Plant Structure & Function 29.2, 29.3, & 29.4
Roots • Major Functions: anchor plant to soil, absorb and transport water and nutrients, and store water and organic compounds • How do they develop? When a seed sprouts it produces a primary root. Can become the largest root (taproot) or develop numerous small roots (fibrous roots)
Types of Roots • Taproot: if the primary root becomes the longest root. • Fibrous roots: Numerous small roots develop and branch • Adventitious roots: specialized roots that grow from uncommon places • Root hairs: increase surface area to increase its ability to absorb water & minerals from soil
Growth Roots increase in length through cell division, elongation, and maturation in the apical meristem in the root tip.
Stems • Three types of stems: • Stolons • Tubers • Fleshy • Main function: adapted to support leaves and transport materials and provide storage
Structures Found in Stems • Xylem: transports water • Phloem: transports nutrients • Epidermis: outer layer of the stem; protects the plant and to reduce the loss of water while still allowing gas exchange to happen • Pith: located in the center of the stem • Vascular Bundles: bundles of vascular tissue scattered throughout the ground tissue.
Cohesion-tension theory: water is pulled up the stem xylem by the strong attraction of water molecules to each other (cohesion) while “sticking” to the walls of the xylem (adhesion)
Leaves • Main function: Primary site of photosynthesis • External appearance: Leaves come in a variety of shapes and sizes; consist of 3 tissue systems (dermal, vascular, and ground)
Monocot vs. Dicot • Flower parts in multiples of three • Major leaf veins parallel • Stem vascular bundles scattered • Flower parts in multiples of four or five • Major leaf veins reticulated (like a net) • Stem vascular bundles in a ring