Digitalis purpurea L. (Scrophulariaceae; Foxglove) is a source of cardiotonic glycosides such as digitoxin and digoxin which are commercially applied in the treatment to strengthen cardiac diffusion and to regulate heart rhythm. This investigation deals with in vitro propagation and elicited production of cardiotonic glycosides digitoxin and digoxin in shoot cultures of D. purpurea L. In vitro germinated seedlings were used as a primary source of explants. Multiple shoot formation was achieved for three explant types (nodal, internodal, and leaf) cultured on Murashige and Skoog (MS) medium with several treatments of cytokinins (6-benzyladenine-BA; kinetin-Kin; and thidiazuron-TDZ) and auxins (indole-3-acetic acid-IAA; α-naphthaleneacetic acid-NAA; and 2,4-dichlorophenoxy acetic acid-2,4-D). Maximum multiple shoots (12.7 ± 0.6) were produced from nodal explants on MS + 7.5 μM BA. Shoots were rooted in vitro on MS containing 15 μM IAA. Rooted plantlets were successfully acclimatized. To further maintain the multiple shoot induction, mother tissue was cut into four equal parts and repeatedly sub-cultured on fresh shoot induction liquid medium after each harvest. On adaptation of this strategy, an average of 18 shoots per explant could be produced. This strategy was applied for the production of biomass and glycosides digitoxin and digoxin in shoot cultures on MS medium supplemented with 7.5 μM BA and several treatments with plant growth regulators, incubation period, abiotic (salicylic acid, mannitol, sorbitol, PEG-6000, NaCl, and KCl), biotic (Aspergillus niger, Helminthosporium sp., Alternaria sp., chitin, and yeast extract) elicitors, and precursors (progesterone, cholesterol, and squalene). The treatment of KCl, mycelial mass of Helminthosporium sp., and progesterone were highly effective for the production of cardenolides. In the presence of progesterone (200 to 300 mg/l), digitoxin and digoxin accumulation was enhanced by 9.1- and 11.9-folds respectively.
Indigofera glandulosa Wendl., (Barbada) belongs to the family Leguminosae, subfamilyPapilionoidae and tribe Indigoferae is widely distributed as weed in India, Indonesia and North Australia. It is an annual herb or sub-shrub growing along roadside and open grassland areas. The plant produce seeds rich in valuable food ingredients such as proteins, carbohydrates, essential amino acids and vitamins. The plant is described as nourishing food for human beings and is believed to possess the qualities of a tonic in Indian medicine. It is highly palatable forage legume; green plants are generally appreciated by domestic animals. Environmentally, it is utilized for the nitrogen enrichment in degraded soil, as the roots produce nodules fixing atmospheric nitrogen. It can be grown in dry regions, therefore appears to drought resistant and at low cost. The plant species remains unexploited although it has high forage and nutritious value. The meagre information on I. glandulosa lead us to explore this neglected and underutilized species to utilize it as food for human beings, forage for animals and for nitrogen enrichment of the soil. The seed viability and seed germination data revealed seed dormancy associated with the hard and impermeable seed coat and it could be overcome by treating the seeds with concentrated sulphuric acid for 10-15 min thus improving the seed germination percentage up to 75%. The result of the present investigation provides preliminary information on agronomical and morphological traits related to yield and biomass production of I. glandulosa from its natural habitat. In addition the detailed survey about taxonomic characters, distribution, cultivation and utilization of I. glandulosa has been documented.
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