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The present study demonstrates the regeneration of plantlets of guava (Psidium guajava L.) from somatic embryos developed under salt-stress conditions. With increasing concentrations of NaCl in induction medium (MS + 4.52 µM 2,4-D + 5% sucrose) from 0 to 200 mM, the number of somatic embryos per responsive explant decreased. Somatic embryos induced on 0–100 mM NaCl containing medium developed into torpedo stages, whereas, the development of somatic embryos that differentiated on 150 and 200 mM NaCl-supplemented medium was arrested prior to torpedo stage and did not undergo maturation phase. Somatic embryos that developed on NaCl-containing medium, showed better germination in the presence of NaCl as compared with those developed on medium without NaCl. The effect of increasing salt-stress was also investigated on plant growth, chlorophyll and carotenoids, Na⁺ and K⁺, and proline and glycine betaine accumulation in in vitro grown plantlets. The level of Na⁺ in leaves increased with increasing concentrations of NaCl in the medium. Accumulation of free proline and glycine betaine in leaves significantly increased with increasing salinity. The results suggest that accumulation of proline and glycine betaine may be important for osmotic adjustment in guava under salinity stress.
An efficient in vitro propagation systemhas been developed for rapid micropropagation of Soapnut (Sapindus trifoliatus Linn.), a medicinally and economically important tree from nodal (axillary bud) segments of seedlings. The frequency of shoot regeneration from seedling node explant was influenced by the age of the seedlings, growth regulators and successive transfer of the mother explant. Explants from 4-week-old seedlings yielded the maximum shoot regeneration frequency (97.22%) on full-strength MS medium supplemented with 1.0 mg l⁻¹ of 6-benzylaminopurine (BAP). After harvesting the newly formed shoots, the mother explants transferred to same medium subsequently produced a maximum of 5.16 shoots per explant after third passage. Further improvement in the morphogenic response occurred when the nodal explants excised from in vitro regenerated shoots were employed, and 6.89 shoots per explant were obtained on the same medium after the third subculture. Optimal rooting (91.67%)was obtained by placing the microshoots in liquid MS medium with 1.0 mg l⁻¹ IBA for 24 h and then transferring to the agar solidified MS medium devoid of IBA. The micropropagated shoots with welldeveloped roots were acclimatized and successfully transplanted to soil with 90% survival rate. Genetic stability of the regenerated plants was assessed using random amplified polymorphicDNA(RAPD). The amplification products were monomorphic in micropropagated plants and similar to those of mother plant. Nopolymorphism was detected revealing the genetic integrity of micropropagated plants. This is the first report of an efficient protocol for regeneration of S. trifoliatus through organogenesis, which can be applied for further genetic transformation assays and pharmaceutical purposes.
A micropropagation method is described for guava (Psidium guajava L.) using nodal expiants from somatic embryo-derived young and aseptic plantlets. Multiple shoots were induced from axillary buds on MS medium containing different concentrations of N6-benzylaminopurine (BAP), either alone or in combination with kinetin (Kn), indole-3-acetic acid (1AA) or a-naphthalene acetic acid (NAA). Medium containing 1 mg l-1 BAP was the most effective for shoot multiplication. In vitro regenerated shoots developed roots either on MS medium alone or on MS medium supplemented with indole-3-butyric acid (1BA). The rooted plantlets were successfully acclimatized.
This article demonstrates the plantlet regeneration from alginate-encapsulated shoot tips of Spilanthes acmella. Shoot tip explants excised from in vitro proliferated shoots were encapsulated in calcium alginate beads. The best gel complexation for encapsulation of shoot tips was achieved using 3% sodium alginate and 100 mM calcium chloride. Maximum percent response for the conversion of encapsulated shoot tips into plantlets was obtained on growth regulator-free full-strength liquid MS (Murashige and Skoog, Physiol Plant 15:473–497, 1962) medium. The addition of MS nutrients in alginate matrix was found to have pronounced effect on shoot and root emergence from alginate beads. Encapsulated shoot tips could be stored at low temperature (4°C) up to 60 days. Plantlets regenerated from encapsulated shoot tips were acclimatized successfully. The present synthetic seed technology could be useful in large-scale propagation as well as short-term conservation and germplasm distribution and exchange of Spilanthes acmella.
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