Rape embryogenesis I. The proembryo development

Proembryo culture: in vitro development of early globular‐stage zygotic embryos from Brassica juncea

“…In vivo embryo development of B. juncea The development of 6. juncea embryo is similar to that of rape (Brassica napus, see results of Tykarska, 1976Tykarska, , 1979, except that the sizes of embryos at the different stages are slightly different (Table 1, Figure 1 a-9. Embryos sequentially passed through globular-, heart-and torpedo-shaped stages to develop into mature seeds.…”

Embryogenesis in Higher Plants: An Overview

“…As shown in Figures 1D, 1E, and 2B, the apical cell of cruciferous embryos next undergoes two longitudinal divisions to produce a four-celled embryo proper (Schulz and Jensen, 1968a;Tykarska, 1976;. A transverse division follows to produce two tiers of cells in an octant stage embryo proper, illustrated in Figures 1F and 2C.…”

“…In many angiosperms, the initial division of the zygote is transverse and asymmetric, generating a small, chalazally oriented apical cell and a large basal cell, as shown in Figure 1C (Pritchard, 1964;Schulz and Jensen, 1968b;Tykarska, 1976;. In animal development, the asymmetric division of progenitor cells is a fundamental mechanism by which cells with unequal cytoplasms and, consequently, different fates are generated (Gurdon, 1992;Horvitz and Herskowitz, 1992).…”

“…In animal development, the asymmetric division of progenitor cells is a fundamental mechanism by which cells with unequal cytoplasms and, consequently, different fates are generated (Gurdon, 1992;Horvitz and Herskowitz, 1992). Similarly, in cruciferous plants, the apical cell gives rise to the bulk of the embryo proper, including the cotyledons, shoot apex, and hypocotyl, whereas a part of the root apex and the suspensor originate from the basal cell (Schulz and Jensen, 1968a;Tykarska, 1976). In other plants, however, the first division of the zygote can be symmetrical, oblique, or longitudinal (Sivaramakrishna, 1978).…”

“…Figures 1H and 2E, the hypophysis, the uppermost derivative of the basal cell, serves as the precursor to the root cortex initials and the central region of the root cap (Schulz and Jensen, 1968a;Tykarska, 1979;. The suspensor is an ephemeral embryonic structure that, as shown in Figure 2E, comprises a single file of 6 to 11 cells in Arabidopsis and oilseed rape, although there are substantial variations in the number and layers of suspensor cells in different plants (Maheshwari, 1950;Wardlaw, 1955;Tykarska, 1976;Marsden and Meinke, 1985;). This structure is thought to function in embryogenesis by pushing the embryo into the nutrient-rich endosperm and, possibly, by serving as a conduit for nutrients and growth factors from the maternal tissue to the embryo (Yeung and Meinke, 1993, this issue).…”