Plant roots are vital in securing the plant to the soil and absorbing water and essential nutrients. Most people do not think much about them since they are hidden underground, but the root systems perform strange mechanisms for their never-ending growth.
Enigma of Spontaneous Oscillations
In 2007, a team of researchers discovered that the genes at the root tip of plants seem to pulsate. The study reported their findings, "Auxin-dependent regulation of lateral root positioning in the basal meristem of Arabidopsis."
The research revealed a strange oscillation that serves as a basic mechanism underlying the growth of plant roots. Experts recognize that understanding this process could help farmers design or choose the best plants for various soil types and climates. This could be very beneficial since we currently experience extreme weather, like floods and droughts, which damages crops worldwide.
To better understand the mechanism of plant growth, experts need to look at processes inside cells. Many chemical reactions and changes in genetic activities happen all the time inside plant cells. Some of these reactions are carried out in response to external signals, like changes in temperature, light, or availability of nutrients. However, there are also components of a plant's developmental program encoded in its genes.
Some of these cellular processes display regular oscillations, where groups of molecules rhythmically appear and disappear every few hours. One of the most famous examples is the circadian rhythm, the internal clock in plants and animals.
Many other examples of spontaneous oscillations occur in nature. Some are fast, like heartbeats and the mitotic cell cycle, while others are slow, like the menstrual cycle and hibernation. An underlying negative feedback loop can often explain these rhythms. This biological response triggers events, repressing the activity it started. Scientists assume the same mechanism could be the case for the root growth pulsation.
Understanding Root Tip Gene Oscillation
After discovering the root tip gene oscillation, scientists noticed that this pulsation leaves an invisible mark. This was discovered by using fluorescent markers that are visible under a microscope. The marks are left at places where the root can grow sideways, providing regular cues to the shape of the root system.
Although the exact cause of pulsation remains unknown, scientists have ruled out the hypothesis that it may be due to circadian oscillations. They know that a lot of feedback loops are involved in this mechanism.
A plant hormone called auxin seems to play a role in this process since it controls almost every aspect of plant development. Charles Darwin confirmed the existence of this essential molecule and its chemical structure around a century ago.
Experts conclude that the oscillating genes related to plant growth are the auxin "targets." When auxin enters a plant cell, the target genes become more active, triggering the removal of "repressors" that block the genetic activity. The experts hypothesize that the genes they block activate the repressors, and this feedback loop triggers the observed oscillations.
The answer to the mystery of the pulsating roots is probably not with one single process but a result of an interplay between different processes. Scientists know the key players, but the exact mechanisms have yet to be discovered.
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