Effect of plant growth regulators on growth and biosynthesis of phenolic compounds in genetically transformed hairy roots of<Emphasis Type="Italic">Panax ginseng</Emphasis> C. A. Meyer

In this study, morphological alterations, biomass growth, and secondary metabolite production of genetically transformed hairy roots ofPanax ginseng C. A. Meyer, were evaluated after administration of plant growth regulators. The addition of benzylamino purine and kinetin to the culture media increased biomass formation and phenolic compound biosynthesis in the hairy roots. α-Naphthaleneacetic acid and indole-3-butyric acid inhibited hairy root growth, however, low concentrations of indole-3-acetic acid slightly increased hairy root growth. Low concentrations of 2,4-Dichlorophenoxyacetic acid profoundly inhibited growth of hairy roots. The addition of plant growth regulators, such as auxin, did not increase total phenolic compounds in hairy roots that did not contain gibberellic acid and cytokinins. Callus formation was induced in cultures suspended in liquid medium amended with benzylamino purine and kinetin. Hairy roots regenerated from these calluses exhibited an active growth pattern with extensive lateral branching in non-amended medium, similar to the growth pattern of the original hairy roots.     

Freezing tolerance in Draba chionophila,a ‘miniature’ caulescent rosette species

Summary Freezing tolerance as a cold resistance mechanism is described for the first time in a plant growing in the tropical range of the Andean high mountains. Draba chionophila, the plant in which freezing tolerance was found, is the vascular plant which reaches the highest altitudes in the Venezuelan Andes (approximately 4700m). Night cycles of air and leaf temperature were studied in the field to determine the temperature at which leaf freezing began. In the laboratory, thermal analysis and freezing injury determinations were also carried out. From both field and laboratory experiments, it was determined that freezing of the leaf tissue, as well as root and pith tissue, initiated at a temperature of approximately-5.0°C, while freezing injury occurred at approximately-12.0°C for the pith, and below-14.0°C for roots and leaves. This difference in temperature suggests that the plant still survives freezing in the-5.0 to-14.0°C range. Daily cycles of leaf osmotic potential and soluble carbohydrate concentration were also determined in an attempt to explain some of the changes occurring in this species during the nighttime temperature period. A comparison between Andean and African high mountain plants from the point of view of cold resistance mechanisms is made.     

Hairy root and tissue cultures of <Emphasis Type="Italic">Leucojum aestivum</Emphasis> L.—relationships to galanthamine content

Galanthamine, an isoquinoline alkaloid acetylcholinesterase inhibitor, is an important agent used all around the world for the symptomatic treatment of senile dementia of the Alzheimer’s type. The production of this metabolite and the availability of the plant are limited and prompted the search for an alternative way to obtain this valuable metabolite using in vitro cultures of Leucojum aestivum L. It is known that cell differentiation level shows a major influence upon the accumulation of alkaloids. For this reason, tissue cultures of L. aestivum showing different stages of morphogenesis controlled by exogenous growth regulators were established. Agrobacterium rhizogenes strain LBA 9402 has been tested for its capacity to induce hairy roots of this monocotyledonae plant.     

The Effect of Growth Regulators on Quality Parameters and Ginsenosides Accumulation in Panax quinquefolium L. Roots

