Remote Sensing Techniques for Assessing Water Deficits and Modeling Crop Response

Water availability and temperature are 2 primary environmental parameters that frequently limit plant growth. The effects of these factors are difficult to separate; however, this paper will be directed primarily at water deficit. Plant responses to water deficit have been difficult to model because of different response times involved and the problem of quantifying water deficit (severity vs. duration). For example, response times for cell enlargement and leaf abscission are much different and yet their direct effects on transpiration and photosynthesis may be the same. Transpiration and photosynthesis are key processes in crop yield models. Transpiration is an energy-consuming process, which is strongly controlled by leaf area and stomatal conductance. Photosynthesis, on the other hand, is a quantum-requiring process, which is dependent to a large extent upon the interception of visible light and the diffusive conductance of CO 2 . Solar radiation provides both energy for transpiration and quanta for photosynthesis.