Figure 1 in Cell structure and microtubule organisation during gametogenesis of Ulva mutabilis Føyn (Chlorophyta)

Figure 1: Time course of induced gametogenesis and discharge of gametangia from Ulva mUtabilis in relation to the swarming inhibitor (SWI) synthesis and action (summary of new and previous results). Gametogenesis was induced in Ulva mUtabilis [mutant slender sl-G(mt +)]. The "determination phase" and "differentiation phase" are defined as described by Stratmann et al. (1996). The "swarming phase" is the time period when gamete release can be induced by light or a medium change, or may occur later spontaneously. (A) Regular vegetative G1 cell cycle phase in which gametogenesis can be induced by the removal of sporulation inhibitors SI-1 and SI-2 from the medium. (B) Regular vegetative S phase in which the genome is replicated normally or, after induction of gametogenesis, the period of SWI synthesis and excretion. (C) Next G1 phase after induction of gametogenesis. (D) Next S phase after induction of gametogenesis and accumulation of starch granules. (E) Time of irreversible commitment to gametangium differentiation. (F) Period of progamete formation, chloroplast reorientation and papilla initiation. (G) Period of progamete multiplication to 16 cells, and papilla maturation. (H) Period of gamete and pore cap maturation. (I) Period when the exit pores are open and when gamete release can be induced by light and/or depletion of SWI in the medium. (J) Period when the gametangia become insensitive to SWI and gamete release may occur spontaneously and asynchronously. Figure is from Wichard and Oertel (2010) with permission of © Wiley 2010. Images show the transformation of blade cells into gametangia. Microscopic images for stages a, f, h and i are shown (scale bars: 25 µm).