TOWARD UNDERSTANDINO ECOSYSTEMS
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6. Outdoor environments.
These are the most complex of all environments.
(i) Solar radiation-zerotoverystrongwithebroadspectralrenge.
Thermal radiation - ubiquitous, generally moderate in intensity and broad spectral range.
(ii) Convection- weak to strong depending on amount of wind.
(iii) Conduction - may be significant for animal resting on
warm or cold stratum. Often not significant.
(iv) Evaporation or transpiration - may be highly significant.
B. LEAF TEMPERATURES
The general pattern of leaf temperatures in natural situations of
various exposures and different air temperatures is known, see Gates
(1963, 1964), Gates and Janke (1966), Lange (1959), Salisbury and
Spomer (1964), and Raschke (1958). Fully exposed sunlit leaves are
from a few degrees to 20°C above air temperature and shade leaves are
approximately at air temperature or a few degrees below air temperature. Hence adjacent leaves on the same plant, exposed to sunlight and
shaded, may have temperatures aa much aa 25°C different. A leaf exposed to a cold night sky may be as much aa 6 or 7°C below air temperature. Lange (1959) discovered “under” temperature leaves for some
plants of Mauretaniu and Gates et ul. (1964) independently discovered
this same phenomena for the temperature of fully sunlit Mimdus leaves.
These are plants which grow in wet soil and can transpire readily. Very
rapid transpiration rates drop the leaf temperature below air temperature when the leaf is fully exposed to intense sunlight and at high air
temperatures. In the case of Mimulus there was a remarkable amount
of temperature control for sunlit leaf temperatures remained between
about 26 and 34°C when air temperature varied from 19” to 37°C. The
temperature of any part of a plant is a direct consequence of the instantaneous climate nearby this particular plant part. If a plant is of considerable extent or size there is no such thing aa a single climate for
the plant. There is a different climate for each and every part of the
plant. It is a matter of choice by the investigator as to how finely to
divide the plant and its environment when attempting to understand
the interaction between the two. Temperature is important to the
plant through chemical reactions which are temperature dependent,
including destructive thermochemical reactions at high temperatures
which cause protein denaturation and other molecular breakdown.
V I . ECO-PHYSIOLOUY
It is not sufficient to predict the temperature and transpiration rate
of a plant, one must also understand the consequence of temperature
15
6. Outdoor environments.
These are the most complex of all environments.
(i) Solar radiation-zerotoverystrongwithebroadspectralrenge.
Thermal radiation - ubiquitous, generally moderate in intensity and broad spectral range.
(ii) Convection- weak to strong depending on amount of wind.
(iii) Conduction - may be significant for animal resting on
warm or cold stratum. Often not significant.
(iv) Evaporation or transpiration - may be highly significant.
B. LEAF TEMPERATURES
The general pattern of leaf temperatures in natural situations of
various exposures and different air temperatures is known, see Gates
(1963, 1964), Gates and Janke (1966), Lange (1959), Salisbury and
Spomer (1964), and Raschke (1958). Fully exposed sunlit leaves are
from a few degrees to 20°C above air temperature and shade leaves are
approximately at air temperature or a few degrees below air temperature. Hence adjacent leaves on the same plant, exposed to sunlight and
shaded, may have temperatures aa much aa 25°C different. A leaf exposed to a cold night sky may be as much aa 6 or 7°C below air temperature. Lange (1959) discovered “under” temperature leaves for some
plants of Mauretaniu and Gates et ul. (1964) independently discovered
this same phenomena for the temperature of fully sunlit Mimdus leaves.
These are plants which grow in wet soil and can transpire readily. Very
rapid transpiration rates drop the leaf temperature below air temperature when the leaf is fully exposed to intense sunlight and at high air
temperatures. In the case of Mimulus there was a remarkable amount
of temperature control for sunlit leaf temperatures remained between
about 26 and 34°C when air temperature varied from 19” to 37°C. The
temperature of any part of a plant is a direct consequence of the instantaneous climate nearby this particular plant part. If a plant is of considerable extent or size there is no such thing aa a single climate for
the plant. There is a different climate for each and every part of the
plant. It is a matter of choice by the investigator as to how finely to
divide the plant and its environment when attempting to understand
the interaction between the two. Temperature is important to the
plant through chemical reactions which are temperature dependent,
including destructive thermochemical reactions at high temperatures
which cause protein denaturation and other molecular breakdown.
V I . ECO-PHYSIOLOUY
It is not sufficient to predict the temperature and transpiration rate
of a plant, one must also understand the consequence of temperature