摘要:

AbstractIntensity, spectral characteristics and localization of the UV‐laser (337 nm) induced blue‐green and red fluorescence emission of green, etiolated and white primary leaves of wheat seedlings were studied in a combined fluorospectral and fluoromicroscopic investigation. The blue‐green fluorescence of thegreen leafwas characterized by a maximum near 450 nm (blue region) and a shoulder near 530 nm (green region), whereas the red chlorophyll fluorescence exhibited maxima in the near‐red (F690) and far‐red (F735). Theetiolated leafwith some carotenoids and traces of chlorophyll a, in turn, showed a higher intensity of the blue‐green fluorescence with a shoulder in the green region and a strong red fluorescence peak near 684 to 690 nm, the far‐red chlorophyll fluorescence maximum (F735) was, however, absent. The norfluorazone‐treatedwhite leaf, free of chlorophylls and carotenoids, only exhibited blue‐green fluorescence of a very high intensity. In green and etiolated leaves the blue‐green fluorescence primarily derived from the cell walls of the epidermis and the red fluorescence from the chlorophyll a of the mesophyll cells. In white leaves the blue‐green fluorescence emanated from all cell walls of epidermis, mesophyll and leaf vein bundles. The shape and intensity of the blue‐green and red fluorescence emission is determined by the reabsorption properties of chlorophylls and carotenoids in the mesophyll, thus giving rise to quite different values of the various fluorescence ratios F450/F690, F450/F530, F450/F735 and F690/F735 in gre

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00762.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractRecently we reported on the stimulating effect of a cold dark pretreatment (cold‐dp) on the chlorophyll accumulation (Schönbohm et al., 1988) and on the CO2‐ and O2‐gas exchange (Schönbohm and Czeska‐Werner, 1990) during de‐etiolation of wheat leaves under white light.The goal of the present paper was to study the effect of a cold‐dp on the accumulation of chloroplast pigments, on the kinetics of fluorescence quenching, on the synthesis ofCab‐proteins and on the amounts ofcab‐transcripts during de‐etiolation under white light.The following results were obtained:1Not only the chlorophyll synthesis but also the synthesis of xanthophylls and of β‐carotene is highly increased by a cold‐dp.2The kinetics of the PAM‐fluorescence curves demonstrate that the activity and co‐operation of the two photosystems start earlier and with higher efficiency during de‐etiolation in cold‐dp than in warm‐dp wheat leaves.3The amount ofcab‐transcripts can be elevated by a cold‐dp.4The amount ofCab‐proteins during de‐etiolation is much higher in cold‐dp than in warm‐dp wheat leaves.The presented data are in accordance with our earlier published results. Consequences of these results on seedlings growing under natural conditions with fluctuating tem

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00763.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractPeroxisomes from mung bean hypocotyl (Vigna radiataL.) degrade 2‐oxoisocaproate, the transamination product of leucine, via isobutyryl‐CoA and propionyl‐CoA to acetyl‐CoA. The methyl group at the C‐3 position forms a barrier to β‐oxidation. This barrier is overcome in the peroxisomes by several enzymatic steps. Senecioate (3‐methylcrotonate), 2‐hydroxyisovalerate, and 2‐oxoisovalerate were detected as free acid intermediates. Senecioate, formed from 3‐methylcrotonyl‐CoA, is transformed by enzymatic hydrolysis to 2‐hydroxyisovalerate. 2‐Hydroxyisovalerate is then oxidized to 2‐oxoisovalerate in an H2O2‐producing reaction, exhibiting 1:1 stoichiometry of the products, by a 2‐hydroxyacid oxidase which is different from the peroxisomal marker enzyme glycollate oxidase. 2‐oxoisovalerate is activated by an NAD‐dependent oxidative decarboxylation to isobutyryl‐CoA. Accumulation of 2‐oxoisovalerate in the presence of arsenite, an inhibitor of oxidative decarboxylations, is a feature of this latter pathway of degradation of isovaleryl‐CoA or senecioate. It is concluded that the barrier caused by the methyl group of 2‐oxoisocaproate is surmounted in higher plant peroxisomes in a manner

