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PubMed2002

Effects of exogenous diamines on the interaction between ectomycorrhizal fungi and adventitious root formation in Scots pine in vitro.

Production of free and conjugated polyamines by two ectomycorrhizal fungi, Pisolithus tinctorius (Pers.) Coker and Couch and Paxillus involutus (Batsch) Fr., was studied in vitro. Spermidine was the main polyamine in the mycelium of both fungi. Paxillus involutus also produced large amounts of the diamine putrescine, whereas Pisolithus tinctorius contained traces of the diamine cadaverine and released into the culture medium an unknown compound probably related to cadaverine or N-methylputrescine. Both fungi accelerated adventitious root formation and increased subsequent root growth of Scots pine (Pinus sylvestris L.) hypocotyl cuttings in vitro. Exogenous cadaverine enhanced rooting caused by Pisolithus tinctorius and also promoted mycorrhiza formation by the fungus. Putrescine and Paxillus involutus had a synergistic effect on root initiation, but not on subsequent root growth. We conclude that specific diamines may be involved in the interaction between ectomycorrhizal fungi and adventitious root formation in Scots pine, and that the effects of specific exogenous polyamines are dependent on the fungal strain and its ability to produce these compounds. The finding that Paxillus involutus enhanced rooting and root growth without mycorrhiza formation indicates that fungal-induced rooting is not necessarily related to visible mycorrhiza formation.

Basidiomycota↗
PubMed1968

Gonadotropin promotion of adventitious root production on cuttings of Begonia semperflorens and Vitis vinifera.

Adventitious rooting of Begonia semperflorens cv. Indian Maid and Vitis vinifera cv. Semillon stem cuttings was significantly promoted by human chorionic gonadotropin (HCG). Basal sections of HCG treated cuttings upon which promoted rooting took place had markedly less endogenous gibberellin (GA) activity than non-treated controls or apical sections of treated ones, while changes in auxin levels were not found. HCG also inhibited GA(3)-induced reducing sugar release from embryoless barley endosperm halves. These findings are discussed in the light of a possible analogy to gonadotropin action in animal systems.

Chorionic Gonadotropin↗
PubMed2001

Response to auxin changes during maturation-related loss of adventitious rooting competence in loblolly pine (Pinus taeda) stem cuttings.

Hypocotyl cuttings (from 20- and 50-day-old Pinus taeda L. seedlings) rooted readily within 30 days in response to exogenous auxin, while epicotyl cuttings (from 50-day-old seedlings) rarely formed roots within 60 days. Responses to auxin during adventitious rooting included the induction of cell reorganization and cell division, followed by the organization of the root meristem. Explants from the bases of both epicotyl and hypocotyl cuttings readily formed callus tissue in response to a variety of auxins, but did not organize root meristems. Auxin-induced cell division was observed in the cambial region within 4 days, and later spread to the outer cortex at the same rate in both tissues. Cells at locations that would normally form roots in foliated hypocotyl cuttings did not produce callus any differently than those in other parts of the cortex. Therefore, auxin-induced root meristem organization appeared to occur independently of auxin-induced cell reorganization/division. The observation that N-(1-naphthyl)phthalamic acid (NPA) promoted cellular reorganization and callus formation but delayed rooting implies the existence of an auxin signal transduction pathway that is specific to root meristem organization. Attempts to induce root formation in callus or explants without foliage were unsuccessful. Both the cotyledon and epicotyl foliage provided a light-dependent product other than auxin that promoted root meristem formation in hypocotyl cuttings.

Journal Article↗
PubMed2000

Mechanisms of primordium formation during adventitious root development from walnut cotyledon explants.

In walnut (Juglans regia L.), an otherwise difficult-to-root species, explants of cotyledons have been shown to generate complete roots in the absence of exogenous growth regulators. In the present study, this process of root formation was shown to follow a pattern of adventitious, rather than primary or lateral, ontogeny: (i) the arrangement of vascular bundles in the region of root formation was of the petiole type; (ii) a typical root primordium was formed at the side of the procambium within a meristematic ring of actively dividing cells located around each vascular bundle; (iii) the developing root apical meristem was connected in a lateral way with the vascular bundle of the petiole. This adventitious root formation occurred in three main stages of cell division, primordium formation and organization of apical meristem. These stages were characterized by expression of LATERAL ROOT PRIMORDIUM-1 and CHALCONE SYNTHASE genes, which were found to be sequentially expressed during the formation of the primordium. Activation of genes related to root cell differentiation started at the early stage of primordium formation prior to organization of the root apical meristem. The systematic development of adventitious root primordia at a precise site gave indications on the positional and biochemical cues that are necessary for adventitious root formation.

Plant Roots↗
PubMed1999

Gravitropic response of adventitious roots cultivated in light and darkness on sucrose-free medium.

Elongation of adventitious roots of Dracaena fragrans was investigated under photoautotrophic conditions. Root elongation decreased and stopped when cultures were transferred to darkness. Upon return to light roots renewed growth after a 5 day lag period. During the first two days of intensive new growth roots were agravitropic elongating in random directions. Investigation showed that transient absence of geotropic response was connected with disappearance of starch grains in root tip which occurred due to sucrose starvation of cultures in continuous darkness.

Culture Media↗
PubMed2004

Microarray analyses of gene expression during adventitious root development in Pinus contorta.

In order to investigate the gene expression pattern during adventitious root development, RNA of Pinus contorta hypocotyls, pulse-treated with the auxin indole-3-butyric acid and harvested at distinct developmental time points of root development, was hybridized to microarrays containing 2,178 cDNAs from Pinus taeda. Over the period of observation of root development, the transcript levels of 220 genes changed significantly. During the root initiation phase, genes involved in cell replication and cell wall weakening and a transcript encoding a PINHEAD/ZWILLE-like protein were up-regulated, while genes related to auxin transport, photosynthesis, and cell wall synthesis were down-regulated. In addition, there were changes in transcript abundance of genes related to water stress. During the root meristem formation phase the transcript abundances of genes involved in auxin transport, auxin responsive transcription, and cell wall synthesis, and of a gene encoding a B-box zinc finger-like protein, increased, while those encoding proteins involved in cell wall weakening decreased. Changes of transcript abundance of genes related to water stress during the root meristem formation and root formation phase indicate that the plant roots had become functional in water transport. Simultaneously, genes involved in auxin transport were up-regulated, while genes related to cell wall modification were down-regulated. Finally, during the root elongation phase down-regulation of transcripts encoding proteins involved in cell replication and stress occurred. Based on the observed changes in transcript abundances, we suggest hypotheses about the relative importance of various physiological processes during the auxin-induced development of roots in P. contorta.

Cell Division↗
PubMed2006

Enhanced ginsenoside productivity by combination of ethephon and methyl jasmoante in ginseng (Panax ginseng C.A. Meyer) adventitious root cultures.

Ethephon at 50 microM enhanced both root growth and ginsenoside accumulation in ginseng (Panax ginseng C.A. Meyer) adventitious root cultures, but at 100 microM it inhibited only ginsenoside accumulation. Ginsenoside productivity with 50 microM ethephon was the highest at 1.7 mg l(-1) d(-1) after 8 days of elicitation. However, elicitation with 50 microM ethephon and 100 microM methyl jasmonate (MJ) improved productivity (6.3 mg l(-1) d(-1)) whereas elicitation with 100 microM MJ alone gave only 2.9 mg l(-1) d(-1).

Acetates↗
PubMed1972

Meristematic Activity during Adventitious Root Primordium Development: Influences of Endogenous Auxin and Applied Gibberellic Acid.

Intact brittle willows (Salix fragilis L.) were treated so that developing adventitious root primordia in the stems would be subjected to elevated gibberellic acid or reduced endogenous auxin levels. Observations were made of primordia that were initiated during the experiments and of primordia that were established before the experiments began. The results indicated that as primordia became older and contained more cells, auxin basipetally transported in the stem seemed to be of less importance in determining cell number per primordium. Thus, established primordia depended upon this auxin to a lesser extent than primordia which were being initiated. These observations were explained on the basis of differential contributions during primordium development of cell division in the cambium of the stem and in the primordia themselves. As opposed to the effects of reduced auxin levels, applied gibberellic acid reduced the cell number per primordium most in established primordia. Initiating primordia were least affected by gibberellic acid treatment. Gibberellic acid treatment seemed mainly to reduce intraprimordium cell division, on which continued development of established primordia most depends. Seemingly, at least in brittle willow, applied gibberellic acid blocks the action of auxin in primordium development subsequent to the initiation phase.

