18
DAVID M. GATE8
greater than 1 m.p.h. at the treetop level, the leaf temperature will
drop considerably and the leaf will eeaimilate during a greater period
of the &y.
A shade leaf will remain at or below air tempemture and therefore
Fro. 3. Dii:rnd veristion: (a) S o h rsdietion inaident on an expo8ed and shaded led;
(b) Air temperature end e x p d and ~hsded leaf temperaturee; (c) Tnmepiretion rate of
exposed and eheded leaf; (d) Repreeeate the reletiw, metebolio mtm for an expoad and
for e ehaded leaf.
is not too warm for aasimilation. However, the shade leaf is light limited
for pho:osynthesis and will have a mehbolic response approximating
the curve shown at the bottom of Fig. 3.
In arder to illustrate how very different may be the net photosynthetk rates and respiration rates for leavea of different ~ X ~ ~ E U E M
and climates, eaat facing, weat facing and horizontally oriented leavea