Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Magnesium in biology wikipedia , lookup
Plant nutrition wikipedia , lookup
Ornamental bulbous plant wikipedia , lookup
Plant reproduction wikipedia , lookup
Plant evolutionary developmental biology wikipedia , lookup
Evolutionary history of plants wikipedia , lookup
Plant morphology wikipedia , lookup
Leaves, Roots, Stems Plant organs and their functions Leaves Leaf Parts • Two major parts to the leaf: • Blade • Petiole Leaf microanatomy • Epidermis and cuticle do what? • Mesophyl does what? • Veins do what? • Guard cells in the lower epidermis do what? Photosythesis • The purpose of photosynthesis is to produce organic (carbon-based) molecules (such as sugars). • The plants use these molecules for two purposes: • As an energy source • As building material Roots Types of root systems • Taproot systems: main root, lateral branches. • Fibrous root systems: lose the primary root, replaced by many smaller roots. Root Anatomy • Parts of a root: • Root cap • Root meristem • Zone of elongation • Zone of maturation Roots: Epidermis • Root epidermis lacks a cuticle, and is porous. Usually has many root hairs. • Water enters through membranes of epidermal cells or through spaces between cells. Roots: Cortex • The cortex layer is made up of parenchyma cells. What is the main function of these cells? • Endodermis separates the cortex from the vascular cylinder. Roots: vascular cylinder • Casparian strip around endodermis cells controls water movement. Why? • Pericycle: layer of parenchyma cells, inside of endodermis, from which branch roots can arise. Roots: vascular cylinder • Vascular cylinder contains: • Phloem: what does phloem do? • Xylem: What does xylem do? Stems Stems: Epidermis • In herbaceous plants and young woody plants, the stem is covered with epidermis. • Epidermis secretes cuticle, has stomata, and may be photosynthetic. Stems: Cortex and Pith • Cortex layer contains parenchyma cells and vascular bundles. • Pith makes up the center of the stem, and is absent in hollow stems. Stems: vascular tissue • Vascular bundles are in the cortex. • Between the xylem and phloem is the vascular cambium, a meristem layer. What is it for? Stems: Secondary growth • Secondary growth is seen in woody plants. • This kind of growth produces stronger, thicker stems from the vascular cambium and cork cambium. Stems: wood and bark • What tissue makes up the wood of a tree trunk? (hint: water flows there.) • What tissue makes up the “green bark?” (hint: sap flows there.) • Dead cork cells make up the bark. Stems: Annual Rings • Trees in temperate zones grow at different rates in different seasons, causing annual rings to form. • In some parts of the tropics, if seasons vary little, tree rings are indistinct.