Journal Article↗
PubMed2006

Calcium and calcium-dependent protein kinases are involved in nitric oxide- and auxin-induced adventitious root formation in cucumber.

A few years ago it was demonstrated that nitric oxide (NO) and cGMP are involved in the auxin response during adventitious root (AR) formation in cucumber (Cucumis sativus). More recently, a mitogen-activated protein kinase cascade was shown to be induced by IAA in a NO-dependent, but cGMP-independent, pathway. In the present study, the involvement of Ca2+ and the regulation of Ca2+-dependent protein kinase (CDPK) activity during IAA- and NO-induced AR formation was evaluated in cucumber explants. The effectiveness of several broad-spectrum Ca2+ channel inhibitors and Ca2+ chelators in affecting AR formation induced by IAA or NO was also examined. Results indicate that the explants response to IAA and NO depends on the availability of both intracellular and extracellular Ca2+ pools. Protein extracts from cucumber hypocotyls were assayed for CDPK activity by using histone IIIS or syntide 2 as substrates for in-gel or in vitro assays, respectively. The activity of a 50 kDa CDPK was detected after 1 d of either NO or IAA treatments and it extended up to the third day of treatment. This CDPK activity was affected in both extracts from NO- and IAA-treated explants in the presence of the specific NO-scavenger cPTIO, suggesting that NO is required for its maximal and sustained activity. The in-gel and the in vitro CDPK activity, as well as the NO- or IAA-induced AR formation, were inhibited by calmodulin antagonists. Furthermore, the induction of CDPK activity by NO and IAA was shown to be reliant on the activity of the enzyme guanylate cyclase.

Aminoquinolines↗
PubMedDate not supplied

Genetic analysis of variation for auxin-induced adventitious root formation among eighteen ecotypes of Arabidopsis thaliana L. Heynh.

Eighteen ecotypes and two inbred lines of Arabidopsis thaliana L. Heynh. were analyzed for variation in the number of adventitious roots formed (hereafter referred to as rooting) on seedling hypocotyls in response to auxin treatment. Mean root counts varied from 1.7 to 23.1. Stable high (HA) and low (LA) rooting lines selected from ecotype Columbia, a low rooting ecotype (Mt-0), and unselected Columbia populations were evaluated for vegetative and reproductive growth parameters to determine correlated phenotypic effects of selection for rooting response. High rooting in HA correlated with compact, highly branched shoot growth. Genetic analysis of HA, Mt-0, and their F1, F2, and reciprocal backcross generations indicated that high and low rooting responses in this population may be controlled by several genes acting independently in additive-dominance fashion. Genetic variance partitioned into principally additive effects, with dominance favoring low rooting.

Arabidopsis↗
PubMed1978

Production of adventitious root primordia on hypocotyls of castor bean seedling, infected with Agrobacterium tumefaciens.

The development of sterile secondary tumours on hypocotyls of castor bean seedlings, inoculated with any of the ten isolates of Agrobacterium tumefaciens tested, were observed below the site of the primary tumours. Histopathological studies performed in the present work indicate that the observed secondary tumours were adventitious root primordia and not the ordinary type of secondary tumours. According to the available literature such findings are reported here for the first time. All the tested isolates of the present study were also able to initiate well defined roots in conjunction with crown gall (teratomas) on Bryophyllum crenata and Kalanchoe marmorata, but not in tomato.

Ricinus communis↗
PubMed1989

Relationship between Indole-3-Acetic Acid Levels in Apple (Malus pumila Mill) Rootstocks Cultured in Vitro and Adventitious Root Formation in the Presence of Indole-3-Butyric Acid.

