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Poaceae

life science Maturity 5-7 Next article →

Poaceae is a massive and essential family of flowering plants.

Grass Blades
Grass Blades

These plants are commonly known as true grasses. They belong to a group called monocots. This family includes many things we see every day. You might recognize cereal crops, bamboo, or the grass in a lawn. It is the fifth-largest plant family on Earth. It follows the Asteraceae, Orchidaceae, Fabaceae, and Rubiaceae families in size. With about 780 genera and 12,000 species, Poaceae is nearly everywhere.

South Lawn
South Lawn

The physical structure of a grass plant is quite unique. Most grasses have stems called culms. These culms are usually cylindrical and hollow. They are plugged at the nodes, which are the joints where leaves attach. The leaves are arranged in two ranks and are often alternate. Each leaf has a lower part called a sheath that wraps around the stem. At the junction of the sheath and the blade, there is a small part called a ligule. This membrane or fringe of hairs prevents water or insects from getting into the sheath.

Grasses have evolved a very clever way to grow. Most plants grow from their tips, but grasses grow from the base. This low growth point is called the meristem. Because the growth happens near the ground, the plant can survive being eaten. This allows grasses to cope with frequent grazing by animals or mowing by humans. To protect themselves further, many blades are hardened with silica phytoliths. These tiny particles of silica can discourage animals from eating them. Some species, like sword grass, are even sharp enough to cut human skin.

Koeh-283
Koeh-283

The reproductive parts of Poaceae are also very specific. Flowers are arranged in structures called spikelets. These spikelets can be grouped into larger shapes called panicles or spikes. A single spikelet contains one or more florets. Each floret has an outer bract called a lemma and an inner bract called a palea. The flowers are usually hermaphroditic, meaning they have both male and female parts. Most grasses are anemophilous, which means they are pollinated by the wind. The fruit produced is a caryopsis, where the seed coat is fused to the fruit wall.

Grassbluete numbers clones unlinked
Grassbluete numbers clones unlinked

Scientists classify grasses by how they handle sunlight and water. They use terms like C3 and C4 to describe their photosynthetic pathways. C3 grasses are often called "cool-season" grasses. Examples include wheat, rye, and oats. C4 grasses are called "warm-season" grasses. They have a special leaf anatomy called Kranz anatomy. This allows them to use water more efficiently in hot, dry places. About 46 percent of all grass species are C4 plants. This includes maize, sorghum, and sugarcane.

Saccharum-officinarum2
Saccharum-officinarum2

The history of grasses is written in the earth itself. The name Poaceae was given by John Hendley Barnhart in 1895. The name comes from the Ancient Greek word "póa," meaning fodder. We know grasses are very old thanks to fossils. The oldest known grass fossils were found in China. These microfossils were extracted from the teeth of a dinosaur called Equijubus normani. They date back to about 113 to 100 million years ago. Other fossils have been found in dinosaur dung in India, showing grasses were present during the Cretaceous period.

Anomochloa
Anomochloa

Poaceae is incredibly important to the global economy and ecology. These plants are the most economically important plant family. They provide a huge portion of the world's dietary energy. Rice provides 20 percent of all dietary energy for people. Wheat supplies 19 percent, and maize provides 5 percent. Beyond food, grasses provide building materials like bamboo and straw. They can even be turned into biofuel, such as ethanol from maize.

Finally, grasses shape the very landscapes of our planet. Grasslands, such as prairies and steppes, cover 31 percent of the Earth's land. When you include all grass-dominated areas, they cover about 40.5 percent of the land. This excludes Greenland and Antarctica. Grasses are the dominant vegetation in many habitats, including wetlands and tundras. They support many animals known as graminivores, which are animals that eat grass. This includes cattle, horses, rabbits, and even some insects like grasshoppers.

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🖼️ Images & Media (14)
File:Grassbluete numbers clones unlinked.svg
Grassbluete numbers clones unlinked.svg
File:Grassflowers.jpg
Grassflowers.jpg
File:Koeh-283.jpg
Koeh-283.jpg
File:Saccharum-officinarum2.JPG
Saccharum-officinarum2.JPG
File:Anomochloa.jpg
Anomochloa.jpg
File:Setaria verticillata W IMG 1085.jpg
Setaria verticillata W IMG 1085.jpg
File:Grasses in the Valles Caldera 2014-06-26.JPG
Grasses in the Valles Caldera 2014-06-26.JPG
File:Kangur.rudy.drs.jpg
Kangur.rudy.drs.jpg
FossilPoaceaePollen.tif
File:South Lawn.jpg
South Lawn.jpg
File:Australia vs India.jpg
Australia vs India.jpg
File:Grass covered house in Iceland 1972.jpg
Grass covered house in Iceland 1972.jpg

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