Turnip Seedlings Research Articles

Antiserum againstXanthomonasphytopathogen inhibits host—Pathogen interaction in seedlings ofBrassica campestris

Xanthomonas campestris pv campestris (X.c.c.), the causal agent of crucifer black rot, causes turnip seedlings to collapse and rot. X.c. pv vitians (X.c.v.) is a non-pathogen of turnips and triggers a resistance response. Transconjugants of X.c.c., containing defined fragments of DNA from X.c.v., which have reduced pathogenicity to turnips were constructed. A polyclonal antiserum raised against X.c.v. restored the pathogenicity of one of these transconjugants. Antiserum ‘purged’ by reaction with sonicates of X.c.c. was equally effective in restoring pathogenicity. The purged antiserum recognised considerably fewer components than the original antiserum following Western blotting of bi-dimensional gels. This subset of antigens appeared to be localised primarily on the bacterial cell surface. The results indicate the potential use of purged polyclonal antisera in identifying bacterial determinants that trigger host resistance responses.

Identification of plant-induced genes of the bacterial pathogen Xanthomonas campestris pathovar campestris using a promoter-probe plasmid

A promoter-probe plasmid suitable for use in Xanthomonas campestris pathovar campestris (causal agent of crucifer black rot) was constructed by ligating a broad host range IncQ replicon into the promoter-probe plasmid pKK232-8, which contains a promoterless chloramphenicol acetyltransferase gene. Xanthomonas chromosomal DNA fragments were 'shotgun' cloned into a restriction site in front of this gene, and the resulting library was transferred en masse into Xanthomonas. Individual transconjugants possessing DNA insertions with promoter activity in plants were identified by virtue of their ability to infect chloramphenicol-treated turnip seedlings. Of 19 transconjugants identified in this way five were chloramphenicol resistant both in turnip seedlings and on agar plates. However the remaining 14 were only chloramphenicol resistant in planta, and thus apparently contained plant-inducible promoter fragments. Resistance to chloramphenicol was correlated with increased chloramphenicol acetyltransferase activity for the transconjugants assayed. The promoter fragments were used to isolate genomic clones from a library, and the role of the genes contained in these clones in pathogenicity is being investigated.

Activities and subcellular localization of enzymes responsible for lipolysis and gluconeogenesis during the germination of Brassica campestris cv. esculenta seeds

During the growth of turnip seedlings, two new lipases have been demonstrated, one with a maximum activity at pH 4.5 (acid lipase) and the other with a maxima at pH 8.6 (alkaline lipase). Many different enzymes are involved in gluconeogenesis: catalase, isocitrate lyase, malate synthetase, malate dehydrogenase, aconitase, citrate synthetase, fumarase, glycolate oxidase, phosphoenol-pyruvate carboxykinase. All of these show maximum activity coinciding with the stage in which lipid hydrolysis is maximal and when the accumulation of soluble carbohydrates has also reached its peak. The alkaline lipase as found to be located mainly in the spherosomes, whereas the glyoxysomes contained the following main activities: catalase, isocitrate lyase, malate synthetase, malate dehydrogenase and citrate synthetase. Aconitase, together with cytochrome oxidase and fumarase showed their highest activity in the mitochondria, and the presence of malate dehydrogenase, citrate synthetase and glycolate oxidase was also observed in these organelles. In the membrane-bound fraction, the activities of cytochrome reductase, glycolate oxidase and phosphoenol-pyruvate kinase were marked, although the latter enzyme was even more active in the soluble fraction.

Isolation of Mutants of Xanthomonas campestris pv. campestris Showing Altered Pathogenicity

A procedure has been developed for rapidly inoculating large numbers of turnip seedlings with Xanthomonas campestris pv. campestris, the causal agent of black rot of crucifers. Following mutagenesis bacterial mutants were isolated which showed altered pathogenicity. The mutants gave a range of responses on plants and some were impaired in their ability to grow in seedlings.

Effect of Ethanol Treatment on Apparent Phytochrome Synthesis and Anthocyanin Formation in Turnip Seedlings (Brassica rapa L.)

Summary Ethanol inhibits apparent new synthesis of phytochrome. The inhibition is relieved upon transfer to water. The capacity for anthocyanin formation in response to prolonged far red or blue light following treatment with ethanol is enhanced only in far red light although under both light qualities pre-treatment with ethanol leads to a considerably reduced hypocotyl elongation.

Cabbage Maggot Control, 1979

Abstract Plots were planted and treated Jun 26 at our vegetable entomology research farm in a Lima silt loam soil. Seeds of both crops were planted at 10/ft and treatments were applied using cone seeders. Germination counts were made Jul 16. Turnip seedlings were then thinned to ca 2/ft and cabbage to ca 1/1.5 ft. Plots consisted of a single row, 25 ft long, replicated 4 times in a randomized complete block design. Insecticide applications were based on a 24 in row width. All in-furrow and foliar sprays were applied using a CO2-powered sprayer delivering 82 GPA mounted on one of the cone seeders. Injury ratings were made by pulling 10 roots/plot, washing them, and counting the number of tunnels present. Turnips were examined Sep 10 and cabbage Sep 12.

