Formation Of Globular Embryos Research Articles

Comparative Development of Viable and Aborted Ovules in Phytolacca americana L. (Phytolaccaceae)

Phytolacca americana (pokeweed) can produce more than 80,000 seeds per plant. Plants in this study averaged six shoots per plant; each shoot differentiated 34 racemes. In each inflorescence 40 fruits developed; each fruit produced 10 seeds. In populations near the Maryland-Pennsylvania border, no fruits developed a full complement of seeds; from 40% to 100% of the ovules or seeds aborted. Ovules aborted either during the formation of the female gametophyte or the globular embryo. Approximately 87% of investigated ovules or seeds aborted, with 72% and 15% aborting at the time of female gametophyte or globular embryo formation, respectively. Only young seeds with globular embryos were analyzed quantitatively as ovules aborting at the time of female gametophyte formation had obscure cellular details. Viable ovules had twice as many cells as aborted ovules, which could be attributed to the nucellus. However, both outer and inner integuments of aborted ovules contained more cells, as well as larger cells, than comparably aged viable ovules. Cell size of the nucellus, the obturator, and the dimensions of ovules and locules were greater in aborted ovules also. Abortion was believed to be a result of poor pollination, with a subsequent inhibition of fertilization, resulting from fungal-infected pollen grains.

Somatic embryogenesis and regeneration of plantlets in protoplast cultures from somatic embryos of coffee (Coffea canephora P. ex Fr.)

Somatic embryogenesis was achieved in protoplast cultures of coffee. Protoplasts were isolated from cell suspension-derived somatic embryos of Coffea canephora. After repeated subculture in a medium supplemented with 0.5 mg/l of each of kinetin, 2,4-dichlorophenoxyacetic acid (2,4-D), and naphthaleneacetic acid (NAA), microcalli developed. Transfer of these microcalli to a medium lacking growth regulators resulted in the formation of globular embryos. Upon subculture without growth regulators they grew to well-differentiated embryos, Eventually some of them developed to plantlets which were transferred to the greenhouse for further observation.

Studies on nitrogen metabolism during somatic embryogenesis in carrot. I. Utilization of α-alanine as a nitrogen source

α-Alanine added to a culture medium was incorporated into cells and/or embryos during rapid cell proliferation and globular embryo formation, in which an active protein synthesis was occurring. After the incorporation into cells, α-alanine seemed to be quickly transformed to glutamic acid by alanine aminotransferase and utilized as a nitrogen source. Alanine aminotransferase activity was observed in cells and/or embryos, although the activity decreased during culture period. Utilization of α-alanine by cultured cells as a nitrogen source was discussed in relation to its stimulative effect on somatic embryogenesis.

THE SERIAL OBSERVATION OF EMBRYOGENESIS IN A CARROT CELL SUSPENSION CULTURE

SUMMARYSerial observations were made of the early stages of somatic embryogenesis in a cell suspension culture of carrot (Daucus carota L. cv. ‘Kurodagosun’) using a series of cell clusters which divided synchronously. Three phases were recognized in each of which the rate of cell division was different: the first phase (0 to 3 days) during which cells divided slowly, the second phase (3 to 4 days) during which cells divided very rapidly in the determined locus of the cell cluster, leading to the formation of globular embryos, and the third phase (4 to 6 days) during which cell division occurred at a slower rate than the second phase. Three regions were distinguishable in the cell clusters at the end of the second phase: a transparent region destined to develop into the shoot, an opaque region destined to develop into the root and another opaque region which had ceased to grow, suggesting that the determination of differentiation had already occurred by the end of the second phase. The rapid cell division which occurred in the second phase is considered to be a characteristic event in embryogenesis.

Aspects of DNA, RNA and protein synthesis during somatic embryogenesis in a carrot cell suspension culture

AbstractChanges in DNA, RNA and protein content, incorporation of 3H‐thymidine, 14C‐uridine and 3H‐leucine and template activity of chromatin were investigated in the early process of somatic embryogenesis in a carrot (Daucus carota L. cv. Kurodagosun) cell suspension culture using a synchronous system. An embryogenetic culture in a medium containing 10‐7M zeatin was compared with a non‐embryogenetic culture in a medium containing 10‐7M zeatin and 5 x 10‐7M 2,4‐D. DNA was synthesized very actively prior to and during the formation of globular embryos in the embryogenetic culture. The RNA and protein content per tube increased at an almost constant rate in both cultures, while the rate of incorporation of labelled precursors of RNA and protein rose much more prior to active DNA synthesis in the embryogenetic culture than in the non‐embryogenetic culture. Template activity of chromatin was high in the early stage of embryogenesis in the embryogenetic culture. The results obtained here showed that synthesis and turnover of RNA and protein became active prior to active DNA synthesis in the early stage of embryogenesis, and that these changes at macromolecular levels may play important roles in embryogenesis.