摘要:

Chlorophyf l‐free preparations of plasma membranes from leaves of barley (Hordeum vulgare L. cv. Kristina) and spinach (Spinada oleracea L. cv. Viking II) were obtained by partition in an aqueous dextran‐polyethylene glycol two‐phase system. CJlu‐can synthetase II (EC 2.4,1.34), a marker for the plasma membrane, was highly enriched in both preparations. Silicotungstic acid, a specific stain for the plasma membrane, indicated a purity close to 100% for the barley preparation. Both plasma membrane preparations contained a light‐reducible b‐cytochrome, as shown by low temperature spectroscopy. The plasma membranes had a tow protein content compared to the bulk of intracellular membranes. The polypeptide composition of the barley and spinach plasma membranes showed striking similarities, with.the most prominent polypeptides in the 49‐58 kdalton region, and some further prominent bands in the 30 kcialton region. Some high molecular weight polypeptides in the 73‐110 kdalton region were also typical for the plasma membranes compared to the micro

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb02791.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Ultrastructural, morphometric and physiological techniques were used to determine the consistent chloroplast differences between triazine‐resistant (R) and triazine‐susceptible (S) biotypes ofAmaranthus hybridusL.,Chenopodium albumL., andBrassica campestrisL. All R biotypes had a larger proportion of the chloroplast volume as grana lamellae and a lower proportion of starch and stroma lamellae than S biotypes. In the R biotypes, a greater percentage of grana contain larger numbers of thylakoids per granum. A greater proportion of chlorophyll associated with the light‐harvesting chlorophyllalbprotein and a lower chlorophyllalbratio, traits associated with an increase in grana lamellae, were noted in R biotypes. Chloroplasts of S biotypes could be modified to ultrastructural phenocopies of those in R biotypes by treatment with sublethal levels of the PSII inhibiting herbicides, bentazon, diuron, atrazine and prometon. Despite the structural similarities to R biotypes, the modified S biotypes were not resistant to atrazine as determined by fluorescence measurements. Thus, the structural alterations observed are apparently secondary effects of impaired photosynthetic electron transport in R biotypes, and are not the cause of triazine resis

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb02792.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Excised etiolated cotyledons of cucumber (Cucumis sativusL. cv. Aonagajibai) were continuously irradiated under various intensities of white light. The rate of chlorophyII (Chi) formation during the lag phase reaches a plateau at fluence rates above 1.4 urmol m−2s−1. This is true in both water‐control and benzyladenine (BA)‐pretreated cotyledons. In cotyledons pretreated for 14 h with BA in darkness (in which case, Chl formation is stimulated by BA during both the lag and the steady‐state phases), the increase in the steady‐state rate of Chl formation with increasing light in tensity is stimulated compared to that of the water control over the range of fluence rates, 0. 25‐43 urmol m−2s−1. In cotyledons pretreated for 6 h with BA in darkness (only Chl formation during the lag phase is stimulated), only an increase in fluence rate from 0.25 to 1.4 umol m−2s−1causes a higher increase in the Chl formation in the BA‐treated cotyledons than in the water control. The time course of Chl formation shows that the BA‐induced late‐appearing effect (stimulation of the steady‐state rate) is almost absent at low intensity illumination, but the BA‐induced fast‐appearing effect (elimination of the lag phase) is effective at all intensities. From this evidence, the Chl‐forming process apparently consists of two components, whose periods of operation or light‐intensity requirements are different. BA stimulates the rates of the respective components in both th