Soil crust strength measurement

Abstract Modulus of Rupture measurements on 8 soils treated and untreated with soil conditioner showed that conventional MOR measurements are not appropriate for measuring the strength of rain‐induced soil crusts, because the formation of the crust imposes certain modifications in the method. A modified method for MOR measurements was compared with two other methods of measuring soil crust strength. Results from all three methods correlated well with each other, but gave a correlation of only approximately 0.6 with emergence of turnip seedlings. The disadvantages of the MOR and Fishing Line methods are discussed, and the use of the Shear Vane Penetrometer proposed.

Photocontrol of Anthocyanin Synthesis

Streptomycin enhances the synthesis of anthocyanins and inhibits the synthesis of chlorophylls and the development of chloroplasts in dark-grown seedlings of cabbage (Brassica oleracea), mustard (Sinapis alba), tomato (Lycopersicon esculentum), and turnip (Brassica rapa) exposed to prolonged periods of irradiation in various spectral regions. These results suggest that the contribution of photosynthesis to light-dependent high irradiance reaction anthocyanin synthesis in seedlings of cabbage, mustard, tomato, and turnip is minimal, if any at all. So far, phytochrome is the only photoreceptor whose action in the control of light-dependent anthocyanin synthesis in seedlings of cabbage, mustard, tomato, and turnip has been satisfactorily demonstrated.

Effects of Concentration and Time of Exposure on the Phytotoxicity of Linuron

When seedlings of lettuce and turnip were grown in nutrient solutions containing different concentrations of linuron, the concentration in the shoot at the time when toxicity symptoms appeared was related to the solution concentration. With lettuce, for example, symptoms were recorded after 7 d at 0.15 μg/ml and the shoot concentration was 2.7 μg/g fresh wt. At 0.06 μg/ml, symptoms appeared after 10 d and the shoot concentration was then 1.1 μg/g fresh wt. If grown for different periods in solutions containing linuron and then transferred to fresh nutrient solutions containing no herbicide, turnip or lettuce seedlings which had accumulated 0.7–0.8 μg linuron/g fresh wt developed toxicity symptoms 4 to 6 d later. Seedlings were also treated with linuron after they had grown for different periods in control nutrient solutions. The shoot concentrations attained before toxicity symptoms appeared were higher in those seedlings which were larger when herbicide treatment began. These results show that the herbicide concentration in solution, time of exposure, and age of seedling are interrelated in determining linuron phytotoxicity.

Absorption and Translocation of Atrazine and Linuron by Plants with Implications Concerning Linuron Selectivity

The absorption and translocation of atrazine and linuron by carrot, parsnip, lettuce, and turnip seedlings in culture solutions were measured. There were marked differences among species in the distribution of herbicide within the plant. A high proportion of the linuron absorbed by carrot and parsnip seedlings was retained in their root systems whereas in lettuce and turnip over 60 per cent of the herbicide absorbed was translocated to the shoot. With atrazine, differences were also apparent but were much less marked. The amounts of herbicide translocated were directly proportional to the amounts of water transpired by the plants but the effective concentrations in the transpiration stream were always less than those in the treatment solutions. Examination of the extracts from the different plant species by thin-layer chromatography showed that up to 45 per cent of the linuron translocated in parsnip and carrot was present as metabolites, but little metabolism had occurred in the shoots of lettuce and turnip or in the roots of any of the species. The data suggest that the tolerance of parsnip and carrot seedlings to linuron results from a combination of root fixation and metabolism in the shoot.

Phytochrome and Photosystem I Interaction in a High-Energy Photoresponse

AT LEAST TWO PHOTOREACTIONS CAN BE DEMONSTRATED IN PLANT DEVELOPMENTAL RESPONSES: the low-energy requiring phytochrome system and the high energy reaction. The action of these photoreactions on the formation of anthocyanin by turnip seedlings is discussed. The synthesis of small amounts of anthocyanin can be controlled solely by phytochrome, as evidenced by the red-far-red photoreversible effect of brief irradiations. Appreciable synthesis requires prolonged irradiations, the duration of irradiation being more important than intensity. The data presented suggest that the energy dependence of anthocyanin synthesis arises through photosynthesis. A mechanism for the interaction between photosynthesis and phytochrome is suggested. Under conditions of natural illumination of plants, the concentration of the species of phytochrome that absorbs far-red light may be lower than previously realized.