American ginseng (Panax quinquefolium L.) is a perennial medicinal herb originally grown in Canada and USA, and recently also in China, Australia, Holland and Poland. Several commercial preparations are produced from ginseng roots, that are known for their antifatigue, antitumor, antistress and immune system stimulating functions. The medicinal properties are due mainly to the active components – ginsenosides. In this work, the results of field cultivation experiments are presented that examine the effects of foliar application of several growth regulators on quality parameters and ginsenoside content of P. quinuefolium roots. The growth regulators tested, i.e., kinetin, daminozide, mixture of gibberellic acid (GA₃) with potassium salt of α-naphthalene acetic acid (kNAA) and new preparation – IPO-1 – benzimidazole derivative (obtained from the Institute of Organic Industry in Warsaw – at present during the process of patent), were applied at a concentration of 100 or 200 mg l⁻¹ in the middle of June in the 2nd year of vegetation. After 4 years of cultivation, the roots were dug up and dried, and subsequently the quantitative analysis of individual saponins (R_b1, R_b2, R_c, R_d, R_e, R_g1) by HPLC was performed. Growth regulators significantly affected quality parameters, morphological features and accumulation of individual and total ginsenosides in ginseng roots. Regardless of doses, the plant roots treated with growth regulators had a higher content of total ginsenosides in comparison to the control. The growth regulators also affected individual ginsenosides level and narrowed the ratio of R_b:R_g group. The application of kinetin, daminozide and benzimidazole derivative for foliar spray during 2nd year of American ginseng vegetation caused a significant increase in air dry weight of roots and aboveground parts whereas the mixture of GA₃ and kNAA showed a decreasing effect. An increase of roots size was observed using higher doses (200 mg l⁻¹) of kinetin and daminozide while a decreasing tendency appeared with the application of the other preparations.     

Exploring the structural requirements for jasmonates and related compounds as novel plant growth regulators: A current computational perspective

Jasmonates and related compounds have been highlighted recently in the field of plant physiology and plant molecular biology due to their significant regulatory roles in the signaling pathway for the diverse aspects of plant development and survival. Though a considerable amount of studies concerning their biological effects in different plants have been widely reported, the molecular details of the signaling mechanism are still poorly understood. This review sheds new light on the structural requirements for the bioactivity/property of jasmonic acid derivatives in current computational perspective, which differs from previous research that mainly focus on their biological evaluation, gene and metabolic regulation and the enzymes in their biosynthesis. The computational results may contribute to further understanding the mechanism of drug-receptor interactions in their signaling pathway and designing novel plant growth regulators as high effective ecological pesticides.Key words: jasmonates, amino acid conjugates of jasmonic acid, plant growth regulators, quantitative structure-activity relationship, quantitative structure-property relationship, a mini-review     

Assessment of the biocontrol potential of a Trichoderma viride isolate: Part I: Establishment of field and fungal cellar trials

A field trial has been set up to assess the biological control potential of a Trichoderma viride isolate, T60. This isolate had been shown in previous laboratory tests to be particularly effective against certain basidiomycete decay fungi. Wood was treated with T60 spores using vacuum pressure impregnation in a pilot preservation plant. Treated stakes were planted in the field site along with CCA-treated and untreated control samples. Replicate samples were also set up in an accelerated decay facility employed to give a comparison to the field trial results. This paper describes the setting up and monitoring of the field and fungal cellar trials, and presents results of moisture monitoring and sapstain assessment which indicate that Trichoderma viride isolate T60 has a marked effect on the rate of sapstain development under certain conditions. The paper also discusses the efficacy of pressure impregnation of spore suspensions for use as biological control agents     

<Emphasis Type="Italic">Salicornia ramosissima</Emphasis> population dynamics and tolerance of salinity

Field and greenhouse studies have been conducted to clarify aspects of population dynamics and NaCl tolerance of Salicornia ramosissima J. Woods. Two populations, Varela and Verdemilho, were monitored in the field during two consecutive life cycles and aspects of their morphology and density were recorded monthly. In the laboratory seedlings were exposed to different salinity for 10 weeks and growth and mortality rate were recorded weekly. The growth of the populations differed significantly, possibly because of the different salinities of the two sampling sites and/or genetic adaptations of the two populations to the environmental conditions. The absence of a significant correlation between sediment salinity and stem elongation suggested, however, that salinity, alone was not responsible for the differences observed and was possibly associated with other factors, because of nutritional, edaphic, and microclimatic conditions. S. ramosissima did not develop well in conditions of elevated or moderate salinity; its growth was optimum at low salinity. Optimum development of S. ramosissima may, nevertheless, depend on the total number of large seeds in a population seed bank, because of their greater success in germination and germinability under stress conditions than small seeds.     

