Why do leaves have veins?
For grown-ups: the science
Leaves have veins to move water and sugar, and to help hold the leaf open.
Leaf veins are vascular bundles. Xylem carries water and dissolved minerals mainly from roots to leaves, while phloem transports sugars made in leaves to places that need or store them. Veins also add structural support to the leaf blade.
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Transcript
Look at a leaf in your hand. Why does it have tiny lines running through it?
A leaf’s veins carry water up from the roots. The water helps the leaf make food using sunlight.
Other veins carry sugar from the leaf to the rest of the plant. That sugar gives the plant energy to grow.
The veins also help hold the leaf flat and open. This lets more sunlight reach the leaf.
So, leaf veins are little pathways and supports. They help a plant drink, make food, and grow.