摘要:

Abstract.Non‐differentiated tissue cultures (calli) of tobacco were found to be more sensitive to chloramphenicol (CAP) than differentiated tissues (shoots). The difference is especially manifested in darkness and at an irradiation regime lacking u.v. and blue light. Photodegradation of CAP solutions was demonstrated at moderate light fluence rates (6–15 Wm−2). The evidence indicates that the final products of photodegradation may be toxic or non‐toxic according to the irradiation regime. The implication of the present findings in establishing a selection system for resistance to chemicals, and especially CAP, using plant tissue cultures, is di

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01878.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract.Non‐differentiated tissue cultures (calli) and differentiated tissues (shoots) of tobacco were found to differ in their sensitivity to chloramphenicol (CAP). This phenomenon is especially manifested in darkness and in an illumination regime lacking u.v. and blue light. When the latter are included, CAP's photodegradation products are shown to appear. It seems that one of the main photodegradation pathways is through the production ofp‐nitro‐benzaldehyde (p‐NBA) which is further degraded. The possibility that either acetylation or physiological nitration of CAP is the cause for the differential tolerance was eliminated. The chromatographic and radiographic results indicate thatin vivodegradation of CAP occurs both in calli and in shoot cultures. One of the in vivo degradation products is C

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01879.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract.In germinating seedlings ofSinapis alba, nitrate reductase activity is under phytochrome control and becomes accessible to phytochrome at about 15 h from sowing. The induction of the enzyme with pulses of light is strongly affected by pretreatments given prior to 15 h, also acting through phytochrome. It is shown that the effects of these pretreatments can persist undiminished for a considerable time (>40 h) but do not alter the pattern of the subsequent responsiveness to Pfr. The nitrate reductase response is compared with other data pertaining to a similar response.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01880.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract.The response of stomatal conductance to broadband blue and red light was measured in whole shoots of Scots pine and Sitka spruce, two species which have low stomatal sensitivity to CO2. In Scots pine, blue light was more than three times more effective than red light (on an incident quantum basis) in opening stomata, particularly at low quantum flux densities (<100μmiol m−2s−1). However, the apparent quantum yield of net CO2assimilation rate in blue light was only half that in red light. The contrasting effects of red and blue light on conductance and assimilation led to higher intercellular CO2concentrations (Ci) in blue light (up to 100 μmol mol−1higher) than in red light. Similar results were obtained with Sitka spruce shoots, though differences in the effectiveness of red and blue light were less marked. In both species, both red and blue light increased conductance in normal and CO2‐free air, indicating that neither red nor blue light exert effects through changes in Cior mesophyll assimilation. However, decreases in Cicaused increases in conductance in both red and blue light, suggesting that these direct effects of light are not wholly independe

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01881.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract.Two experiments are described which test the normal correlations that arise between stomatal conductance, net CO2assimilation rate, and intercellular CO2concentration (Ci), using whole shoots ofCommelina communisL. In the first, conductance increased with decreasing Ci, at four different quantum flux densities, such that there was no unique relationship between conductance and quantum flux density or Ci, In the second, conductance increased hyperbolically with increasing quantum flux density while Ciwas held constant at 466, 302, and 46 μmiolmol−1, and the response differed at each Ci. In neither experiment was conductance consistently related to net CO2assimilation rate in the mesophyll. In both experiments high Cisuppressed the response of conductance to light, while there was a large response of conductance to light at low Ci, indicating an interaction between the effects of light and CO2on stomata. The results show that the parallel responses of assimilation and conductance to light result in constant intercellular CO2concentrations, and not that stomata maintain a ‘constant

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01882.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract.Combined gas chromatography‐mass spectrometry has been used to identify 3‐indole acetic acid in an extract from protoplasts of barley. In addition, a study has been made of the effect of light on the rate of catabolism of [2‐14C]‐3‐indole acetic acid by protoplasts, a chloroplast‐rich fraction and a crude cytoplasmic preparation from barley leaves. While light enhanced the rate of catabolism of [2‐14C]‐3‐indok acetic acid by protoplasts and, to a lesser degree, by the chloroplast‐rich fraction, it did not affect the catabolic activity of the crude, cytoplasmic fraction. These findings, when considered along with the data of Sandberg, Jensen&Crozier (1983), imply that the rate of turnover of 3‐indole acetic acid, in both protoplasts and chloroplasts, is more rapid in light t

