Desiccation Of Somatic Embryos Research Articles

Repetitive somatic embryogenesis and plant regeneration in Zizyphus jujuba Mill

A procedure for regenerating Zizyphus jujuba Mill. (Chinese date) plants through repetitive somatic embryogenesis (RSE) was developed. Primary somatic embryos were produced from cotyledon-derived cultures of germinated plants in vitro. The highest induction frequency of primary somatic embryogenesis (PSE) was obtained with a combination of 4.52 μM 2,4-dichlorophenoxyacetic acid (2,4-D), 0.49 μM indole-3-butyric acid (IBA), and 0.44 μM benzyladenine (BA) (17.4%). These primary somatic embryos were multiplied by RSE on media with different plant growth regulator (PGR) combinations. The highest RSE frequency (51.3%), was obtained with 0.58 μM gibberellic acid (GA3). However, the highest number (4.4 per primary somatic embryo) of repetitive somatic embryos was obtained with 0.98 μM 6-r-r-dimethylallylaminopurine (2-iP). For germination of somatic embryos, different PGRs, cold and desiccation treatment were tested. Desiccation of somatic embryos at 25±1°C for 2 wk was the best treatment for germination with epicotyl elongation and root development. Of over 256 plants regenerated, 237 (92.6%) survived.

Desiccation of somatic embryos of Cyclamen persicum Mill.

SummaryTo achieve storable somatic embryos (SE) of Cyclamen persicum, different desiccation conditions and two rehydration methods were tested. Somatic embryos derived from liquid cultures were dried in various relative humidities (r.h.) using desiccators filled with saturated salt solutions. Embryos dried to moisture contents of 24% and higher were able to germinate. For germination of the dried somatic embryos, the mode of rehydration was crucial. Only after imbibition in liquid hormone-free medium tubers were cotyledons and roots formed. Drying in decreasing r.h. (91–57–18%) resulted in low moisture contents of 12% on average, comparable with that found in seeds. Depending on the quality of somatic embryos significant differences were observed between different experiments. Somatic embryos with a high dry-matter content showed germination rates of 60% after desiccation in decreasing r.h. Germinating embryos formed bigger tubers than non-dried controls and developed cotyledons of better quality.

Desiccation decreases abscisic acid content in hybrid larch (Larix X leptoeuropaea) somatic embryos

Previous studies indicated that the high endogenous abscisic acid (ABA) content of hybrid larch (Larix X leptoeuropaea) somatic embryos was correlated with low germination frequency. However, when dried, the germination rate of the somatic embryos improved. Therefore, our present objective was to study the effect of desiccation on the levels of ABA and its glucose ester metabolite. Cotyledonary somatic embryos were subjected to drying treatments at 40C under relative humidities of 98 and 59% for one week and the levels of both ABA and abscisic acid glucose ester (ABAGE) were followed by enzyme‐linked immunoassay (ELISA). During desiccation at 98% relative humidity (RH) both ABA and ABAGE levels decreased in an irregular fashion. Regardless of RH, transient increases in ABA were observed that were paralleled by marked decreases in ABAGE. It is concluded that the desiccation of somatic embryos which leads to a decrease in ABA content, could explain the enhanced germination capacity of such embryos.

Soluble saccharides and cyclitols in alfalfa ( Medicago sativa L.) somatic embryos, leaflets, and mature seeds

Soluble carbohydrates were identified and quantified during development, maturation and desiccation of somatic embryos of alfalfa ( Medicago sativa L.) and compared to soluble carbohydrates in leaflets and mature seeds, to relate changes in soluble carbohydrates to maturation events. Somatic embryos have elevated levels of sucrose. However, in contrast to mature seeds, alfalfa somatic embryos do not accumulate d-pinitol or the galactosyl derivatives of d-pinitol such as galactopinitol A, galactopinitol B and ciceritol. Lower levels of stachyose accumulate during maturation of somatic embryos, but stachyose increases to levels in mature seeds during desiccation of somatic embryos. When stachyose accumulation is limited in somatic embryos, galactinol and digalactosyl myo-inositol increase. Reducing sugars decline to low levels during desiccation of somatic embryos and sucrose: oligosaccharide ratio decreases from 2.7 to 0.9, approaching the ratio 0.2 to 0.3 in mature dry seeds. Except for the lack of pinitol and galactosyl pinitols, changes in soluble carbohydrates during the maturation and desiccation of alfalfa somatic embryos are typical of changes occurring in mature seeds that have been reported to be associated with desiccation tolerance and storability.

Plantlet Regeneration from Encapsulated and Non-encapsulated Desiccated Somatic Embryos of a Forest Tree: Sandalwood (Santalum album L.)

Somatic embryos obtained from embryogenic tissues of sandalwood (Santaium album) were grown on White’s medium containing abscisic acid, (ABA, 1.89, 3.78 or 18.92 μM) and various concentrations of sucrose (87.6 to 350.4 mM) to induce maturation. The embryos were isolated and desiccated for 10, 20 or 30 days: One lot of the desiccated somatic embryos was encapsulated in sodium alginate gel and the other lot was not encapsulated. Both encapsulated and nonencapsulated desiccated embryos showed revival of growth upon rehydration on White’s medium and developed into plants. The desiccation tolerance and regeneration of viable plantlets depended upon the pretreatment given to somatic embryos. Embryogenic tissue subjected to dry state for 30 days showed revival of somatic embryogenesis upon transfer to a fresh nutrient medium. Implications of maturation and desiccation of somatic embryos on its germinability are discussed.