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The present study investigated the effect of gamma irradiation on biomass formation and yield of pharmacologically relevant secondary metabolites in callus cultures induced from different seedling parts (leaf, stem and root). Calli induction and maintenance were performed on MS medium supplemented with 0.5 mg L−1 IAA and 0.4 mg L−1 TDZ and all parameters were recorded after the third 21 days successive subculture post-elicitation. Fresh callus biomass (FCB) expressed as growth index (Gi) was investigated and the higher Gi value (1109%) was recorded on callus culture from leaf explants and irradiated with 10 Gy dose, as compared to untreated control (757%). H. triquetrifolium callus cultures exhibited quantitatively different phenolic compounds (p-OH-benzoic and chlorogenic acid, epicatechin) and naphtodiantrones (hypericin and pseudohypericin). The chromatographic analysis of callus extracts revealed that after gamma rays elicitation with 10 Gy dose, the higher amount of p-OH-benzoic acid was recorded on calli from leaf explant (4.35 mg 100 g−1 DW material) while root callus recorded the highest amount of chlorogenic acid (12.91 mg 100 g−1) over the control (3.55 mg 100 g−1 and 10.22 mg 100 g−1, respectively). The 10 Gy and 20 Gy irradiation doses stimulate the epicatechin accumulation on calli from leaf and stem (126.39 and 148.80 mg 100 g−1) compared to the control samples (98.81 and 101.72 respectively). In this study, small amount of hypericin and pseudohypericin were identified and quantified on irradiated callus cultures initiated from stem and leaf of Hypericum triquetrifolium, but not in root calli. Callus induced from leaf and irradiated with 10 Gy showed the higher amounts of hypericin and pseudohypericin content (0.29 and 4.00 mg 100 g−1 DW material). Phytochemical screening carried out on different elicited callus cultures variants reveal, for the first time, the stimulatory effects of gamma irradiation on the production of phenolic compounds and naphtodiantrones in Hypericum triquetrifolium Turra. The results of this study are interesting and offer an innovative approach of elicitation, not yet widely studied for the Hypericum genus.

To explore the potential for in vitro rapid regeneration of Spanish dagger (Yucca gloriosa 'Variegata'), different concentrations of 6-Benzyladenine (BA), 1-naphthaleneacetic acid (NAA) and combinations of both were evaluated for callus induction initiated on leaf and bud (terminal and axillary buds) explants using Murashige and Skoog (MS) medium. Callus response induction percentage, fresh weight, color and texture of the callus were assessed after 1.5 and 6.0 months in culture. The appropriate medium for callus initiation on leaf explants was MS medium supplemented with 6.0 mg/L NAA. A combination of 0.2 mg/L BA and 1.5 mg/L NAA also exhibited a remarkable callus induction on bud explants. Effect of thidiazuron (TDZ) addition to the culture medium supplemented with BA and NAA at various concentrations (0.0, 0.1, 0.5 or 1.0 mg/L) was investigated. Faster callus growth and more callus proliferationon from bud explants were observed in MS medium supplemented with 0.1 mg/L BA + 1.5 mg/L NAA + 1 mg/L TDZ. Results showed that TDZ was more effective on callus induction than BA or NAA, however some combinations gave direct shoot regeneration. Calli derived from bud explants were whitish to creamy and compact, while calli derived from leaf explants were greenish.

Transgenic Sesbania grandiflora (L.) pers (Fabaceae) and Arabidopsis thaliana (L.) (Brassicaceae) plants harbouring the rabbit cytochrome p450 2E1 enzyme were evaluated for their ability to accumulate heavy metals, potassium (K), calcium (Ca), manganese (Mn), zinc (Zn), copper (Cu), iron (Fe), lead (Pb) and bromine (Br), using X-ray Fluorescence analysis. When grown for 15 days on heavy metal-contaminated soils, transgenic cuttings of S. grandiflora and T3 A. thaliana plants recorded higher dry and fresh weight compared with their respective controls (A. thaliana and S. grandiflora plants transformed with an empty vector). Dry weight of transgenic S. grandiflora plants (0.321 g) was seven times higher than that of the wildtype (0.049 g), and the fresh weight (4.421 g) was about 4.6 times higher. Likewise, the dry weight of CYP450 2E1 A. thaliana (0.198 g) was more than eight times higher than that seen in the control (0.024 g). Moreover, Fe, Mn, K, and Ca concentrations in transgenic plants were significa...

