Different herbicides kill in different ways; some herbicides target photosynthesis, others target amino acid biosynthesis and others may block carotenoid biosynthesis. Regardless of the method, chemical herbicides have only one goal: they kill plants.
Monsanto’s Roundup is no exception – despite engineering plants that are resistant to the chemicals – but weeds are once more getting the upper hand. Will chemistry hold the answers to the age-old battle between cultivated plants and so-called weeds?
Weed-Killers Don’t Discriminate
When you apply a weed killer to any plant, there is– for the most part — not one iota of difference between an Asparagus Fern and a Tea Rose. Sure, the plants look vastly different but current chemical agents are not quite sophisticated enough to know the differences between a fern and a rose.
Roses, reportedly, are one of the most developed plants in human history. Your prized roses are not designed to survive long droughts, herbicides or any ‘man-made element;’ the rose was specifically bred for human aesthetics – just to look and smell pretty. Their hybridized, developed nature presents a possible problem in this era of rapid change.
Non-native invasive species adapt easily in the current conditions, however. The hearty, invasive plants have undergone longer periods of evolutionary change—a survival of the fittest scenario—while an over-hybridized rose is more likely to face problems associated with in-breeding. What can you do to save your favorite flowers from the invasive plants that can take over your lawn and garden so easily?
The answer may lie in the use of bio-technology to give plants the genetic tools they need to survive. U.S. companies like Monsanto have developed herbicide-resistant crops by selectively changing the growing patterns of corn, cotton, or soy beans – could Roundup-resistant roses be next?
John Franz, Ph. D., at Monsanto Corp. invented Roundup in mid-1971 and the herbicide immediately swept the competition aside – this herbicide remains popular among everyday users.
Glyphosate acts by disrupting aromatic amino acid biosynthesis (also known as the shikimate acid pathway) – it competes with pyruvate in the reaction with shikimic acid – the pyruvate is unable to bond with the shikimate. From beginning to end, the shikimate acid cascade takes seven steps; and it is the sixth step that the glyphosate disrupts.
After Monsanto introduced the herbicide glyphosate, it soon became the leading herbicide on the market – it knocked down or killed any plant in range. This included crops, unfortunately, so scientists developed plants with the ability to resist Roundup.
However, the weeds could not be fooled very long. In the mid-1990s, weeds evolved to resist wide-spectrum herbicides like Roundup (glyphosate).
Descent of Plants; Ascent of Humanity
So where does that leave us? The current scientific community is scrambling to adjust to the paradigm shift that evolution has thrown. Insects and animals evolve as rapidly as the plant kingdom so it should have not come as a surprise to many.
The problem of herbicide resistance lies in ‘reproduction.’ Rapidly-reproducing species — those likely to adapt quickly compared to species that re-produce slowly — have the advantage in a climate where there is higher carbon dioxide (CO2), abundant water, and warmer temperatures.
Whether the next plant-protection paradigm is longer-lived than the current one may depend upon how well we understand the patterns of evolutionary change. It may also dictate how we, as a species, survive climate change. Is there another biotech answer just around the corner? Only time will tell.