Maintenance of constant leaf temperature by plants. I. Hypothesis--limited homeothermy
1988
The relationship between the temperature of a plant and the temperature of its environment is an important consideration in the study of thermal stress. Plants are generally assumed to be poikilotherms that exist in eurythermal environments and some variation in plant temperature is thought to be normal for the plant. Recent investigations in our laboratory have indicated that the thermal dependencies of enzymes from several plants are more characteristic of those from homeotherms than eurytherms. Thus, while it is assumed that thermal variation is normal for a plant, the thermal dependencies of the enzymes of the plant suggest that such variation may be stressful. We present a conceptual framework for the active maintenance of a normative, or characteristics, temperature by the plant. We propose that the lower limit of the temperature of a plant is controlled by its environment while the upper limit, even under a wide variety of conditions, can be controlled by the plant and maintained at a normative value. We suggest the term "limited homeothermy" to describe this type of thermal behavior by the plant. We propose three constraints on the maintenance of the normative temperature by the plant; (1) sufficient energy influx to raise its temperature to the normative value, (2) sufficient water supply for transpiration, and (3) humidity low enough to allow for cooling to the normative temperature.
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