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01883.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract.Fully expanded leaves of 25°C grownPhaseolus vulgarisand six other species were exposed for 3 h to chilling temperatures at photon flux densities equivalent to full sunlight. In four of the species this treatment resulted in substantial inhibition of the subsequent quantum yield of CO2uptake, indicating reduction of the photochemical efficiency of photosynthesis. The extent of inhibition was dependent on the photon flux density during chilling and no inhibition occurred when chilling occurred at a low photon flux density. No inhibition occurred at temperatures above 11.5°C, even in the presence of the equivalent of full sunlight. This interaction between chilling and light to cause inhibition of photosynthesis was promoted by the presence of oxygen at normal air partial pressures and was unaffected by the CO2partial pressure present when chilling occurred in air. When chilling occurred at low O2partial pressures, CO2was effective in reducing the degree of inhibition. Apparently, when leaves of chilling‐sensitive plants are exposed to chilling temperatures in air of normal composition then light is instrumental in inducing rapid damage to the photochemical efficiency of photosynthe

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01884.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract.H+efflux from the trap lobes ofDionaea muscipulaEllis (Venus's flytrap) was measuredin vitro.FC, IAA, and 2,4‐D markedly increase the rate of H+efflux within minutes of their addition to the incubation medium whereas ABA and DES cause the rate to decrease. Consequently, the H+efflux mechanism ofDionaeais considered to be similar to the H+extrusion pumps of other higher plants in this respect. However, the H+extrusion mechanism ofDionaeamay be unusual in that long‐term exposure of the trap lobes to known secretion elicitors— bactopeptone, NH4+, Na+, urea, thiourea, glycine or xanthine—also causes a large increase in the steady‐state rate of H+efflux from the trap lobes. Since the observed H+effluxes primarily correspond to the adaxial surface of the trap lobes and show similar time‐ and secretion elicitor‐dependencies to the responses seenin situ, it appears that the H+effluxes measuredin vitrobear a direct relationship to those observed in the intact, actively secreting plant.Three of the secretion elicitors that were tested— K+, NH4+, and urea—have rapid effects on the rate of H+extrusion in addition to their long‐term effects. K+and NH4+cause a rapid acceleration of H+efflux whereas urea causes a rapid deceleration or, at high external concentrations, reversal of the net flux. The effect of K+is inferred to result from K+‐H+exchange between the tissue and bathing medium. Studies with structural analogues of NH4+and urea and inhibitors of the assimilation of reduced nitrogen suggest that the effects of NH4+and urea result from the pH‐perturbing consequences of their metabolism subsequent to their absorption. These effects are considered to be auxiliary to the elicitation of secretion.It is proposed that H+efflux from the trap lobes is mediated by a K+‐H+exchange mechanism, the activity of which is modified by long‐term exposure to secretion elicitors and/or short‐term exposure to factors which alter the avai

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01885.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract.Quantum (photon) yields for CO2uptake on an absorbed photon fluence rate (PFR) basis (φa) were determined for a number of diploid and tetraploid species under a range of experimental conditions. Little variation in φawas found either between species or across ploidy levels, which suggests that there are no intrinsic differences in the kinetics of CO2fixation. Variations in photosynthetic rate or quantum yield expressed on an incident PFR basis (φj) were found to be largely due to differences in leaf absorptance. On this basis these results do not support the biochemical evidence showing ploidy‐related differences in the Km(CO2) of ribulose ‐1,5‐bisphosphate carboxylase/oxygenase. However, there are obvious difficulties in relatingin vitroenzyme kinetic data toin vivostudies and these problems are d

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01886.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract.The stomatal behaviour of a California chaparral shrub was compared with that predicted by a model of optimal water‐use efficiency (Cowan&Farquhar, 1977). The daily courses of stomatal conductance, evaporation, and assimilation were calculated as was the derivative of evaporation with respect to assimilation (∂E/∂A). The derivative ∂E/∂Awas not constant, and the measured courses of conductance were not optimal, but daily courses of evaporation and assimilation were usually very close to what would have been predicted had ∂E/∂Abeen constant. This discrepancy arises because evaporation and assimilation are sometimes so severely constrained by the microenvironment that stomatal conductance has almost no e

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1983.tb01887.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY