Dark Growth and the Associated Phenomenon of Age-dependent Photoresponses in Fern Gametophytes |
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Authors: | COOKE, T. J. PAOLILLO, D. J., JR |
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Affiliation: | Section of Botany, Genetics and Development, Cornell University Ithaca, New York, U.S.A. 14853 |
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Abstract: | The cross-sectional area of the growing tip of a fern filamentundergoes an age-dependent decline over the period of darknessthat precedes an experimental light treatment. This dark-mediateddecline accounts for the appearance of age-dependent responsesto light treatments. Moverover, monochromatic irradiation experimentsshow that the cross-sectional areas of filaments do not manifestsignificant age-dependent variation in response to light treatmentsof sufficient energy. Because it is the cross-sectional arearather than the elongation rate that exhibits the direct responseto light in the control of filament growth, it follows thatthere is no evidence for age-dependent changes in photosensitivityof the filaments. Regression analyses establish that pre-germinationlight treatments do not affect subsequent patterns of dark growth;instead, stress calculations suggest that the tapering of thecross-sectional area may be referable to a state of stress-straindisequilibrium within the filament tip. These and other characteristicsof age-dependent growth responses of fern filaments are summarizedin a general working model. fern gametophytes, age-dependent photoresponses, stress analysis, Onoclea sensibilis |
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