摘要:

Growth substances, α‐naphthaleneacetic (NAA) and kinetin, had an important role in the regulation of lateral root (LR) formation in lettuce (Lactuca sativaL. cv. Grand Rapids) seedling roots. NAA (10‐5M) was a potent stimulator of LR initiation and caused a 600% increase in the number of lateral root primordia (LRP) compared to untreated roots. NAA was required for only the first 20 h of the 72 h treatment period for maximum stimulation of LRP initiation. Kinetin (2 × 10‐5M) effectively prevented the spontaneous formation of LRP and inhibited the NAA‐stimulated production of LRP. Kinetin inhibition was maximal during the first 20 h of NAA treatment and this effect was not overcome by subsequent supply of NAA. Also, lettuce roots were most sensitive to kinetin at 20 h of NAA treatment, when the first signs of cell division were observed in the

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05643.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Thin cell layers excised from tobacco (Nicotiana tabacumL. cv. Samsun) stem internodes, with an appropriate exogenous hormonal balance, were able to form a greater number of roots, and in a larger percentage of the explants (93%) than when they were excised from pedicels (40%). The developmental sequence of root formation and explant growth were followed by histological analysis. Free and bound [trichloroacetic acid (TCA)‐soluble and ‐insoluble] putrescine and spermidine increased in the explants, particularly when root meristemoids appeared. These meristemoids originated in the superficial (day 6 in culture) or deep (days 10–11) layers and inside the newly formed callus (day 25). At those times, TCA‐soluble and, to a lesser extent, TCA‐insoluble bound putrescine predominated over the other polyamines. Spermine was always present in trace amounts. Polyamines decreased again when root and callus formation was completed (day 30). The involvement of these three classes of polyamines (free, TCA‐soluble and ‐insoluble) in morphogenic processes

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05644.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The biosynthesis of cotton (Gossypium hirsutumL. ‘Stoneville 208′) peroxidase (EC 1.11.1.7) has been investigated in an organ culture system, since this enzyme may play a role in cell wall biogenesis or host defense mechanisms. Electrophoretic analysis of proteins from cotton ovule cultures indicated relatively few proteins being released into the surrounding medium. De novo synthesis of released peroxidase and other medium proteins was determined by in vivo labeling of ovule cultures with [35S]‐methionine. Analysis of labeled culture medium by denatured gel electrophoresis followed by fluorography showed incorporation of isotope into 2 major proteins with molecular weights of 30 kD and 56 kD, as well as a limited number of minor proteins. Similar analysis of native isoelectric focusing gels coupled with autoradiography demonstrated [35S]‐methionine incorporation into 2 major proteins with pI values of 4.3 and 5.0. The pI 5.0 protein was shown to have a molecular weight of 30 kD. The pI 4.3 protein had a molecular weight of 56 kD and was shown to be peroxidase by activity staining. Minor radiolabeled proteins were observed in the cationic region of the isoelectric focusi

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05645.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Superoxide dismutase (EC 1.15.1.1.) and catalase (EC 1.11.1.6.) activities ofFrankiacells grown in the presence of ammonium were very high in comparison with those of other prokaryaotes and particularlyRhizobium. Furthermore, these activities were significantly enhanced under nitrogen‐fixing conditions where vesicles were produced. By using a single‐step sucrose gradient,Frankiavesicles were isolated and appeared intact and free of hyphal contamination. The contents of superoxide dismutase and catalase in the purified vesicles were similar to those in preparations containing both vesicles and hyphae. These results suggest an important role of superoxide dismutase and catalase in the protection of the overall nitrogen‐fixation process against O2inFrankiavesicles. Beside the protective role played by the thick walls of the vesicles, the presence of specialized enzymes is empha