Involvement of Plant Hormones and Plant Growth Regulators on in vitro Somatic Embryogenesis

In spite of the importance attained by somatic embryogenesis and of the many studies that have been conducted on this developmental process, there are still many aspects that are not fully understood. Among those features, the involvement of plant hormones and plant growth regulators on deTermining the conversion of somatic onto embryogenic tissues, and on allowing progression and maturation of somatic embryos, are far away from being completely comprehended. Part of these difficulties relies on the frequent appearance of contradictory results when studying the effect of a particular stimulus over a specific stage in somatic embryogenesis. Recent progress achieved on understanding the interaction between exogenously added plant growth regulators over the concentration of endogenous hormones, together with the involvement of sensitivity of the tissues to particular hormone groups, might help clarifying the occurrence of divergent patterns in somatic embryogenesis, and in tissue culture in general. The aspects described above, emphasizing on the effect of the concentration of plant hormones and of the addition of plant growth regulators during the different phases of somatic embryogenesis, will be reviewed in this paper. Citations will be limited to review articles as much as possible and to individual articles only in those cases in which very specific or recent information is presented.     

Analogous effects of arbuscular mycorrhizal fungi in the laboratory and a North Carolina field

Although arbuscular mycorrhizal (AM) fungi are ubiquitous symbionts of plants, the mutualism has rarely been tested in nature. In experiments designed to explore the ecological relevance of associations between different fungal and plant species in a natural environment, plant species were infected with different species of fungi and grown in separate trials in the laboratory and a North Carolina (USA) field. The benefits to plants varied dramatically as plant species were grown with different species of AM fungi. Effects of mycorrhizal fungi in nature were generally correlated to effects in the growth chamber, suggesting that laboratory data do reflect dynamics between plants and AM fungi in the field. Initial size at transplant and experimental block were also significant predictors of plant growth in the field. Correlation statistics between laboratory and field data were weaker when analyses involved plant species less responsive to infection by any AM fungus, suggesting that the response of a species to inoculation is a good predictor of its sensitivity to specific AM fungi in the field. AM fungal identity appears to influence the growth and reproduction of plants in the field.     

Plant signals and fungal perception during arbuscular mycorrhiza establishment

Arbuscular mycorrhizal (AM) fungi are obligate symbionts that need their plant hosts to complete their life cycle. In the absence of the plant, germlings arrest growth after a few days and retract most of their cytoplasm back into the multinuclear spores. The spores can germinate again during more favorable conditions. How AM fungi recognize compatible host roots and activate their symbiotic program is not yet understood. However, research in this field in the last years has shed light into this topic. We, and others, have approached some of these aspects by studying changes in fungal gene expression observed at early stages of development, before and at the plant recognition stage in an attempt to identify genes and proteins featuring as key regulators in the switch between the asymbiotic and symbiotic style of life. The molecular bases of this recognition process are now starting to be understood and point to common signaling pathways shared with other microbe-plant associations and to arbuscular mycorrhiza specific signaling pathways.     

红树植物淹水胁迫响应研究进展

潮汐淹水是红树植物面临的主要环境胁迫之一,也是导致目前红树林造林成活率低的一个关键因子。由于长期适应于水淹生境,红树植物发育出一套适应于潮间带生长的抗淹水机制。综述了与红树植物相关的抗淹水胁迫响应机制,包括了形态结构、生长、水分和光合作用、膜脂过氧化系统和根系脱氢酶系统、内源激素和胁迫多胺等5个方面。提出应用人工潮汐系统研究红树植物的淹水抗性机理是确定不同种类红树植物的耐淹水能力的有效手段。并指出生长的研究是淹水胁迫响应研究的基础,而与分子手段相结合的激素水平的研究将在红树植物抗性胁迫研究中得到重视。     

Studies of the Relationship between the Growth Rate of Young Plants and their Total-N Concentration using Nutrient Interruption Techniques: Theory and Experiments

