Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Plants, Soils, and Climate

Committee Chair(s)

Sterling A. Taylor


Sterling A. Taylor


A. A. Bishop


R. L. Smith


Plant responses to different soil moisture regimes have been extensively studied. Because of interactions between the soil, plant and climatic factors, few convincing generalizations concerning the influence of soil water on the transpiration of water by plants have been established. Generally single factors or at most the interaction of two have been studied at any one time. Useful theories describing the conditions of water retention in plant tissues and movement of water through plants have been proposed. Equally useful theories have been suggested for describing the retention and transmission of water in soil. The integration of these theories and their applications to evapotranspiration remains to be elucidated. This indicates a need for studying the total free energy path that causes water transport from soil to atmosphere through plants.

Two interrelated categories of processes or factors, atmospheric desiccation and rate of soil water uptake, need to be studied simultaneously. The energy status of plant water, herein called total plant water potential, in conjugation with soil water potential appears to be critically involved in the process of water transfer through the soil-plant-atmosphere system. Plant water potential is the best criterion for detecting the degree of plant water stress.

By studying water retention and flow properties of both plants and the supporting soil, one may be able to find relations that will help to predict the behavior of plants as they remove water from soil. For example, water retention characteristics of drought resistant plants may suggest reasons why some desert plants survive desiccating conditions that cause death to more succulent plant species.

The major objective of this study was to investigate the influence of soil water potential and atmospheric environment on both the transpiration rates and components of the plant water potential.



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