Gibberellin stabilizes microtubules in onion leaf sheath cells

Summary Colchicine and cremart (O-ethyl O-(3-methyl-6-nitrophenyl) N-sec-butylphosphorothioamidate) disrupt microtubules in leaf sheath cells of onion plants (Allium cepa L. cv. Senshu-Chuko) and cause cell swelling to make the basal parts of the plants bulbous. Gibberellin A₃(GA₃) protects microtubules from disruption by colchicine and cremart and suppresses the swelling caused by them. GA₃ also protects microtubules from disruption by low temperature.     

Functional characterisation of a cytokinin oxidase gene DSCKX1 in Dendrobium orchid

Cytokinin oxidase plays an important role in the cytokinin regulatory processes. We have cloned a novel putative cytokinin oxidase, DSCKX1 (D endrobium Sonia cytokinin oxidase), by mRNA differential display from shoot apices of Dendrobium Sonia cultured in the presence of BA. The DSCKX1 gene appears to have three alternative splicing forms and its expression of DSCKX1 was induced in a tissue-specific manner by cytokinins. In transgenic orchid plants overexpressing DSCKX1, the elevated level of cytokinin oxidase activity was accompanied by a reduction of cytokinin content. These plants exhibited slow shoot growth with numerous and long roots in vitro. Their calli also showed decreased capability of shoot formation. Conversly, antisense transgenic plants showed rapid proliferation of shoots and inhibition of root growth combined with a higher endogenous cytokinin content than wild-type plants. Thus DSCKX1 appears to play an important role on cytokinin metabolism and the related developmental programmes in orchid.     

Mitigation of growth retardation effect of plant defense activator,acibenzolar-<Emphasis Type="Italic">S</Emphasis>-methyl,in amaranthus plants by plant growth-promoting rhizobacteria

Four rhizobacterial strains and acibenzolar-S-methyl (ASM), a chemical activator, which suppressed foliar blight of amaranthus (Amaranthus tricolor L.) caused by Rhizoctonia solani Kühn were evaluated for their effect on plant growth. The experiments were performed both under sterile and non-sterile soil conditions, in the presence or absence of the pathogen. In all cases, plants treated with ASM showed significant reduction in growth, as determined by shoot length, and shoot and root dry weight when compared to other treatments. The growth retardation effect of ASM was more profound with respect to shoot length. Reduction in shoot length was least when plants were treated with a combination of the chemical activator and Pseudomonas putida 89B61 under non-sterile soil conditions in the absence of the pathogen. Both under sterile and non-sterile soil conditions, in the presence of the pathogen, reduction in shoot length due to application of ASM was diminished significantly when plants were treated with rhizobacterial strain Pseudomonas fluorescens PN026R. Combined use of plant growth-promoting rhizobacteria (PGPR) and ASM was found to be beneficial as the growth retardation effect of the plant defense activator was reduced by the growth-promoting ability of the rhizobacteria.     

Regeneration and characterization of plants from potato root lines transformed by Agrobacterium rhizogenes

Summary Transformed root lines were obtained after infection of leaf segments and tuber discs of tetraploid potato cvs Bintje and Desirée with Agrobacterium rhizogenes. In response to shoot induction, about 10% of the root lines produced shoots through callus formation. The tests for opine suggest that all 26 shoot lines of cv Bintje (Ri-Bintje) and 13 of Desirée (Ri-Desirée) were transformed. All shoot lines were tetraploid except for one octoploid subshoot line of cv Desirée; no aneuploids were observed. With the exception of two shoot lines derived from the same root line, all other Ri-Bintje plants showed a pattern of phenotypic variation, generally observed among transformed plants. In contrast, the phenotype of Ri-Desirée plants was uniform and normal; variation was observed in tuber form and size. Phenotypic variation observed among Ri-plants appeared to be mainly root line-dependent, particularly for height of plants and tuber size and form. Variation was also observed within root and shoot lines and was more pronounced among the Ri-Bintje plants. Segregation of phenotypic characteristics was observed among transformed plants, resulting in the occurrence of phenotypes resembling the control. Chromosomal stability and the frequent reversion to normal phenotype of Ri-plants make A. rhizogenes particularly suitable as a virulence vector in the binary transformation system for the transfer of desirable genes.     