Contributions of Photosynthesis and Phytochrome to the Formation of Anthocyanin in Turnip Seedlings

Turnip seedlings (Brassica rapa L.) irradiated for 24 hours with radiation at 720 nanometers synthesize chlorophyll a and anthocyanin. Antimycin A and 2,4-dinitrophenol, which are known to reduce cyclic photophosphorylation, also reduce anthocyanin synthesis. Noncyclic photophosphorylation is inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea and o-phenanthroline. These compounds promote cyclic photophosphorylation and anthocyanin synthesis. On the basis of these findings it is suggested that the photomorphogenic response of anthocyanin synthesis in turnip seedlings arises in part through photosynthetic activity.Phytochrome involvement in turnip seedling photomorphogenesis is evidenced by the photoreversibility of anthocyanin synthesis in response to 5-minute irradiations with red or far red light. The inhibition of anthocyanin synthesis by 2,4-dinitrophenol does not arise from a destruction of phytochrome photoreversibility.It is suggested that plant photomorphogenic responses to prolonged far red irradiations arise through the photochemical activation of at least two pigment systems; namely, the photosynthetic pigments and phytochrome.

Photocontrol of anthocyanin formation in turnip seedlings

When irradiated for a period of 48 hours with light of restricted wave-lengths in the red and far-red regions, maximum anthocyanin content in hypocotyls was found at 730 nm; in cotyledons the yield at 716 was almost equal to that at 730 nm.In hypocotyls the effectiveness of 703, 716 and 760 nm light was much increased if plants were transferred to red light after 6 hours. The intermediate wave-length band centred at 703 nm was ineffective when given alone but led to a high yield if followed by red light. When given before far-red light (standard far-red field), 6 hours at 703 nm reduced anthocyanin yield in the same way as red light; when given after 6 hours of far-red, however, 703 nm light did not act like red light to sustain a high rate of anthocyanin synthesis.It is concluded that two reactions are involved in the photocontrol of anthocyanin formation in turnip seedlings.

Photocontrol of anthocyanin formation in turnip seedlings

Kinetic studies of anthocyanin formation in far-red and red light given in various combinations have shown that the responses to the two wave-lengths are different and depend on the sequence of irradiation. Red light reduced the effectiveness of subsequent prolonged far-red regardless of whether red began the irradiation or was interposed after several hours of far-red. However, far-red eventually regained some activity to a degree which depended on seedling age and the duration of the initial exposure to red light. It is suggested that red light may act by destroying the labile form of phytochrome (presumed to be required for far-red action) and that the resumption of far-red activity may indicate new synthesis of such phytochrome.When given after several hours of far-red, the yield in prolonged red light was markedly increased and, in intact hypocotyls, anthocyanin synthesis then proceeded as rapidly in red as in far-red. Far-red also increased the yield in subsequent red light when given after an initial irradiation with read and, under these conditions, anthocyanin yield in hypocotyls was even greater if seedlings were transferred to red light than if the far-red was continued. Red light appeared to favour formation of anthocyanin in the hypocotyl and it is possible that the action of red is to block synthesis in the cotyledons thus leading to an increased translocation of substrate to the hypocotyl. A number of treatments increased the yield of cotyledons in red light but, unlike the hypocotyls, they never reached that obtained with far-red. Several observations indicated that the increased effectiveness of red, when given after far-red, might be due to the accumulation of substrate in far-red, which is then converted to anthocyanin by the action of the stable form of phytochrome.

Photocontrol of anthocyanin formation in turnip seedlings

As measured by in vivo spectrophotometry the phytochrome content in etiolated turnip seedlings was higher in cotyledons than in hypocotyls; in the latter, it is confined to the apical part. During early growth in darkness the amount increased in both tissues to a maximum, reached about 40 hours after sowing; the levels then gradually declined. Separation of seedlings into hypocotyl and cotyledons increased the rate of phytochrome loss in the former, but not in the latter.Following 5 minutes of red light P frdecayed very rapidly in darkness; after 1.5 hours all of the phytochrome was present as P r, which was presumably not converted initially. In continuous red light the total phytochrome was reduced to below the detection level within 3 hours. Seedling age markedly affected the loss of phytochrome following red light; more was destroyed in older than in younger hypocotyls and apparent new synthesis occurred only in young seedlings. The capacity to synthesise phytochrome differed in cotyledons and hypocotyl. In cotyledons, synthesis occurred following shots of red light varying from 10 seconds, to 6×I minute, but the amount of newly formed phytochrome was not related to the amount destroyed: after 5 hours of continuous red light no new synthesis occurred. In hypocotyls, the amount of phytochrome synthesised was related to the amount previously destroyed, and the phytochrome content after 24 hours of darkness was similar following all red light treatments of 1 minute or longer: new synthesis occurred following 5 hours of continuous red light.In far-red light phytochrome decayed very slowly, approaching the limit of detection after 48 hours. In cotyledons some loss was already observed after 5 hours of far-red and, in hypocotyls, after about 10 hours.These results are discussed in relation to the possible role of phytochrome as the pigment mediating anthocyanin synthesis in prolonged far-red light.

