AW: Solar tracking

Buschmann, Henrik buschmann at
Thu Jan 27 05:19:57 EST 2000

Hallo Talbot,
i dont agree totaly: concerning the flux of water i believe it is better to
call these events growth (as a generalization). The receptor should be
cryptochrome (at least when blue light is the signal).  
Anyhows, what your saying about cotton (in contrast to sunflower) sounds
interesting to me. Do you know any literature concerning cotton (and solar

-----Ursprüngliche Nachricht-----
Von: tbrooks [mailto:tbrooks at]
Gesendet am: Montag, 24. Januar 2000 14:17
An: patrickhall at; buschmann at
Betreff: Solar tracking

    Solar tracking, or heliotropism, is a phytochrome mediated response.
Phytochrome is a pigment sensitive to blue light.  Basically what happens is
blue light falls on phytochrome which induces a signal transduction cascade
of ion exchanges, most often in stem tissue.  The end result of this signal
transduction is the movement of water into tissues (again, most often the
stems areas), elongating or stiffening a portion such that the desired organ
now faces the sun.  For example, at sunrise, the tissue on the west side of
the stem would become more rigid and point a leaf to the east.  As the sun
moves, the relative amount of "signal" being transmitted by phytochrome
moderates accordingly, allowing the organ (a leaf or flower) to track the
sun.  I do not know the number of plants out there that do this, but some
great examples are sunflower (flowers track) and cotton (leaves track).  I
can't post to the group from my server, but thought you might find this
interesting none the less.
Talbot J. Brooks
Graduate Student Researcher
4331 E. Broadway Rd.
Phoenix, AZ 85040
Office: (602) 379-4356 ext. 262
Fax:    (602) 379-4355
tbrooks at <mailto:tbrooks at> 
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