Introduction

This chapter focuses on plant growth curves. The world-population growth curve is an exponential curve. What do plant growth curves look like? Because water is the most important soil physical factor affecting plant growth, it is important to quantify plant growth to determine effects of water stress. In any experimental dealing with plant–water relations, some measure of plant growth (e.g., height, biomass) should be obtained. Plant growth curves also exemplify quantitative relationships. The chapter seeks to understand basic principles of plant–water relations. If equations can be developed to show relationships, then one can predict what is going to happen. Equations describing plant-growth curves demonstrate how one can quantify, and thus predict, plant growth. The chapter first considers the growth of the bacterium Escherichia coli. In the early nineteenth century, when plants and animals were being classified, the bacteria were arbitrarily included in the plant kingdom, and botanists first studied them. Even though bacteria are not plants or animals, we can follow their growth to understand plant growth curves.