Open AccessPhototropic response of the stage I Phycomyces sporangiophore to a pulse of blue light
Author(s) -
Masashi Iino,
Eberhard Schäfer
Publication year - 1984
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.81.22.7103
Subject(s) - phototropism , phycomyces , coleoptile , elongation , irradiation , curvature , fluence , blue light , biophysics , biology , optics , physics , botany , materials science , mathematics , geometry , ultimate tensile strength , nuclear physics , metallurgy
Positive phototropic curvature ofPhycomyces sporangiophores (stage I) induced by a short pulse (10 sec) of blue light has been characterized. The curvature response, measured 40 min after irradiation, increases with increasing fluences up to ≈10-4 J·m-2 ; it then decreases and becomes nearly 0 at a fluence of ≈10-1 J·m-2 . The threshold fluence is found near 10-7 J·m-2 , indicating over 1000-fold higher sensitivity than the first positive phototropism of grass coleoptiles. Positive curvature of the sporangiophore becomes detectable 5 min after irradiation and increases with time up to ≈40 min. During the course of this curvature development, overall elongation growth of the sporangiophore is first stimulated and then inhibited. The relationship between the phototropic response and the response in overall elongation growth is discussed, and it is suggested that the primary mechanisms of these responses are distinct.