Composition of Excised and Attached Sterile Pea Roots--Loss of Cell Nucleic Acids

The composition of excised cultured pea-root tips has been comparedwith aseptically cultured attached root tips. Expressed in cellularterms, the cultured excised roots showed a reduction in nitrogenousand nucleic acid constituents. The cells of attached roots hadapproximately 2-, 4-, 5- and 4-fold amounts of protein, solublenitrogen, ribonucleic acid and deoxyribo-nucleic acid respectively,as compared with excised roots cultured in the same medium.Cultured root meristems did not contain the quiescent zone normallyfound in attached roots. It is suggested that the observed reductionin RNA and DNA per cell does not impair the ability of cellsto divide and expand normally and, further, that there is surplusnucleic acid in attached root cells not obligatory for fullexpression of the genome.     

Nuclear DNA contents of Pisum genotypes grown in vivo and in vitro

Summary The nuclear DNA content of prophase nuclei in root tips of two cultivars and two primitive lines of Pisum sativum and of Pisum fulvum have been determined, using a scanning microdensitometer. The nuclear DNA contents differed significantly between the genotypes investigated but there was no correlation with their supposed phylogenetic positions.A loss of 73% of the DNA from cells of aseptically cultured excised pea roots has been recently reported (Abbott, 1971). In marked contrast to this claim, our measurements of the nuclear 4C DNA content of root tip meristematic cells have shown that there is no significant loss in excised roots compared with attached roots.     

Role of manganese in low-pH-induced root hair formation in<Emphasis Type="Italic"> Lactuca sativa</Emphasis> cv. Grand Rapids seedlings

Root hair formation is induced by low pH in lettuce (Lactuca sativa L. cv. Grand Rapids) seedlings cultured in mineral medium. The role of mineral concentrations in this phenomenon was investigated, especially for manganese. When lettuce seedlings were cultured in media that were deficient in calcium (Ca), manganese (Mn), boron (B) or molybdenum (Mo), morphological changes were induced in roots. Deficiency of other nutrients had little effect on root hair formation. Ca or B deficiency inhibited the growth of the main root and the formation of root hairs, regardless of pH. Mn or Mo deficiency increased root hair formation at pH 6 and suppressed main root growth slightly. In contrast, increasing the Mn concentration suppressed low-pH-induced root hair formation. The Mn content of roots grown at pH 4 was only about 15% of that at pH 6. In contrast, the Mo content of roots grown at low pH was about six times that of roots grown at neutral pH. These results suggest that root hair formation induced by low pH is at least partly mediated by decreased Mn uptake in root cells.     

Thiophene accumulation in relation to morphology in roots of Tagetes patula

Roots of marigold (Tagetes patula L.) accumulate thiophenes, heterocyclic sulfurous compounds with strong biocidal activity. In detached roots cultured in vitro, the thiophene content was 5 mol·(g fresh weight)^-1 which is 25-times higher than in roots attached to the plant. In roots derived from tissues transformed by Agrobacterium tumefaciens and A. rhizogenes, the morphology and thiophene content varied with the bacterial strain used. Transformation stimulated the elongation of the root tips and the formation of lateral roots but lowered the thiophene level to 20–50% relative to the concentration in untransformed detached roots. A negative correlation was found between the number of laterals in a root system and the thiophene content. Extensive branching and a decrease in thiophene accumulation was evoked in untransformed roots by indole-3-acetic acid (1–10 mol·l^-1) added to the medium. Within the roots, the highest thiophene concentrations were found in the tips. The results indicate that auxin directly or indirectly plays a role in the regulation of the thiophene level in root tips.Abbreviations B5 Gamborg's B5 medium - IAA Indole-3-acetic acid     

GROWTH AND DEVELOPMENT OF CULTURED RADISH ROOTS

Excised cultured roots of Raphanus sativus L. cv. White Icicle elongate and produce a few lateral roots but do not increase in diameter. Lateral expansion is effected when both an auxin (indoleacetic acid or naphthaleneacetic acid) and a cytokinin (benzyladenine) are applied at the cut end of the root. The growth regulator effects are apparent first in the pericycle and subsequently in the procambium. Both of these groups of cells divide, producing large numbers of secondary derivatives. The increase in number of cells is reflected in an increase in root diameter. When cultured roots are treated with auxin only, a limited number of pericycle cells divide and lateral roots develop. When roots are treated with cytokinin only, all pericycle cells divide and a multiseriate zone of pericycle-derived cells develops. The procambium is not markedly affected by application of a single growth regulator. The distinct and separable responses of pericycle cells to different regulators suggest that the pericycle can be characterized in a functional, as well as a topographic, sense.     

