30 8 Leaves Leaf Structure And Arrangment Biology Libretexts

30 8 Leaves Leaf Structure And Arrangment Biology Libre Figure 30.8.1 30.8. 1: parts of a leaf: a leaf may seem simple in appearance, but it is a highly efficient structure. petioles, stipules, veins, and a midrib are all essential structures of a leaf. within each leaf, the vascular tissue forms veins. the arrangement of veins in a leaf is called the venation pattern. Figure 30.10.1 30.10. 1: mesophyll: (a) (top) the central mesophyll is sandwiched between an upper and lower epidermis. the mesophyll has two layers: an upper palisade layer and a lower spongy layer. stomata on the leaf underside allow gas exchange. a waxy cuticle covers all aerial surfaces of land plants to minimize water loss.

30 8 Leaves Leaf Structure And Arrangment Biology Libre There are two basic forms of leaves that can be described considering the way the blade (or lamina) is divided. leaves may be simple or compound. figure 30.9.1: simple and compound leaves: leaves may be simple or compound. in simple leaves, the lamina is continuous. (a) the banana plant (musa sp.) has simple leaves. Xylem and phloem are two types of vascular tissues. xylem transports water and dissolved minerals upward from the roots to the leaves and phloem transports food manufactured on the leaves downward. describe parallel, pinnate, and palmate venation. parallel venation is veins that are usually parallel to each other along the length of the leaf. Leaves may be simple or compound (figure 30.23). in a simple leaf, the blade is either completely undivided—as in the banana leaf—or it has lobes, but the separation does not reach the midrib, as in the maple leaf. in a compound leaf, the leaf blade is completely divided, forming leaflets, as in the locust tree. The primary function of leaves is to collect sunlight and make food by photosynthesis. in a deciduous plant, leaves seasonally turn color and fall off the plant. they are replaced with new leaves later in the year. an evergreen plant keeps its green leaves year round. it may have needle like leaves to reduce water loss.