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Germination in spores of Dryopteris filix‐mas : Regulation of rhizoid elongation as a second phytochrome‐mediated response
Author(s) -
Yatsuhashi Hiroko,
Turnwald Stefan,
Scheuerlein Robert
Publication year - 1996
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.1996.980223.x
Subject(s) - phytochrome , rhizoid , elongation , germination , botany , biology , phytochrome a , spore , biophysics , red light , biochemistry , materials science , arabidopsis , gene , mutant , metallurgy , ultimate tensile strength
Spore germination in Dryopteris filix‐mas occurs via a cascade of cellular responses, and chlorophyll formation, mitosis or rhizoid elongation are commonly used as parameters to determine spore germination. Detailed investigations of these parameters led to the hypothesis that they are regulated by different, independent phytochrome‐mediated responses. This concept could be confirmed, as is described in this paper which demonstrates that perception of light via phytochrome occurs within two different phases separated in time. Presence of the far‐red absorbing phytochrome form, P fr , for 36 h, induces chlorophyll formation and the first unequal cell division, by which a rhizoid initial and a protonemal initial are formed (first phytochrome‐mediated response). However, rhizoid elongation requires a second period of P fr , presence (second phytochrome‐mediated response). There is a clear temporal distinction between the first and the second phytochrome‐mediated response with respect to the coupling of P fr to the transduction chain; P fr is unable to induce rhizoid growth until 60 h after the start of the first red irradiation. The effectivity of P fr for inducing the second response shows an optimum at ca 96 h after the beginning of the presence of P fr ; thereafter, it declines slowly. The fluence‐response relationship and the presence of red/far‐red reversibility demonstrate that rhizoid elongation is a low‐fluence response mediated by phytochrome and is independent of the first phytochrome response.