Light-induced inhibitors from intact and cultured caps of Zea roots

Growth inhibitors were assayed from extracts of intact (attached) and of excised (cultured) root caps of Zea mays L., cv. Merit, the roots of which show a positive geotropic response only after exposure to light. If caps are intact at the time of illumination, at least two inhibitory substances are produced, an acid inhibitor and a neutral inhibitor, whereas if caps are detached from roots, placed in culture and then illuminated only the neutral inhibitor is formed. Cycloheximide retards inhibitor production in both intact and cultured caps. When [¹⁴C]mevalonic acid is included in the culture medium and the caps are illuminated, 15–25% of the recoverable ¹⁴C cochromatographs with the neutral inhibitor, whereas in caps cultured in the dark, this radiolabelling pattern is not observed. Cyloheximide in the light reduces the incorporation of ¹⁴C into compounds cochromatographing at the R_f of the neutral inhibitor. It is suggested that the neutral inhibitor may be important in the light-induced bending of roots.Abbreviations ABA abscisic acid - CH cycloheximide     

Role of ascorbic acid in auxin induced cell elongation

Summary Cytochemical detection of ascorbic acid in cultured root tips of Zea mays shows that dividing cells accumulate ascorbic acid in the cytoplasm. The localization pattern alters in the root tip as the cells begin to elongate. In elongating cells ascorbic acid is distinctly localized on cell walls. Ascorbic acid content per cell inreases with the onset of cell elongation. Fully elongated cells contain fivefold more ascorbic acid than meristematic cells. Cytophotometric analysis reveals a sharp and positive correlation (r=+0.93) between percentage increase in content of ascorbic acid per cell and corresponding increase in cell size at different phases of cell elongation. IAA treatment to the roots raises the content of ascorbic acid per cell with a parallel increase in size of cell. Involvement of ascorbic acid in IAA induced cell elongation is discussed.     

黄花蒿化感作用机理的初步研究

运用室内培养皿生物测定方法,对黄花蒿克生作用进行的研究结果表明,黄花蒿水浸提液对小麦幼苗生长有明显的抑制作用,且抑制强度随浸提液浓度升高而加强。其对小麦根的抑制作用比对叶的抑制作用强。对受体小麦根尖压片的观察统计表明,黄花蒿的水浸提液影响了小麦根尖分生区细胞有丝分裂的正常进行,并随着供体黄花蒿水浸提液浓度的升高,小麦根尖分生区分裂期细胞数目下降;受体材料小麦的一些生理生化测定指标表明,黄花蒿水浸提液使供试小麦根系活力稍有减弱,可溶性蛋白含量明显升高,使根的核酸含量升高而叶的核酸含量降低;使叶绿素含量有较明显降低。     

瘤菌根菌对铁皮石斛根系形态的影响及其共生关系的研究

为了解瘤菌根菌(Epulorhizasp.)与铁皮石斛(Dendrobiumofficinale)根系的共生关系及其对根系农艺性状的影响,用液体培养瘤菌根菌浇灌无菌盆栽铁皮石斛苗根部共培养,观察石斛根的表型和超微结构变化,并用分子检测鉴定菌丝是否定殖根中。结果表明,瘤菌根菌菌丝能侵入根的皮层细胞,诱导生成菌丝团形成共生关系。共生后的菌丝能提高IAA含量,诱导根系结构发生改变生成侧根,增大了根系体积,促进根系的生长并显著提高根系活力。瘤菌根菌与铁皮石斛根共培养后建立共生关系形成菌根且能定殖于根中,诱导根系结构的变化,侧根的形成对石斛生长具有重要作用。     

