Somatic embryos

Embryo cultures may be established from embryos removed from sterilized seeds, ovules, or fruits. The embryos produced from cell culture technique, known as somatic embryos, can be isolated and germinated to provide one plant per explant. Embryo culture can be employed for the rapid production of seedlings from seeds which have a protracted dormancy period. The method has many potential advantages over traditional propagation systems, such as fast turnaround, genetic uniformity, mass production, and propagation of disease-free plants. 

Fig. 4. Two spin-filter bioreactors configured in series for the growth of embryogenic cells and the promotion of somatic embryo maturation on a large scale. The stage 1 bioreactor is for cell proliferation and operates on a continuous culture mode the stage 2 bioreactor is for somatic embryo maturation and operates in a perfusion mode...

Pelissier, B., Bouchefra, O., Pepin, R., and Freyssinet, G., Production of isolated somatic embryos from sunflower thin cell layers, Plant Cell Rep., 9, 47-50, 1990. 

Fourier descriptors have been found valuable for the description of rather smooth contours such as the ones of somatic embryos [85-87]. The contour signature defined as R(s) =f(s) where R(s) is the distance between the centroid G and a point of the contour (Fig. 15), of normalized curvilinear abscissa s with respect to an origin O, is holomorph and can be written as ... 

Fig. 16. Concavity index measurement a Schematic somatic embryo b Convex bounding polygon, c Residual set...

Figure 5. Alfalfa embryogenesis. A. An alfalfa somatic embryo, E, about to germinate, which is surrounded by callus C. B. Plantlets rooting. C. Regenerated plants in gravel in the greenhouse.

B. A somatic embryo at a later stage of development. C. Somatic embryo beginning to germinate, comparable to the whole embryo shown in Figure 5A. 

Joseph, T., Yeoh, H.-H. and Loh, C-S. (1999) Cyanogenesis in somatic embryos and plantlets of cassava (Manihot esculenta Crantz). ]. Sci. Food Agric., 79,1071-4. 

Lindemann, P and Luckner, M. (1997) Biosynthesis of pregnane derivatives in somatic embryos of Digitalis lanata. Phytochemistry, 46, 507-13. 

From studies done on the in vitro propagation and somatic embryology (16-18) in borage, it appears that it is possible to produce GLA from cotyledonary somatic embryos. However, the authors observed that the system needs to be adapted to liquid media to facilitate large-scale production. 

Many researchers have so far investigated tissue culture of P. somniferum [131, ref. cited therein], and most cultured P. somniferum cells, either as callus or cell suspensions, readily produced sanguinarine and its analogs [130-137], but rarely, if even, produce morphinan alkaloids [138]. Kamo et al. [139], Schuchmann and Wellmann [134], and Yoshikawa and Furuya [140] reported the production of morphinan alkaloids in redifferentiated organs, either shoots or somatic embryos, and their results emphasize the importance of the degree of cell differentiation for the biosynthesis of morphinan alkaloids. 

The transformed cells of P. somniferum easily formed somatic embryos instead of roots. MAFF clone 1, which was the most embryogenic, accumulated about 10-fold higher levels of morphinan alkaloids than did non-transformed embryogenic callus (Table 20). Williams and Ellis... 

Regeneration of embryos was observed when the unorganized cells obtained in 3 WP liquid medium were statically cultured on the solid medium in the light. These results imply that the degree of cell differentiation as shoots or somatic embryos in transformed cultures seems to be associated with the formation of morphinans as well as non-transformed cultures. 

GC-MS analysis, Bialek et al. [45,51] found that tryptophan conversion to lAA accounted for essentially all of the lAA production in seedlings of bean, in contrast to results from similar studies in Lemna plants, maize embryos, Arabidopsis seedlings and carrot somatic embryos [42-44,52]. 

DPA-GS is a major metabolite of ABA in, among others, soybean seeds [96], tomato plants [97], and sunflower embryos [98]. Suspension cultures of maize cells [99] and of somatic embryos of white spruce [100] convert ABA almost quantitatively to PA. ABA-GS is present in tomato plants [101]. 

These contents were still lower (one sixteenth) than those in the shoot culture, however, it is noteworthy that cardenolides which production were mainly reported to be produced in aerial parts or in organs related to aerial parts (e.g. shoot-forming calli or somatic embryo) (2, 3) were produced in hairy root cultures at relatively high contents. This study might be helpful in investigating the factors which affect cardenolide biosynthesis. 

Improvement in taste or texture of vegetables and fruits, such as better tasting celery stalks and tomatoes with higher solids content (13). Somaclonal variations for selection of desirable variants, and somatic embryos (artificial seeds) have been especially useful in genetic engineering of improved vegetables. Several of these new crop varieties will be on the market within 2 to 4 years. 

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