Influences of Plant Moisture Stress, Solar Radiation, and Air Temperature on Cotton Leaf Temperature1

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Abstract
The influences of cotton plant relative turgidity (RT), solar radiation (RS), and air temperature at plant height (TA) on leaf temperature (TL,) and leaf minus air temperature (TL — TA) were studied during two crop seasons. The daily data show that (a) a decrease in relative turgidity from 83 to 59% resulted in a 3.6C increase in leaf temperature, and (b) a unit increase in solar radiation (from about 0.5 to 1.5 ly min‐1) resulted in a 9 to 10C increase in leaf temperature. These same changes in relative turgidity and solar radiation resulted in 2.7 to 3.7 and 8 to 10C increases, respectively, in (TL — TA). Seasonal average (TL — TA) was 4C. Leaf temperature and (TL — TA) could be estimated from the seasonal data with an average standard error of 1C by RT, RS, and TA in linear multiple regression analyses. The results of these studies show that variations in plant moisture stress significantly alter leaf temperature and leaf minus air temperature. However, variations in insolation must be carefully monitored under intermittent cloud conditions to account for their influences on plant leaf temperature.