摘要:

Abstract.Oligosaccharides that exert biological effects on higher plants (other than as carbon or energy sources) have been termed‘oligosaccharins'. A limited number of specific oligo‐β‐glucans derived from fungal cell walls exhibit oligosaccharin activity, at very low doses, switching on the synthesis of phytoalexins. The structural requirements for this biological activity are stringent, and there is strong evidence that the oligosaccharins of fungal origin act through a receptor in the plant cell membrane. Chemically unrelated oligosaccharins can also be produced by partial digestion of pectins and xyloglucans from higher plant cell walls. In some cases, for example, the α‐l‐fucosylated oligoxyloglucans that antagonise the growth‐promoting effect of auxin, these plant‐derived oligosaccharins have relatively strict structural requirements for activity and act at ∼10−6mol m−3; these may act via specific receptors. In other cases, for example, the growth‐promoting action of other oligoxyloglucans, the stringency is somewhat lower and the activity is only seen at ∼10−3mol m−3, and these oligosaccharins are proposed to influence growth through their ability to modulate the activity of an enzyme, cellulase. A third class of plant‐derived oligosaccharins, the oligo‐α‐galacturonides, appear to have much less stringent structural requirements; a number of unrelated physiological responses are evoked by the same range of oligo‐α‐galacturonides at ∼10−3to 1 mol m−3. We suggest that these oligosaccharins may act via a mechanism not involving a specific receptor, perhaps by interacting with the plasma membrane to

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1991.tb01535.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.The productivity of the prickly‐pear cactusOpuntia ficus‐indica, which is cultivated worldwide for its fruits and stem segments, was predicted based on the responses of its net CO2uptake to soil water status, air temperature and photosynthetic photon flux density (PPFD). Each of these environmental factors was represented by an index with a maximum value of unity when that factor was not limiting net CO2uptake over a 24‐h period. The water index, the temperature index, and the PPFD index were determined for 87 sites in the contiguous United States using data from 189 weather stations and for 148 sites worldwide using data from 1464 weather stations. The product of these three indices, the environmental productivity index (EPI), was used to predict the productivity ofO. ficus‐indicaunder current climatic conditions and under those accompanying a possible increase in the atmospheric CO2level to 650μumol mol−1. Sites with temperatures always above ‐10°C and hence suitable for prickly‐pear cultivation numbered 37 in the United States and 110 worldwide; such sites increased by 43 and 5%, respectively, for the global warming accompanying the elevated CO2. Productivity ofO. ficus‐indicawas at least 15 tonnes dry weight hectare−1year−1, comparable to that of many agronomic crops, for 20 sites with temperatures always above ‐10°C in the contiguous United States and for 12 such sites worldwide under current climatic conditions; such sites increased by 85 and 117%, respectively, under the elevated CO2condition, mainly because of direct effects of the atmospheric CO2level on net CO2uptake. In summary, simulations based on EPI indicate thatO. ficus‐indicamay presently be advantageously cultivated over a substantial fraction of the earth's surface, such regions increasing markedly with a future doublin

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1991.tb01536.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Glycine max(L.) Merr. was grown under several light conditions to determine the role of red and far‐red radiation in plant adaptation to vegetation shade. Neutral density,‘neutral’ density with elevated far‐red radiation, and green shade treatments were used in a greenhouse, producing calculated phytochrome photostationary state (Pfr/Pr+Pfr) values of 0.68, 0.63 and 0.51, respectively. Cool‐white fluorescent lamps either alone or in conjunction with far‐red fluorescent lamps were used in a growth chamber, providing Pfr/Pr+Pfrof 0.79 and 0.61, respectively. Daily photo‐synthetically active radiation was about 25% of daylight and was approximately equal for both greenhouse (2.15MJ m−2) and growth chamber (2.57MJ m−2). Developmental stage 4 weeks after sowing was similar for all treatments, but axillary growth and rates of leaf area and dry matter accretion differed between plants from greenhouse and growth chamber. Light conditions simulating vegetation shade (i.e. a low ratio of red to far‐red radiation) significantlypromotedpetiole elongation andretardedthe rate of stem elongation in both greenhouse and growth chamber experiments. Other aspects of growth either were not significantly altered by spectral quality or were not modified consistently in both greenhouse and growth chamber environments. Net photosynthetic rates measured under growth conditions for unifoliate and first trifoliolate (TF1) leaves of growth chamber plants between 9 and 21 d after sowing were generally unaffected by spectral quality, but supplemental FR enhanced TF1leaf area expansion. The latter effect was not correlated with increased dry matter accumulation. The significance of spectral quality for adaptation of soybeans to canopy closure and intercr

