Oscillatory Transpiration in a Cotton Plant: II. A MODEL

A generalized conceptual model of oscillatory transpirationin a cotton plant growing in a nutrient solution under constantenvironmental conditions is presented. The model is based uponthe results and observations of an experimental study and thecontemporary literature. It incorporates the values of parameters,of initial and boundary conditions, and of significant variablesin the transpiration stream. A non-linear coupling consistingof a hysteresis loop with a time-variant constraint acting betweenthe guard cell potential and stomatal resistance is proposed.Mathematical equations based upon the network variables weresolved via a simulation language (CSMP—IBM/360). The modelshowed gradually damped oscillations early in the light periodand sustained oscillations later in the light period. The resultingsimulation output agrees satisfactorily with pattern of oscillationsobserved in vivo. Root resistance changes through the day causedminimal effect on oscillation. The principal causal effect foroscillatory behaviour appeared to be due to stomatal effects.