Photocontrol of anthocyanin formation in turnip seedlings

The insertion of a dark period during irradiation with far-red resulted in the occurrence of a second lag-phase in the synthesis of anthocyanin when the seedlings were returned to light. The length of this second lag-phase was similar, to the first. It is suggested that the action of far-red light may not involve gene activation but rather the formation of substrate(s); the lag-phase may arise from ratelimiting steps in the synthesis of anthocyanin pigment.

Photocontrol of anthocyanin synthesis in turnip seedlings

Separation of hypocotyls and cotyledons of turnip seedlings (Brassica rapa) reduced the yield of anthocyanin from the former. Feeding with a combination of phenylalanine, acetate and glucose (PAG) considerably increased anthocyanin synthesis in these excised hypocotyls. In blue light the yield equalled that of the controls with cotyledons attached but, in far-red, the maximum obtained was never more than 55% of the controls.A long pre-treatment with red light markedly reduced anthocyanin formation in far-red. In young seedlings (presumed to be still capable of de novo phytochrome synthesis) this effect could largely be overcome by feeding with the same phenylalanine-acetate-glucose medium used with isolated hypocotyls but, in older seedlings, feeding did not prevent the effect of pre-irradiation with red light. It is concluded that red light not only destroys phytochrome but also leads to substrate disappearance.Without feeding pre-irradiation with red did not materially affect the yield from blue light; the addition of the phenylalanine-acetate-glucose mixture caused a significant increase compared with treatments without pre-red in both older and younger seedlings, particularly in the hypocotyl. The blue sensitive system thus appears to be independent of phytochrome destruction.Feeding also increased yields in red light. In water 72 hours red was no more effective than 24 hours: with PAG the longer irradiation period resulted in a considerably increased yield, especially in younger seedlings. The low yields in red light thus appear to result partly from substrate deficiency.

Photocontrol of anthocyanin formation in turnip seedlings

The substitution of far-red for the first six hours of a prolonged irradiation with red light resulted in a large increase in anthocyanin yield, which was greater than the combined yields from far-red and red when the two treatments were given separately. When intermittent far-red irradiation was followed by a single short exposure to red, a considerable amount of anthocyanin was formed, although each treatment given separately had little effect. Four hours continuous far-red alone yielded some anthocyanin and also resulted in a further large increase in the effect of a short red treatment; this terminal red effect was fully reversible by a subsequent brief exposure to far-red. It is concluded that at least two photochemical reactions are involved in the responses to red and far-red, the first leading to the formation of substrate(s) used in the second reaction.When red light preceded exposure to the far-red/red irradiation sequence, the far-red enhancement effect was almost entirely lost and the anthocyanin yield approached that in red light. The effect of the red pre-irradiation treatment is attributed to destruction of phytochrome and it is suggested that phytochrome is the only pigment mediating anthocyanin synthesis in red and far-red. A possible interpretation is that the "high-energy" reaction in far-red and the low energy red/far-red reversible reaction are mediated by different forms of phytochrome.The substitution of blue for the first six hours of a prolonged irradiation with red light also resulted in a synergistic increase in anthocyanin yield; the enhancement effect of blue light was, however, not prevented by prior exposure to red. It is concluded that phytochrome is not the only pigment mediating the reactions occurring in blue light. The synergism between blue and red suggests that the "high-energy" reaction in blue light may lead to the production of substrates for phytochrome action.

Photocontrol of anthocyanin formation in turnip seedlings

Photocontrol of anthocyanin formation in turnip seedlings

Photocontrol of anthocyanin formation in turnip seedlings

The substitution of red or blue light for the first six hours of prolonged irradia tion with far-red light reduced anthooyanin formation by about 60% ; red or far-red light similarly substituted for blue light had little effect. It is concluded that the effects of prolonged irradiation with blue and far-red depend, in part at least, on different photoreceptors. The effects of pre-treatment with red or blue light also occurred when only short exposures to light were given, and were reversed by immediate brief exposures to far-red. The depressing effect of a short pre-irradiation treatment was largely prevented if seedlings were kept at low temperature or in an atmosphere of nitrogen in the dark period before transfer to the prolonged far-red treatment. The effect of the pre-irradiation treatment is attributed to enzymatic destruction of phytochrome following conversion to the PF R form, and it is suggested that anthocyanin synthesis in far-red light largely depends on phytochrome, possibly due to the maintenance of a low level of PFR in the tissue by the absorption tail of PR in the far-red. A pre-irradiation treatment with red also decreased the inhibitory effect of far-red on hypocotyl elongation but did not change the response to blue light.