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1991.tb01537.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.An account is given of an investigation of net ionic currents and specific ion fluxes occuring during the initiation of organogenesis in detached leaves ofGraptopetalum paraguayenseE. Walther, in which a dramatic change in growth polarity is cytomorphologically evident 3–5 d after leaf detachment from the plant. Using the vibrating probe, it was possible to identify a peak of ionic current which is focused over the area of the leaf base where organogenesis is initiated. This net current is largest during the initial 12h after leaf detachment. With ion‐selective microelectrodes capable of measuring H+, K+and Ca2+ion fluxes simultaneously in the same region of the leaf base, H+and K+fluxes remain relatively steady during the initial 24 h after detachment, while a large lanthanum‐sensitive Ca2+influx decreases by 50% from 2 to 12h. By 24h, Ca2+transport is dominated by an efflux. We present evidence from a quantitative comparison of the ion current data collected using these two techniques, that Ca2+, H+and K+transport accounts for the major electrogenic ion fluxes during 2 and 12 but not 24 h after leaf detachment. The possibility is addressed that these ion currents, which precede organogenesis, and in particular the predominant Ca2+flux, play a role in the establishment of growth polarity in higher plant ti

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1991.tb01538.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Elevated levels of CO2in the atmosphere are expected to affect plant performance and may alter global temperature patterns. Changes in mean air temperatures that might be induced by rising levels of CO2and other greenhouse gases could also be accompanied by increased variability in daily temperatures such that acute increases in air temperature may be more likely than at present. Consequently, we investigated whether plants grown in a CO2enriched atmosphere would be differently affected by a heat shock than plants grown at ambient CO2levels. Plants of a C3annual (Abutilon theophrasti), a C3annual crop (Sinapis alba) and a C4annual (Amaranthus retroflexus) were grown from seed in growth chambers under either 400 or 700cm3m−3CO2, and were fertilized with either a high or low nutrient regime. Young seedlings ofS. alba, as well as plants of all species in either the vegetative or reproductive phase of growth were exposed to a 4‐h heat shock in which the temperature was raised an additional 14–23°C (depending on plant age). Total biomass and reproductive biomass were examined to determine the effect of CO2, nutrient and heat shock treatments on plant performance. Heat shock, CO2, and nutrient treatments, all had some significant effects on plant performance, but plants from both CO2treatments responded similarly to heat shocks. We also found, as expected, that plants grown under high CO2had dramatically decreased tissue N concentrations relative to plants grown under ambient conditions. We predicted that high‐CO2‐grown plants would be more susceptible to a heat shock than ambient‐CO2‐grown plants, because the reduced N concentrations of high‐CO2grown plants could result in the reduced synthesis of heat shock proteins and reduced thermotolerance. Although we did not examine heat shock proteins, our results showed little relationship between plant nitrogen status and the ability of a plant to tolerate an acute increas

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1991.tb01539.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Pressure chamber (PC) and thermocouple pyschrometer (TP) were used to determine leaf water potential in tomato (Lycopersicon esculentumMill.), eggplant (Solanum melongenaL.) and bean (Phaseolus vulgarisL.) seedlings subjected to normal watering regime, drought or chilling temperature. The PC readings were corrected for apoplastic osmotic potential. Similar results were obtained in all species. In unchilled plants, the PC and TP measurements corresponded within a potential range of ‐0.1 to ‐2.5MPa, but discrepancies between the two methods often occurred in chilled plants, with PC water potentials 0.2 to 1.4 MPa higher (less negative) than TP values. The PC measurements appeared spuriously high in chilled plants. In droughted plants leaf dehydration occurred in both the blade and the petiole, whereas in chilled plants, water deficit was generally observed only in the bl

