A primary vein, also known as the midrib, is the main vascular structure running through the center of a

leaf A leaf (: leaves) is a principal appendage of the plant stem, stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leav ...

. The primary vein is crucial for the leaf’s efficiency in

photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...

and overall health, as it ensures the proper flow of

material A material is a matter, substance or mixture of substances that constitutes an Physical object, object. Materials can be pure or impure, living or non-living matter. Materials can be classified on the basis of their physical property, physical ...

s and structural integrity. It serves several critical functions, including structural support, as the primary vein helps the leaf maintain its shape and structure;

food Food is any substance consumed by an organism for Nutrient, nutritional support. Food is usually of plant, animal, or Fungus, fungal origin and contains essential nutrients such as carbohydrates, fats, protein (nutrient), proteins, vitamins, ...

and

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

transportation, as it contains xylem and phloem tissues that transport

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

s, and nutrients to and from the leaf; and connection to the stem, as it links the leaf to its vascular system, facilitating the exchange of materials between the leaf and the rest of the

plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...

. From the primary vein, secondary and tertiary veins branch out, forming a network that distributes resources throughout the leaf. The arrangement of veins, including the primary vein, varies among plants. Reticulate venation occurs in dicots, where the primary vein branches into a network; parallel venation is found in monocots, where multiple veins run parallel to each other.

References

Leaf morphology {{Biology-stub