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THE PHOTOBIOLOGY OF FERN GAMETOPHYTES. II. THE PHOTOCONTROL OF FILAMENTOUS GROWTH AND ITS IMPLICATIONS FOR THE PHOTOCONTROL OF THE TRANSITION TO TWO‐DIMENSIONAL GROWTH
Author(s) -
Cooke Todd J.,
Paolillo Dominick J.
Publication year - 1979
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1979.tb06238.x
Subject(s) - protein filament , fern , gametophyte , growth rate , elongation , biology , botany , materials science , biochemistry , geometry , mathematics , pollen , ultimate tensile strength , metallurgy
Current descriptions of the photocontrol of the filamentous growth of fern gametophytes contain several apparent photobiological anomalies. These anomalies are the result of the fundamental assumption that the rate of filament elongation is the growth parameter under direct photocontrol. This paper constructs and tests a model for the photocontrol of filamentous growth: k = A(dl/dt), where k, A, and (dl/dt) represent a constant rate of volume increase, the cross‐sectional area of the filament tip, and the rate of filament elongation, respectively. This model predicts that the photocontrol of filamentous growth could involve the direct regulation of the cross‐sectional area. Because this alternative perspective resolves the apparent photobiological anomalies, the photoresponse of the cross‐sectional area should represent the correct measure of the photocontrol over filamentous growth. It follows from the experimental results that the photocontrol of filamentous growth does not antagonize but rather preconditions the transition to two‐dimensional growth. Therefore, the original grounds for postulating that the transition in growth form involves the photoinduction of specific genes for two‐dimensional growth are no longer valid.