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00764.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractWhen exposed to constant white light for four weeks, isolated nodes ofChara fragilisDesv. regenerated side branches, rhizoids, and multicellular protonemata, the latter being similar to those germinated from oospores. When kept in darkness the nodes developed protonemata exclusively. These were single‐celled, colourless, and tip‐growing and, with the light microscope, they looked like rhizoids. Upon exposure to blue light, but not to red or far‐red, the growth rates of the protonemata rapidly declined, the cell apices swelled, and the nucleus migrated acropetally. Within 24 h the cells went through the first of a series of divisions resulting in the formation of multicellular protonemata. When returned to darkness after a blue light pulse of 5 h the cell divisions proceeded normally, but the protonemata showed etiolated growth. While growth of the internode was drastically promoted, the development of the multicellular apex and the lateral initial were suppressed. Both uni‐ and multicellular etiolating protonemata showed negative gravitropism but were phototropically insensitive. It is argued that the single‐celled protonema is an organ specialized for the penetration of mud covering the nodes or oospores ofCharaand thus serves to search for light, comparable to etiolated hypocotyls and stems in seedlings of high

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00765.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractDetailed morphometric analysis of cell shapes and an immunofluorescent study of microtubules were carried out on primary roots ofZea maysL. Two types of cells were found to be formed within the postmitotic isodiametric growth (PIG) region of the root cortex that were differentially responsive to low level of exogenous ethylene. The innermost and central cell rows of the cortex were sensitive to ethylene treatment and showed a disturbed distribution of cortical microtubules (CMTs) as well as changed polarity of cell growth, whereas the 2–3 outermost cell rows were less sensitive in this respect. This suggests that post‐mitotic cells of the inner cortex are specific targets for ethylene action. These properties of the inner cortex are compatible with its cells being involved in the formation of aerenchyma; they may also favour root growth in compacted soil. By contrast, the specific properties of the outer cortex indicate that this tissue domain is necessary for the gaseous impermeability and the mechanical strengthening of subjacent aerenchymatous cortex, especially in the mature region of the root.Ethylene affected neither the pattern of cortical cell expansion in the meristem nor the position of the PIG region with respect to the root tip. This contrasts with gibberellin‐deficiency which affected these parameters in both parts of the cortex. These observations indicate a fundamental difference between the role of these two phytohormones in the morphogenesis and development of maize

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00766.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractA monoclonal antibody PA3‐2‐B3, IgG1(Λ) is described which specifically recognizes phaseic acid and shows very little cross‐reactivity (0.14%) with abscisic acid or dihydrophaseic acid (0.88%). Based on this antibody, an enzyme immunoassay was developed which displays a linearity range from 15 pg to 3 ng of phaseic acid. Results obtained with this assay agree with those obtained by gas chromatography‐electron capture detection. Using the novel enzyme immunoassay, as well as an established immunoassay for abscisic acid, levels of these two compounds in leaves ofPhaseolus vulgariswere determined as a function of plant age, water stress, recovery from stress, and feeding of abscisic acid through the transpiration stream. The production of phaseic acid in a microsomal system from bean leaves was demonstrated. The results show a regulation of the plant's capacity to metabolize abscisic acid to phaseic acid as a function of wate

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00767.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractLateral root development in onion is accompanied by a variety of anatomical and permeability changes in some cells of the adventitious root. The endodermal Casparian band of the parent root is disrupted early in the development of the lateral but later extends so as to be continuous with the developing Casparian band of the new root. The lateral root emerges through a longitudinal split in the adventitious root exodermis and epidermis. Following this, the cell walls and intercellular air spaces adjacent to the lateral become incrusted with suberin and a small amount of lignin, forming a collar of modified tissue around the lateral. Subsequent radial expansion of the lateral distorts the adjacent cells of the adventitious root and forces a tight association between it and the lateral. The apoplastic permeability of lateral/parent root junctions was tested using Cellufluor, an apoplastic fluorescent dye which binds to cellulose. Prior to lateral root emergence, no dye enters the parent root cortex due to the Casparian band of the exodermis. Immediately after emergence, dye often penetrates through the break in the exodermal Casparian band and diffuses into the first cortical cell layer. However, when the collar of suberized cells develops (two days after lateral root emergence), movement of the dye into an undisturbed adventitious root is usually prevented (i.e., in 77% of the cases examined). In contrast, only 17% of the root systems which were transplanted just prior to treatment excluded the dye. This indicates that the apoplastic seals around the laterals are sensitive to movement and we recommend that only undisturbed root systems be used for permeability studies.

