| Popis: |
As shown previously 1,2), dark-grown, wax-rich cells of Euglena gracilis contain profoundly degenerate proplastids with no internal structure except for a single prothylakoid lying close to the envelope. When these cells are transferred to an inorganic medium containing ammonium salt as nitrogen source and aerated in darkness for 5 to 6 days, an early development of proplastids occurs using wax (and paramylum) as sources of carben and energy 3). The early development includes formation of rudimentary pyrenoid (propyrenoid) at the site adjacent to the prolamellar body, which appears earlier in the peripheral region of the proplastid. The peripheral single prothylakoid becomes paired along part of its length, and a portion of the paired prothylakoid becomes extended and enfolded in the propyrenoid. No further development of proplastids was observed during prolonged dark incubation of these Euglena cells. This paper describes the observations made when these dark-incubated Euglena cells were exposed to light at different intensities including the low intensity threshold (3–7 ft-c) for chloroplast development 4). |
