As early as 1897, Charles Darwin recognized that roots were more than just an anchor of plants to the ground, noting;
“â¦ There is no structure in plants more marvelous, in terms of its functions, than the tip of the radicle. [â¦.] It is hardly an exaggeration to say that the tip of the radicle thus endowed, and having the power to direct the movements of the neighboring parts, acts like the brain …“
Seven years later, the term “rhizosphere” was first introduced by agronomist and plant physiologist Lorenz Hiltner, as “the area around a plant root which is inhabited by a unique population of microorganisms. influenced by chemicals released by plant roots â.
Over a century later, here at the John Innes Center, we continue to learn more about the substantial impact of roots on their environment.
For example, Maria Hernandez-Soriano is a soil chemist, intrigued by the complexity of the chemical and biological processes that take place in the soil and make it healthy and productive.
Recently, his work has focused on the effect of wheat roots on the surrounding soil and whether there are any specific traits in certain varieties that could benefit both the crop and the surrounding soil.
We asked Maria what else was there to learn from these âunderground explorersâ.
âThe ability of the roots to explore and exploit the soil is crucial for the plant to adapt and survive the challenges of different stresses, for example in the event of drought or low nutrient availability, which means that they have to detect any change in the environment and react accordingly.
Since the soil conditions are not uniform, it means that no two roots are equal. Added to this complexity, root research has its limits, especially compared to aerial plant organs in terms of accessibility.
Certain root systems, such as the fig tree Ficus, in the Transvaal, South Africa, can extend over 100 m underground. Meanwhile, a record rye, Secale cereals, was found to have a root system spanning 623 km.
Just like with roots, there is still so much to explore underground and luckily, imaging techniques help us delve deeper into the complexity and plasticity of root system architecture.
These technological advances, coupled with a growing understanding of the importance of the root system and rhizosphere, allow us to make rapid advances in the field.
Roots aren’t just explorers or anchors, and they don’t just absorb water and nutrients.
One thing we keep looking at is the different compounds that roots release into the soil. They take water and nutrients from the soil to nourish the plant, but they also release a complex mixture of compounds in the soil that we call root. The amount of carbon, for example, fixed by photosynthesis that plants can transfer to the soil in the form of root exudates, varies from 20 to 40%.
Besides carbon, other molecules in the root exudates act as an intriguing form of communication between the plant and the inhabitants of the soil. Essentially through the roots and the compounds they release, the plant communicates with the surrounding soil, and we know that through soil microbes this communication is two-way.
For my own project in Professor Tony Miller’s lab, I’m interested in the roots of wheat.
Modern wheat varieties are the result of intensive selection for aerial traits, but for a long time we forgot to research whether there were any underground traits, which could benefit not only the plant but also the health of the soil.
It has become evident that the functions of the soil microbiome are a major contributor to the supply of essential nutrients to crops. This has created an urgent need to identify underground features that can support and improve soil health and key ecosystem functions such as nutrient cycling and food provision.
We are now investigating this and more specifically how root exudates can control the activity of microbial guilds that inhabit the rhizosphere of wheat.
In particular, I am interested in the roots of older varieties of wheat which have the ability to control the guilds of the microbiome involved in the nitrogen (N) cycle.
We collected rhizosphere soil through the Watkins collection held at the Genetic Material Resource Unit of the John Innes Center and a population derived from an old variety which has a strong ability to control the transformation of N in the soil.
For this rhizosphere soil, we explored which microbes and fungi live there and what their main functions are.
Together with Simon Griffith and Luzie Wingen, we have obtained preliminary results that indicate a strong link between the wheat genome and the abundance and activity of N-ring microbes, and we are now exploring this communication deeper in the genome. wheat and combining this information with root architecture analysis.
I use RhizoVision image analysis software to measure and from a single image we can measure up to 40 physical characteristics of root length, density, lateral roots across varieties of corn.
We can relate this information to important processes such as nitrogen uptake by plants. Thanks to the photographic platform of the John Innes Center, we can obtain images with sufficient resolution to perform the analysis (Fig. 1a).
In this figure, a crown of wheat from a plant grown in the field was analyzed for a large number of physical characteristics (Fig. 1b) with different colors indicating a different root diameter.
Outside of the John Innes Center, current research and activities in the field vary across disciplines and scales, highlighted in the recent scientific program. IRSS11 colloquium and Rooting2021 which took place with the motto “Root biology never sleeps”.
We explored the questions we try to answer on the backside of plants and how we advance science and technology to reveal critical roots secrets that may hold the future of agriculture and soil health.
The main results of the conference will be available as a âconference reportâ in New Phytologist, currently being prepared by the ambassadors.
It is an exciting time for root research, as what we learn will play an important role in the future of agriculture, helping us to grow crops that can efficiently use soil as a source of water and food. nutrients while supporting soil health.