Micropropagation of Rosmarinus officinalis L.

Single-node stem segments of Rosmarinus officinalis L. var. genuina forma erectus proved better explants than shoot tips (ca. 2 cm long) for extablishment of field-grown plants in aseptic cultures. Benzylaminopurine was far more effective than kinetin for shoot induction in shoot tips excised from aseptically-grown plants. Maximum numbers of shoot buds (ca. 14) were formed per explant at 0.2 mgl^-1 benzylaminopurine in 30 days. After further growth of isolated shoots and treatment with 0.25 mgl^-1 indolepropionic acid for 7 days, 80% shoots produced roots. In vitro raised plantlets were successfully grown in soil to plants. About 5,000 plants could be produced from a single nodal segment in 1 year.NBRI Research Publication No. 195 (N.S.)     

OsIMA1增强水稻对镉逆境的适应性

铁(Fe)是植物生长发育所必需的营养元素而镉(Cd)是对植物有害的元素且对植物Fe和Cd的吸收存在拮抗作用。OsIMA是一类正调控水稻Fe吸收的一类小肽,其过表达可以促进Fe的积累。为探究OsIMA是否参与水稻对Cd胁迫的适应性,该研究以水稻为研究材料,利用荧光定量PCR分析了OsIMA基因的表达水平,通过遗传转化和CRISPR/Cas9基因编辑技术构建了OsIMA1过表达植物和ima1突变体植物,评估了OsIMA1过表达和突变体植物在Cd逆境条件下的株高,并利用电联耦合等离子体质谱法测量了根和地上部的Fe和Cd含量。结果表明:(1)Cd处理后,OsIMA1和OsIMA2的转录水平上调。(2)OsIMA1过表达植物比野生型植物对Cd胁迫更耐受。(3)ima1功能缺失突变体比野生型植物对Cd胁迫更敏感。(4)OsIMA1过表达植株根系的Cd含量较高,而ima1突变体植株地上部的Cd含量较高。综上所述,OsIMA1通过限制Cd从根向地上部的转运以增强水稻对Cd逆境的适应能力,该研究结果为定向培育耐Cd作物提供了理论参考。     

Plant biomass partitioning and chemical defense: Response to defoliation and nitrate limitation

Summary Plant growth and allocation to root, shoot and carbon-based leaf chemical defense were measured in response to defoliation and nitrate limitation inHeterotheca subaxillaris. Field and greenhouse experiments demonstrated that, following defoliation, increased allocation to the shoot results in an equal root/shoot ratio between moderately defoliated (9% shoot mass removed) and non-defoliated plants. High defoliation (28% shoot mass or >25% leaf area removed) resulted in greater proportional shoot growth, reducing the root/shot ratio relative to moderate or non-defoliated plants. However, this latter effect was dependent on nutritional status. Despite the change in distribution of biomass, defoliation and nitrate limitation slowed the growth and development ofH. subaxillaris. Chronic defoliation decreased the growth of nitrate-rich plants more than that of nitrate-limited plants. The concentration of leaf mono- and sesqui-terpenes increased with nitrate-limitation and increasing defoliation. Nutrient stress resulting from reduced allocation to root growth with defoliation may explain the greater allocation to carbon-based leaf defenses, as well as the defoliation-related greater growth reduction of nitrate-rich plants.     