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05646.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Diurnally grown barley (Hordeum vulgareL. cv. Clipper) seedlings of various ages (3–4, 5–6 and 10–11‐days‐old) were transferred to darkness for 17 h and changes in leaf fresh weight, chlorophylla, chlorophyllband protochlorophyllide measured. The results were consistent with previous evidence of a light‐independent chlorophyll biosynthetic pathway in light‐grown barley. There was a net gain in chlorophyll (μg leaf‐1) in 5–6‐ and 10–11‐day‐old plants after 17 h dark treatment. The amounts of chlorophyll that accumulated were similar (5.9 and 4.3 μg Chl leaf‐1), despite a twofold difference in leaf size at T0. The rate of leaf expansion in 5–6‐day‐old plants greatly exceeded the rate of chlorophyll accumulation and leaves were noticeably paler after dark treatment i.e. there was a reduction in chlorophyll concentration (μg g fresh weight‐1) in spite of an increase in chlorophyll content (μg leaf‐1). The ability of light‐grown barley to accumulate chlorophyll in darkness was a function of seedling age. Very young seedlings (3–4‐day‐old) generally lost chlorophyll in darkness. The decrease in chlorophyll per leaf resulted mainly from loss of chlorophyllb. Preferential loss of chlorophyllbresulted in dramatic increases in the chlorophylla:bratio. Since 3–4‐day‐old seedlings (1) accumulated 5‐aminolevulinic acid in the presence of levulinic acid at a rate comparable to older seedlings, and (2) converted exogenous 5‐aminolevulinic acid to chlorophyll in the absence of light, it is unlikely that failure of the youngest plants to accumulate chlorophyll in darkness was due to blocks at these steps in the pathway. Net loss of chlorophyll (μg leaf‐1) in 3–4‐day‐old seedlings in darkness was eliminated by the addition of chloramphenicol, which occasionally produced a small, but significant, gain in total chlorophyll. These results imply that chlorophyll degradation in young barley leaves is strongly influenced by the chloroplast genome, and is a major factor influencing changes in chlorophyll levels in darkness. The present findings are consistent with the suggestion that the failure of 3–4‐day‐old barley seedlings to accumulate chlorophyll in darkness may be due to chlorophy

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05647.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

A hypertonic mannitol shock enhanced K+uptake byBeta vulgarisL. (cv. early flat Egyptian) storage tissue slices and also increased the inositol 1,4,5‐trisphosphate [Ins(1,4,5)P3) content of the slices as well as ofSorghum bicolorL. (cv. Hazera) andVigna radiataL. (cv. unknown) roots. K+uptake byB. vulgarisslices could be enhanced, in the absence of mannitol, by application of effectors that mimic products of the phosphatidylinositol 4,5‐bisphosphate (PIP2) turnover cycle. Maximal Ins (1,4,5)P3content was found 10 min after hypertonic induction and maximal K+uptake was obtained 10 min later. The hypertonic mannitol shock, administered to intactB. vulgarisslices, also enhanced the phosphorylation of a 39 kDa protein in the plasmale

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05648.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The Mg2+‐dependent activity of the tonoplast pyrophosphatase (PPase) was investigated by measuring proton transport and by using the acridine orange technique on intact vacuoles of the aquatic liverwortRiccia fluitansL. In solutions with both Mg2+and pyrophosphate present, a number of complexes are formed, which could all influence the enzymatic and hence the transport activity of the PPase. Therefore, the individual concentrations of these complexes were calculated and their contributions to proton transport across the tonoplast were tested. From these experiments we conclude that Mg2+has three different roles: (i) Mg2+stimulates transport activity of the PPase. (ii) Mg2PPiinhibits PPase‐mediated H+transport, (iii) MgPPi* (= MgPPi2‐+ MgHPPi‐) is the substrate with an apparent K1/2= 5–10 μM, with no discrimination between MgPPi2

