Comparison of in Situ and in Vitro Regulation of Soybean Seed Growth and Development

Abstract

The growth characteristics of soybean (Glycine max [L.] Merr.) embryos in culture and seeds in situ were found to be similar, but developmental differences were observed. Embryos placed in culture when very small (<2 milligrams dry weight) failed to attain the maximal growth rates attained by embryos which were more mature when placed in culture. When nutrient levels were maintained in the culture medium, embryos continued to grow indefinitely, reaching dry weights far in excess of seeds matured in situ. Apparently, maternal factors were important in early and late development during the determination of maximum growth rate and the cessation of growth. Embryo growth rate was not affected by substituting glucose plus fructose for sucrose in the medium, nor by hormone treatments, including abscisic acid. Glutamine was found to give substantially better growth than glutamate, however. Contrary to prior reports, the response of soybean embryo growth rate to irradiance was found to be primarily an artifact of the effect of irradiance on media temperature. Across seven genotypes the correlation coefficient between seed growth rate in situ and embryo growth rate in vitro was 0.94, indicating essentially all of the variability of in situ seed growth rate between cultivars could be attributed to inherent growth rate differences associated with the embryos. The response to temperature was very similar for both embryos in culture and seeds in situ at temperatures below 30 degrees C. Beyond that temperature, embryo growth rate continued to increase, while seed growth rate did not. The implication is that in situ seed growth rate is determined by the inherent growth potential of the embryo at low to moderate temperatures; however, at higher temperatures, the maternal plant is unable to support the rapid growth rates that the embryo is capable of attaining under conditions of unlimited assimilate supply.

Regeneration of soybean (Glycine max L. Merrill) through direct somatic embryogenesis from the immature embryonic shoot tip

“…Jang et al (2001) reported that application of asparagine in cell suspension medium had greater effect on formation of embryogenic clumps. Likewise, many researchers emphasised the addition of glutamine during embryo development mainly to increase the size of the embryos (Dyer et al 1987;Lippmann and Lippmann 1993). Previously, in soybean, these two amino acids were tested only in cell suspension cultures i.e.…”

Post-Sieve Element Transport of Sucrose in Developing Seeds

“…Across seven genotypes, the in vitro growth rate of cultured cotyledons accounted for their in situ growth rates indicating that growth and hence solute transport was under cotyledon control (Dyer et al 1987). These conclusions are supported by the findings that both the in vitro (Hanson 1988) and in vivo (Hanson 1986) sucrose fluxes from the coats of developing soybean seed were not correlated with seed growth rates.…”

“…For grain legume seed, the in vivo supply of assimilates to the outer surfaces of the cotyledons (Patrick and McDonald 1980;McDonald et al 1995c) can be reproduced readily in vitro by incubating excised cotyledons in a culture solution (Litchner and Spanswick 1981a;Patrick 1981;Dyer et al 1987;McDonald et al 1 9 9 5~;see Fig. 2b).…”

Somatic Embryogenesis and Synthetic Seed II

“…Studies of zygotic soybean and bean (Phaseolus vulgaris) embryos cultured in vitro suggest that seed growth rate and maturation are controlled by the embryo (TeKrony et al 1979;Adams and Rinne 1981;Egli et al 1981;Dyer et al 1987), and parallel that of embryos in planta (Long et al 1981). Studies of zygotic soybean and bean (Phaseolus vulgaris) embryos cultured in vitro suggest that seed growth rate and maturation are controlled by the embryo (TeKrony et al 1979;Adams and Rinne 1981;Egli et al 1981;Dyer et al 1987), and parallel that of embryos in planta (Long et al 1981).…”