Regression equations expressing reflectance of incidentlight from the upper (adaxial) surface of single leaves as a function of their relative turgidity and water content were developed. Reflectance at the 1.45‐ and 1.93‐µ water absorption bands was significantly related (p = 0.01) to the leaf relative turgidity or water content. However, because of variations in internal leaf structure associated with the availability of water during leaf development, the ability to predict the leaf water status from reflectance easurements was poor. With cotton (Gossypium hirsutum L.) the greatest change in reflectance occurs when the relative turgidity is below 70% and the leaves are visibly wilted. Within the relative turgidity range, 70 to 80%, reflectance changes are small and may not be definable for predictive purposes because of variation among leaves of field‐grown cotton caused by age differences and osmotic stresses.

No abstract

No abstract

Average measured ET curves and ET/RS curves were developed for estimating short‐period (7 to 14 days) or seasonal ET for cotton grown under wet, moderate, and dry soil moisture regimes on a medium‐ and a fine‐textured soil in the Lower Rio Grande Valley of Texas. Maximum average ET rates ranged from 0.46 cm per day for the dry moisture regime to 0.74 cm per day on the wet moisture regime on the medium‐textured soil compared with 0.46 to 0.76 cm per day on the dry and wet moisture regimes, respectively, on the fine‐textured soil. Comparison of the two estimating methods indicated that cotton ET estimates made from average ET were as reliable as estimates made from ET/RS and solar radiation.