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb02793.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The effects of photosynthetically active radiation (PAR), leaf temperature and the leaf‐to‐air water vapor concentration drop on net CO2uptake and water vapor conductance were surveyed for 14 species of ferns. Most previous studies indicated that ferns have extremely low maximal rates of net CO2uptake, below 2 umol m−2s−1, whereas the average maximal rate observed here at 250C was 7 umol m−2s−1. Net CO2uptake reached 90% of saturation at an average PAR (400 to 700 nm) of only 240 umol m−2s−1, consistent with the typically shaded habitats of most ferns. Maximal CO2uptake rates were positively correlated with the PAR for 90% saturation (r2=0.59), the chlorophyII per unit leaf area (r2=0.30), the water vapor conductance (r2=0.65), and the CO2residual conductance (r2=0.69). A higher water vapor conductance (gwv) was correlated with a greater fractional change in gwv as the leaf‐to‐air water vapor concentration drop (Δcwv) was raised from 5to20 g m−3(r2=0.90). Specifically, for species with low gwvof about I mm s−1the ratio of gwvat Δcwv= 5 g m−3to that at Δcwv= 20 g m−3was near 1, but it was near 2 for species with gwvof about 4 mm s−1. Such a relationship, which can prevent excessive transpiration, has apparently not previously been pointed out

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb02794.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The effect of daylength extension with narrow spectral bands on the flowering of a long‐day plant,Brassica campestrisL. cv. Ceres, was investigated to obtain clues to the identity of the photoreceptor involved. Extension of a 9 h photoperiod with 5 h of light pulses at various wavelengths resulted in maximal flowering occurring after irradiation at 710 nm, less at 730 nm, and none at 550, 660 and 750 nm. Flowering at 710 and 730 nm was negated by simultaneous exposures at 550 nm, but not at 660 nm. A short preirradiation at 660 nm enabled a following irradiation at 750 nm to induce flowering. This latter induction was prevented by 550 nm irradiation.Short flashes of light at 710 nm induced flowering that was negated by a following flash at 550 nm but not at 660 nm. The negation by 550 nm radiation was prevented by subsequent flashes at 710 nm, indicating photoreversibility. A flash at 660 nm enabled subsequent light flashes at 750 nm to initiate flowering that was reversed by a following 550 nm flash.From the results showing the necessity of red and far‐red lights, it is proposed that flowering in this long‐day plant is due to two photoreceptors ‐ one is phytochrome and the other an unknown pigment with far‐red, green photoreversible properties. By using fluence response data, it is deduced that the unidentified photoreceptor has weak absorption bands in the far‐red, but has a strong absorption band in the green. Flowering is induced when effects of red light absorbed by phytochrome interact with effects of far‐red light absorbed by the unidentified

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb02795.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The effect of Ca2+, Mg3+and Ni2+on root elongation was studied inAlyssum bertoloniiDesv., a nickel‐accumulating and serpentine endemic species. The results confirm the detoxifying action of Ca2+which reduces the toxic effect of Mg2+and Ni2+on root development. In addition, Ca2+and Mg2+interact positively in depressing Ni2+uptake. The combined effect of these two ions is of relevance for the mechanism of nickel tolerance inA. bertoloni

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb02796.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Ethylene was produced byVerticillium dahliaeKleb. grown in liquid Czapek's medium. The rate of ethylene production was enhanced by light but was not affected by shaking or the growth rate of the cultures. L‐, D‐ and DL‐methionine, DL‐ethionine anda‐keto‐y‐methylthiobutyric acid (KMBA) were good substrates for ethylene production. KMBA may be an intermediate in ethylene production and it appears to be degraded to ethylene either enzymatically by peroxidase or photochemically in the presence of riboflavin. Addition of riboflavin or briefly heating the cultures to 100°C enhanced ethylene production greatly, while the addition of sodium azide, potassium cyanide and catalase were very inhibitory. The SS4 (non‐defoliating) pathotype ofV. dahliaeproduced significantly more ethylene (up to 108.4 nl ethylene h1from 20 ml‐10‐day‐old cultures) than did the T9 (defoliating) pathotype with all substrates tested. The results suggest that the in vitro rate of ethylene production is not related to the relative virulence of pathotypes ofV. dahliaeon cotton. A number ofVerticilliumspecies,Fusarium oxysporumf. sp.vasinfectumandColletotrichum dematiumvar.truncatumwere able to produce ethylene in liquid Czapek's medium containing 1 mML‐methionine under continuous light. Riboflavin, although highly stimulatory to ethylene production, caused a fungicidal reaction to all the fungi tested in Czapek's medium containing L‐methionine under continuous light. The fungicidal effect of the riboflavin‐methionine‐light combination occurred at concentrations of riboflavin and methionine less than 1.33 μMand 0.5 mM, respectively. No fungicidal activity was detected when the cultures were grown in total darkness or when either methionine or riboflavin was