In vitro rooting response and indole-3-acetic acid (IAA) levels were examined in two genetically related dwarfing apple (Malus pumila Mill) rootstocks. M.26 and M.9 were cultured in vitro using Linsmaier-Skoog medium supplemented with benzyladenine (BA), indole-3-butyric acid (IBA), and 1,3,5-trihydroxybenzoic acid (PG). Rooting response was tested in Lepoivre medium supplemented with IBA and PG. IBA concentrations of 12.0 and 4.0 micromolar induced the maximum rooting percentages for M.9 and M.26, respectively. At these concentrations rooting response was 100% for M.26 and 80% for M.9. Free and conjugated IAA levels were determined in M.26 and M.9 shoots prior to root inducing treatment by high performance liquid chromatography with fluorescence detection and validated by gas chromatography-mass spectrometry using (13)[C(6)]IAA as internal standard. Basal sections of M.26 shoots contained 2.8 times more free IAA than similar tissue in M.9 (477.1 +/- 6.5 versus 166.6 +/- 6.7 nanograms per gram fresh weight), while free IAA levels in apical sections of M.26 and M.9 shoots were comparable (298.0 +/- 4.4 versus 263.7 +/- 9.3 nanograms per gram fresh weight). Conjugated IAA levels were significantly higher in M.9 than in M.26 indicating that a greater proportion of total IAA was present as a conjugate in M.9. These data suggest that differences between M.26 and M.9 rooting responses may be related to differences in free IAA levels in the shoot base.

Journal Article↗
PubMed1990

Flavonoid Accumulation Is Correlated with Adventitious Roots Formation in Eucalyptus gunnii Hook Micropropagated through Axillary Bud Stimulation.

Eucalyptus gunnii Hook microcuttings, obtained in vitro through axillary bud stimulation, show different rooting responses on the same rooting medium depending on the physiological state induced by cytokinins used in the previous multiplication medium. 6-Furfurylamino purine and 6-(4-hydroxy-3-methylbut-2-enylamino)purine induced a physiological state characterized by high sensitivity of microcuttings to the rooting stimulus exerted by the auxin 3-indolebutyric acid, but N(6)-benzyladenine did not produce the same effect. The former physiological state was characterized by an increased accumulation of two endogenous flavonoids (identified as quercetin glycosides) which may be markers of a well defined physiological state. They could have some direct influence on the rooting processes of the explants cultivated in vitro.

Journal Article↗
PubMed1992

[Cytological observation on culture of embryo in vitro of Tripterygium hypoglaucum (level.) Hutch].

This paper for the first time reports the embryo culture in vitro of Tripterygium hypoglaucum. Callus, adventitious roots and adventitious protuberances were induced from the cultured embryos in vitro. Multi-buds at the excised embryo tip were also observed at the same time. Cytohistological examination showed (1) callus was histologically easy to be induced to form adventitious roots; (2) callus on the cotyledons was originated from the epidemical and subepidemical cells of the cotyledons, and the adventitious roots were originated from the disperse meristematic tissue or vascular tissue in the callus obtained from cultured excised embryos.

Culture Techniques↗
PubMed2006

Water uptake by roots of Hordeum marinum: formation of a barrier to radial O2 loss does not affect root hydraulic conductivity.

The adventitious roots of Hordeum marinum grown in stagnant deoxygenated solution contain a barrier to radial O2 loss (ROL) in basal zones, whereas roots of plants grown in aerated solution do not. The present experiments assessed whether induction of the barrier to ROL influences root hydraulic conductivity (Lpr). Wheat (Triticum aestivum) was also studied since, like H. marinum, this species forms aerenchyma in stagnant conditions, but does not form a barrier to ROL. Plants were grown in either aerated or stagnant, deoxygenated nutrient solution for 21-28 d. Root-sleeving O2 electrodes were used to assess patterns of ROL along adventitious roots, and a root-pressure probe and a pressure chamber to measure Lpr for individual adventitious roots and whole root systems, respectively. Lpr, measured under a hydrostatic pressure gradient, was 1.8-fold higher for individual roots, and 5.6-fold higher for whole roots systems, in T. aestivum than H. marinum. However, there was no difference in Lpr between the two species when measured under an osmotic driving force, when water moved from cell to cell rather than apoplastically. Root-zone O2 treatments during growth had no effect on Lpr for either species (measured in aerobic solution). It is concluded that induction of the barrier to ROL in H. marinum did not significantly affect the hydraulic conductivity of either individual adventitious roots or of the whole root system.

Hordeum↗