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00768.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractCardiac glycoside transport was investigated on the organ and whole plant level. Uptake experiments were carried out with shoot and root cultures ofDigitalis lanata. In both systems primary cardenolides, i.e., those with a terminal glucose in their oligosaccharide side chain, were taken up against their concentration gradient, whereas the glucose‐free secondary cardenolides were not. Active uptake of primary cardenolides was further evidenced by KCN inhibition of uptake. Using plantlets grownin vitrothe long‐distance transport of primary cardenolides from the leaves to the roots was demonstrated. Cardenolides were also detected in etiolated leaves, induced on plants with green leaves, which are supposed to be unable to synthezise cardenolidesde novo, providing further evidence for long‐distance transport. Several primary cardenolides were detected in the honeydew excreted by aphids fed onDigitalis lanataleaves, indicating that the phloem is a transporting tissue for cardenolides. On the other hand, the xylem sap obtained by applying the pressure‐chamber technique was cardenolide‐free. It was concluded that inDigitalisprimary cardenolides serve as both the transport and the storage form of cardenolides. After their synthesis they are either stored in the vacuoles of the source tissue or loaded into the sieve tubes, from which they are unloaded at other sites where they are trapped in the vacuoles of the respective si

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00769.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractCyanelles fromCyanophora paradoxacan easily be isolated and assayed for their carrier composition by the silicone oil filtering technique. The present investigation demonstrates a Pi‐translocator transferring phosphate, dihydroxyacetone phosphate and 3‐phosphoglycerate in a counter exchange mode in cyanelles as in chloroplasts of higher plants. The uptake of Piis inhibited by dihydroxyacetone phosphate, phosphoglycerate and glucose‐6‐P, only poorly by phosphoenolpyruvate and not by 2‐phosphoglycerate. The inhibitors pyridoxalphosphate and 4,4′diisothiocyanostilbene‐2,2K'disulfonic acid at low concentration also affect Pi‐uptake. Cyanelles probably transport photosynthate (reductant and ATP) by triosephosphates. This is the first demonstration of a phosphate translocator in an organism of a low evolutionary scale. Cyanelles also transport glucose which proceeds in two phases. In the lower concentration range (≤ 2.5 mM), glucose penetrates by facilitated diffusion, whereas transport follows first‐order kinetics at higher amounts (>2.5 mM). In the low concentration range, glucose‐transport is affected by high concentrations of 3‐O‐methylglucose and fructose. The physiological role of the glucose‐transport carrier inCyanophorais doubtful. It may function in transporting glucose into cyanelles if the carbon level inside them becomes lim

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00770.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe present investigation showed that isolated cyanelles fromCyanophora paradoxaselectively enriched glutamine from the external medium, whereas glutamate poorly penetrated into these organelles. Glutamine uptake proceeded in two phases, presumably involving a low and a high affinity system. The uptake of glutamine was significantly enhanced by 2‐oxoglutarate and light. Inhibitor experiments indicated that glutamine and 2‐oxoglutarate were converted to glutamate by a ferredoxin‐dependent glutamate synthase (GOGAT) reaction inside the cyanelles, and the glutamate formed at best slowly left these organelles. Such results were obtained independently of each other by measuring either the14C‐glutamine uptake or the 2‐oxoglutarate and glutamine‐dependent O2evolution. Glutamine is suggested to be the N‐compound which is supplied to the eukaryotic host. Glutamine could be exported jointly with 2‐oxoglutarate, possibly employing a common carrier. Cyanelles have apparently evolved glutamine (and oxoglutarate) carrier(s) with properties not yet described for any

ISSN:0932-8629    

DOI:10.1111/j.1438-8677.1993.tb00771.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY