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Wild plant species are of great interest as a source of pharmacologically valuable compounds but a great number of them are endemic and/or endangered ones. Modern plant biotechnology can provide reliable methods for their utilization without disturbing natural populations. In vitro culture methods for Rhodiola species are being intensively developed to include them into various biotechnological programmes. Aim. Development of a protocol for direct Rhodiola rosea L. plant regeneration from leaf explants. Methods. The leaves of R. rosea aseptically growing plants were used as the explants. Several variants of Murashige and Skoog (1962) agar-solidified culture medium supplemented with different combinations of auxins (1-naphthaleneacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-D)) and cytokinins (kinetin and 6-benzylaminopurine (BAP)) were estimated as potential regeneration-inducing media. Regeneration frequency was calculated as the percentage of leaves that produced shoots. Results. The use of MS medium supplemented with 2.5 mg/l BAP and 1.0 mg/l 2,4-D allowed inducing shoot formation with 100% frequency. An increase in the 2,4-D content up to 2.5 mg/l and decrease in BAP content to 1.0 mg/l resulted in decreasing of the regeneration frequency to 62.5%. Regeneration frequency was 25% and 62%, respectively, on the media containing 1.0 mg/l kinetin + 2.5 mg/l 2,4-D and 2.5 mg/l kinetin + 1.0 mg/l 2,4-D. Conclusions. R. rosea leaf explants have demonstrated high regeneration capacity with using the studied combinations of plant growth regulators. MS medium supplemented with 2.5 mg/l BAP and 1.0 mg/l 2,4-D allowed inducing shoot regeneration in leaf explants with the frequency of 100%. The frequency of regeneration was lower in the case of substitution of BAP for kinetin. The other types of morphogenesis (formation of adventitious roots and/or callus) were also observed.

Water hyssop (Bacopa monnieri (L.) Pennell) is a medicinal plants. Its upper and lower halves of leaf explants were incubated in Murashige and Skoog (MS) medium supplemented with 0.25, 0.50 and 1.0 mg/L benzylaminopurine (BA) for 8 weeks; the explants were exposed to white (W) and red and blue (R and B, respectively) light-emitting diodes (LEDs), at 4:1, 3:1, 2:1 and 1:1 R and B light ratios, respectively. Shoot regeneration (100%) was achieved from all explants at all applied concentrations of BA and LED types. All explants showed different BA concentration requirements for regeneration of the maximum number of shoots. Longer shoots were obtained on medium with 0.25 mg/L BA. The W LED lighting system was found to be more effective for regenerating the maximum number of shoots (26.11) per explant (on the upper half of the leaf). Conversely, longer and shorter shoots were generated under 1:1 R:B and W LEDs, respectively. The number of shoots per explant ranged from 9.67-24.0 (full leaf), 6.33-25.92 (lower half of the leaf) and 7.33-27.33 (upper half of the leaf), respectively, in response to BA and LED light. Shoot length ranged from 0.94-1.90 cm (full lamina), 0.70-2.11 cm (lower half of the leaf) and 0.93-1.83 cm (upper half of the lamina) in response to BA and LED lifght. Regenerated shoots were successfully rooted using indole-3-butyric acid (IBA) and acclimatized in the aquarium provided with tap water.

The organogenesis potential is different among cultivars and must be optimized for individual genotype. Shoot organogenesis capacity from in vitro leaves and root organogenesis capacity of in vitro shoots in six clonal apple rootstock cultivars were compared. The shoot organogenesis capacity was highly genotype dependent. 'GM256' was found to be the most responsive genotype for shoot regeneration from leaf explants among the cultivars, showing high regeneration percentage on all tested media. The effects of basal medium composition and cytokinins on shoot regeneration were different depending on rootstock genotype. Optimum regeneration occurred on Murashige and Skoog (MS) basal medium for '71-3-150', and optimum regeneration occurred on Quoirin and Lepoivre (QL) basal medium for '60-160' and 'ПB'. Thidiazuron (TDZ) was more effective than 6-benzylaminopurine (BA) for Malus prunifolia (Y), whereas TDZ and BA were not significantly different for the other cultivars. All rootstock cultivars showed high root organogenic capacity. The percentage of rooting reached more than 90% and the mean root number per plantlet ranged from three to five. The optimum rooting medium was different for different rootstock cultivars. Optimum root organogenesis occurred on half-strength QL medium for 'GM256' and 'Y', and for 'ПB' and 'JM7' on one-quarter-strength MS medium. [ABSTRACT FROM AUTHOR]

Carbenicillin, a well-known antibiotic, has been reported to have growth regulator-like activity in vitro for some plant species. In the present paper we add horseradish ( Armoracia rusticana) to the list of plants exhibiting such responses. This project began as an effort to eliminate latent bacterial contamination among established in vitro horseradish plants. Carbenicillin (100 mg L) added to regeneration medium eliminated all visible bacterial contaminants. Unexpectedly, carbenicillin-grown explants regenerated adventitious shoots faster (14 days) than those on control medium (21 days). In addition eight of 11 horseradish cultivars grown on carbenicillin produced more adventitious shoots per explant than control. At much higher levels (2,000 mg L) carbenicillin was found to retard somatic embryogenic callus induction. Based on these observations we suggest that carbenicillin at moderate levels enhances shoot development in horseradish. The mode of action of carbenicillin’s growth regulator-like activity needs to be investigated. [ABSTRACT FROM AUTHOR]

The morphology of horseradish (Armoracia rusticana P. Gaertn., B. Mey & Scherb.) leaves varies through the growing season. The leaves range from laminate (complete) in the summer to pinnate (fern-leaf) toward the end of the growing season in the fall, with intermediate types appearing regularly. The causes of these changes are not understood. To determine whether leaf morphology affects their ability to regenerate adventitious shoots in vitro, laminate, pinnate, and intermediate leaves of 10 horseradish cultivars were established in vitro. Laminate leaves were more likely to regenerate shoots (77%) than other leaves (23%). It is recommended that laminate leaves be used as explants to regenerate horseradish plants in vitro. [ABSTRACT FROM AUTHOR]