Effects of cyanide, salicylhydroxamic acid, and temperature on respiration and germination of spores of the fern Sphaeropteris cooperi

During the first 96 h of culture, germinating spores of the fern Sphaeropteris cooperi (F. v. Muell.) Tryon showed a gradual rise in respiratory activity to a maximum of about 6.5 μl 0₂ h^?1 mg^?1 dry wt. This was followed by a transitory decline in rate, concluded by a second respiratory rise preceding the emergence of the rhizoid after 192 h of culture. Oxygen uptake during the first 120 h of germination was insensitive to 1 m M potassium cyanide (KCN) but was inhibited by 1 m M salicylhydroxamic acid (SHAM); however, beyond this time cyanide showed increasing inhibitory effectiveness whereas SHAM became less effective. Regardless of time of application, KCN had no effect on germination. Maximum inhibition of germination by SHAM was achieved if applied up to 120 h after culture initiation, after which spores became insensitive to SHAM. Heat treatment (50°C for 90 min) during the cyanide-resistant phase of respiration (0 h–120 h) induced cyanide-sensitive respiration and completely inhibited spore germination. Elevated temperatures had little effect if applied during the cyanide-sensitive phase (beyond 120 h). Temperature inhibited spores regained their ability to germinate if maintained in culture until the cyanide-resistant pathway was restored and then subjected to a second photoinductive light treatment. These results suggest the presence and possible involvement of the cyanide-resistant, alternative respiratory pathway during germination of Sphaeropteris cooperi spores.