摘要:

Embryogenic cultures of cultivated carrot (Daucus crotacv. Scarlet Nantes) were initiated from seedling hypocotyls on hormone‐containing nutrient medium and from wounded zygotic embryos on hormone‐free medium. Both of these cultures were maintained with continuous multiplication as unorganized, embryogenic cell masses on hormone‐free medium at pH 4.0, containing NH+4as the sole nitrogen source. When grown on hormone‐free medium at pH 4.0, neither culture contained any elongated cells. Virtually all cells were densely cytoplasmic and nearly spherical. Some cells were enlarged, not densely cytoplasmic, but always spherical. When either culture was transferred to an auxin‐containing medium at pH 5.8, numerous elongated cells were produced. Elongated cells were observed when either naphthaleneacetic acid or 2,4‐dichlorophenoxyacetic acid was used, and whether the nitrogen source was NH+4alone or a combination of NH+4and NO−3. Elongated cells were more abundant when a combined nitrogen source was used. When cultures containing elongated cells were transferred to and multiplied on hormone‐free or hormone‐containing medium buffered at pH 4.0, all elongated cells disappeared after 2 weeks. No elongated cells were observed in any of the lines tested at pH 4.0. These results clearly show that it was the pH of the culture medium and not the presence or absence of an auxin or the nitrogen source(s) that permitted or prevented cell elongation in the embryogeni

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb04696.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Interaction between induction of carbonic anhydrase (CA) activity, induction of inorganic carbon (Ci) concentrating mechanisms and the photorespiratory glycolate pathway has been studied in wild type 6145c and photorespiratory mutant 18–7F (low in phosphoglycolate phosphatase activity) cells ofC. reinhardtii. Cell transfer from high CO2(5%, v/v) to low CO2(0.03%) provoked an increase of extracellular and total (extracellular plus intracellular) CA in both wild type and mutant cells. During adaptation to low CO2conditions, both strains excreted ammonium to the medium at a similar rate in the presence ofl‐methionine‐d‐l‐sulfoximine (MSX), an inhibitor of glutamine synthetase (GS). MSX also provoked ammonium excretion by air adapted wild type and mutant cells, even though both strains had high levels of CA activity and of Ciconcentrating activities.GS increased in both strains after transfer from high to low CO2conditions. However, this increase was abolished by aminooxyacetate, an inhibitor of the glyoxylate‐serine aminotransferase, and by glycolaldehyde, an inhibitor of triose phosphate to ribulose 1,5‐bisphosphate conversion. CA synthesis did not occur in the presence of either aminooxyacetate or glycolaldehyde. Algae grown in high CO2in the presence of aminooxyacetate did not induce Ciconcentrating mechanisms. Integration of these three processes, i.e., CA synthesis, Ci‐concentration, and photorespiratory glycolate pathway is proposed in the framework of carbon metabol

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb04697.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Raphanusanin is a plant growth‐inhibiting substance which plays an important role in light growth inhibition and phototropism of radish hypocotyls. We investigated the effect of raphanusanin on indole‐3‐acetic acid (IAA)‐mediated orientation of microtubules (MT) in the outer epidermal cells of radish hypocotyl segments using immunofluorescence microscopy. IAA‐mediated MT reorientation preceded cell elongation induced by IAA. A change of IAA‐mediated MT orientation from longitudinal to transverse started within less than 15 min after IAA treatment, while significant growth promotion induced by IAA was found within about 30 min. The IAA‐mediated transverse MT orientations were significantly inhibited by simultaneously added raphanusanin. We also investigated the effect of raphanusanin on the MT orientation of the segments pretreated with IAA. The change of MT orientation induced by raphanusanin preceded growth inhibition of the segments. Within about 60 min after its application, raphanusanin initiated inhibition of the steady‐state elongation pre‐induced by IAA, while IAA‐mediated transverse MT orientations started to change into longitudinal orientations within less than 30 min after application of raphanusanin. Based on these results, it is suggested that raphanusanin induces growth inhibition through interference with the auxin‐med

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb04698.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

A transducer was developed to record the circadian movement of the individual leaflets inOxalis regnelliiMig. The method can easily be adapted to measure other kinds of plant movements as well. It is based on the detection of the shadow each leaflet casts on the small side of a specially formed Perspex plate. The light is guided through the Perspex and collected by a phototransistor, which provides an electrical signal that is proportional to the light intensity falling onto it. The output signal can be made a linear function of the leaf angle. This equipment was used in experiments to study the coupling between the 3 leaflets inOxalis. Pulses of 4 h of red light were given to one of the leaflets, the two others were shielded from the light. A phase response curve was determined for each leaflet, but there was no significant difference in the phase response between the 3 leaflets. Experiments were also made in which the 3 leaflets were separated physically by cuts along the petiole between the pulvini. In this case ultradian oscillations were observed.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb04699.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

An investigation of the regeneration ability of explants taken from the floral stem ofBrassica napusvar.oleiferawas performed in the winter cultivars Darmor and Bienvenu. Our purpose was to compare the regeneration ability of the two genotypes, to compare the competence of the different tissues of the stem and then to study histologically the regeneration of shoots. A strong genotypic effect was observed between the two cvs; Bienvenu had a poorer ability to produce shoots when cultured in the presence of benzyladenine: regeneration commenced later; the percentage of explants producing shoots and the number of shoots per regenerating explant were much lower. The comparison between the regeneration ability of different explants, i.e stem segments, internal stem segments, thin cell layer and peels, showed that the superficial tissues were able to regenerate roots but not shoots. Contrariwise, internal stem segments regenerated only shoots. The origin of shoots was investigated in stem segments of cv. Darmor. A kinetic histological analysis showed the basic role played by phloem and phloem‐associated cells in shoot formatio

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb04700.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Nodulated lucerne plants (Medicago sativaL. cv. Aragón) were supplied with 20 mMnitrate. Anaerobically isolated bacteroids ofRhizobium melilotifrom these plants were able to denitrify after 48 h treatment.R. melilotibacteroids behave as total denitrifiers, reducing nitrate to dinitrogen: when acetylene was omitted from the assay medium very little nitrous oxide was recovered. The onset of denitrification activity was coincident with the induction of nitrite reductase activity (EC 1.7.99.3) whereas nitrate reductase activity (EC 1.7.99.4) was constitutive. Whole nodules from plants receiving several doses of nitrate were assayed, in a nitrate‐free medium, to monitor denitrification activity dependent on nitrate within the nodules. Denitrification activity was detected after 2 days of 20 mMnitrate supply or after 3 days in the presence of 10 or 5 mMnitrate. These results are discussed in relation to current controversy about nitrate entry into the infection region of nodules. It is concluded that this process occurs more rapidly than suggested in recent resear

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb04701.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Bean plantlets (Phaseolus vulgarisL. cv. Topcrop) were stressed at the age of 16–18 days by gradual (2–8%) or abrupt addition of 6% (w/v) polyethylene glycol Mw 6000 (PEG 6000) to Hoagland solution. Leaf conductance, photosynthesis, internal CO2partial pressure (Ci), relative water content (RWC), water content/dry weight (H2O/DW), apoplastic PEG concentrations and weight of leaves, stems and roots were determined. Leaf conductance, photosynthesis and Ciwere determined on non‐detached primary leaves, and leaf potentials (water, osmotic and turgor potentials) were investigated in freshly detached (non‐rehydrated) primary leaves, both in treated and control plants; RWC and osmotic potential were also assessed at the null turgor point. Low PEG 6000 concentrations induced early and evident decrease in leaf conductance and photosynthesis, whereas Cidecreased only moderately and tended to recover during advanced stress. There were moderate though significant decreases in RWC and H2O/DW, no change or increases in water potential, no significant changes in osmotic potential and a moderate but significant increase in turgor potential. Even when referred to null turgor point, RWC significantly decreased and osmotic potential was unchanged. It was concluded that apoplastic PEG 6000 accumulation at evaporating sites would account for the early decrease in conductance which would also justify the unchanged or the prevalent increase in water potential and turgor potential. The subsequent PEG diffusion and concentration in the leaf apoplastic water would have induced the RWC and H2O/DW decrease and the final turgor flexion doc

