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Plant

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Plants are eukaryotic organisms that belong to the kingdom Plantae. Most plants are photosynthetic, which means they capture energy from sunlight to survive. They use a green pigment called chlorophyll to drive this process. This pigment is located inside specialized structures called chloroplasts. Using these tools, plants turn carbon dioxide and water into sugars. These sugars serve as the primary energy source for the plant.

The freshwater alga Spirogyra
The freshwater alga Spirogyra

While most plants make their own food, some are parasitic. These exceptions have lost the genes required for photosynthesis. Instead, they obtain their energy by living off other plants or fungi.

Plant cell structure-en
Plant cell structure-en

At the cellular level, plant cells have unique features. They possess a large, water-filled central vacuole. This organelle allows the cell to change size while keeping the cytoplasm volume constant. Plant cells also have a strong, flexible cell wall made mostly of cellulose. This wall sits outside the cell membrane and prevents the cell from bursting when it swells with water. Most plants are multicellular, meaning they are made of many cells. These cells organize into specialized tissues. For example, vascular tissue includes xylem and phloem. These act like internal transport systems to move water and nutrients.

Rhynia stem
Rhynia stem

The biological structure of a plant includes several vital organs. Roots are designed to absorb water and minerals from the soil. Stems provide physical support and transport synthesized molecules throughout the organism. Leaves serve as the primary sites for photosynthesis. Flowers are specialized organs used for reproduction.

Plant Anatomy
Plant Anatomy

Plants reproduce through two main methods: sexual and asexual. Sexual reproduction involves a complex lifecycle called alternation of generations. This process moves between a diploid sporophyte stage and a haploid gametophyte stage.

Alternation of generations simpler
Alternation of generations simpler

Asexual reproduction allows a plant to grow new individuals from structures like runners, tubers, or bulbs. This creates genetic clones of the parent plant.

Our understanding of plants has changed significantly over many centuries. In ancient times, Aristotle classified all living things into two groups: plants and animals. He believed plants possessed a "vegetative soul." Later, the scientist Linnaeus developed a modern classification system. He called the plant kingdom Vegetabilia. Today, scientists use genome sequencing to define plant groups more accurately. We now recognize the clade Viridiplantae, which includes green algae and land plants. This group contains many different types, such as mosses, ferns, conifers, and flowering plants.

Folio Materia Medica Dioscurides Met 13.152.6 (cropped)
Folio Materia Medica Dioscurides Met 13.152.6 (cropped)

The evolutionary history of plants began in the water. Fossil evidence suggests multicellular freshwater eukaryotes existed over 1,000 million years ago. The first true land plants appeared around 450 million years ago during the Ordovician period. By the Devonian period, plants had developed basic features like roots and leaves. During the Carboniferous period, massive forests of clubmosses and horsetails dominated swampy areas. The first seed plants, known as early gymnosperms, also appeared during this time. Later, flowering plants emerged around 200 million years ago during the Triassic. This led to a rapid radiation of species during the Cretaceous period.

Devonianscene-green
Devonianscene-green

There is immense diversity within the plant kingdom. There are approximately 382,000 accepted species of plants. The vast majority, about 283,000 species, are seed-producing plants. Flowering plants are particularly successful, making up 85% to 90% of all species. Plants vary wildly in scale. Some, like desmids, are only 10 micrometres across. Others are massive, such as the Sequoia sempervirens, which can reach 120 metres in height.

PIH 1830 Scots Pine (Pinus sylvestris) graft clone collection in Röykkä Finland
PIH 1830 Scots Pine (Pinus sylvestris) graft clone collection in Röykkä Finland

These plants are essential to Earth's life support systems. They release a large portion of the world's molecular oxygen. They also create the sugars that power most global ecosystems.

Texas invasive Musk Thistle 1
Texas invasive Musk Thistle 1

Humans have a deep and ancient connection to plants. We have domesticated plants for millennia to provide grain, fruit, and vegetables. Beyond food, plants are vital for many industries. They provide materials for building, ornaments for decoration, and fibers for writing. Plants are also a massive source of diverse medicines. The scientific study of these organisms is called botany, which is a major branch of biology. By studying plant genomes, scientists can learn how they resist diseases or survive environmental stress. This knowledge helps us understand the complex systems that sustain life on our planet.

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🖼️ Images & Media (42)
File:Alternation of generations simpler.svg
Alternation of generations simpler.svg
File:Plant cell structure-en.svg
Plant cell structure-en.svg
File:Plant Anatomy.svg
Plant Anatomy.svg
File:The freshwater alga Spirogyra.jpg
The freshwater alga Spirogyra.jpg
File:PIH 1830 Scots Pine (Pinus sylvestris) graft clone collection in Röykkä Finland.jpg
PIH 1830 Scots Pine (Pinus sylvestris)...
File:Rose espalier Niedernhall.JPG
Rose espalier Niedernhall.JPG
File:France Loiret La Bussiere Potager 05.jpg
France Loiret La Bussiere Potager 05.jpg
File:Conocephalum conicum (e, 144739-474742) 1022.jpg
Conocephalum conicum (e, 144739-474742) 1022.jpg
File:Asterophyllites Equisetiformis.jpg
Asterophyllites Equisetiformis.jpg
File:RowOfPlants.JPG
RowOfPlants.JPG
File:Devonianscene-green.jpg
Devonianscene-green.jpg
File:Petrified Araucaria cone.jpg
Petrified Araucaria cone.jpg

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