The photos below illustrate the effect of explant size on embryogenic capacity in two genotypes of soybean. The top row is ‘Jack,’ which has a high embryonenic capacity, while the bottom row is ‘Benning,’ which has a low embryogenic capacity. In each case, the cotyledons in the photos came from immature embryos which were (from left to right) 3, 4, 5, or 6 mm long. Photos were taken after 30d on MSD40 medium. Both photos are at the same magnification.
The effect of size has been extensively documented:
J. P. Ranch, L. Oglesby, and A. C. Zielinski. 1985. Plant regeneration from embryo-derived tissue cultures of soybean by somatic embryogenesis. In Vitro Cell. Dev. Biol. 21:653-657.
U. B. Barwale, H. R. Kerns, and J. M. Widholm. 1986. Plant regeneration from callus cultures of several soybean genotypes via embryogenesis and organogenesis. Planta 167:473-481.
T. D. Ghazi, H. V. Cheema, and M. W. Nabors. 1986. Somatic embryogenesis and plant regeneration from embryogenic callus of soybean, Glycine max L. Plant Cell Rep. 5:452-456.
T. Komatsuda and K. Ohyama. 1986. Callus and somatic embryo formation by immature embryo culture in soybean. Japan J. Breed. 36( Suppl 2):230-231.
X-H. Feng, X.-C. Jiang, and Q.-Q. Shao. 1989. Plant regeneration from immature cotyledonous tissue cultures of soybean by somatic embryogenesis. Sci. Chi. Ser. B. 32:58-63.
T. D. Kien, A. Mehandjiev, and C. B. Phuc. 1989. Factors influencing the somatic embryogenesis in soybean (Glycine max. L. Merr). C.R. Acad. Bul. Sci. 42:91-93.
A. Nadolska-Orczyk and W. Orczyk. 1994. New aspects of soybean somatic embryogenesis. Euphytica 80:137-143.