Vergara - 1976 - Physiological and morphological adaptability of ri

PHYSICS CONTROLLED ENVIRUNIWENT AND PLANT (BROWIH 155
atfeet photosynthesis and transpiration. Therefore phytotron studies should go together with
rhizotrori studies, i.e. root environment studies.
itlirchell: I agee. and this can be done. It requires extra equipment and one must decide
whether the problem justifies the additional cost. Otten it will.
EVANS: In the table indicating increased transpiration rates at higher temperatures in spite of
equal saturation deficits. the temperatures presumably were controlled air temperatures. ‘ilVere
leaf temperatures measured? Ilow did they relate to the air temperatures and to the transpiration
rates’?
ilfitchell: Leaf temperatures were measured. liVhere transpiration was less. leaf temperature
increased more above air temperature.
EvANs: The use of natural light in phytotrons certainly has its disadvantages in terms of cost.
short-term variability. and low winter light at high latitudes, but until we are more confident
that we understand all the major effects of light, such as those on flowering and tillering, it
would surely be a rish to build only artificially lit installations.
ilfilcheli: Comparison always has to be made with naturally lit installations and particularly
with a wide range of field conditions. This can often be done with simple field facilities. Our
experience shows there is eoneiderable flexibility in the artificial-light regime. and that adverse
effects seen in artificially lit conditions are frequently due to unsatisfactory combinations of
temperature and humidity which impose temperature- and moisture-stress on the plants. In
many cases apparently adverse effects were found to be almost identical with plant responses in
the field when they met the same combinations of temperature. light intensity. and humidity.