The classic plant morphology text by Goethe, who declared, "all is leaf"-
Goethe intuits a common mathematical basis for forms, "No wonder that the earth expresses itself outwardly in leaves, it so labors with the idea inwardly. The atoms have already learned this law, and are pregnant by it."
As Blake put it, "To see a World in a Grain of Sand And a Heaven in a Wild Flower, Hold Infinity in the palm of your hand And Eternity in an hour." Therefore, as many plant parts are evolutionarily modified leaves, understand the Leaf to see "Heaven in a Wildflower". Further, "Eternity in an hour" is Einstein's Relativity.
Nice article on vascularization in animals-
Precisely the same mathematical optimality forces in play. There are deep interrelations between plumbing and structural stiffness. Their shared features are tapered branched tubing networks with internal hydrostatic pressure. The base pressure is Gibbs zero-point energy, and circulation is Gibbs free-energy component.