What are leaf veins and what function do they perform? What are stomata? What is the lower epidermis?

Leaf veins are a group of cells belonging to two different types of tissues – conductive and mechanical. Here sieve tubes are distinguished. Organic nutrients are transported through them. Also, the veins have vessels through which inorganic nutrients move.
Mechanical fibers in leaf veins provide elasticity and flexibility to the leaf.
The stomata are a special type of cells through which various types of gas exchange take place (respiration, photosynthesis). Consists of: two guard cells and between them a stomatal gap.
The lower epidermis is the skin layer on the lower surface of the leaf blade.