air spaces – reservoirs for carbon dioxide and water cuticle layer – waxy coating (cutin) to prevent water loss stomates (stomata) – pores in the epidermis for gas exchange. Stomates close as CO 2 or H 2 O levels drop, or high temperature. Transpiration occurs through them. closed open
Stomates open (or close) due to water and ion movement. Ions such as K+ and Cl- flowing into the guard cells causes hypotonic osmotic conditions.
Veins – groups of thick-walled cells forming round tubes within the spongy layer, usually surrounded by a single layer of cells. These “vascular” tissues carry water (xylem) & sugars, the products of photosynthesis (phloem).