Photocontrol of the Germination of Onoclea Spores: III. Analysis of Germination Processes by Means of Cycloheximide.

Possible involvement of protein synthesis in the germination of Onoclea sensibilis spores was investigated by temporarily applying 0.1 mm cycloheximide before and after photoinduction. Cycloheximide was shown to inhibit protein synthesis, but not to act as an uncoupler of respiration. When cycloheximide was added before or shortly after photoinduction, spore germination was inhibited with the half-maximal inhibition attained in 30 to 45 minutes and the maximal inhibition in 2 hours of incubation. When the time of the inhibitor treatment was delayed after photoinduction, the spores escape from the inhibitory effect of cycloheximide slowly during the first 8 hours and abruptly thereafter with a half-maximal time of 10 hours. If spores are washed free of exogenous cycloheximide and subsequently irradiated, their ability to germinate can be reinstated in distilled water with a half-maximal time of 12 hours. The kinetics of recovery were identical and of apparent first order, regardless of whether cycloheximide treatments were given before or after photoinduction. These results are interpreted to indicate that the normal course of germination of Onoclea spores requires the continuous synthesis of a short lived enzyme that functions in the germination processes at about 10 hours after photoinduction. The cycloheximide-sensitive step follows in the germination processes an anaerobiosis-sensitive step, but precedes the time of acetocarmine uptake or visible signs of protrusion.