20
UAVID M. GATES
‘rho iukgral under the net photoeynthesis and respiration curves
givw an approximate measure of the productivity of the leaf. The
values below the line are negative and represent the consumption of
energy. Normally net photosynthesie is sufficiently poaitive to mom
than componmte for the loss by respiration. The total productivity of a
whole plant, including euch large and complex individuals a8 8 tree,
can be estimated from the sums of the reaponsea of each and every leaf
on the plsnt. The technique is described below &B applied to qtimating
the total water usage by a tree or a stand.
Time of day
FIG. 6. D i m 1 variation of relative metabolic rates for a fully expoeed horizontal leaf
on a hot, cleer day end on a 0001, clear day each with little wind end with much wind.
(a) Hot day, wind 2 m.p.h. T d n 20’C. Tm.= 4OoC; (b) Hot day, wind 1 m.p.h.; ( 0 ) Cool
day, wind 2 m.p.h. Tmln IOOC, T , , 20°C; (d) Cool dey, wind 1 m.p.h.
Nurcerous other examples could be given, but these will suBce to
illustrate the method suggested here for carrying through to its physiological consequences the interaction between the plant and the environment. A small plant with a finite number of leaves is easily
analyzed and the total response summed for all the leaves. A tree ia
another matter and must be treated from a statistical standpoint.
c. CLIMATE AND PHYSIOLOGY O F A TREE
In order to deal with a plant aa large and complex aa a tree one must
recognixe that various regions of a tree have very different climatee.
A tree is partitioned into units such as the upper, middle, and lower
thirds of the foliage with height and then subdivide these into north,
east, south and west sectors. These larger units can be further divided
into tlle leaves op the periphery and leaves in the interior of the foliage.
Hence one may have 24 separate foliage units to consider, each with a
different exposure. Each foliage unit may contain 6 000, 10 000 or more
individtlal leaves and within each unit a “characteriafic” leaf can be
~pecih6. The climate of ewh foliage unit ia deeoribed aocording to the
UAVID M. GATES
‘rho iukgral under the net photoeynthesis and respiration curves
givw an approximate measure of the productivity of the leaf. The
values below the line are negative and represent the consumption of
energy. Normally net photosynthesie is sufficiently poaitive to mom
than componmte for the loss by respiration. The total productivity of a
whole plant, including euch large and complex individuals a8 8 tree,
can be estimated from the sums of the reaponsea of each and every leaf
on the plsnt. The technique is described below &B applied to qtimating
the total water usage by a tree or a stand.
Time of day
FIG. 6. D i m 1 variation of relative metabolic rates for a fully expoeed horizontal leaf
on a hot, cleer day end on a 0001, clear day each with little wind end with much wind.
(a) Hot day, wind 2 m.p.h. T d n 20’C. Tm.= 4OoC; (b) Hot day, wind 1 m.p.h.; ( 0 ) Cool
day, wind 2 m.p.h. Tmln IOOC, T , , 20°C; (d) Cool dey, wind 1 m.p.h.
Nurcerous other examples could be given, but these will suBce to
illustrate the method suggested here for carrying through to its physiological consequences the interaction between the plant and the environment. A small plant with a finite number of leaves is easily
analyzed and the total response summed for all the leaves. A tree ia
another matter and must be treated from a statistical standpoint.
c. CLIMATE AND PHYSIOLOGY O F A TREE
In order to deal with a plant aa large and complex aa a tree one must
recognixe that various regions of a tree have very different climatee.
A tree is partitioned into units such as the upper, middle, and lower
thirds of the foliage with height and then subdivide these into north,
east, south and west sectors. These larger units can be further divided
into tlle leaves op the periphery and leaves in the interior of the foliage.
Hence one may have 24 separate foliage units to consider, each with a
different exposure. Each foliage unit may contain 6 000, 10 000 or more
individtlal leaves and within each unit a “characteriafic” leaf can be
~pecih6. The climate of ewh foliage unit ia deeoribed aocording to the