Agent Orange – Part Two – On the Origin of Agent Orange

The general consensus regarding the inception of Agent Orange, the infamous herbicide used during the Vietnam War, is that its origins lay in a laboratory somewhere back in the mid-twentieth century. However, I would argue that its actual origins lie in the Victorian era. I believe its story starts in 1881 with an English naturalist and the publication of his book ‘The Power of Movement of Plants‘. Although you might not have heard of this before, I guarantee that the majority of you will have heard of a book he published twenty-two years earlier, ‘On the Origin of Species’. Yes, I believe the story of Agent Orange began with Charles Darwin.

Charles Darwin is best known throughout the world for the development of the theory of evolution and natural selection, but few know that he was a distinguished botanist who had published several books on the subject. According to his autobiography, Darwin always had a love of plants starting at a very early age which continued on his voyages on the HMS Beagle until his later years, when he turned his home and the surrounding countryside into somewhat of a botanical field station. It is at this time, despite repeated bouts of illness, that he began to study the movement of plants. He performed numerous experiments to investigate the effects of unidirectional light on seedlings and discovered that plants would always bend towards the light unless their tips were removed or covered up. We now know this effect as phototropism, and that it is caused by a class of plant hormones (AKA “plant growth substances” here in the UK) called auxins.

Auxins are a class of compounds that are made in the tip of the plant that stimulates cell elongation and cell division. They are transported cell-to-cell via the PIN proteins which only work in one direction but can be flipped in certain conditions. For example, blue light can interfere with the PIN protein’s polarity, causing it to move auxin in the opposite direction out of the cell. As a result, we get an accumulation of the hormone on the shady side of a plant which causes the cells on the dark side to enlarge and thus bend. This eventually will move the tip of the plant towards the light. Of course, Darwin knew nothing about this mechanism, but his work laid the foundation for subsequent experiments.

The first person to isolate and determine the structure of an auxin (indole-3-acetic acid) was Kenneth V. Thimann, an English-American plant physiologist and microbiologist. This discovery was not only a major contribution to our basic understanding of plant development but of great importance to the agriculture and horticulture industries because, in low concentration, auxins could enhance the growth of plants. However, in higher concentrations, it could kill it. This is because auxins also stimulate the production of ethylene which activates an enzyme that digests the cell wall between the leaf and the stem. This causes the leaves to fall and the plant to eventually die.

On September 1st, 1939, Germany invaded Poland under the false pretext that Poles had carried out a series of sabotage operations against German targets near the border, which started the Second World War. In the six years that the war lasted, efforts were made by the Americans and British to develop herbicidal weapons to be used on the enemy. During this time, a Geoffrey Emmett Blackman working for Imperial Chemicals Industries (ICI) developed a synthetic auxin that showed great potential as a weed killer. The military potential of this compound immediately occurred to the research workers, who passed details to the government. The compound was tested and the British government considered using it to destroy German crops, but in September of 1942, Churchill dropped the scheme on the ground of costs and time it would take to build a production plant. At the same time, he was researching compounds that had similar properties for the Agricultural Research Council (ARC) who gave the details to John Anderson, who was responsible for the organisation of Britain’s civilian and economic resources for the war. Anderson then arranged for scientists from both ICI and the ARC to conduct field trials at the Ministry of Agriculture’s experimental station at Rothamsted. One of the compounds identified as potential anti-crop weapons was 2,4,-D. Informationabout 2,4-D, including a proposed synthetic pathway and designs for a production plant, was given to the to the Americans to potentially be used against Japan’s rice crops. In early 1945, the American army ran tests on various combinations of herbicides and deployment methods, which it was hoped would eventually be used in Operation Downfall.

2,4-Dichlorophenoxyacetic acid (2,4-D)

Operation Downfall was the proposed Allied plan for the invasion of Japan which planned, among other things, to use herbicide to starve the Japanese into submission. The plan, however, was abandoned when the Japanese surrendered following the atomic bombings of Hiroshima and Nagasaki and the Soviet declaration of war. On September 2nd, 1945, a Japanese delegation formally signed the instrument of surrender on board the USS Missouri, marking the official end of World War Two.

After the war, herbicides like 2,4-D found themselves being used alongside agriculture resulting in increased yields in what is now known as the Green Revolution. During this time, military research and development into anti-crop technology slowed to a trickle in Britain but continued full throttle in America. It is estimated that over 12,000 potential herbicides were tested at Fort Detrick, the US Army’s chemical and biological warfare establishment in Maryland during this time. The emphasis was still on anti-crop weapons, but the target was now food supplies in the USSR and Eastern Europe. During this time, scientists working at Fort Detrick discovered work done by a plant physiologist, Arthur Galston, investigating ways to speed up the flowering and fruiting of soybeans. 

During the Second World War, Galston was a graduate student at the University of Illinois whose research focused on finding a chemical means to make soybeans flower and fruit earlier, so that they could mature before the end of the growing season. He discovered that exposing soybeans to the synthetic auxin 2,3,5-triiodobenzoic acid (TIBA) would speed up the flowering but also noted that if the concentration was too high, all the leaves would drop off and kill the plant. He published his findings in his Ph.D. thesis titled ‘Physiology of Flowering With Special Reference to Floral Initiation in Soybeans’ in 1943, which earned him his doctorate in botany. Eight years later in 1951, researchers at Fort Detrick used Galston’s compounds as a prototype for devising a more potent and effective herbicide. They soon developed 2,4,5-T which, when mixed in a 1:1 ratio with 2,4-D, became what is known today as Agent Orange.

2,4,5-Trichlorophenoxyacetic acid (2,4,5-T)

Work spanning decades went into the development of agent orange, from people who wanted to know more about the world, to people who wanted to better the world, to even some who wanted to use it as a weapon, thinking they were helping the world.

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About Myles Power (580 Articles)
My name is Myles Power, and I run the educational YouTube channel, powerm1985. I spend what little free time I have sharing my love of SCIENCE! through home experiments, visiting sites of scientific interest, and angrily ranting at pseudoscience proponents. I am also one of the founding members of the podcast 'The League of Nerds' - which I co-host with James from 'The History of Infection'.

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