A vascular plant is any plant that has vascular tissue, a system of specialized cells that transports water, nutrients and signals throughout the plant, including its roots, stems and leaves, and that also provides structural support for it. This system allows vascular plants to grow much larger and occupy a greater variety of terrestrial habitats than non-vascular plants.
The two main components of vascular tissue are xylem and phloem. Xylem consists of dead cells that form hollow tubes that transport water and dissolved minerals upwards from the roots. These cells also provide structural support because of the lignin in their cell walls. Phloem, which consists of living tissue, transports organic compounds produced in the leaves, such as sugars and amino acids, to other parts of the plant, including to the flowers and fruits. In trees, phloem is the innermost layer of the bark.
The total number of species of vascular plants is currently estimated at more than 390,000. They are broadly classified into two main categories: seed vascular plants and non-seed vascular plants. Seed vascular plants includes flowering plants and conifers. Flowering plants account for about 94 percent of the total vascular plant species. Non-seed vascular plants, which include ferns and horsetails, reproduce via spores.