The biosphere begins from the ground up. With help from photosynthetic bacteria in the oceans, land plants generate the oxygen needed by complex animals. They also make food for everyone else, but they couldn’t do either job without a lot of help from their single-celled assistants.
Fungi Most Beautiful
The website Fauna & Flora International, champions of biodiversity, published a piece by Michelle Villenueve that commands attention — not just because it can help prevent loss of farmland, but because the hero of the story is so tiny. She begins with the “conflict” in the novel, the depletion of farmland because of chemical fertilizers and loss of nutrients. Small farmers, out of tradition, tend to cut down forests for new cropland after their soils become unproductive, or spray chemical fertilizer to extend the use of existing land. Both practices are unsustainable. Nature has a better way.
Alternatively, it is possible to make normally inaccessible soil nutrients available to plants. This can be achieved in a number of ways, and one interesting emerging area of study is in the association between plants and fungi. As it turns out, about 90% of flowering plants worldwide engage in a symbiotic relationship with a fungus that colonises root systems. The fungus amplifies and extends the range of the plant’s root system, allowing it to absorb previously inaccessible soil nutrients; in return, the plant supplies the fungus with the carbon it needs. These mutually beneficial fungal networks are called mycorrhizae, and it is now thought that mycorrhizal associations are what originally allowed plants to colonise Earth 450 million years ago — wow! [Emphasis added.]
The mythical vision of something that “is now thought” by certain evolutionists to have occurred in the dim dark past may give Ms. Villenueve a “wow” moment, but lest we get distracted by a sub-plot, the real “wow” in the story goes to the fungal network. “Marvellous mycorrhizae” comprise “the fungal networks that boost food production,” her title states. How do they work? The answer is, “in many ways.”
Where mycorrhizal associations exist, up to one kilometre of fungal filaments can be found per gram of soil.This dense network, capable of exploring a volume of soil a thousand times greater than that reached by the roots, brings more macronutrients to the plant — the same ones that you will find in most common chemical fertilisers. Not only that, but mycorrhizae also increase a plant’s ability to absorb vital micronutrients, such as zinc and calcium.
In addition to improved nutrient uptake, mycorrhizae confer bioprotective power on their host plants. The mycorrhizal network forms a protective shield against soil-borne pests and pathogens, enveloping the root tips and protecting them from attack. This, in turn, reduces the need for the application of chemical pesticides and fungicides.
Plants enjoying a commensal relationship with fungi are healthier, stronger, and better protected than those sprayed by commercial fertilizers and pesticides. That deserves a big wow. The article shows a photo of the rich, dark soil at the roots of a maize plant growing in mycorrhizal soil.
The issue now is how to motivate farmers to use the fungus-assisted soil. Till now, chemical sprays have been less labor-intensive than mycorrhizal solutions.
Still, there is hope on the horizon. In recent years the number of agricultural companies and start-ups conducting research in this area has been ‘mushrooming’. Fungal bio-fertilisers and fungus-coated seeds are becoming more widespread and showing great promise for sustainable yield increases in greenhouse-based trials. FFI looks forward to continuing to deploy both traditional and modern solutions in this exciting emerging area as we work towards our conservation goals in partnership with farming communities.
Another technology could benefit from nature’s solutions. There’s another small helper clinging to the roots of plants: nitrogen-fixing bacteria. These bacteria have enzymes called nitrogenases that hold the secret of cracking dinitrogen (N2) molecules, with their tough triple bonds, into forms that can combine with other molecules, such as ammonia (NH3). Artificial systems for fixing nitrogen, such as the Haber process, are highly energy-intensive, but bacteria do it an ambient temperature. According to a January 2020 paper in the Plant Biotechnology Journal, learning that secret could lead to a “green revolution.” The paper shows progress at one stage that is “paving the way for future studies in the engineering of nitrogen fixation,” but engineers aren’t there yet.
Routing the Root
Have you ever wondered how roots find their way to water? Perhaps watching roots grow in a science class display or on a documentary film has prompted the question. What is the mysterious sense that prompts root hairs to grow in the direction of the nearest water supply? Scientists at Goethe University asked the question, and sought clues using Light Sheet Fluorescence Microscopy.
Plants use their roots to search for water. While the main root digs downwards, a large number of fine lateral roots explore the soil on all sides. As researchers from Nottingham, Heidelberg and Goethe University of Frankfurt report in the current issue of “Nature Plants”, the lateral roots already “know” very early on where they can find water.
The high-tech microscope technique allowed Daniel von Wangenheim to image dividing cells in 3-D on a root hair. On one side, the root was exposed to air. On the other, it was exposed to agar with water.
To his surprise, he discovered that almost as many lateral roots formed on the air side as on the side in contact with the nutrient solution. As he continued to follow the growth of the roots with each cell division in the microscope, it became evident that the new cells drive the tip of the root in the direction of water from the very outset, meaning that if a lateral root had formed on the air side, it grew in the direction of the agar plate.
“It’s therefore clear that plants first of all spread their roots in all directions, but the root obviously knows from the very first cell divisions on where it can find water and nutrients,” says Daniel von Wangenheim, summarizing the results. “In this way, plants can react flexibly to an environment with fluctuating resources.”
You can watch von Wangenheim at work in a video summary of the experiments. “It is known that roots branch toward water availability!” the caption begins. “But how?” The micrographs are impressive, but it’s not clear the research answered the question. Somehow the lateral branches head toward water right from the first cell division. It’s nice to know the direction to go before starting, but how does a blind root do it? The team’s paper in Nature Plants is titled, “Early developmental plasticity of lateral roots in response to asymmetric water availability.” In conclusion, “the external hydrological environment regulates lateral root morphogenesis.” But how?
We conclude that external water availability profoundly influences lateral root formation during organ emergence. Lateral roots are critical for exploring large volumes of soil for nutrients and moisture. To efficiently acquire water, plants have developed mechanisms that drive lateral root outgrowth towards external water availability.
Uh, OK. But how? Did plants “develop mechanisms” by intelligent design, or by chance?
It appears that plant “epistemology” (how they know what they know) is superior to man’s, and will continue to elude our brightest scientists for some time to come. The “root” of the problem is in assuming blind chance was capable of photosynthesis, mycorrhizal networks, nitrogen fixing, and optimizing searches for water. Design scientists, understanding good design when they see it, might do better at paving the way to a green revolution.
For an encouraging ending, watch the video posted by the BBC News that joins plant design with human ingenuity. The result is transforming a glum refugee camp in a Jordanian desert into a happy, thriving community. This kind of science is good for everybody — and that deserves a big “Wow!”