By Maud Hinchee, PhD, Chief Science Officer, Agricen Sciences
Getting a good start is key to a germinating seed’s need to “survive and thrive.” Essential to this process is establishing a root system that creates a strong foothold and provides access to available nutrients and water. But how does the emerging seedling root do this?
It turns out that the new root is constantly making choices about where and when to grow based on the environment it encounters. Guided by its “root brain,” it makes decisions that maximize its access to water and nutrients as quickly as possible.
The root brain is found in the transition zone of the root tip – the area between the region of cell division and cell elongation. A good look at this control point in the root can be seen in this microscopic time-lapse view of a growing root. Here, the root receives and integrates multiple sensory signals in response to environmental cues. It can then respond to those cues by adjusting the rate and direction of its growth to ensure it has the best access to water and nutrients. By “deciding” which cells divide or elongate, the root can change where and how fast it moves through the soil.
This root brain does not act alone. Much as chemical signaling in our nervous system carries signals to and from our brains, similar processes happen in the plant. The plant hormone auxin, for instance, interacts with plant cells in a similar way that neurotransmitters (chemical messengers) interact with our own nerve cells to carry messages. Auxin is crucial to the root’s perception of and response to environmental signals, and helps to control things such as the timing and rate of cell elongation, as well as potential sites for lateral root production.
The plant can even call in allies to obtain more auxin and bolster its root growth potential. In a microscopic barter, roots exude carbohydrates that act as food offerings to soil microbes. The microbes, in turn, produce auxins to be consumed by the plant as a supplement that supports to the plant in its goal to produce larger, more branched root systems.
The root systems of young seedlings not only rely on their decision-making capacity to survive and thrive, but they also have another strong ally – the farmer. Farmers help by applying fertilizers, growth stimulators or other products that assist a plant in growing strong roots or accessing nutrients and water. For example, the signaling molecules in some agricultural biostimulants provide messages that assist the root brain in making critical decisions that affect when, where and how a root system develops.
The capacity for roots to assess and respond to the environment is a major part of how a plant wins the survival campaign for water, nutrients, light and space. Root growth and development decisions made now and in the future can make or break a plant’s success—and the farmer is a key partner in helping the plant survive and thrive.
Dig deeper into the soil by downloading our Soil Microbiology & Biochemistry Booklet.