Biology helps understand the blessing of grasses

Photo credit: Ochir-Erdene Oyunmedeg via Unsplash.

The newspaper Science offers a special section devoted to grasses. Bianca Lopez, Pamela J. Hines and Caroline Ash present the cover story with surprising facts about these “often undervalued” plants. In “The unsung value of weed,” they say,

Grasses are very diverse, but only six or seven grass species provide most of the calories consumed by humans. … In addition to cultivated fields and pastures, grassy ecosystems (Poaceae and Alismatales) cover large swathes of the planetforming earthly meadows and seagrass meadows. meadows creating and stabilizing fertile soil; store carbon; generate oxygen; and providing animal habitat, building materials and food. Even so, these species and systems are often undervalued. Land-use conversion and climate change pose threats, as do climate change mitigation efforts that prioritize carbon stored in trees over that stored in grasslands. However, grasses could offer solutions to many of our societal challenges, if only we fully recognize their diversity and value. [Emphasis added.]

Appreciate the meadows

Here are some points to better appreciate the 12,000 known species of grasses.

  • Grasslands store about a third of the world’s terrestrial carbon stocks.1
  • Most of us will have eaten, stomped on, or burned some grass in the last 24 hours.2
  • 50% of the calories consumed by humans come from three species of grass: wheat, rice and corn.2
  • Meat, eggs and dairy products come from animals that eat grass.2
  • Grasses are the predominant plants on all continents except Antarctica.2

Not all grasses live on land. About 72 species divided into 4 families are “seagrasses” that live in water.3

  • Seagrasses have adapted to live underwater, where light is limited, where salt and nutrients can be problematic, and where soils can become highly toxic.3
  • Seagrass is the only underwater flowering plant in the world.4
  • Seagrass “grasslands” are important carbon dioxide sinks that can provide significant carbon sequestration, but are declining due to human activity. Conservationists are considering ways to help them recover.3
  • Seagrasses support the biodiversity of fish, reptiles, crustaceans, echinoderms and other marine organisms like sea cucumbers, clams, manatees, sea turtles and crocodiles that use them for food or shelter.3, 4
  • Along with mangroves and coral reefs, seagrass beds help stabilize coastlines. They also reduce water acidity and purify water of viruses, bacteria and heavy metals, helping coral reefs to thrive.3.4
  • Seagrasses can be used as building material, fertilizer and habitat for farming seafood. When cotton becomes scarce, it can be used as an alternative fiber for clothing.4

The Smithsonian Ocean site adds additional praise for herbaria:

Seagrass beds can form dense seagrass beds, some of which are large enough to be seen from space. Although they often receive little attention, they are one of the most productive ecosystems in the world.Herbariums provide shelter and food for an incredibly diverse community of animalsfrom tiny invertebrates to large fish, crabs, turtles, marine mammals and birds.

Classification of grass

Since grasslands make up nearly 40% of Earth’s terrestrial biosphere,5 it is worth getting to know these amazing and diverse plants that do so much for us.

All grasses are angiosperms (flowering plants) in the monocot clade, which means that their leaves have parallel venation and spring from a single seed leaf (cotyledon). They comprise about 20% of the 60,000 known species of monocots. So, although all grasses are monocots, the majority of monocots are not grasses, but other beautiful and useful plants like orchids, lilies, asparagus, and pineapples. The roots of grasses are fibrous, which makes them good for binding soil and preventing wind erosion while providing habitat for earthworms, moles and gophers. We all know the term “grass roots” as a metaphor for bottom-up grassroots movements.

Grasses have long been a staple in a balanced diet. The endosperm of grass seeds (whole grains) is rich in protein, carbohydrates, lipids, vitamins and fiber. They are also good sources of metalloenzymes Michael Denton deals with the essential elements for life: iron, copper, zinc and magnesium.

Although all grass genomes are collinear (i.e. genes in the same order), the details are surprisingly varied. Note McSteen and Kellogg,2

Beneath this widely conserved genomic architecture lies great diversityincluding nucleotide variation (single nucleotide polymorphisms), gene structure, and even the presence or absence of genes. The nucleotide differences between two lines of Zea mays (maize) are higher than those between humans and chimpanzees. Genes central to plant structure in maize are absent from wheat and rice, and vice versa. In other words, not all grasses have the same complement of genes and their morphology is modified accordingly.

Make good use of grasses

Artificial selection – a form of clever design – has enriched our lives with tall ears of corn derived from meager teosinte, whole wheat bread, nutritious rice in Chinese and Mexican foods, and long rows of canned cereals in groceries, not to mention sugar. to sweeten our tea and coffee. Even some drinks are derived from grasses, such as beer from barley and rum from sugar cane. Corn waste has recently augmented our transportation fuel with ethanol.

Only a few grasses have been domesticated for food. There could be a lot more nutrition in “orphan crops” that have yet to be exploited. But none of the benefits we enjoy could have been amplified by plant breeders unless the ingredient information had first been encoded in the genomes of cultivated grasses. Artificial selection is only possible because of information originally engineered into the plants and animals we favor.

Grass lawns beautify our yards, and decorative species like pampas and Mexican feather embellish our gardens. Grassy fields provide venues for sports such as golf, football and baseball. With their pleasing shades of green that tickle the cones of our eyes at the center of human color sensitivity, grasses enhance our lives in so many ways.

Many happily refer to “God’s green earth” when they think of natural beauty, and grasses are a big part of that glorious picture of the world. Why should our planet be so blessed with these wonderful plants that do so much for the biosphere? Grasses are prime examples of the universe’s prior fitness for complex life that Michael Denton elucidated so clearly and passionately in his Preferred Species Series. It is likely that humans and other complex animals could not exist without these abundant and nutritious little plants that help bind the biosphere together. Let’s admire the grass under our feet.


  1. Bai and Contrufo, “Soil Carbon Sequestration in Grasslands: Current Understanding, Challenges, and Solutions.” Science August 4, 2022: 377:6066, pages 603-608.
  2. McSteen and Kellogg, “Molecular, Cellular, and Developmental Basis of Grass Diversity.” Science August 4, 2022:377:6066, pages 599-602.
  3. Unsworth et al., “The global role of seagrass conservation.” Science August 4, 2022:377:6066, pages 609-612.
  4. Swansea University press release, “The value of seagrasses for the future of the planet is far greater than we appreciate.” August 5, 2022.
  5. Buisson et al., “Ancient Grasslands Guide Ambitious Goals in Grassland Restoration.” Science August 4, 2022:377:6066, pages 594-598.
  6. Harvard Nutrition Source“whole grain”.

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