<Emphasis Type="Italic">In vitro</Emphasis> regeneration and plant establishment of <Emphasis Type="Italic">Tylophora indica</Emphasis> (Burm. F.) Merrill: Petiole callus culture

Summary A protocol has been developed for high-frequency shoot regeneration and plant establishment of Tylophora indica from petiole-derived callus. Optimal callus was developed from petiole explants on Murashige and Skoog basal medium supplemented with 10μM2,4-dichlorophenoxyacetic acid +2,5μM thidiazuron (TDZ). Adventitious shoot induction was achieved from the surface of the callus after transferring onto shoot induction medium. The highest rate (90%) of shoot multiplication was achieved on MS medium containing 2.5μM TDZ. Individual elongated shoots were rooted best on halfstrength MS medium containing 0.5μM indole-3-butyric acid (IBA). When the basal cut ends of the in vitro-regenerated shoots were dipped in 150μM IBA for 30 min followed by transplantation in plastic pots containing sterile vermiculite, a mean of 4.1 roots per shoot developed. The in vitro-raised plantlets with well-developed shoot and roots were successfully established in earthen pots containing garden soil and grown in a greenhouse with 100% survival. Four months after transfer to pots, the performance of in vitro-propagated plants of T. indica was evaluated on the basis of selected physiological parameters and compared with ex vitro plants of the same age.     

Restricted cell/cell communication in the shoot apex ofSilene coeli-rosa during the transition to flowering is associated with a high mitotic index rather than with evocation

Summary Plants ofSilene coeli-rosa given 5 or more long days (LDs) flowered, even when the LDs were followed by 48 hours of darkness before their return to short days (SDs). The mitotic indices of shoot apices from induced plants shortly after induction were significantly higher than the indices of shoot apices from vegetative plants. Two major mitotic peaks were observed in the shoot apices of plants given 7 long days (LDs) on day 8. One coincided with that reported byFrancis andLyndon (1979).Cell to cell movement was tested in the shoot apices of vegetative and LD treated plants using probes with a molecular size of 749 daltons (fluorescein-hexaglycine) and 847 daltons (fluorescein-leucyl diglutamyl leucine). These probes showed some movement in the shoot apices of both short day (SD) and LD treated plants, but fluorescein-leucyl diglutamyl leucine was immobile in the induced apices of 7 LD plants on day 8 at time intervals which coincided with major mitotic activity in the shoot apex. Symplasmic restriction in the shoot apex was also observed in plants given 8 LDs (i.e., plants not returned to SDs on day 7).In plants that were placed in 48 hours of darkness after the 7 LD treatment or in plants given 5 LDs, there was no strong peak in the mitotic index, even though all these LD treatments resulted in 100% flowering. In such plants no symplasmic restriction was found in the shoot. Thus the symplasmic restriction on day 8 of 7 LD plants is associated with the high mitotic index, but neither of these phenomena is an essential part of the evocation process.Abbreviations F(Glu)₂ L-glutamylglutamic acid conjugated to fluorescein isothiocyanate isomer I (F-) - F(Gly)₆ F-hexaglycine - FLGGL F-leucyl-diglutamyl-leucine - F(PPG)₅ F-the pentamer (propyl-propyl glycine) - LD long day - LDs long days - SD short day - SDs short days     

Ammonium and nitrate nutrition inPlantago lanceolata L. andPlantago major L. ssp.major