RELATIONSHIPS BETWEEN GROWTH RATES AND NUCLEIC ACID CONTENTS IN THE ROOTS OF INBRED LINES OF CORN

Woodstock , Lowell W., and Folke Skooc . (U. Wisconsin, Madison.) Relationships between growth rates and nucleic acid contents in the roots of inbred lines of corn. Amer. Jour. Bot. 47(9) : 713–716. Illus. 1960.—A study has been made of the rates of elongation and nucleic acid contents of the roots of inbred lines of Zea mays, var. W-158, A-374B, W-58, W-28, 8A, and W-148. A direct proportionality was found between the ribosenucleic acid contents (μg./root) of the apical 3 or 6 mm. of the roots (roughly equivalent to their growing tips) and their rates of elongation. This strict, quantitative relationship to growth rate appears to be specific for RNA; it was not found for DNA, and it was independent of the size of the root. A detailed study of one line (W-58) has shown, furthermore, that the ribosenucleic acid content in the root tip decreases with time in proportion to the decrease in the growth rate of the root.     

Occurence and regulation of Calvin cycle enzymes in non-autotrophic Beggiatoa strains

A field isolate of Bradyrhizobium japonicum which failed to attach polarly or firmly to soybean roots was compared with the laboratory isolate I-110 for its relative rate of growth, piliation, attachment and nodulation. Both isolates grew at a comparable rate in yeast extract-gluconate medium as well as in soybean root exudate, produced comparable amounts of soybean lectin binding polysaccharide, infected through curled root hairs and developed effective nodules. Approximately 5% of cells in cultures of 110 possessed pili but none were detected in cultures of 1007 by electron microscopy. Light microscopic observations of root hairs from roots exposed to 1007 and 110 inoculum showed no polarly attached cells of 1007 and approximately 100 cells of 110 polarly attached per mm root hair length. Plate counting of firmly bound cells released by sonication indicated that the number of 1007 cells firmly adhering was at least 1000-fold lower than the number of 110 cells attached. The significance of polar, firm and weak attachment in the initiation of symbiotic interactions is discussed.Dedicated to the menory of Harry E. Calvert     

The Uptake of Cytokinins by Protoplasts and Root Sections of Brassica campestris

The effect of cytokinins was studied on the incorporation of ¹⁴C-labelled precursors into the nucleic acid fraction of protoplasts isolated from callus or roots of Brassica campestris. Protoplasts from callus and roots took up ¹⁴C-uridine from the incubation medium and incorporated this precursor into the ribonucleic acid fraction during the experimental period of 16 h. Low concentrations of kinetin (10^?8-5 × 10^?6M) did not stimulate the incorporation, and kinetin inhibited this process at higher concentrations (5 × 10^?5M). This result led to an investigation on the uptake of cytokinins by protoplasts of roots. In contrast to a rapid uptake of radio-actively labelled adenine and uridine. protoplasts from roots took up only small amounts of labelled kinetin. zeatin, zeatin riboside and zeatin nucleotides from the incubation medium. Root sections took up far more adenine and kinetin than protoplasts from roots. The ratio between the amount of kinetin taken up and applied was much higher for the sections than for protoplasts, indicating that intact root cells took up kinetin far more rapidly than protoplasts. It is suggested that the plasmalemma and cell wall play an essential role in the uptake of cytokinins or that the differences in the uptake rates are related to differences between the rates of metabolism of cytokinins in root sections and in protoplasts.     

An interchangeable system of hairy root and cell suspension cultures ofCatharanthus roseus for indole alkaloid production

Hairy roots ofCatharanthus roseus obtained by co-cultivation of hypocotyl segments withAgrobacterium rhizogenes, and cultured in SH (Schenk and Hildebrandt) basal medium, formed two types of calli when subcultured in SH medium with 1 mg/1 -naphthaleneacetic acid and 0.1 mg/l kinetin. One of them, a compact callus, when re-subcultured in SH basal medium gave rise to hairy roots again. A rhizogenic cell suspension culture was established from this type of callus. When cultured in SH medium with growth regulators, the rhizogenic callus produced catharanthine at a level of 41% of the level in the initial hairy roots. Upon transfer to SH basal medium, regenerated hairy roots produced this alkaloid at the original level of 1.5 mg/g dry wt. Using this cell/hairy root interchange system a new management system for hairy root culture in bioreactors has been devised and examined involving production of biomass in the form of a cell suspension in medium supplemented with growth regulators, and catharanthine production by hairy roots regenerated from these cells in medium without growth regulators.Abbreviations NAA -naphthaleneacetic acid - SH Schenk and Hildebrandt - SHNK SH medium + 1 mg 1^–1 NAA + 0.1 mg 1^–1 kinetin     

