Plant Structure Roots Stems Leaves

Plant Organs Roots Stems Leaves

Plant Tissue Dermal Tissue  Outer covering - epidermis Often have thick waxy coating called cuticle Helps prevent water loss and protects from infection Vascular Tissue  Forms transport system Xylem – composed of tracheids and vessel elements for water transport Phloem – composed of sieve tube elements and companion cells for sugar transport

Ground Tissue  Between dermal and vascular tissue  Three cell types Parenchyma – photosynthesis; lots of chloroplasts Collenchyma – support in growing portions Sclerenchyma – strength in mature parts

Meristematic Tissue  Where continuing plant growth occurs  a lot of cell division takes place (mitosis)  Apical meristem – found at the end of roots and shoots Grow in length  Lateral meristem – Produce new vascular tissue and cork Grow in width

Roots Two main types:  Taproots – primary root that grows long and thick Small secondary roots  Fibrous roots – branched roots that are similar in size Help prevent erosion

Roots Structures  Root cap – tough layer of cells at the end that protect the new cells as it moves through soil  Root Hairs – attached to epidermis and increase surface area and absorption

Roots Functions  Anchor plant in soil  Food/sugar storage  Absorb water and nutrients from soil Use active transport to pump mineral ions into the plant Water follows ions  osmosis Creates a strong pressure, forcing water upward Called root pressure

Stems Large variety  Examples: tubers, bulbs, tree trunks, barrel cactus, flower stems Functions  Produce leaves, branches, and flowers  Hold leaves up to sunlight  Transport between roots and leaves  Support

Stems Structure  Nodes – where leaves attach  Internodes – regions between nodes  Buds – undeveloped tissue that can produce new stems and leaves  May develop woody tissue (wood is the layers of xylem)

Leaves Function  Photosynthesis centers  Gas Exchange Structure  Blades – thin, flattened sections  Petiole – think stalks that attach leaf to stem  Mesophyll – specialized ground tissue where most photosynthesis takes place  Stomata – tiny openings for gas exchange (CO 2 and O 2 )

 Stomata Surrounded by guard cells (open and close) Respond to changes in water pressure, wind, and temp. Water is also lost from stomata  transpiration Plant must balance gas exchange and water loss

Transport in Plants Movement of water through plant is made possible by  Root pressure  Capillary action – tendency of water to rise in thin tubes Due to cohesion and adhesion (hydrogen bonding!!!)  Transpiration – as water leaves through the leaves, more water is pulled upward Called transpirational pull

Movement of sugars and nutrients  Sugars moved from source (where produced) to sink (where used or stored) Sugar source is typically leaves Sugar sink is usually roots or fruits  As sugars move, water moves, creating pressure changes that allow phloem to transport food