Primary and secondary somatic embryogenesis in Jatropha curcas L. From leaf transverse thin cell layers

An efficient method for plant regeneration in Jatropha curcas L. via primary and secondary somatic embryogenesis culture from ex vitro leaves of 6-month-old plants was presented in this study. Leaves were cut into transverse thin cell layers (tTCLs) and cultured on MS medium supplemented with kinetin (KIN) at 0.5, 1.0, 1.5, and 2.0 mg/l in combination with indole-3-butyric acid (IBA) at 0.1, 0.5, and 1.0 mg/l or 2,4-dichlorophenoxyacetic acid (2,4-D) at 1.0, 1.5 and 2.0 mg/l . The highest embryogenic callus formation rate (89.3%) was obtained on medium supplemented with 1.0 mg/l KIN and 1.5 mg/l 2,4-D. The calli were selected for the study of primary somatic embryogenesis on MS medium containing 2,4-D (0.01, 0.03, 0.05, and 0.07 mg/l) or KIN (0.5, 1.0, 1.5, and 2.0 mg/l). The highest primary somatic embryos formation rate (76.67%) was achieved on MS medium supplemented with 1.0 mg/l KIN. The primary embryos were cultured on medium supplemented with KIN (0.1, 0.5, 1.0, 1.5, and 2.0 mg/l) combined with 0.2 mg/l indole-3-butyric acid (IBA) or 0.05 mg/l 2,4-D. The combination of 1.5 mg/l KIN and 0.05 mg/l 2,4-D was suitable for secondary embryos formation. Embryos proliferated rapidly, and the highest number of secondary embryos (77.5 embryos) wasobtained from a single primary embryos inoculated. Results also showed that the addition of proline (0.75 g/l) or spermidine (0.15 mM) to the culture medium increased the number of secondary embryos considerably. The fully developed plantlets exhibiting healthy roots and shoots were obtained when somatic embryos were sub-cultured onto B5 medium containing 1.5 mg/l IBA.

Plant thin cell layers: update and perspectives

Thin cell layers (TCLs) are small and versatile explants for the in vitro culture of plants. At face value, their morphogenic productivity may appear to be less than conventional explants, but once the plant growth correction factor and geometric factor have been applied, the true (potential) productivity exceeds that of a conventional explant. It is for this reason that for almost 45 years, TCLs have been applied to the in vitro culture of almost 90 species or hybrids, mainly ornamentals and orchids, but also to field and vegetable crops and medicinal plants. Focusing on 12 new studies that have emerged in the recent past (2013-2015), this paper brings promise to other horticultural species that could benefit from the use of TCLs.

The Untapped Potential Of Plant Thin Cell Layers

Thin cell layers (TCLs), which contain a small number of cells or tissues, are explants excised from different organs (stems, leaves, roots, inflorescences, flowers, cotyledons, hypocotyls/epicotyls, and embryos). After almost 45 years of research, this culture system has been used for several monocotyledonous and dicotyledonous plants of commercial importance, and for model plants. The limited amount of cells in a TCL is of paramount importance because marker molecules/genes of differentiation can be easily localized in situ in the target/responsive cells. Thus, the use of TCLs has allowed, and continues to allow, for the expansion of knowledge in plant research in a practical and applied manner into the fields of tissue culture and micropropagation, cell and organ genetics, molecular biology, biochemistry, and development. Starting from a brief historical background, the actual and potential uses of the TCL system are briefly reviewed.

POTENCIAL DE REGENERACIÓN DE Psychotria ipecacuanha (Rubiaceae) A PARTIR DE CAPAS DELGADAS DE CÉLULAS

<p>Conociendo las propiedades medicinales de la especie vegetal <em>Psychotria</em> <em>ipecacuanha</em> (Brot.) Stokes, su crítico estado de conservación, así como las dificultades que presenta para la propagación efectiva, el presente estudio tuvo como objetivo evaluar su potencial de propagación por los sistemas de regeneración <em>in vitro</em>, organogénesis y embriogénesis somática. Para este propósito, capas delgadas de células (CDCs) de tallos y de hojas, así como segmentos foliares fueron sometidos a diferentes tratamientos con reguladores de crecimiento y condiciones de luz. Además se estableció el efecto de diferentes longitudes de onda vía diodos emisores de luz (LEDs), sobre la regeneración en estos explantes y nudos provenientes de plantas <em>in vitro</em>. Los resultados obtenidos mostraron que los segmentos de hoja y las CDCs de tallo sembrados en el medio de cultivo MS suplementado con las combinaciones de los reguladores de crecimiento IBA + BAP e IBA + TDZ formaron embriones somáticos y brotes. Los cortes histológicos realizados corroboraron estos dos tipos de origen. Se encontró que bajo la condición lumínica 16/8, se alcanzaron los mejores resultados de inducción de brotes y embriones. En cuanto al efecto de las diferentes longitudes de onda de luz, se encontró que las correspondientes al rojo, verde y blanca, favorecieron el crecimiento y desarrollo de brotes y la inducción de embriones somáticos. El desarrollo de los brotes a partir de los nudos no presentó diferencias estadísticas entre los tratamientos con LEDs, por lo que se recomienda el uso de la luz blanca continua y con fotoperiodo durante el proceso de multiplicación y desarrollo de estos.</p><p><strong>Regeneration Potential of <em>Psychotria Ipecacuanha</em> (Rubiaceae) from Thin Cell Layers </strong></p><p>Knowing the medicinal properties of the plant specie <em>Psychotria ipecacuanha</em> (Brot.) Stokes, its critical condition and the difficulties for its effective propagation, the present study aimed to assess the potential of propagation of <em>P. ipecacuanha</em> by <em>in vitro</em> systems of regeneration, organogenesis and somatic embryogenesis. For this purpose, thin cell layers (TCL) of stems and leaves, as well as leaf segments were subjected to different treatments of plant growth regulators and light conditions. Furthermore, the effect of different wavelengths via light emitting diodes (LED’s), was established for the regeneration in these explants and nodal explants from <em>in vitro</em> plants. The results showed that leaf segments and stem TCL, cultured in MS medium supplemented with the combinations of growth regulators IBA + BAP and IBA + TDZ, formed somatic embryos and shoots. The histological sections supported the two types of source. It was found that the best results in shoot induction and embryos were achieved under the light condition 16/8-h light/dark. Regarding the effect of different wavelengths, it was found that those corresponding to red, green, and white supported the growth and shoot development as well as somatic embryos induction. The shoots development from the nodal explants did not show statistical differences between LEDs treatments, so the use of a continuous white light and photoperiod is recommended during their multiplication and development.</p>