Liquorice plant is considered one of the important medicinal and economical plants. It is rich with many compounds, minerals, vitamins, and even plant hormones. This research is aimed to study the possibility of using callus tissue extracts as an alternative to plant growth regulators added to the culture media. A factorial experiment was implemented to find out the appropriate combination between 2, 4-D and BA for callus induction on Liquoricenode explants. It was found that a combination of 2 mg/l 2, 4-D with 2.5 mg/l BA is the best one for callus induction and maintenance using MS medium. Water and alcoholic extracts were prepared from callus tissue at concentrations (0, 2, 4, 6, 8 or 10) ml/l then added to culture medium as an alternative to plant growth regulators. The effect of these concentrations on growth and development of tissues and organs for some plants was studied using soya bean, potato and wheat plants for this purpose. Results showed that water extract induced shoot proliferation from potato single nodes. Both types of extracts increased soya bean callus fresh weight significantly. It was found also that water extract was more effective than alcoholic one in increasing vegetative and root parts in germinating wheat seeds.

Sesbania grandiflora (L.) pers (Fabaceae) and Arabidopsis thaliana (L.) (Brassicaceae) were genetically engineered to constitutively express the rabbit cytochrome p450 2E1 enzyme aiming at increasing their activity toward trichloroethylene (TCE) and dichlorodiphenyltrichloroethane (DDT) removal Successful generation of Sesbania and Arabidopsis transgenic plants was verified using p450 2E1 specific PCR and confirmed by western blot analysis. Gas chromatography (GC) analysis revealed that small cuttings of Sesbania and third generation (F3) Arabidopsis transgenic plants exposed to TCE and DDT in small hydroponics' vessels accumulated more TCE and DDT compared to plants transformed with the empty vector. Furthermore, both transgenic plants were more effective in breaking down TCE and DDT with a 2-fold increase in TCE metabolism. Two independent Arabidopsis lines showed that DDT was metabolized about 4-fold higher than that detected in non transformed plants. Similarly, S. grandiflora cuttings removed 51 to 90% of the added DDT compared with only 3% removal in controls transformed with the null vector. Notably, stability of rabbit cytochrome p450 2E1 was confirmed using third generation Arabidopsis plants that displayed higher potential for the removal of two important pollutants, TCE and DDT compared with the controls.

An in vitro selection method was developed for Coleus blumei to enhance salt tolerance of this amenity species. Leaf disc explants were incubated on a Murashige & Skoog medium containing benzylaminopurine, 2 mg l-1, and napthalene acetic acid, 1 mg l-1, which initiated both callus and plantlets from the explants. A large number of explants were incubated on this differentiating medium containing 90 mM NaCl, which inhibited over 90% of plantlet formation. Surviving plantlets. were grown to maturity, when apical cuttings were taken and propagated. Plants were also allowed to flower and set seed. Cuttings from the selected regenerated plants showed consistently better growth in the presence of NaCl than unselected cuttings. Seed progeny of selected plants also showed more vigorous growth in the presence and absence of NaCl than progeny from unselected plants. The in vitro selection was compared with the results of an earlier in vivo selection to assess the contribution from tissue culture derived somaclonal variation. Progeny from the in vitro selection showed a higher level of tolerance than progeny from the in vivo selection.

SummaryThe amenity species Coleus blumei and Salvia splendens were irrigated with increasing concentrations of NaCl under glasshouse conditions. Salt was either added to the plants from the seedling stage onwards at one of the following concentrations, 0, 30, 60,120 or 180 mM NaCl up to six weeks (Expt. I), or, starting from 0 mM NaCl, the concentration was increased by 15 mM NaCl per week to a final concentration of 210 mM NaCl at 14 weeks (Expt. II). In Expt. I leaf number, leaf area, shoot and root weight progressively decreased in Coleus. However, Salvia root and shoot weights showed a pronounced fall at 30 mM NaCl and total leaf abscission occurred at NaCl concentrations above 60 mM NaCl within six weeks. Leaf thickness increased in both species over the sampling period. Where there was a gradual increase in NaCl concentrations (Expt. II), growth of Coleus and Salvia was much less inhibited at concentrations of NaCl found to be inhibitory in Expt. I. In both the concentration of Na+ in the roots incr...