bladnerven

Bladnerven, or leaf veins, are the vascular tissue network within leaves that facilitates transport and provides structural support. They form a system of vascular bundles that deliver water and minerals from the stem (via xylem) and distribute the products of photosynthesis to non-photosynthetic tissues (via phloem). The network typically includes a prominent midrib with branching secondary and tertiary veins, and a system of minor veins that permeate the leaf blade.

Venation patterns vary among plants. In many dicotyledons the veins form a reticulate network, whereas many monocots show parallel venation running from base to tip. Veins are composed of xylem and phloem enclosed by protective tissues called the bundle sheath; in many leaves the arrangement places xylem on the upper side of the bundle and phloem on the lower side.

Development and function: Veins originate from the leaf's procambium during development and become connected to the stem's vascular system. Besides transport, the vein network provides mechanical support and helps maintain leaf shape under physical stress. The density and pattern of veins influence hydraulic conductance and mechanical stability, helping leaves cope with environmental challenges.

Ecological and taxonomic relevance: Vein density and venation pattern vary with leaf type and environment, affecting photosynthetic capacity and water use. Venation is widely used in plant identification and paleobotanical studies. In agriculture and breeding, vein pattern can influence irrigation efficiency, transpiration, and overall leaf performance.