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05649.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Stress‐induced changes in proteins of molecular weights of 25 and 27 kDa are reported for NaCl‐adapted cells of Shamouti orange (Citrus sinensisL. Osbeck) and the cultivated VFNT cherry tomato (Lysopersicon esculentumMill.), respectively. Salt‐adapted cell lines of both species grew much faster in the presence of salt than non‐adapted cells and their growth rate was similar to that of non‐adapted cells in the absence of salt. Sodium dodecyl sulfate‐extractable citrus and tomato polypeptides were analyzed by one‐ and two‐dimensional polyacrylamide gel electrophoresis (PAGE). The enhancement of a citrus 25 kDa protein associated with salt tolerance was actually resolved only on two‐dimensional PAGE. It is a constitutive protein, i.e. it was present in salt‐tolerant ceils whether grown in the presence or absence of salt. The NaCl‐induced changes of the tomato 27 kDa protein could be resolved on one‐dimensional PAGE. This protein was first markedly suppressed by a salt shock and the time required for its recovery was dependent on the degree of salt tolerance. Prolonged adaptation resulted in an increase of this protein. Protein profiles of citrus and tomato cells grown in the absence and presence of salt revealed that while in citrus the level of most proteins was suppressed in the presence of salt, the opposite was true for tomato proteins under similar conditions. Comparison between the changes in citrus and tomato and results already published for tobacco show that many salt‐induced changes in proteins are species‐specific and that no

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05650.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The nectar ofStrelitzia reginaeAit. was analysed using enzymatic methods and found to contain glucose, fructose and sucrose. Sugar composition changed considerably over the nectar producing period: there was an increase in the amount of glucose (41%) and fructose (32%) between the early and middle stage of secretion and thereafter a decrease of 13 and 24%, respectively, towards the end of secretion. Although the amount of sucrose secreted was initially as much as the glucose and fructose combined, it subsequently decreased, first by 14% and then by 70% at the end of the secretory period so that, whereas in the initial stages of secretion sucrose was quantitatively the dominant sugar, glucose and fructose made up the major part of the nectar as secretion reached its conclusion.The amounts of potassium and sodium remained at the same low level (around 150 and 30 μg g‐1[w/v) respectively) throughout secretion, while calcium (initially 18 μg g‐1) and magnesium (initially 8.0 μg g‐1) increased by 47 and 56% respectively, between the early and late stages of secretion. No free amino acids, inorganic phosphate or iron could be detected. Enzymatic analysis revealed only a trace amount of starch. Transmission electron micrographs from both immature and mature plants, however, showed starch grains among other cytoplasmic remnants in the nectary lumen. Mitochondria, vesicles, lipid droplets and ribosomes could also be identified among the luminal cytoplasmic

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05651.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Mesophyll protoplasts isolated from peeled oat (Avena sativaL. cv Victory) leaves with 1% (w/v) Cellulysin in 20 mMKPO4, pH 5.5 and 0.6Msorbitol retain about 6% of the polyamine oxidase (PAO, EC 1.4.3.4) activity of the whole peeled leaf. However, more than 99% of the oat leaf PAO activity is apoplastic and can be extracted by vacuum infiltration with 200 mMNaCl and this procedure extracts no activity for the cytoplasmic marker enzyme glucose‐6‐phosphate dehydrogenase (G6PD, EC 1.1.1.49). By these criteria we consider PAO in oat leaves to be totally apoplastic and PAO found in the isolated protoplast to be contamination. The degree of protoplast contamination by PAO depends on the pH and ionic strength of the isolating and washing medium. It can be eliminated by washing protoplasts in 0.6Msorbitol with 100 mMKPO4, pH 6.5. Pellets of lysed protoplasts incubated with dialyzed apoplastic enzymes in 5 mMKPO4, pH 5.5 adsorb about 87% of the added PAO activity but only about 25% of the added peroxidase (EC 1.11.1.7) activity. The adsorbed activity can be solubilized from the pellet by extraction with 1MNaCl. The results demonstrate that weakly ionically bound cell wall enzymes may contaminate protoplasts isolated and purified by conventional techniq

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1989.tb05652.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY