shoot enhanced root growth relative to that in plants with shoots at a relative humidity of 50% (13.0 g H2O m−3). Therefore, for these seedlings growing in the dark, impairment of root growth at low O2concentrations was not a consequence of water deficits in the shoot or of other shoot‐root interactions.Total soluble sugars and amino acid concentrations were generally greater at low (0.02–0.06 mol O2m−3) than at high O2concentrations (0.16–0.25 mol O2m−3). This applied specifically to the root apices (0–2 mm) and expanding (2–15 mm) tissue except in some experiments where sugar concentrations in expanding tissue were slightly greater at high than at low O2concentrations.Critical O2pressures for respiration of excised root segments were approximately 0.117 and 0.065 mol O2m−3in the expanding and expanded zones of the roots, respectively. In contrast, the critical O2pressure exceeded 0.20 mol O2m−3in the apex, suggesting that O2supply for metabolic processes is most likely to be sub‐optimal in this zone. Our results show clearly that the adverse effects of low O2concentrations are unlikely to be a consequence of substrate shortage for either respiration or synthesis of macromolecules; low rates of ATP regeneration in growing root tissues are the logical cause for impaired growth in young seedlings while the

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604603

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.Short‐term fumigation ofSpinacia oleraceawith 380 μg m−3H2S (250 ppb) resulted in a rapid accumulation of water‐soluble SH‐compounds in the shoots. After 1 h exposure a substantial increase in the SH‐content was already detectable and maximal accumulation, three‐ to four‐fold that in control plants, was observed after 24 h of exposure. Irradiation during H2S exposure only slightly affected the rate and level of SH‐accumulation. H2S fumigation did not affect the water‐soluble SH‐content of the roots. Glutathione was the sole water‐soluble SH‐compound accumulating upon exposure to H2S. It was calculated that during the first hour of exposure to 380 μg m−3H2S 39% of the possible absorbed H2S was converted into glutathione. The SH‐content of the water‐soluble proteins of the shoots was not affected by H2S exposure. When fumigation was stopped, a rapid decrease in glutathione content was observed and after 48 h the content was comparable to that of the control plants. Contrary to H2S, SO2fumigation did not result in a rapid accumulation of glutathione in spinach shoots. The possible role of glutathione accumulation dur

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604605

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.Water stress created by withholding irrigation in mung bean resulted in decreased leaf water potential and nodule moisture content. Decreased leaf water potential was associated with decreased activity of nitrogenase, glutamine synthetase (GS), asparagine synthetase (AS), aspartate amino transferase (AAT), xanthine dehydrogenase (XDH) and uricase. However, the activity of glutamate dehydrogenase increased three‐fold under severe stress. The activity of allantoinase and allantoicase was not affected by moderate stress but decreased under severe stress. Thein vitroproduction of allantoic acid from allantoin and uric acid in the cytosol fraction decreased more than its production from xanthine and hypoxanthine. The production of NADH also decreased under stress.During recovery from severe stress, the activity of XDH and uricase further decreased, whilst that of allantoinase and allantoicase increased compared to the control. This corresponded with the higher content of ureides during recovery. The recovery in other enzymes was not complete although leaf water potential and nodule moisture content recovered fully within 24

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604608

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.Measurements of the photosynthetic photon flux density (400–700 nm) and of the spectral distribution of photon flux density across the 370–800 nm waveband, were made under both clear and overcast sky conditions above and at various positions within twoPinus radiatacanopies of different stocking but similar leaf area indices. The spectra obtained for the daylight conditions (i.e. above forest canopy) were generally similar to those published previously. The spectra for shadelight within the forest canopy showed no blue peak which was characteristic of previously reported measurements which were restricted to the diffuse radiation component. There was almost neutral absorption within the 400–700 nm waveband, and typical lower attenuation in the 700–800 nm waveband. The blue: red ratio was largely unchanged by either canopy type or sky conditions and varied between 0.57 and 0.81. The red: far‐red ratio in shadelight was between 0.22 and 0.41 under clear sky and between 0.68 and 0.95 under overcast sky conditions. Values for daylight were between 1.16–1.22. Calculated phytochrome photoequilibrium values in shadelight were approximately 0.35 under clear sky and 0.46 under overcast sky conditions. In each case there appeared to be no differences between the two canopies with respect to these min

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604610

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.Continuous high resolution measurement of sugar beet leaf extension over 5 d in growth chambers showed average leaf extension rates (LER) in darkness to be from three to six times those in light for plants growing in non‐salinized media. The changes in LER in light‐dark transitions occurred within seconds, a response which was more rapid than stomatal opening or closing. When the growth medium was salinized to 100 mol m−3NaCl, LER's were reduced by about 50% in darkness and 90% in light, markedly increasing the ratio of dark to light LER.A 2‐d episode of root‐zone salinity imposed midway through a 5‐d period of measurement decreased LER and produced higher leaf temperatures. LER and diurnal leaf temperature patterns reverted to their pre‐salinized levels when root‐zone salinity was removed. Thus, the effects of short episodes of high sodium chloride in the growth medium appear to be reversible, suggesting a water stress mechanism of growth reduction rather than toxicity

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604611

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.The response of the adenylate energy charge (AEC) ratio and the adenine nucleotide pools to nutrients was studied in two perennial marsh plant species. Adenine nucleotide levels and the AEC ratio were measured inSpartina patens(Alton) Muhl. plants which were grown in the greenhouse at various nutrient levels as well as inSpartina alternifloraLoisel. transplants removed from the field but maintained in marsh soil amended with different nutrient supplements. In addition, adenine nucleotide concentrations were measured in both species in their natural environment and compared with that of the same species grown in the greenhouse with a complement of nutrients.The addition of nutrients stimulated an increase in the individual and total adenylate pools and the AEC ratio. Low nutrient levels resulted in extremely reduced adenylate pools. The AEC ratio was significantly affected in some instances, but did not decrease proportionately with the adenine nucleotide level and was typically maintained at values above 0.60. The adenine nucleotide concentrations measured in the leaves of both species were significantly higher in greenhouse‐grown plants compared to field plants, but the AEC ratios were not significantly different.Because the AEC ratio in plants can be significantly affected by nutrient level. AEC response in field investigations should be planned with attention to the potential effect of dissimilar nutrient levels among study site

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604613

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.Black alder seedlings were exposed to 12 weeks of sublethal water stress by watering only when visibly wilted. Control seedlings were watered regularly throughout the treatment period. Stressed seedlings exhibited significant osmotic adjustment of over 0.4 MPa. The water stress treatment also significantly reduced leaf size, increased epicuticular wax content, and increased the root shoot ratio. The response of leaf conductance to decreasing leaf water potential was influenced by the previous water stress treatment Stressed seedlings had a much lower initial leaf conductance, but showed a gradual drop in leaf conductance as leaf water potential decreased; whereas, control seedling leaf conductance fell rapidly. These morphological and physiological modifications in response to moisture stress have the potential for significantly improving black alder drought tolerance.

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604616

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.A new method is described for determining the boundary layer resistance over wet filter paper exposed within a leaf cuvette, based on the energy balance of the filler paper. The boundary layer resistance is calculated by an iterative procedure from measurements of the relative humidity and temperature of the air in the cuvette. Comparisons between the new and the conventional method, involving measurement of the filter paper temperature, show close agreement.To simplify the method further, a graph has been constructed for the relationship between boundary layer resistance and cuvette relative humidity at temperatures from 15 to 35°C, determined at one value of the ratio of the flow rate through the cuvette to the filter paper area.An analysis of errors suggests that the new method is less sensitive than the conventional to errors in temperature and humidity

ISSN:0140-7791    

DOI:10.1111/1365-3040.ep11604618

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY