Foliage temperature: Effects of environmental factors with implications for plant water stress assessment and the CO₂/climate connection

Abstract

Throughout the summer and fall of 1985, several day-long sets of foliage temperature measurements were obtained for healthy and potentially transpiring water hyacinth, cotton, and alfalfa plants growing in a sealed and unventilated greenhouse at Phoenix, Arizona, along with concurrent measurements of air temperature, vapor pressure and net radiation, plus, in the case of the water hyacinths, leaf diffusion resistance measurements. Some data for these plants were additionally obtained out of doors under natural conditions, while dead, nontranspiring stands of alfalfa and water hyacinth were also monitored, both out of doors and within the greenhouse. Analyses of the data revealed that plant nonwater-stressed baselines, i.e., plots of foliage-air temperature differential versus air vapor pressure deficit for potentially transpiring vegetation, were (1) curvilinear, as opposed to the straight lines which have so often appeared to be the case with much smaller and restricted data sets, and (2) that these baselines are accurately described by basic theory, utilizing independently measured values of plant foliage and aerodynamic resistances to water vapor transport. These findings lead to some slight adjustments in the procedure for calculating the Idso-Jackson plant water stress index and they suggest that plants can adequately respond to much greater atmospheric demands for evaporation than what has been believed possible in the past. In addition, they demonstrate that the likely net radiation enhancement due to a doubling of the atmospheric carbon dioxide concentration will have little direct effect on vegetation temperatures, but that the antitranspirant effect of atmospheric CO 2 enrichment on foliage temperature may be substantial. Hatfieldet al., 1980; Clawson and Blad, 1982; Gieser et al., 1982; Hatfield, 1982; Bonnano and Mack, 1983; Steiner et al., 1985] and to predicting crop yields fidso et al., 1977b, 1979a, b, 1980; Hatfield et al., 1978, 1979; Reginato et al., 1978; Walker and Hatfield, 1979; Jackson et el., 1980; Smith et al., 1985]. Also acquired was the ability to remotely detect the presence of certain plant diseases [Pinter et al., 1979; Nilson, 1984, 1985a, b, c] and the means to predict the potential for the mass flow of gases in aquatic plants [Dacey, 1980, 1981a, b; ldso, 1981]. In the area of climate, little work has been done on the effects of plant foliage temperature [Dickinson, 1983]. Apart from some early analyses of air temperature regimes over tropical islands covered with lush vegetation [Priestly, 1966; Priestly and Taylor, 1972], the first study to directly confront the topic was that of Dickinson et el. [1981], who developed a simple parameterization of plant water flow for use in a global climate model. Shortly thereafter, Shukla and Mintz [1982] demonstrated the importance of such work to the climate modeling enterprise by showing that vegetation-induced changes in the evapotranspiration at the Earth's surface can significantly modify the global fields of rainfall, temperature and ...

Crop water stress maps for an entire growing season from visible and thermal UAV imagery

“…UAV platforms now enable the collection of remotely sensed temperatures with higher spatial and temporal resolution than those collected by satellites and manned aircraft. Temperatures from canopies are closely related to air and soil water content, actual transpiration and crop water stress (Idso et al, 1986;Jackson et al, 1987). If a crop has insufficient water supply, stomata will close in order to limit water loss through transpiration.…”

Stomatal response to humidity in a sugarcane field: simultaneous porometric and micrometeorological measurements*

“…Yet in studies in which the relationship between remotely sensed leaf temperature and D^ revealed no apparent stomatal response to V (e.g. Idso et al, 1986) leaf temperatures were frequently ca. 10°C below, and occasionally nearly 35 °C below, air temperature.…”

“…tance (Idso et al, 1986). Water hyacinth was considered to exhibit boundary layer conductance of ca.…”

“…Application of an energy budget model to the relationship between remotely sensed leaf temperatures (difference between canopy and air temperatures) and associated air saturation deficits (D) has not indicated a signifieant stomatal response to V. The commonly observed stomatal response to V (or related quantity, D) has been considered to be no more than an artifaet, associated with enclosure of leaves in porometers or cuvettes, for whieh mathematical corrections have been suggested (Idso, Allen & Kimball, 1987). These conclusions derive from radiometrie measurements of canopy temperature and energy budget calculations, with specific assumptions regarding boundary layer properties of leaves outside of cuvettes (Idso, Clawson & Anderson, 1986).…”

Energy balance concept in the evaluation of water table management effects on corn growth: Experimental investigation

“…The daily crop evapotranspiration has also been successfully estimated from one-time measurement of the day using a factor readily calculated from day of year and time of day for latitudes between 60øS and 60øN [Jackson et al, 1983]. Extensive work has been done to relate plant water stress to the canopy temperature [Idso, 1982;Jackson, 1982;Jackson et al, 1977Jackson et al, , 1981Idso et al, 1981Idso et al, , 1982Idso et al, , 1984 Idso et al, , 1985Idso et al, , 1986]. Idso et al [1981] and Jackson et al [1981] developed an index for crop water status known as crop water stress index (CWSI).…”