Physical-mechanistic parameterization of plant transpiration rates can be performed by relating it to stomatal conductance, as done in Ags models (A for net CO2 assimilation and gs for stomatal conductance to water vapor). A model of this kind was developed by Jacobs (1994), describing the transpiration rate as a response to environmental factors like air humidity, temperature and radiation. The model does not consider the effect of drought stress on plants, and in order to simulate transpiration rates in drought-stressed plants, semi-empirical parameterizations of the variables CO2 compensation point, mesophyll conductance gm, maximum CO2 assimilation rate Am,max, dark respiration Rd, and leaf angular distribution G need to be adapted. The main objective of this research proposal is to develop a numerical algorithm for the Jacobs (1994) model to estimate transpiration rates with adequate physical parameterizations for conditions of drought stress. To do so, physical and semi-empirical parameterizations will be tested under optimum and drought stress conditions, and the performance of different parameterizations to each drought condition will be evaluated. The methodology will follow these steps: (1) systematic literature revision to select physical parameterizations for CO2 compensation point, gm, Am,max, Rd, and G; (2) design of numerical algorithms containing the physical and semi-empirical parameterizations; (3) performing tests to determine the sensitivity of estimated transpiration to variables CO2 compensation point, gm, Am,max, Rd, and G; and (4) calibration and testing of routines with physical and semi-empirical parameterizations of the model, using data obtained in a recent field experiment.
News published in Agência FAPESP Newsletter about the scholarship: