The experiment was conducted outdoors in MTT’s Jokioinen
campus in south west Finland(60480
N,23280
E),in a glass-roofed
shelter to protect the tubes and monitoring equipment from rain.
The shelter had metal meshwork walls that permitted the passage
of air and light.The light conditions in the shelter corresponded
closely to those under the open sky and there was no artificial
lighting in the vicinity of the shelter that affected illumination of
the tubes.The water bath was positioned so that the longer side
was oriented E-W.The DARK treatment was achieved by covering
the tubes with a three-ply thickness of brown garden cloth from
21:30 to 03:30 each night(all times relating to the experiment are
expressed in standard time).The cloth was draped in a tent-like
fashion over a ridge at a height of 1.5 m above the tube surfaces.
To the human eye,this induced complete darkness under the cloth.
The AMB treatment remained constantly under ambient light.