Can you picture a scientific development so revolutionary that it caused professionals to throw caution to the wind? An economic impact so widespread and sudden that scientists across the country scrambled to catch up? Few scientific developments in history posed a danger like the industrialization of herbicides.
Since the employment of man-made herbicides by the farming industry manual labor on farms has been reduced significantly due to a diminished need for weeding, tilling is no longer necessary due to increased soil health, and yield loss due to pests has nosedived from roughly 37% down to 9%.
The birth of the petrochemical industry happened near the end of World War 2. In 1945 farmers across the nation began using 2,4-Dichlorophenoxyacetic Acid (2,4-D). Fortunately for the farmers, 2,4-D is easily manufactured and available in large quantities.
In 1946 the State Department made an official statement discouraging the use of 2,4-D because of a need for further experimental information. This statement was almost universally ignored.
With Federal support, scientists across the nation and beyond worked cooperatively to study the possible long-term dangers on the soil and crops while farmers disregarded their warnings. To everybody's relief, 2,4-D has proven to be safe and remains one of the most popular compounds in herbicides. (Norris-Tull 2020)
Herbicides using Green (Plant) Biotechnology target vital enzymes in the weeds, sabotaging their ability to survive. This can happen in a variety of ways, all lethal and targeted to undesirable plants. With a variety of undesirable plants in farms and elsewhere, herbicides may be combined to be as versatile as necessary.
The destruction or inhibition of Amino Acids is a common tactic for effective herbicides. Amino acids are the building blocks of proteins which serve vital functions within cells. Amino acid deformities disable the function of proteins, causing the swift death of the cell. The use of these herbicides is evidenced by discolorations or deformities in plant structure.
Photosynthesis is another essential function thrashed by many herbicides. The target when attacking photosynthesis is chloroplasts, which are organelles within cells that exclusively perform that function. Primarily, photosynthesis inhibition occurs at the site of electron transfer. The cell can no longer produce nutrients or energy and soon starves to death.
An indirect crippling of photosynthesis is the destruction of Pigments. Pigments accommodate the cells by protecting chlorophyl (which performs photosynthesis) from sunlight damage. They give plants their green color, so after Pigment Inhibitors are applied the plant turns white. The chlorophyl decomposes, leaving cells unable to perform photosynthesis.
Hormones in Growth Regulation of the cells can also be a target. 2,4-D herbicide, discussed above, is among this classification. Growth hormones in the cells accumulate, signaling the plant to constantly grow despite not having the nutrients to do so. Vital resources are depleted and the cells die.
Fatty Acids within cells are crucial for lipid production. Lipids are necessary for cell membranes and plant growth. Herbicides inhibit the enzyme Acetyl Co-A Carboxylase to prevent lipid synthesis. Symptoms are first observed in new growth of the plant. Cells can't grow healthily, so new leaves turn purple and die. The oldest and most developed cells in the plant take the longest to wither.
Seedling Growth inhibitors must be applied after crop emergence but before weed emergence. There are two methods of attack
Nitrogen Metabolism Inhibitors damage the intracellular function of converting ammonia to other nitrogen-related compounds. Glutamine synthetase is the target enzyme. This is required for building proteins and DNA in the cells. Plant cells are forced into necrosis, turning brown and withering due to inability to use nutrients correctly.
Last, but not least, are Cell Membrane Disruptors. After exposure to sunlight these herbicides create hydrogen peroxide to destroy cell membranes. The plant turns brown due to necrosis within hours. (Dayan 2019)
Scientists are always inventing new ways to destroy weeds with herbicides, making them more adaptable, environmentally friendly, and effective.
The ability of life to overcome adversity has been proven countless times throughout history. The challenge of herbicides is no exception. Over time, weeds that have mutations rendering herbicides non-effective replace those that are vulnerable. New herbicides, posing new environmental risks, must be developed to destroy the mutated weeds and the cycle continues. The invention of new biochemical herbicides is constant, and for the foreseeable future, this work is never-ending.
Whether adapted to mutated weeds or crafted to be more environmentally friendly, new herbicides are often restricted to Genetically Modified (GM) Crops. These crops are given some form of immunity to protect them from herbicides dangerous to them. Three approaches are used when crafting these changes.
These changes are made with great care, ensuring that the crops don't become toxic or dangerous as a food source.
A newer approach in herbicides is the use of Biocontrol Agents; living organisms ranging from viruses to vertebrates that destroy specific plants. These are selected or designed to destroy only the undesirable weeds while leaving desirable crops untouched. Only one application is necessary because they survive and reproduce so long as there are undesirable plants to feed on.
Bio control is inexpensive but has rarely had successful long-term effects. Significant results can take considerable time, perhaps over a decade, to manifest. It is also difficult to predict or control, sometimes expanding to the destruction of desirable vegetation.
These complications make research into biocontrol unpopular and unprofitable, but it may eventually become a powerful tool for weed control. (Norris-Tull, 2020)
Herbicides crafted by Green Biotechnology are a complex and essential tool for modern farming and gardening. Beginning with 2,4-D and expanding to countless forms today, scientists work tirelessly to make their herbicides effective and environmentally friendly. They are creative, discovering and inventing a variety of strategies to kill weeds as safely and efficiently as possible so that farmers can provide inexpensive food in abundance.
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Dayan F. E. (2019). Current Status and Future Prospects in Herbicide Discovery. Plants (Basel, Switzerland), 8(9), 341. https://doi.org/10.3390/plants8090341
Norris-Tull, D. (2020, July). Management of invasive plants in the Western USA. Management of Invasive Plants in the Western USA. Retrieved January 22, 2022, from https://www.invasiveplantswesternusa.org/