Composition of essential oil in genetically transformed roots of <Emphasis Type="Italic">Ruta graveolens</Emphasis>

The composition of essential oil obtained by hydrodistillation from genetically transformed roots of common rue (Ruta graveolens L.) was analyzed. Using gas chromatography and complex gas chromatography-mass spectrometry, it was established that the major component of rue essential oil was a root-specific sesquiterpene geijerene comprising 67% of total amount of volatile compounds. In essential oil of cultured rue roots, furocoumarins characteristic of intact plant roots were found, viz. osthole, halepensin, and rutacultin. The content of essential oil in genetically transformed rue roots was 0.23% of root dry weight, which is comparable with that in the roots of intact plants. The long-term maintenance in the in vitro cultured rue roots of a capability for the synthesis of essential oil major components characteristic of intact plants allows their usage for studying the physiological activity of these volatile compounds and their putative role in the plant root interaction in biocenoses.     

根结线虫对文冠果苗木根系结构与生长及矿质养分分布特性的影响北大核心CSCD

以根结线虫侵染的文冠果一年生苗木为材料,观察分析苗木根系的形态和显微结构,植株生长发育以及主要矿质养分在苗木中的分布特性,并分析不同矿质元素与线虫侵染的关联关系,以揭示根结线虫对文冠果苗木生长发育的影响机制。结果表明:(1)受根结线虫侵染的文冠果苗木根系形成根结,依据根结发生程度分为0(对照,正常植株)、2、3、4级;与对照相比,具有根结的文冠果苗木根系解剖结构特征主要表现为皮层相对较厚,木质部排列扭曲,导管较少,射线数目较少且分布不均匀;韧皮细胞内含物明显较多;多个巨细胞及细胞空腔主要存在于韧皮部。(2)具根结的苗木株高和地径较对照均增加,且株高增幅达显著水平(P<0.05)。(3)具根结苗木根、茎、叶部位的N、P含量均较对照下降,根部降幅达显著水平(P<0.05),其中具2~4级根结的根部N含量分别较对照显著下降7.8%、16.0%和29.5%,P含量分别显著下降15.6%、7.1%和43.3%;根部Fe含量、Zn含量显著上升,2~4级根结根系中Fe含量较对照分别增加1.56倍、0.81倍和3倍,Zn含量分别增加1.11倍、1.56倍和1.78倍;具3和4级根结的苗木根系中K含量较对照显著增加(P<0.05),具2和4级根结的苗木叶片中K含量较对照分别显著下降61.5%和47.0%。(4)苗木根部、茎部N元素含量对于根结线虫侵染的响应最明显,且其含量随侵染程度的增大而降低,叶部Mg元素含量与根结线虫侵染率、K元素含量与整株苗木生物量均呈显著负相关关系(P<0.05)。该研究为根结线虫对文冠果苗木养分吸收利用及运转的影响提供了一定的理论依据。     

Nucleic Acid Metabolism of Vicia faba during Germination and Growth

During the growth of Vicia faba seedlings in the absence of an external nitrogen supply, the cotyledons decreased rapidly in dry weight and nucleic acid content. In the developing shoot the dry weight increased rapidly for four weeks and then very slowly over the next two weeks growth; the nucleic acid content of the shoot increased to a maximum after 4 weeks growth and decreased in amount during the next 2 weeks. On the other hand the roots increased in both dry weight and nucleic acid content throughout the growth period, although they only accounted for a small proportion of the total dry weight and nucleic acid content of the plant. These changes during germination and growth are discussed in relation to those occurring during these developmental stages in other plants.     