With the aims (1) to test whether the different natural occurrence of twoPlantago species in grasslands is explained by a different preference of the species for nitrate or ammonium; (2) to test whether the different occurrence is explained by differences in the flexibility of the species towards changes in the nitrogen form; (3) to find suitable parameters as a tool to study ammonium and nitrate utilization of these species at the natural sites in grasslands, plants ofPlantago lanceolata andP. major ssp.major were grown with an abundant supply of nitrate, ammonium or nitrate+ammonium as the nitrogen source (0.5 mM). The combination of ammonium and nitrate gave a slightly higher final plant weight than nitrate or ammonium alone. Ammonium lowered the shoot to root ratio inP. major. Uptake of nitrate per g root was faster than that of ammonium, but from the mixed source ammonium and nitrate were taken up at the same rate. In vivo nitrate reductase activity (NRA) was present in both shoot and roots of plants receiving nitrate. When ammonium was applied in addition to nitrate, NRA of the shoot was not affected, but in the root the activity decreased. Thus, a larger proportion of total NRA was present in the shoot than with nitrate alone. In vitro glutamate dehydrogenase activity (GDHA) was enhanced by ammonium, both in the shoot and in the roots.In vitro glutamine synthetase activity (GSA) was highest in roots of plants receiving ammonium. Both GDHA and GSA were higher inP. lanceolata than inP. major. The concentration of ammonium in the roots increased with ammonium, but it did not accumulate in the shoot. The concentration of amino acids in the roots was also enhanced by ammonium. Protein concentration was not affected by the form of nitrogen. Nitrate accumulated in both the shoot and the roots of nitrate grown plants. When nitrate in the solution was replaced by ammonium, the nitrate concentration in the roots decreased rapidly. It also decreased in the shoot, but slowly. It is concluded that the nitrogen metabolism of the twoPlantago species shows a similar response to a change in the form of the nitrogen source, and that differences in natural occurrence of these species are not related to a differential adaptation of nitrogen metabolism towards the nitrogen form. Suitable parameters for establishing the nitrogen source in the field are thein vivo NRA, nitrate concentrations in tissues and xylem exudate, and the fraction of total reduced nitrogen in the roots that is in the soluble form, and to some extent thein vitro GDHA and GSA of the roots. Grassland Species Research Group. Publ. no 118.     

Chemical defense production in Lotus corniculatus L. II. Trade-offs among growth,reproduction and defense

Summary Ecological trade-offs between growth, reproduction and both condensed tannins and cyanogenic glycosides were examined in Lotus corniculatus by correlating shoot (leaves and stem) size and reproductive output with chemical concentrations. We found that cyanide concentration was not related to shoot size, but that condensed tannin concentrations were positively correlated with shoot size; larger plants contained higher tannin concentrations. Both tannin and cyanide concentrations were depressed when plants produced fruits. Defense costs change as plants mature and begin to reproduce. These trade-offs indicate that cost of defense chemical production cannot be predicted merely on the basis of molecular size, composition or concentration.     

Somatic hybrids between<Emphasis Type="Italic"> Arabidopsis thaliana</Emphasis> and cytoplasmic male-sterile radish (<Emphasis Type="Italic">Raphanus sativus</Emphasis>)

Somatic hybrids were produced by protoplast fusion between Arabidopsis thaliana ecotype Columbia and a male-sterile radish line MS-Gensuke (Raphanus sativus) with the Ogura cytoplasm. Forty-one shoots were differentiated from the regenerated calli and established as shoot cultures in vitro. About 20 of these shoots were judged to be hybrids based on growth characteristics and morphology. Molecular analyses of 11 shoots were performed, confirming the hybrid features. Of these 11 shoots, eight were established as rooted plants in the greenhouse. Polymerase chain reaction and randomly amplified polymorphic DNA analyses of the nuclear genomes of all analyzed shoots and plants confirmed that they contained hybrid DNA patterns. Their chromosome numbers also supported the hybrid nature of the plants. Investigations of the organelles in the hybrids revealed that the chloroplast (cp) genome was exclusively represented by radish cpDNA, while the mitochondrial DNA configuration showed a combination of both parental genomes as well as fragments unique to the hybrids. Hybrid plants that flowered were male-sterile independent of the presence of the Ogura CMS-gene orf138.Abbreviations CMS Cytoplasmic male sterilityCommunicated by M.R. Davey     

Variation in growth and ion accumulation between two selected populations of Trifolium repens L. differing in salt tolerance

