32
DAVID M. GATES
growth or production as a function of light and temperature. Cell enlargement, growth, and increased mam will occur for many plants
during darkness as well ( ~ 8 during daylight. If the basic functional
relationships are known between the rate of dry weight increw per
unit leaf area and leaf temperature aa well as with the light level, then
once again the statistical approach can be applied for summing up the
effects of many leaves and many units or volumes of leaves with various
climat,ic conditions.
Much work has been done to determine production of vegetation in
terms of the rate of dry weight increase per unit leaf area as a function
of the growing season on a week by week basis. The results always
contain large amounts of scatter and inevitably represent the integration of all climatic and edaphic factors week by week. It is extremely
difficult from this to sort out specific causal relationships.
I n orc!er to proceed with the methods recommended here several
things mnst be done. Firstly, some very good laboratory data must be
taken under controlled conditions concerning production as a function
of light and temperature. The relationship, if any, between dry weight
increase per unit area, or some other measure of production, and the
water usage or transpiration rate must be established. Since the transpiration rate for a plant can be calculated rather accurately as a function
of the clinate near a leaf it may be straightforward to extend this to
growth or production. The procedure should be tested for single plants
first and then applied to stands of plants. It is clear that as individual
plants are placed into an array involving a certain number of neighboring plants that mutual interference and competition begin to occur.
These matual effects can be taken into account when formulating the
input for s computational program.
Secondly, it is necessary to produce a good mathematical description
of plant canopies or leaf arrangement. For a single plant this is relatively simple. One can describe the size of each leaf according to some
important dimension such as the characteristic dimension described
earlier. The orientation of each leaf can be described and the degree of
shading of one leaf by another as a function of time of day. When a
regular array of single plants is formed, such as for a crop, it is &ill
straightforward to classify the leaves, their sizes and their orientations.
It is possible also to classify their degrees of exposure aa a function of
time of day. A t the mme time the climate around each class of leaves
can be described. From this the energy budget of a “characteristic”
leaf of each class can be worked out. From the energy budget the leaf
temperatuTe and the resulting physiology can be estimated for the
diurnal conditions of each “characteristic” leaf. Then one can ~ u m the
total prodwtion of all leaves within a given foliage unit, then sum all
DAVID M. GATES
growth or production as a function of light and temperature. Cell enlargement, growth, and increased mam will occur for many plants
during darkness as well ( ~ 8 during daylight. If the basic functional
relationships are known between the rate of dry weight increw per
unit leaf area and leaf temperature aa well as with the light level, then
once again the statistical approach can be applied for summing up the
effects of many leaves and many units or volumes of leaves with various
climat,ic conditions.
Much work has been done to determine production of vegetation in
terms of the rate of dry weight increase per unit leaf area as a function
of the growing season on a week by week basis. The results always
contain large amounts of scatter and inevitably represent the integration of all climatic and edaphic factors week by week. It is extremely
difficult from this to sort out specific causal relationships.
I n orc!er to proceed with the methods recommended here several
things mnst be done. Firstly, some very good laboratory data must be
taken under controlled conditions concerning production as a function
of light and temperature. The relationship, if any, between dry weight
increase per unit area, or some other measure of production, and the
water usage or transpiration rate must be established. Since the transpiration rate for a plant can be calculated rather accurately as a function
of the clinate near a leaf it may be straightforward to extend this to
growth or production. The procedure should be tested for single plants
first and then applied to stands of plants. It is clear that as individual
plants are placed into an array involving a certain number of neighboring plants that mutual interference and competition begin to occur.
These matual effects can be taken into account when formulating the
input for s computational program.
Secondly, it is necessary to produce a good mathematical description
of plant canopies or leaf arrangement. For a single plant this is relatively simple. One can describe the size of each leaf according to some
important dimension such as the characteristic dimension described
earlier. The orientation of each leaf can be described and the degree of
shading of one leaf by another as a function of time of day. When a
regular array of single plants is formed, such as for a crop, it is &ill
straightforward to classify the leaves, their sizes and their orientations.
It is possible also to classify their degrees of exposure aa a function of
time of day. A t the mme time the climate around each class of leaves
can be described. From this the energy budget of a “characteristic”
leaf of each class can be worked out. From the energy budget the leaf
temperatuTe and the resulting physiology can be estimated for the
diurnal conditions of each “characteristic” leaf. Then one can ~ u m the
total prodwtion of all leaves within a given foliage unit, then sum all