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1991.tb01540.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.The significance of blue light‐stimulated stomatal conductance for carbon assimilation (A), stomatal conductance (g), intercellular CO2(Ci), stomatal limitation of A (L), transpiration (E) and water use efficiency (W = A/E), was determined in a C4and a C3species. W and L were evaluated for steady‐state gas exchange with constant, saturating red light (As, gs, Es), and for the integrated gas exchange above the steady state baseline induced by a single, brief pulse of blue light (Ap, gp, Ep). Sugarcane (Saccharumspp. hybrid), a C4grass, and soybean (Glycine max) a C3dicot, were compared. Sugarcane exhibited typical C4behaviour, with A saturing at Ciof ca. 200 μmol mol−1, compared to>500 μmol mol−1in soybean. Steady‐state W was also considerably higher in sugarcane. The extent of stomatal opening in response to a blue light pulse, from baseline (gs) to the maximum value of conductance during the opening response (gm), was similar in the two species. More rapid opening and closing of stomata in sugarcane resulted in a smaller integrated magnitude of the conductance response (gp) than in soybean. At the peak of the blue light response, both species exhibited similar levels of L. During the response to the pulse of blue light, A and Ciincreased and L decreased to a greater extent in sugarcane than in soybean. As a result, the gas exchange attributed to the stomatal response to blue light exhibited a higher ratio of Apto Ep(Wp) in sugarcane than in soybean. This Wpwas lower in both species than was the Wsassociated with the steady state gas exchange. The two species did not differ in the rate of induction of photosynthetic utilization of elevated Ci. The greater stimulation of A in sugarcane was attributed to its C4attributes of greater carboxylation efficiency (slope of the A versus Cirelationship), lower gsand prevailing Ci,s, and greater Lsunder steady‐state red illumination. Despite saturation of A at low levels of Ciin C4species, the gas exchange attributed to the stomatal response to blue light decreased L and contributed considerably to carbon acquisition, while maintaining the high level of W associated with

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1991.tb01541.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Guard cells are uniquely differentiated to transduce signals into the metabolic and ion transport processes that result in turgor‐driven stomatal movements. We tested the hypothesis that these highly specialized cells are terminally differentiated. Guard cell protoplasts were isolated from abaxial epidermal tissue of leaves ofNicotiana glauca(Graham) and cultured in a medium designed for culturing mesophyll protoplasts ofNicotiana tabacum.Protoplasts were incubated at densities of 2–5 × 1011cells m−3in eight‐well microchamber slides under 50μmol m−2s−1of photons of continuous fluorescent light at 25°C. When the medium was modified by the addition of 100mol m−3of sucrose and by buffering with 10mol m−3of MES buffer at pH 6.1, cell division began within 96h of the time the culture was initiated. After 9d of culture, 80% of surviving cells had synthesized new cell walls, had dedifferentiated, and were dividing to form small colonies. Callus tissue was visible after 4–5 weeks. We conclude that guard cells ofNicotiana glaucaare not terminally differentiated, and that guard cell protoplasts of this species have the capacity to grow, synthesize c

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1991.tb01542.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.The effect of growth temperature on biomass production and photosynthesis of nearly‐isonuclear triazine‐resistant and ‐susceptibleSenecio vulgarisL. bio‐types was investigated. Plants were grown in growth chambers with day/night temperatures of 13/8, 20/15 and 30/25°C, and were harvested 35, 42, 49 and 56d after planting (DAP). The S biotype produced more shoot dry weight than the R × SBC6biotype, and the S × RBC6biotype produced more shoot dry weight than the R biotype at all DAP and growth temperature combinations. The S and S × RBC6biotypes had greater photosynthetic rates than the R X SBC6and R biotypes, respectively. Thus, plants containing the susceptible chloroplast genome produced more biomass and had greater photosynthetic rates than those with the resistant chloroplast genome, when in association with the same nuclear genome. There was no differential temperature effect on biomass production of isonuclear plants possessing resistant or susceptible chloroplast genomes. However, there was a large differential temperature effect on the amount of biomass produced by plants containing different nuclear genomes (R or S) in association with the same chloroplast genome. The R nuclear genome appeared to be better adapted to cooler growth temperatures while the S nuclear genome was better adapted to warmer growth

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1991.tb01543.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Net photosynthesis and transpiration rates of potato plants, grown in pots in the greenhouse, were measured at various light irradiances and ambient CO2concentrations, 3d after inoculation with second stage juveniles ofGlobodera pallida.Gas exchange rates, both in darkness and in light, and the initial light use efficiency were strongly reduced by nematodes. Stomatal conductance of infected plants was lower than that of control plants and showed little response to decreasing ambient CO2concentration. The maximum internal CO2concentration of infected plants was lower than that of control plants.Globodera pallidareduced photosynthesis also by apparent non‐stomatal effects.The effects ofG. pallidaon gas exchange rates are similar to the effects of abscisic acid in the transpiration stream and of abiotic stresses in the root environment. Apparently, there is a general response of plant roots to adverse conditions. The reduction of photosynthesis may be an important factor in yield reduction by potato cyst nematode

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1991.tb01544.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY