2005. The root respiration rates were high in the early
morning; toward noon, the rates decreased even though
the root temperature increased. At night, the rates tended
to be lower than those in the daytime. Although the
diurnal pattern of the intact respiration rate differed
among root samples, the most pronounced feature was
the rapid increase in the root respiration rate at sunrise
(0600 hours on September 9, 2005). The rates at sunrise
were two-to-five-fold larger than earlier rates.
In the manipulation experiment under open air using
saplings of Q. crispula in 2007, the intact root respiration
rate responded to changes in the light environment of
the above-ground parts of the plant. Figure 5 is an
example of the time course of Pn, E, Rr, and Tr of one of
the saplings during the experiment. Pn became depressed