Soil‐ and atmosphere‐induced plant water stress in cotton as inferred from foliage temperatures

Abstract

Foliage temperatures of cotton obtained by means of infrared thermometry, along with air wet and dry bulb temperature measurements, were used to investigate certain relationships existing between the water contents of soil and air and the ability of the crop to maintain transpiration at the potential rate. It was found that as soil water content is progressively depleted fo!lowing an irrigation, departure from potential transpiration begins to occur at smaller and smaller values of air vapor pressure deficit in a regularly predictable fashion. It was also demonstrated that the plant water potential of cotton transpiring at the potential rate is a function of the air vapor pressure deficit and that the difference between this base value and the tension that develops under nonpotential conditions is a unique function of a newly developed plant water stress index. Finally, an example of the application of this foliage temperature-based index to evaluating the effects of an irrigation event is presented.

Foliage temperature as a means of detecting stress of cotton subjected to a short-term water-table gradient

“…While this value of the upper limit was obtained from a small number of measurements, it was obtained on a canopy of similar architecture adjacent to the experimental plots. The value so obtained is similar to values for other crops (Jackson et al, 1981;Idso et al, 1982a;Jackson, 1982) and is reasonably close to that found for cotton by Idso et al (1982b).…”

“…To interpret the effect of the flooding on the canopy temperature, we followed the method of Jackson et al (1983), Jackson (1982) and Idso et al (1982a) in developing a stress index. In order to avoid confusion with the Crop Water Stress Index (CWSI) defined by them for studying crop response to soil water deficits, we define a more general Crop Stress Index (CSI) that encompasses plant stress as a result of short-term flooding.…”

“…Little information on canopy temperature is available when other causes of plant stress, such as those associated with excess soil water or plant diseases are encountered. This work was designed to evaluate the utility of cotton foliage temperature as an indicator of crop stress resulting from short-term flooding and to determine the subsequent effects on evapotranspiration and photosynthesis as proposed by Idso et al (1982aIdso et al ( , 1982b.…”

Enclosing leaves for water potential measurement and its effect on interpreting soil-induced water stress

“…Although the diurnal change in this error has been shown for a number of species (Turner and Long, 1980) the relationship to atmospheric evaporative demand, as measured by the air vapor pressure deficit (AVPD), has not been shown. This note examines this relationship for cotton and the effect that the error has on the sensitivity of the relationship between the plant water stress index derived from canopy temperature measurements and the soil-induced plant water potential as shown by Idso et al (1982).…”

“…The soil-induced component of the leaf pressure potential of cotton (Gossypium hirsutum L.) can be underestimated in absolute magnitude by up to 44% if ~x exp values are used in the calculation. Removing this error by using ~x enc values subsequently improves both the discriminating ability of the plant water stress index proposed by Idso et al (1982) and the accuracy of the estimate of the soil-induced component of leaf xylem pressure potential. …”