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb02797.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Achenes ofLactuca sativaL. cv. Grand Rapids were treated with (±) 2‐[14C]‐abscisic acid (ABA) at 105‐ or 2‐106M for 6, 12, 24, 48 or 96 h in darkness at 24°C. They were then extracted in 80% ethanol. Two acidic diethyl ether phases which contained the free acids and the acids released after mild alkaline hydrolysis respectively, were analyzed as well as the radioactivity which remained in the final aqueous phase. For treatment durations between 6 and 96 h, the major part of the radioactivity was found in the free phase, in the form of ABA. For treatment durations up to 48 h, no radioactivity was detected at the Rf of phaseic acid or dihydrophaseic acid (free and hydrolysed phases). After 96 h culture on 105M ABA, dihydrophaseic acid was present, but only in very small quantities. Two ABA metabolites were detected. One was characterized as β‐d‐glucopyranosyl abscisate since its Rf was the same as that of an authentic sample in three different solvent systems and also since it released ABA on mild alkaline hydrolysis. It increased steadily with time and represented the main metabolite. The other metabolite found in the aqueous phase after mild alkaline hydrolysis and extraction with ether at pH 3 was a very polar compound, resistant to alkaline hydrolysis in the presence of concentrated ammonia and to methylation. It was, however, metabolized by apple embryo, yielding essentially dihydrophaseic acid and an ester which released dihydrophaseic acid on mild alkaline hydrolysis. These results indicate that under the conditions tried, the metabolism of [14C]‐ABA by lettuce achenes leads almost exclusively to the formation of conjugates, oxidative metabolism of ABA being almost non‐existent. Separate analysis of the integuments and of the endosperm plus embryo after culture of whole achenes for 48 h in the presence of 105M [14C]‐ABA showed that ABA metabolism occurred only in the en

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb02798.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The reductive carboxylation of α‐ketoglutarate by purified NADP+‐isocitrate dehydrogenase (EC 1.1.1.42) from maturing castor bean seeds (Ricinus communis L.) has been characterized. The optimum pH for the reaction was 6.5, whereas pH 8.5 was optimum for oxidation of isocitrate (forward reaction). The enzyme utilized NADH as well as NADPH as the reducing agent in the reverse reaction, but only NADP+in the forward reaction. The Km values for NADPH and NADH were 0.044 and 2.8 mMrespectively, and for α‐ketoglutarate and HCO34.1 and 3.7 mM.The enzyme was activated by various cations including Mg2+, Mn2+, Co2+, Zn2+, Ni2+and Co2+. Km values for Mg2+Mn2+, Co2+and Zn2+were 12, 34, 37 and 49μMresp

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb02799.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Apples (Pyrus malusL. cv. Golden Delicious) were kept at 0°C (temperature favourable for removal of embryo dormancy), and at 12 or 35°C (conditions inducing freezing resistance). At different intervals seeds were sampled, and germinability and survival to rapid freezing (‐7°C for 30 min) in embryos were determined. Lipids from embryos of the same samples were extracted and separated into triacylglycerol, diacylglycerol and polar lipid fractions. Certain fatty acids were then quantified in all fractions. Low temperature (0°C) of fruit storage promoted temporary accumulation of only tri‐ and diacylglycerols, whereas 12 and 35°C treatments resulted in an increase solely of polar lipid content. These relations were confirmed in experiments with transfer of fruits from one temperature of storage to another. Changes in the levels of certain fatty acids followed the pattern of total lipids of the three main classes. Together with earlier data, the results suggest that the changes in reserve lipids are related to the dormancy status of the embryo, whereas the changes in polar lipids reflect the resistance to rapid

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1984.tb02800.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY