Developmental potentialities of leaf primordia of Osmunda cinnamomea. III. Studies of the effects of homogenized, determined leaf primordia on expression-potential of undetermined leaf primordia

Further evidence is presented in support of the hypothesis that a morphogenetic factor, or factors, is present in older primordia which is transmitted to younger primordia to influence the latter to develop as leaves rather than shoots. P3 primordia, undetermined at the time of excision, are expressed as leaves at a level of 60.0% when explanted to a simple, defined medium containing, in addition, homogenate of determined P12 primordia and at a level of 70.0% when grown on medium containing homogenate of P13 primordia. By contrast, undetermined whole P3's are expressed as shoots approximately 70.0% of the time when excised and explanted to: (1) a homogenate-free medium, or (2) medium containing homogenate of undetermined P3's. Of greater significance is the observation that undetermined P3's are expressed as shoots at approximately the same level when excised and explanted to medium containing homogenate of determined P14 primordia. The relevance of these phenomena to a physiological aging process is briefly discussed.