Poaceae

Poaceae, also called Gramineae, is a large family of flowering plants known as true grasses. They include cereal grasses, bamboos, and the grasses found in natural grasslands, lawns, and pastures. With around 780 genera and 12,000 species, Poaceae is the fifth-largest plant family.

These plants are very important for people and the world. They provide staple foods like maize, wheat, rice, oats, barley, and millet, which give a big part of the energy in our diets. Grasses also give feed for meat-producing animals and can be used as building materials or for biofuel.

Grasses have special stems that are hollow except at the nodes and narrow leaves that grow from the base. Grasslands, where grasses are the main plants, cover about 40.5% of the Earth's land area, apart from Greenland and Antarctica. Though we often call many plants "grasses", some like seagrasses, rushes, and sedges are not true members of the Poaceae family but are related plants.

Description

Grasses are plants that can live for one year or many years. Their stems, called culms, are usually round and hollow. Grass leaves grow in one plane and have parallel lines. Each leaf has a part that wraps around the stem and a flat part that can sometimes be sharp.

Grass flowers are small and grouped together in special clusters called spikelets. These spikelets contain one or more tiny flowers, each surrounded by special leaf-like parts. Most grass flowers can make their own seeds and are pollinated by wind, though sometimes insects help.

Grass blades grow from the base, which helps them stay strong even when animals eat them or when they are cut. There are different types of grasses based on how they grow and when they are active. Some grow best in cooler weather, like wheat and rye, while others prefer warmer weather, like maize and sugarcane.

Taxonomy

The name Poaceae was given in 1895 by John Hendley Barnhart. It is based on an older group of plants described by Robert Brown in 1814.

Grasses are very versatile plants. They grew widely near the end of the time when dinosaurs lived. Fossils show that grasses lived alongside dinosaurs and have adapted to many places, like rainy forests, dry deserts, cold mountains, and areas between tides. Today, grasses are the most common plant type and give food and energy to many animals.

Before 2005, scientists thought grasses first appeared about 55 million years ago. But newer fossils found in India show they existed as early as 66 million years ago. Even older fossils from China, dating to about 113–100 million years ago, show early grass types.

There are about 12,000 grass species in around 771 groups, split into 12 smaller families. Some well-known grasses include wheat, barley, oats, rice, bamboo, and many kinds used in lawns and fields.

Distribution

The grass family is one of the most widely distributed groups of plants on Earth. Grasses grow on every continent, even Antarctica. The Antarctic hair grass, Deschampsia antarctica, is one of only two flowering plants that naturally live on the western Antarctic Peninsula.

Ecology

Grasses are the most common plants in many places, like grasslands, salt marshes, reed swamps, and steppes. They can also be found in almost every other land area, even if they aren't the main plant there. When large areas are mostly grass, we call these places grasslands. These include pampas, steppes, and prairies. Many animals depend on grass for food, such as cattle, sheep, horses, rabbits, grasshoppers, and some butterflies and moths. Even animals that usually eat other things might munch on grass sometimes.

Grasses are special because the part that grows new leaves is near the bottom of the plant. This means they can grow back quickly after being cut or eaten. Long ago, the appearance of large animals that eat grass helped grasses spread. Without these animals, areas cleared by fires would be taken over by trees. But grazing animals help grasses by trampling small tree seedlings, allowing grasses to stay strong.

Sexual reproduction and meiosis

Sexual reproduction and meiosis have been studied in rice, maize, wheat, and barley. This research helps improve crops because meiosis, a special kind of cell division, is important for plant breeding. In plants, the development of male and female cells happens later than in animals, during flowering. The change from one growth stage to another starts when meiosis begins.

Uses

Grasses are very important to humans for many reasons. They help us grow food, make things we use every day, and even help keep our environment healthy.

Grasses are important for food. Many of the foods we eat come from grasses, like wheat, rice, and corn. These plants give us most of the calories we need to live. They also give us sugar from sugarcane and yummy bamboo shoots used in many dishes. Grasses also feed animals like cows, horses, and sheep.

Grasses are also used to make many things. We use them to build homes, make paper, create clothing, and even build furniture. Some types of grasses, like bamboo, are very strong and can be used instead of wood. Grasses also help clean water and keep soil in place.

Role in society

Grasses have been important to people for thousands of years. They are grown to feed people and animals, and they are used to make beer, like barley or wheat. In many neighborhoods, having a well-kept lawn shows that someone cares about their home and the area around them. Sometimes, especially in places where it doesn't rain much, there are rules about when people can water their lawns.

There are many sayings about grass. For example, "The grass is always greener on the other side" means that something else might seem better than what you have. "Don't let the grass grow under your feet" means you should keep moving and not wait around. "A snake in the grass" warns about hidden dangers. And "When elephants fight, it is the grass that suffers" means that innocent people can get hurt when others argue.

Image gallery

Here are some pictures of different grasses and their parts:

• Grass seeds, a mixture of 90% Festuca rubra and 10% Festuca ovina.
• Leaves of Poa trivialis showing the ligules
• Bamboo stem and leaves, nodes are evident
• A Chasmanthium latifolium spikelet
• Wheat spike and spikelet
• Spikelet opened to show caryopsis
• Harestail grass
• Grass
• Roots of Bromus hordeaceus
• Barley mature spikes (Hordeum vulgare)
• A grass flower head (meadow foxtail) showing the plain-coloured flowers with large anthers
• Anthers detached from a meadow foxtail flower
• Setaria verticillata, bristly foxtail
• Setaria verticillata, bristly foxtail
• Oryza sativa, Kerala, India