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In this study, we evaluated the feasibility of using mass cultivation of the adventitious roots of Echinacea purpurea in balloon type bubble (air-lift) bioreactors to produce caffeic acid derivatives, which have pharmaceutical and therapeutic values. An approximately 10 fold increase in biomass and secondary compounds was observed after 4 weeks of culture in balloon type bubble bioreactors (5 L capacity containing 4 L of half strength MS medium). In addition, a linear relationship was observed between the concentration of biomass and the sucrose and ion consumption rate. Furthermore, the concentration of biomass in the bioreactor culture was found to increase as the conductivity decreased. An inoculum density of 7 g/L FW and an aeration rate of 0.1 vvm were found to be suitable for inducing the accumulation of biomass and secondary metabolites. Of the three caffeic acid derivatives evaluated (caftaric acid, chlorogenic acid, and cichoric acid), the concentration of cichoric acid was the highest (26.64 mg/g DW).

Plant adventitious root culture in bioreactors is a promising alternative for the efficient production of medicinal herbs. Adventitious roots of Pseudostellaria heterophylla were induced from callus and then cultivated in a siphon-mist bioreactor. An orthogonal test established that the optimal medium for adventitious root induction was MS medium supplemented with 1.0 mg/L naphthaleneacetic acid and 2.0 mg/L 3-indolybutyric acid. Under these conditions, the average root number was more than 14 on each 1.0 cm diameter callus and the rooting rate reached 100%. The bioreactor was equipped with an integral siphon-spraying device designed to automatically supply the liquid medium. The operation parameters of the bioreactor were assessed by varying the mist interval and the aeration velocity. The mist interval was negatively related to average growth rate of the adventitious roots and positively related to saponin and polysaccharide content. A relatively high aeration rate was necessary to achieve the maximum biomass production, but the secondary metabolite production was not enhanced by increasing the aeration velocity.

Many aspects of plant development are associated with changing concentrations of the phytohormone auxin. Several stages of root formation exhibit extreme sensitivities to exogenous auxin and are correlated with shifts in endogenous auxin concentration. In an effort to elucidate mechanisms regulating development of adventitious roots, an ethyl methanesulfonate-mutagenized M2 population of Arabidopsis was screened for mutants altered in this process. A recessive nuclear mutant, rooty (rty), displayed extreme proliferation of roots, inhibition of shoot growth, and other alterations suggesting elevated responses to auxin or ethylene. Wild-type Arabidopsis seedlings grown on auxin-containing media phenocopied rty, whereas rty seedlings were partially rescued on cytokinin-containing media. Analysis by gas chromatography-selected ion monitoring-mass spectrometry showed endogenous indole-3-acetic acid concentrations to be two to 17 times higher in rty than in the wild type. Dose-response assays with exogenous indole-3-acetic acid indicated equal sensitivities to auxin in tissues of the wild type and rty. Combining rty with mutations conferring resistance to auxin (axr1-3) or ethylene (etr1-1) suggested that root proliferation and restricted shoot growth are auxin effects, whereas other phenotypic alterations are due to ethylene. Four mutant alleles from independently mutagenized populations were identified, and the locus was mapped using morphological and restriction fragment length polymorphism markers to 3.9 centimorgans distal to marker m605 on chromosome 2. The wild-type RTY gene product may serve a critical role in regulating auxin concentrations and thereby facilitating normal plant growth and development

We tested desiccation and/or vitrification procedures to cryopreserve the adventitious roots of Panax ginseng, the source of commercially produced ginsenosides. When only desiccation was applied, the post-freeze survival of 3- to 4-mm root tips was less than 14% regardless of the composition of the preculture medium or the explant origin. Callus formation was frequently observed after cryopreservation. In contrast, 90% survival and 32.5% root formation efficiency were achieved after cryopreservation when a vitrification protocol was followed. Adventitious root cultures in flasks and bioreactors were reestablished from root tips cryopreserved by vitrification. A prolonged lag-phase and lower biomass production were recorded in post-freeze-regenerated cultures compared with control roots that were subcultured four times in flasks. However, biomass accumulations did not differ between control and regenerated roots at the end of the sixth subculturing period. After 40 days of culture in bioreactors, a mean value of 12.5 g dw L-¹ was recorded for post-freeze-regenerated cultures versus 9.1 g dw L-¹ for the control roots. Production of triol and diol ginsenosides in our bioreactor cultures also was enhanced after cryopreservation, by 41.0% and 89.8%, respectively. These results suggest that the vitrification method is successful for cryopreservation of P. ginseng adventitious roots.

We describe a gene that is expressed in lateral and adventitious root primordia of Arabidopsis. The gene was Identified by expression of a transposon-borne promoterless beta-glucuronidase gene in lateral root primordia. The gene designated LRPt for lateral root primordium 1 and its corresponding cDNA were cloned and sequenced. The expression pattern of the gene in lateral root primordia was confirmed by in situ hybridization with LRP1 cDNA probes. The LRP1 gene encodes a novel protein. LRP1 expression is activated during the early stages of root primordium development and is turned off prior to the emergence of lateral roots from the parent root. Insertion of the transposon in the LRP1 gene disrupted its expression. To evaluate the homozygous insertion line for a mutant phenotype several aspects of wild-type lateral root development were analyzed. A mutant phenotype has not yet been identified in the insertion line; however there is evidence that the gene belongs to a small gene family. LRP1 provides a molecular marker to study the early stages of lateral and adventitious root primordium development

To determine the role of adventitious roots in supplying water to Ipomoea pes-caprae (L.) Sweet (Convolvulaceae), we examined the effects of water deficit on water uptake and the growth patterns of leaves and shoots. After stopping the water supply from the primary root or adventitious roots, the water-uptake rate of the other root system increased steeply within 90-100 min to a level of 90% of the pretreatment water-uptake rate of the whole plant. Thus, the primary and adventitious roots can compensate for a decrease in the water-uptake rate of the whole plant caused by dehydration. The continuous growth of leaves and shoots after dehydration suggests that an increase in the water-uptake rate by either root system can support plant growth, although the growth rates of immature leaves in plants with no water supply from the primary or adventitious roots were lower than in controls. We conclude that the water supply from adventitious roots contributes to the survival and growth of plants, and will be important for vegetative propagation.

We treated cultured tobacco leaf segments with brassinolide (BL) and naphthalene acetic acid (NAA) and determined that optimum concentrations of NAA for adventitious root, trichome-like root, and calli formation were, respectively, 10∨-6, 10∨-5, and 10-⁴ M. In the adventitious root formation group, the number and length of adventitious roots were increased at lower concentrations of BL; however, they became trichome-like roots at higher levels of BL. The trichome-like root formation group showed better development when a low concentration of BL was added. However, at higher concentrations of BL, trichome-like root production was reduced, forming calli instead. In the calli formation group, more calli were formed at low BL concentrations and after persistent exposure to BL regardless of BL concentration, and the size of the leaf segments increased. The CNT103 gene, which is expressed at the root tips showed increased levels of expression at BL concentrations up to 10∨-9 M and decreased levels of expression at BL concentrations over 10∨-9 M in the adventitious roots, trichome-like roots, and calli formation groups.

This study was conducted with the aim of developing an efficient heat reflux extraction of caffeic acid derivatives from dried adventitious roots of Echinacea purpurea obtained in bioreactor cultures. Water, methanol (20, 40, 60, 80, and 100%), and ethanol (20, 40, 60, 80, and 100%) were used as solvents for the extraction of caffeic acid derivatives. Another parameter used for the optimisation was the solvent temperature during extraction. The treatment of samples with 60% ethanol at 60 deg C for 2 h proved to be the most suitable procedure. This treatment was also responsible for the higher yields of total phenolics, flavonoids, and polysaccharides.

Adventitious roots were produced directly from root segments of Panax ginseng seedlings when cultured on an MS solid medium containing 3.0 mg L-¹ IBA. Omitting NH₄NO₃ from this medium greatly enhanced both the frequency of adventitious root formation and the number of roots per explants. This frequency declined markedly with the age of the root, but could be increased through repeated sub-culturing events. A two-step procedure that included NH₄NO₃- free media for the first two weeks of culture, followed by transfer onto media containing NH₄NO₃ for another four weeks, greatly improved total fresh weights of these adventitious roots compared with a method of continuous culture over six weeks in media that always contained NH₄NO₃.

Poplar shoots raised in vitro were induced to root by incubation on an auxin (NAA) containing medium for 7 h. After 13 days on an auxin-free medium, 97% of the treated shoots had rooted. The introduction of known antiauxins (PCIB, PBA, POAA) into the rooting expression auxin-free medium, after the 7-h induction by NAA, completely (PCIB and PBA) or severely (POAA) inhibited rooting. The exclusion of calcium from the expression auxin free medium reduced the percentage of rooting by about 42%. The inhibition was still higher in the presence of EGTA, a calcium chelator. Lanthanum chloride, a calcium channel blocker, also completely inhibited rooting, when incorporated into the auxin free medium, with or without calcium. These results support previous hypotheses about the implication of both endogenous auxin and calcium in the late phases of the adventitious rooting process.[PUBLICATION ABSTRACT]