ULRICH N AF 



The Rockefeller Institute 



On the Physiology of Antherldlum Formation 



in Ferns' 



CONTROL OF ANTHERIDIUM FORMATION IN 

 DIFFERENT GROUPS OF FERNS 



Dopp (5) demonstrated that an extract from mature prothalli of 

 Pteridium aqiiilinum hastened the onset of antheridium formation 

 in young prothalli of this fern species by a few days and in the pro- 

 thalli of Athyrium filix-mas by a few weeks. Dopp envisaged the pos- 

 sibility that the promotion of antheridium formation was the result 

 of nonspecific growth inhibition. Subsequent investigations (9), 

 though, led to the conclusion that the activity of the extract must 

 be attributed to a specific factor which controls antheridium forma- 

 tion during normal development. 



An assay was devised which took advantage of the observation 

 that the prothalli of Onoclea sensibilis failed to form any antheridia 

 spontaneously under the prevailing conditions of culture but re- 

 sponded readily if extract from mature prothalli of Pteridium aquili- 

 niim was added (see Figure lA, B). Conditions were further defined 

 under which the extract from 7-week-old prothalli of Pteridium 

 nquilinum was active to a dilution of 1:30,000. This increased the 

 activity obtained by Dopp by a factor of about 300. Under these same 

 conditions of culture the active substance accumulated to almost as 

 high an activity in the medium (9). The available data show that 

 this substance must be active at a dilution of 1.6 X 10"^ o^' l^^s (9). 



Studies on the activity spectrum of the factor disclosed that it 

 was active toward the tested representatives of seven out of the nine 

 subgroups of the family Polypodiaceae listed by Eames (7): The As- 



*This investigation was supported in part by research grants (NSF G-3225 and 

 NSF G-6144) from the National Science Foundation. 



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