Two divergent populations of T. repens cv. Haifa developed from two generations of recurrent selection for shoot chloride concentration, were grown in the greenhouse at 0 and 40 mol m^–3 NaCl. Over two harvest cycles at 40 mol m^–3 NaCl, the population selected for a low concentration of chloride in the shoot maintained a significantly lower chloride and sodium concentration compared with those plants selected for a high shoot chloride concentration. The distribution of chloride in the shoots was further examined in a subsample of plants from both populations. In all plants, concentrations of chloride were lower in the expanding and fully expanded leaves than in the older leaf tissue or petioles.While there were no significant differences in the photosynthetic rates between lines, shoot yields and relative leaf expansion rates were higher in the low chloride population. Plant death was greater in plants selected for high shoot chloride. These results suggest that selections based on measurements of low shoot chloride concentrations may be successful in developing a cultivar of T. repens with improved salt tolerance.     

A comparative study of growth strategies in two varieties of Arrhenatherum elatius

Growth strategies of the two varieties of Arrhenatherum elatius were studied. The two varieties studied were: onion couch, which produces bulbous swollen internodes and is an arable weed of local importance, whilst tall oat-grass is more widely distributed. An experiment in which the two varieties were grown at different densities in monoculture and were harvested at intervals, highlighted various aspects of the competitive relation between the two varieties and an annual crop. Significant and consistent differences were found between the two varieties for most of the attributes measured during the two growing seasons. Tall oat-grass allocated a greater proportion of its whole shoot dry weight to producing vigorous aerial tillers, whereas onion couch allocated a greater proportion of its whole shoot dry weight to the development of basal internodes. The regulation of tiller number as a reaction to increasing density in tall oat-grass is achieved by high tiller mortality, whereas in onion couch, this stress is expressed by small tiller mortality. Growth pattern shown by the two varieties of A. elatius reflect the adaptive strategies evolved by them in two different habitats and are due to the genetic factors which determine the presence or absence of their characteristic basal internodes.     

Effects of thidiazuron on micropropagation of rose

Summary Rose (Rose hybrida L.) plants were micropropagated by axillary shoot proliferation method. Maximum number of microshoots per shoot tip explant were obtained on MS medium supplemented with 5 to 10&#x00B5;M thidiazuron (TDZ). The microshoots formed rooted plants on MS hormone-free medium. No difference in the rooting of microshoots produced on medium containing TDZ or N⁶-benzyladenine was observed. The regenerated plants were successfully transplanted to the field and appeared similar to the parent plant in morphologic features.     

Effects of arbuscular mycorrhiza (AM) on health ofLinum usitatissimum L. infected by fungal pathogens

Effects of arbuscular mycorrhizal (AM) symbiosis on health ofLinum usitatissimum infected by fungal pathogens were investigated exemplarily. Physiological and biochemical analyses were done to explain the mechanisms underlying the AM effects. AM plants showed increased resistance against the wilt pathogen (Fusarium oxysporum f. sp.lini), the level of this effects depended on the plant cultivars which all showed the same level of root colonization by arbuscular mycorrhizal fungi (AMF). In contrary to that, AM plants were highly susceptible against the shoot pathogenOidium lini, but they suffered less than non-AM plants in terms of shoot fresh weight, CO₂ assimilation and content of sucrose in shoot apex. This indicates that AM not only activates resistance mechanisms but also can induce tolerance against pathogens. The concentration of phytohormones such as auxin- and gibberellin-like substances were increased in shoots of AM plants. In roots the ethylene production was increased, too. Furthermore the content and composition of free sterols were highly altered in leaves of AM plants. Root infection by AMF caused an increased respiratory activity and a reduced degree of DNA methylation, but both modifications only occurred in infected root parts indicating an increasing gene activity. The presented results suggest that nearly all parts of a plant are influenced by AM but not in the same manner. In the case of mildewed linseed the effect of AM on plant health was impressing, it indicates that AM has an ability to induce tolerance.     

The effects of daminozide on the levels of Indol-3yl-acetic acid and gibberellins in radish (Raphanus sativus L.) in relation to the control of storage root growth

The levels of indol-3yl-acetic acid and gibberellins were determined in shoots and storage roots of radish (Raphanus sativus L.) at various times during the vegetative growth cycle of control plants and plants in which the root to shoot ratio was modified by daminozide treatment. In control plants the onset of storage organ growth was preceded by a change in the hormone root to shoot ratio to favour the root. There was a general reduction in hormone levels in daminozide-treated plants but the pattern of their distribution in roots and shoots was very similar to that in control plants. Thus the effects of daminozide on increased storage root growth cannot be explained in terms of altered root to shoot hormone ratios.     

Plant regeneration capacity of mesophyll protoplasts from Brassica napus and related species

Protoplasts from a total of thirty-six genotypes of Brassica species – B. napus, B. campestris (syn. B. rapa), B. juncea, and three distant relatives, Orychophragmus violaceus, Isatis indigotica and Xinjiang wild rape – were analysed for shoot regeneration using a feeder culture system. With the exception of B. campestris and Xinjiang wild rape, some genotypes of all the species could regenerate plants with high efficiency (above 20% of isolated calli initiating shoots). Several genotypes with high regeneration ability were elite breeding lines. Culture conditions as well as genotype had a significant impact on shoot regeneration frequency. In particular, silver nitrate added to the regeneration medium at doses of 6 and 30 μM improved shoot regeneration frequency to 25.4% and 52.2% of isolated calli, respectively, compared to 7.3% percent shoot regeneration without silver nitrate in seven responsive genotypes. Addition of silver nitrate to the regeneration medium also induced shoot regeneration in non-responsive genotypes. Intact plants could be obtained within three months from protoplast isolation in the regenerative genotypes using the current culture system. Advantages of mesophyll protoplasts as compared to protoplasts isolated from hypocotyls for genetic manipulation in Brassica species are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Salicylic acid and salicylic acid glucoside in xylem sap of <Emphasis Type="Italic">Brassica napus</Emphasis> infected with <Emphasis Type="Italic">Verticillium longisporum</Emphasis>

Salicylic acid (SA) and its glucoside (SAG) were detected in xylem sap of Brassica napus by HPLC–MS. Concentrations of SA and SAG in xylem sap from the root and hypocotyl of the plant, and in extracts of shoots above the hypocotyl, increased after infection with the vascular pathogen Verticillium longisporum. Both concentrations were correlated with disease severity assessed as the reduction in shoot length. Furthermore, SAG levels in shoot extracts were correlated with the amount of V. longisporum DNA in the hypocotyls. Although the concentration of SAG (but not SA) in xylem sap of infected plants gradually declined from 14 to 35 days post infection, SAG levels remained significantly higher than in uninfected plants during the whole experiment. Jasmonic acid (JA) and abscisic acid (ABA) levels in xylem sap were not affected by infection with V. longisporum. SA and SAG extend the list of phytohormones potentially transported from root to shoot with the transpiration stream. The physiological relevance of this transport and its contribution to the distribution of SA in plants remain to be elucidated.     

In vitro propagation of Catalpa ovata G. Don

Plants of C. ovata were regenerated in vitro from shoot tips and nodal explants as well as from cotyledon-derived calluses. For shoot proliferation from shoot tips and nodal segments, Schenk and Hildebrandt (1972) or Lloyd and McCown (1980) basal media, supplemented with 6-benzyladenine (2.2–22.2 μM) alone or in combination with indole-3-acetic acid (0.6 μM), were used. Shoot regeneration through organogenesis was achieved by culturing cotyledons on Schenk and Hildebrandt medium containing indole-3-acetic acid (0.6 μM) and 6-benzyladenine (4.4 μM) or zeatin (22.8 μM). TLC and HPLC analysis showed that the multiple shoots and micropropagated plants exhibited similar iridoid patterns as those of the leaves of original plants of C. ovata. The highest levels of catalpol and catalposide (8.2 and 2.4 % of dry weight, respectively) were found in aerial parts of three-month-old in vitro regenerated plants. This revised version was published online in June 2006 with corrections to the Cover Date.