Alternative assumptions about the utilization of stored nitrogenare used to derive two different models for predicting how thegrowth rate of both the whole plant and its shoot vary withtheir respective total-N concentrations following interruptionof the external N supply. Model 1 predicts that plant growthshould follow monomolecular kinetics after the supply is interrupted,with the resulting relative growth rates linearly related tototal-N concentration. Model 2 predicts that plants grow logisticallyonce N is withheld, with their relative growth rates varyinglinearly with the reciprocal of total-N concentration. The versionsof the models derived for the shoot are similar to those forthe whole plant, but include an additional term to allow fortransfer of N to the roots as deficiency increases. Tests ofthe models were carried out using data from N interruption experimentswith young cabbage and lettuce plants (containing either highor low nitrate concentrations) which were grown hydroponicallyin nutrient recirculating units. The results showed that therewas little statistical difference between the fits of the twomodels to the growth data over the range tested, but that model1 was unsatisfactory because the estimates of its parameterswere inconsistent with assumptions about the physiological processescontrolling growth, and because its predictions became unrealisticwhen extrapolated to conditions of acute N deficiency. Model2 did not suffer from either of these problems and provideda better mechanistic interpretation of the data, yielding predictionsthat were in close agreement with the observed relationshipbetween relative growth rate and total-N concentration for boththe whole plant and its shoot. The curvilinear form of thisrelationship for model 2 differs from the linear form of othermodels derived from measurements in experiments where therewas a continuing but restricted supply of external N to plants.This implies that the relationship between relative growth rateand total-N concentration may vary depending on whether or nota plant has to rely entirely on its internal reserves of N intimes of shortage. The results also showed that the size ofthese reserves governed the amounts of N transferred to theroots as deficiency developed. Transfer of N was greater incabbage than lettuce because of a greater capacity to adaptby increasing root growth at the expense of the shoot.Copyright1994, 1999 Academic Press Cabbage, deficiency, dilution, hydroponics, lettuce, model, nitrogen, nitrate, nutrient recirculation units, relative growth rate, shoot, total-N concentration, whole plant     

<Emphasis Type="Italic">Acmella radicans</Emphasis> var. <Emphasis Type="Italic">radicans: In vitro</Emphasis> culture establishment and alkamide content

Summary Acmella radicans var. radicans propagation was established in vitro. This plant belongs to the Asteraceae from which some species are known for their insecticide, fungicide and antibacterial activity. The complete Murashige and Skoog (MS) medium was the best in assisting seed germination. In order to obtain shoots in vitro, a complete MS medium and half-strength MS medium were assayed with explants from leaves, nodes, and internodes. The best medium for shoot production was the half-strength MS medium with no addition of plant growth regulators, and the highest shoot propagation was from single-node explants. Regeneration of roots on shoot explants in the medium was obtained without the addition of growth regulators. Of the plantlets that were acclimated, 90% of them were obtained from rooted shoots with completely expanded leaves. The alkamide content was evaluated for each tissue and the higher concentration was observed in flower heads. The main alkamides present in the leaves and the flower heads were N-(2-phenylethyl)-2Z,4E-octadienamide and 3-phenyl-N-(2-phenylethyl)-2-propenamide. This study describes the methodology for the establishment and propagation of Acmella radicans in vitro and the evaluation of different tissue alkamide contents in vitro and in the field.     

<Emphasis Type="Italic">Agrobacterium rhizogenes</Emphasis>: recent developments and promising applications

Agrobacterium rhizogenes is the etiological agent for hairy-root disease (also known as root-mat disease). This bacterium induces the neoplastic growth of plant cells that differentiate to form “hairy roots.” Morphologically, A. rhizogenes-induced hairy roots are very similar in structure to wild-type roots with a few notable exceptions: Root hairs are longer, more numerous, and root systems are more branched and exhibit an agravitropic phenotype. Hairy roots are induced by the incorporation of a bacterial-derived segment of DNA transferred (T-DNA) into the chromosome of the plant cell. The expression of genes encoded within the T-DNA promotes the development and production of roots at the site of infection on most dicotyledonous plants. A key characteristic of hairy roots is their ability to grow quickly in the absence of exogenous plant growth regulators. As a result, hairy roots are widely used as a transgenic tool for the production of metabolites and for the study of gene function in plants. Researchers have utilized this tool to study root development and root–biotic interactions, to overexpress proteins and secondary metabolites, to detoxify environmental pollutants, and to increase drought tolerance. In this review, we provide an up-to-date overview of the current knowledge of how A. rhizogenes induces root formation, on the new uses for A. rhizogenes in tissue culture and composite plant production (wild-type shoots with transgenic roots), and the recent development of a disarmed version of A. rhizogenes for stable transgenic plant production.     

