The control of development in Acetabularia crenulata by light

1. The elongation of Acetabularia crenulata cells ceases abruptly at morphogenesis; all further growth normally takes the form of cap (gametangium) expansion. Cell volume, however, increases without inflection during the phases of stalk elongation and cap expansion until the cap reaches a terminal size. At this time growth stops altogether. 2. The following developmental parameters are sensitive in various ways to both photoperiod and light intensity; a) time from the start of an experiment to morphogenesis, b) cell length at morphogenesis, c) cumulative amount of incident irradiation needed to produce morphogenesis, and d) proportion of cells reaching maturity. 3. The effects of short days on morphogenesis, but not on elongation or chlorophyll content, can be largely replaced by high intensity illumination. At low intensities parallel effects were observed in 8-, 16- and 24-hour light regimes and are correlated with concurrent effects on growth. 4. The experiments do not support the developmental scheme proposed earlier by Beth. Another scheme is presented which is based on a steadily increasing irradiation requirement throughout development. This scheme is compatible with all the evidence available at present. © 1965 Springer-Verlag.

Duke Scholars

Author John W. Terborgh Environmental Sciences and Policy