The Root of the Matter
<span style="font-size: 1.5rem;">Locked within the soil and rarely given the light of day, it comes as no surprise that roots are often overlooked. But buried within the ground, botanists unearth a hidden world.</span>
You may recall that there are three primary types of root systems: tap roots, fibrous roots, and adventitious roots. They tunnel into the earth, sensing and absorbing the nutrients needed to support the plant’s life. These subsurface networks are incredibly attuned to their environment, as roots can recognize changes in pressure, light, gravity, and moisture and detect phosphorus, salt, nitrogen, toxins, and other plants’ chemical signals.
As the root structure expands, a complex microbiome develops, teaming with microorganisms like bacteria and fungi. This lively community can act as another line of defense for plants, potentially assisting in the suppression of diseases or helping identify nutrient sources.
Plants use all of the information absorbed from their root systems and associated microbiomes to respond to their surroundings effectively. Roots might be forced to reroute their growth pattern if they detect obstacles like buried rocks or the competing root systems of nearby plants. Some roots, like those of the thale cress, can emit chemicals to regulate their microbiomes, warding off parasitic microorganisms or encouraging symbiotic relationships. Certain plants can even take this to the extreme, like some species of eucalyptus, exuding chemicals from their root systems to snuff out the competition in a natural form of biochemical warfare called allelopathy.
These tangled interrelationships between plants and their environment lead some roots to take on unusual forms.
The thinnest roots on the planet belong to those plants inhabiting the fynbos shrubland in South Africa. This incredibly diverse ecosystem is filled with plant species that have adapted to the region’s extreme heat, developing minuscule roots roughly a tenth of a millimeter in thickness. These spindly roots spread across the scrubland in dense underground thickets to find every spare nutrient the desert-like environment offers.
These shrubland species are not the only South African species with unusual roots. Dwelling in the Kalahari desert just north of the shrubland is the shepherd’s tree, known for its gnarled white trunk and prodigious root systems. In search of water and nutrients, the roots of shepherd’s trees will bore deep into the earth, digging up to 230 feet down (roughly the wingspan of a 747 airplane). But not all roots grow downwards. Some, like those of Corydalis conorhiza, leave the ground behind entirely, instead snaking up through the snow in southern Russia to find resources to survive the harsh winters.
Curious to explore the diversity of roots? An archive of illustrations documenting the structures of thousands of root systems is available online through the Plant Sociological Institute of Austria. The curated collection started by botanist Lore Kutschera includes diagrams of everything from carrot cousins to birch trees.