Efficient in vitro regeneration of fireweed,a medicinal plant

Epilobium angustifolium L. (fireweed) is a medicinal plant that has been used to treat diarrhea, mucous colitis, irritable-bowel syndrome, skin problems, prostate problems, menstrual disorders, asthma, whooping cough, and hiccups. A highly efficient and rapid regeneration system via multiple shoot formation was developed for fireweed. Explants (leaf, petiole, root, and stem segments) excised from sterile seedlings were cultured on medium supplemented with different concentrations and combinations of various plant growth regulators. Explant browning, a major problem for regeneration, was overcome by adding 100 mg/l ascorbic acid to all prepared media containing growth regulator combinations. Root explants formed more shoots than other explants. Best shoot proliferation was obtained from root explants cultured on media with 0.1 mg/l BA and 0.5 mg/l IAA. Regenerated shoots were transferred to rooting media containing different concentrations of IAA, IBA, NAA or 2,4-D. Most shoots developed roots on medium with 0.5 mg/l IAA. Rooted explants were transferred to vermiculate in Magenta containers for acclimatization and after 3 weeks they were planted in to plastic pots containing potting soil and maintained in the plant growth room.     

Nutrient uptake and growth of barley as affected by soil compaction

A field experiment with different levels of compaction was carried out on a mouldboard ploughed silty clay, with the objective of studying the effects on plant nutrient uptake and growth. Soil from the field was also used in laboratory studies of carbon and nitrogen mineralization, and plant uptake of water and nutrients. In the field, low as well as high bulk densities reduced biomass production and nutrient uptake of barley (Hordeum vulgare L.) compared to intermediate bulk densities, where grain yield was approximately 20% higher. In the beginning of the growing season, the concentration of phosphorus and potassium was lowest in plants grown in the loosest and in the most compacted soil, and suboptimal for plant growth. The uptake of nutrients transported by diffusion was more affected by compaction than for nutrients transported by mass flow. The reasons for lowered uptake in loose compared to moderately compacted soil could be reduced root-to-soil contact, a low diffusion coefficient for nutrients and/or reduced mass transport of water to seed and roots. Differences in plant nutrient concentrations between treatments gradually declined until harvest. Immediately after compaction there was probably oxygen deficiency in the compacted soil since the air-filled porosity was critically low, but as the soil dried out, mechanical resistance to root growth may have become a more important growth-limiting factor. In the laboratory study, severe compaction reduced carbon mineralization and uptake of water and nutrients by roots, and caused denitrification. There were only small differences between loose and moderately compacted soil in carbon mineralization, nitrogen concentration in the soil, uptake of water and nutrients and dry matter yield. The large yield increase due to recompaction in the field was not reproduced in the laboratory. Possible reasons are differences in soil temperature between the field and laboratory, in the sowing and fertilizing methods, the pretreatment of the soil and in the spatial variability of bulk density. It is possible that recompaction is needed only in the uppermost part of the soil, which is the loosest, dries out first, and is where the seed as well as the fertilizer are placed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Theobroma cacao L.: an axillary bud in vitro propagation procedure