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb04702.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Polyclonal antibodies raised against NAD‐dependent glyceraldehyde‐3‐phosphate dehydrogenase (D‐glyceraldehyde‐3‐phosphate:NAD+oxidoreductase [phosphorylating], EC 1.2.1.12) from the plant cytosolic fraction of soybean [Glycine max(L.) Merr. cv. Williams] nodules were used to study the subcellular location of the enzyme and its relative distribution between infected, interstitial and cortical cells of soybean (cv. Lincoln) nodules. Post‐embedding immunogold labelling was carried out on nodules harvested 5, 12, 19 and 25 days after the first sign of nodulation. Labelling for glyceraldehyde‐3‐phosphate dehydrogenase was observed over the cytoplasm and nuclei of infected and uninfected cells, as well as over the nucleoid regions of bacteroids. In 5‐day‐old nodules, label also bound adjacent to the peribacteroid membranes. Statistical analysis of the number of gold particles per cell area indicated that in 5‐day‐old nodules, glyceraldehyde‐3‐phosphate dehydrogenase was distributed equally between infected, interstitial and cortical cells, but in older nodules the enzyme was more prominent in the interstitial and cortical

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb04703.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The organogenic potential of thin layer stem explants of non‐reproductive tobacco plants was tested on a hormone‐free medium and under various hormonal conditions. A comparison was made between thin layers excised from normal and transgenic plants at the same developmental stage. The transgenic plants were transformed by insertion of TR‐ and TL‐DNA fromAgrobacterium rhizogenes1855 root‐inducing plasmid. The aim was to identify hormonal conditions capable of stimulating the expression of the flowering competence present in the differentiated stem tissues at the induced stage before any visible sign of transition to reproductive development. Flower neoformation, observed at the end of the culture period (day 25), occurred on untransformed thin layers only with kinetin treatment. Explants from transgenic plants showed flower bud regeneration on hormone‐free medium, indoleacetic acid alone (1 μM), kinetin alone (1 μM), and most abundantly on indoleacetic acid plus kinetin (1 μMeach). No flower formation was observed on indolebutyric acid plus kinetin (10 μMand 0.1 μM, respectively) in both normal and transgenic explants. The latter treatment enhanced rooting instead, above all in the transgenic explants. On hormone‐free medium vegetative bud formation was well expressed both by untransformed and transgenic explants, and enhanced by the combined, equimolar concentrations of indoleacetic acid and kinetin.The results show that cytokinin allows flowering in florally determined stem explants from normal plants. In the transgenic explants, the flowering response increases when indoleacetic acid is added to cytokinin, thus suggesting a role for auxin in enhancing the expression of the florally determined state in thin cell layers of non

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb04704.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

We have isolated and sequenced cDNA and genomic clones fromArabidopsis thalianawhich specify a 241 residue protein with 84% sequence identity to a photosystem I Type I chlorophylla/b‐binding (CAB) protein from tomato. The open reading frame is interrupted by three introns which are found at equivalent positions as the corresponding introns in the tomato gene. Comparison to the amino acid sequence of other CAB proteins confirms that all CAB proteins share two regions of very high similarity. However, near the N‐terminus and between the conserved regions this light‐harvesting complex I (LHCI) protein, as other LHCI proteins from other plant species, has sequence motifs which appear to be PSI‐specific. Restriction analysis of genomic DNA shows that theArabidopsisprotein is encoded by a single‐

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1992.tb04705.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY