The spatial distribution of a plant species is limited by the range of climatic conditions to which the species can adapt. Temperature is one of the most significant determinants of plant distribution, but except for the effects of lethal limits, little is known about physiological changes in responses to differences in environmental temperature. In this study, temperature coefficients of non‐photosynthetic metabolism have been determined in the normal environmental temperature range for selected annual and perennial plants. Distinct differences were found in the temperature coefficient of metabolism of woody perennial plants from high latitudes and high elevations and closely related low‐latitude and low‐elevation plants. Low‐latitude and low‐elevation woody perennials have Arrhenius temperature coefficients for metabolism that are larger than those for congeneric high‐latitude and high‐elevation plants. The Arrhenius temperature coefficient is not rapidly adapted to new environments. A simple function was developed relating Arrhenius temperature coefficient to latitude and elevation for accessions of three, woody, perennial species complexes of plants collected from a wide geographic range but grown in common gardens. Within these taxa, plants that experience broader ranges of temperature during growth in their native habitat have smaller temperature coefficients. Temperature coefficients also varied with growth stage or season. No similar relationship was found for annuals and herbaceous perennials. For the plants tested, Arrhenius temperature coefficients are high during early spring growth, but shift to lower values later in the season. The shift in Arrhenius temperature coefficients occurs early in the season for southern and low‐elevation plants and progressively later for plants from further north or higher elevation. The changes in Arrhenius temperature coefficients result largely from increases in plant metabolic rates at lower temperatures while little change occurs in the rates at higher temperatures. Altering the temperature dependence of the control of metabolic rate is apparently an important means of response to climate change.
Abstract.A thermodynamic model describing the relation between plant growth and respiration rates is derived from mass-and enthalpy-balance equations. The specific growth rate and the substrate carbon conversion efficiency are described as functions of the metabolic heat rate, the rate of CO2 production, the mean oxidation state of the substrate carbon produced by photosynthesis, and enthalpy changes for conversion of photosynthate to biomass and CO2. The relation of this new model to previous models based only on mass-balance equations is explored. Metabolic heat rate is shown to be a useful additional measure of respiration rates in plant tissues because it leads to a more explicit description of energy relations. Preliminary data on three Zea mays (L.) cultivars are reported. The model suggests new rationales for plant selection, breeding and genetic engineering that could lead to development of plants with more desirable growth rates.
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