An axillary bud derived in vitro propagation procedure for Theobroma cacao is described. The method allows bud expansion and elongation, including leaf development, as early as 13 days after placing explants on establishment medium. Shoots have been maintained in culture vessels for six months with little evidence of decline. Propagules have been induced to form roots, hardened off, and moved to the greenhouse within six weeks of initial explant establishment. Some plants have been in the greenhouse for twelve months and are growing in an apparently normal manner. No major differences in response from UF-667 or EQX-100 derived seed-grown trees were found suggesting that the method may not be limited by genotype. Long-term growth without added plant growth regulators has been seen in over 2400 explants.Abbreviations NAA naphthaleneacetic acid - IBA indolebutyric acid - BAP benzylaminopurine - WPM Lloyd-McCown woody plant medium Published as paper No. 8148, Journal Series, Pennsylvania Agricultural Experiment Station     

The effect of plant growth regulators on growth, morphology and condensed tannin accumulation in transformed root cultures of Lotus corniculatus

This study concerns the effects of four different classes of plant growth regulators on root morphology, patterns of growth and condensed tannin accumulation in transgenic root cultures of Lotus corniculatus L. (Bird's-foot trefoil). Growth of transformed roots in 2,4-dichlorophenoxyacetic acid (2,4-D) resulted in decreased tannin levels relative to controls at concentrations of 10^-6 M and above, while gibberellic acid (GA₃) inhibited tannin accumulation at concentrations of 10^-7 M and above. Benzyladenine (BA) had little effect at low concentrations (10^-7 M and below) but resulted in an increase in tannin levels at 10^-6 M. Abscisic acid had little effect on levels of condensed tannins at any of the concentrations used. Experiments involving growth regulator addition and medium transfer demonstrated that 2,4-D inhibition of tannin accumulation could be reversed by GA₃ and BA, while GA₃ downregulation could only be reversed by the addition of 2,4-D. Although 2,4-D inhibited tannin accumulation, addition of 2,4-D to root cultures grown for 14 or 28 days in the absence of plant growth regulators stimulated both growth and tannin biosynthesis. Characteristic alterations in root morphologies accompanied growth regulator-mediated modulation of tannin biosynthesis. Growth in 2,4-D resulted in partially de-differentiated root cultures while growth in GA₃ produced roots with an elongated phenotype. Restoration of tannin biosynthesis in 2,4-D-treated roots was accompanied by root re-differentiation and the production of new lateral roots.Abbreviations ABA abscisic acid - BA benzyladenine - 2,4-d 2,4-dichlorophenoxyacetic acid - GA₃ gibberellic acid 3 - FW fresh weight     

茄子野生近缘种托鲁巴姆试管微扦插繁殖技术研究

嫁接栽培是茄果类蔬菜防治土传病害和提高产量的重要措施之一。茄子野生近缘种托鲁巴姆(Solanums torvum)因综合抗性强,成为茄子和番茄嫁接的常用优良砧木。但是,由于托鲁巴姆种子的发芽率、发芽势和发芽指数较低,苗龄较长,限制了其在工厂化育苗中的大规模应用,因此迫切需要开发其他方法及相应技术体系提高托鲁巴姆的育苗效率,降低育苗成本。为优化托鲁巴姆微扦插技术,该研究探索并优化了试管内微扦插繁殖托鲁巴姆技术,以无菌播种获得初代无菌苗的茎段为外植体,通过在培养基中添加植物生长调节剂,对比不同浓度植物生长调节剂对托鲁巴姆微扦插繁殖过程中的影响。结果表明:(1)托鲁巴姆在不同培养基中,腋芽诱导、继代增殖和生根培养的效果存在显著差异,初代芽诱导的最佳培养基为MS+KT 0.5 mg·L^-1+IBA 0.1 mg·L^-1,出芽率达90%。(2)继代扦插最佳培养基为MS+IBA 0.4 mg·L^-1,培养30 d的增殖系数达6.11,植株长势健壮。(3)最佳生根培养基为1/2MS+IBA 0.2 mg·L^-1,生根培养30 d,单株一级根数4.56条,最长根长125.80 mm、根粗0.50 mm,根系发达。采用试管内微扦插技术繁殖托鲁巴姆种苗,操作简单,增殖系数较高,可满足快速繁育种苗的要求。该研究结果为托鲁巴姆的工厂化规模育苗提供了新途径。