Free Radical Scavenging Activity and Comparative Metabolic Profiling of In Vitro Cultured and Field Grown Withania somnifera Roots

Free radical scavenging activity (FRSA), total phenolic content (TPC), and total flavonoid content (TFC) of in vitro cultured and field grown Withania somnifera (Ashwagandha) roots were investigated. Withanolides analysis and comprehensive metabolic profiling between 100% methanol extracts of in vitro and field grown root tissues was performed using high performance thin layer chromatography (HPTLC) and gas chromatography-mass spectrometry (GC-MS), respectively. Significantly higher levels of FRSA, TPC, and TFC were observed in in-vitro cultured roots compared with field grown samples. In addition, 30 day-cultured in vitro root samples (1MIR) exhibited a significantly higher FRSA (IC₅₀ 81.01 μg/mL), TPC (118.91 mg GAE/g), and TFC (32.68 mg CE/g) compared with those in 45 day-cultured samples (1.5MIR). Total of 29 metabolites were identified in in vitro cultured and field grown roots by GC-MS analysis. The metabolites included alcohols, organic acids, purine, pyrimidine, sugars, and putrescine. Vanillic acid was only observed in the in vitro cultured root samples, and higher level of the vanillic acid was observed in 1MIR when compared to 1.5MIR. Therefore, it is suggested that 1MIR might serve as an alternative to field grown roots for the development of medicinal and functional food products.     

Improvement of ginsenoside production by jasmonic acid and some other elicitors in hairy root culture of ginseng (Panax ginseng C. A. Meyer)

Summary Hairy root cultures of Panax ginseng, established after the infection of root sections with Agrobacterium rhizogenes KCTC 2703, were cultured in phytohormone-free Murashige and Skoog (MS) liquid medium containing different concentrations of jasmonic acid and some other elicitors, in order to promote ginsenoside accumulation. Jasmonic acid in the range 1.0−5.0 mg l⁻¹ (4.8–23.8 μM) strongly improved total ginsenoside production in ginseng hairy roots. Peptone (300 mg l⁻¹) also showed some effect on ginsenoside improvement; however its effect was much weaker than that of jasmonic acid. Ginsenoside content and productivity were 58.65 and 504.39 mg g⁻¹, respectively. The Rb group of ginsenoside content was increased remarkably by jasmonic acid, while Rg group ginsenoside content changed only slightly compared to controls. However, jasmonic acid also strongly inhibited ginseng hairy root growth.     

Flavonoid Production in Transformed Scutellaria baicalensis Roots and Ways of Its Regulation

A root culture of skullcap (Scutellaria baicalensisGeorgi) transformed with pRi T-DNA was initiated by the inoculation of sterile seedlings with Agrobacterium rhizogenes(wild-type strain A-4). The flavonoid concentration in cultured roots comprised 5% of the root dry weight and was maintained essentially constant during a subculture. For four weeks of culturing, the weight of the roots increased by 20–30 times; when the roots were cultured for a longer time and with periodic enrichment of the nutrient medium, their weight increased 50-fold. Skullcap roots were shown to synthesize flavones characteristic of intact roots (wogonin, baicalein, and baicalin). The addition of 0.01–1 mM L-phenylalanine (a precursor of flavonoids) to the nutrient medium affected neither root growth, nor their flavonoid concentration. Root elicitation with 100 M methyl jasmonate for 72 h increased the flavonoid content per flask and per root dry weight by 1.8 and 2.3 times, respectively.     

Effects of explant types and media salt strength on growth and secondary metabolite accumulation in adventitious roots of <Emphasis Type="Italic">Periploca sepium</Emphasis> Bunge

In order to study the capabilities of Periploca sepium adventitious root induction in different types of explants, we selected leaves, roots and stems with or without buds. The growth of adventitious roots and periplocin content in these roots were determined. In order to investigate the suitable media salt strength, we cultured the adventitious roots in different salt strength (0.25, 0.50, 1.0, 1.5, 2.0) of Murashige and Skoog (MS) media supplemented with 1 mg/l indole butyric acid (IBA) and 30 g/l sucrose. The results showed that both leaf and root explants were proven suitable for the adventitious root induction; however, the stems could hardly induce adventitious roots no matter whether the stems had buds or not. Further studies reported that adventitious root proliferation and periplocin production derived from root explants were higher than those derived from leaf explants. So the root explants were the optimum explants for adventitious root induction, growth and periplocin production. The salt strength experiment showed that with the increasing salt strength (1.0–2.0 MS), adventitious root growth decreased significantly, as well as periplocin content in comparison with lower (0.25–0.5 MS) salt strength media.