Planta

, Volume 209, Issue 3, pp 290–298

Phytochrome-controlled phototropism of protonemata of the moss Ceratodon purpureus: physiology of the wild type and class 2 ptr–mutants

  • Heike Esch
  • Elmar Hartmann
  • David Cove
  • Masamitsu Wada
  • Tilman Lamparter
Article

DOI: 10.1007/s004250050635

Cite this article as:
Esch, H., Hartmann, E., Cove, D. et al. Planta (1999) 209: 290. doi:10.1007/s004250050635

Abstract.

Phototropism and polarotropism in protonemata of the moss Ceratodon purpureus are controlled by the photoreceptor phytochrome. One class of phototropism mutants is characterised by growing randomly when kept for a prolonged time (5 d or longer) in unilateral red light. It was found that a subclass of these mutants grows faster than the wild type, the rate of cell division and the length of the cells being increased. This difference is found for light-grown and dark-grown filaments. It is therefore suggested that the mutant phenotype neither results from a defect in phytochrome photoconversion nor from a defect in phytochrome-gradient formation. Instead, it is possible that a factor which is involved in both signal transduction of phototropism and regulation of cell size and cell division is deregulated. If dark-grown mutant filaments are phototropically stimulated for 24 h, they show a weak phototropic response. Phototropism and polarotropism fluence-rate effect curves for mutants were flattened and shifted to higher fluence rates compared with those for the wild type. With wild-type filaments, a previously unreported response was observed. At a low fluence rate, half of the filaments grew positively phototropically, while the other half grew negatively phototropically. It seems that under these conditions, a phytochrome gradient with two maxima for the far-red-absorbing form of phytochrome (Pfr) within the cross-section of the cell is displayed by the response of the filaments. At higher fluence rates, all filaments of the wild type grew towards the light. These data and results from microbeam irradiation experiments and from phototropism studies with filaments growing within agar, indicate that light refraction plays an important role in the formation of the Pfr gradient in phototropism of Ceratodon.

Key words: Cell division Ceratodon Phototropism Phytochrome Polarotropism 

Copyright information

© Springer-Verlag Berlin Heidelberg 1999

Authors and Affiliations

  • Heike Esch
    • 1
  • Elmar Hartmann
    • 1
  • David Cove
    • 2
  • Masamitsu Wada
    • 3
  • Tilman Lamparter
    • 1
  1. 1.Institut für Pflanzenphysiologie und Mikrobiologie, Freie Universität Berlin, Königin Luise Str. 12–16, D-14195 Berlin, GermanyDE
  2. 2.Department of Biology, The University of Leeds, Leeds LS2 9JT, UKGB
  3. 3.Department of Biology, Tokyo Metropolitan University, Minami-Ohsawa, 1-1, Hachioji-shi, Tokyo 192-03, JapanJP