9507240 Ortega The overall goal of Dr. Ortega's previous theoretical and experimental research was the development of quantitative relationships that describe growth (enlargement) and water uptake of single fungal and plant cells. These inestigations have produced three simultaneous and interrelated governing equations (Augmented Growth Equations) that describe the behavior of cell wall extension, water uptake, and turgor pressure. The overall objective of the proposed research is to extend (modify, adapt, and/or augment) the previously established Augmented Growth Equations to study cell wall extension, water transport, and solute transport in plant tissue. Some long-term objectives are (a) to establish governing equations that describe wall extension behavior, water transport behavior, and solute transport behavior for growing plant tissue, plant organs, and whole plants, (b) to determine the magnitude and behvior of the inclusive biomechanical and biophysical parameters, and (c) to elucidate the biological mechanisms used to control the magnitude and behavior of these parameters. The volumetric elastic modulus, E, is an important biomechanical parameter that controls the amount of elastic cell wall extension that occurs when the turgor pressure changes, and participates in the regulation of water transport in plant cells and plant tissue during dynamic conditions such as growth, day/night cycles (diel patterns), and periods of water stress. Importantly, E is a function of the turgor pressure, E(P). It follows that comprehensive models of water trnasport, growth, and plant responses to diel patterns and water deficits, must employ accurate values for E and account for its dependence on turgor pressure. It has been difficult to obtain accurate extimates of Estat, and to determine its dependence on pressure, using the pressure chamber because the pressure is not measured directly by the pressure chamber method. Recently, Dr. Ortega has developed a new pressure probe method (whi ch measures the turgor pressure directly) to determine Estat and its dependence on turgor pressure, Estat(P). Investigations are proposed to use this new pressure probe method to measure Estat(P) for dehydrating and rehydrating pea stems (Pisum sativum L.). The results obtained from dehydration and rehydration experiments will be compared to determine whether there is significant hysteresis in the pressure-volume relation for cells in pea stem tissue. Also, it is not known how Estat(P) compares with Einst(P). Investigations are proposed to determine Estat(P) and Einst(P) for the same cells and tissue, to elucidate the relationship between the two values.
