Invention of Ecocide: Agent Orange, Vietnam, and the Scientists Who Changed the Way We Think About the Environment

THREE: Agent Orange before Vietnam

33 CHAPTER THREE AgenT orAnge before vIeTnAm agent orange has a split lineage. The history of its component chemicals , 2,4-d and 2,4,5-t, begins with one of Charles Darwin’s lesser-known biological theories. The history of the military weapon Agent Orange begins on the eve of World War II, when the demands of total war sparked one scientist ’s insight that weed killers had military value. In the late 1870s, Darwin began to study the mechanisms that regulated plant growth; at the time there were no accepted answers to questions that would form the basis of plant physiology: Why do plant shoots grow upward in defiance of gravity? What causes stems to bend around objects that obstruct sunlight? Is there a particular part of the plant that controls growth, or is the process decentralized throughout the organism? With the assistance of his son Francis, Darwin conducted experiments with 320 plant species, paying particular attention to the movement of seedlings when exposed to varying degrees of light. At nearly six hundred pages, the resulting publication, The Power of Movement in Plants (1880), reads like an endless scientific diary. Still, Darwin managed to fit his central hypothesis into a concluding paragraph: Circumnutation [bending] is of paramount importance in the life of every plant; for it is through its modification that many highly beneficial or necessary movements have been acquired. When light strikes one side of a plant, or light changes into darkness, or when gravitation acts on a displaced part, the plant is enabled in some unknown manner to increase the always varying turgescence [swollenness] of the cells on one side; so that the ordinary 34 CHAPTER THREE circumnutating movement is modified, and the part bends either to or from the exciting cause; or it may occupy a new position, as in the so-called sleep of leaves.1 In other words, Darwin discovered that the stimulus of growth transferred from one part of a plant (the tip of a shoot) to another (the stem). When Darwin either shaded the tip with miniature cups or snipped it from the plant altogether, the stem would not bend toward light as it would under normal conditions, thus demonstrating the existence of “some unknown manner” of transmission that directed plant growth from top to bottom. These were the last of Darwin’s major scientific discoveries; he died in 1882.2 Darwin’s transmission hypothesis provided the foundation for all future discoveries involving plant growth regulation, on two levels. First, his experiments demonstrated the existence of a growth stimulus that could be isolated and studied. Second, researchers could concentrate their efforts on the tip of the plant. Over the next thirty years, scientists’ understanding of plant growth expanded rapidly. E. H. Salkowski discovered indole-3-acetic acid (iaa) in 1885, which turned out to be the growth substance whose existence Darwin had postulated five years earlier. In 1911 Peter Boysen-Jensen replicated Darwin’s earlier manipulation of plant tips, adding the step of placing pieces of gelatin between the tip and the stem. Boysen-Jensen observed that the gelatin separator did not affect the stem’s growth response and hypothesized that the growth “messenger” was likely a chemical process. Subsequent experiments by Arpad Paal (1918) and H. Soding (1925) involving observations following plant cuttings and light variations further confirmed the Boysen-Jensen chemical hypothesis. Then in 1926 a Dutch graduate student, F. W. Went, isolated the growth substance into a nonliving medium rather than allowing it to diffuse into the stem as his predecessors had done. Went chose agar, a seaweed-derived jelly that absorbed the growth substance from the isolated tips. When Went placed the agar back on the shoot, the young plant behaved as if it had never been severed in two. This proved the existence of a growth substance. Went named this substance auxin, from the Greek auxein, “to grow.”3 The discovery and identification of unique plant hormones proved to be the methodological counterpart to Darwin’s scientific process. Darwin had opened a Pandora’s box for hormonal manipulation of a given plant’s physiology with the knowledge that plant growth was controlled by biochemi- AGENT ORANGE BEFORE VIETNAM 35 cal reactions that could be isolated and quantified. Scientists in Germany, Britain, and the United States subsequently raced to create chemical solutions that could influence natural growth-regulating reactions. In 1933 the potential for hormone...