NOT ON AP: NEEDED FOR BACKGROUND Plant Structure and Growth

The Diversity of Angiosperms Angiosperms (flowering plants) can be divided into 2 major categories: Monocots – have one seed leaf (cotyledon) Dicots – have 2 seed leaves (cotyledons)

Monocots Monocots have only 1 cotyledon (seed leaf) Examples of monocots: Corn, wheat, lilies, orchids, palms

Dicots Dicots have 2 cotyledons (seed leaves) Examples of dicots: Roses, clover, tomatoes, oaks, daisies

Woody vs. Herbaceous Plants Angiosperms can also be subdivided into the groups of woody and herbaceous plants Woody plants are made of cells with thick cell walls that support the cell body Examples: trees, shrubs, vines Herbaceous plants do not produce wood as they grow, and instead have smooth stems Examples: dandelions, sunflowers

Anatomy of an angiosperm

Angiosperm structure Three basic organs: Roots (root system) fibrous: mat of thin roots taproot: one large, vertical root Stems (shoot system) nodes: leave attachment internodes: stem segments axillary bud: dormant, vegetative potential terminal bud: apex of young shoot Leaves (shoot system) blade petiole

Plant Organ Systems Dermal (epidermis): single layer of cells for protection Cuticle: a waxy coating on many leaves and stems Vascular (material transport) xylem: water and dissolved minerals roots to shoots phloem: food from leaves to roots and fruits Ground (photosynthesis, storage, support): tissues that are neither dermal or vascular Pith: internal to the vascular tissue Cortex: external to the vascular tissue

Plant Growth Life Cycles annuals: complete their life cycle in 1 year or less (wildflowers; food crops) biennials: complete their life cycle in 2 years or less (beets; carrots) perennials: live many years (trees; shrubs) Meristems: have indeterminate growth cycles apical: tips of roots and buds; primary growth lateral: cylinders of dividing cells along length of roots and stems; secondary growth (wood)

The Root System What do roots do? Types of root systems Anchor the plant in the soil Absorb minerals and water Store food Types of root systems Fibrous root system Found mostly in monocots Taproot system Found mostly in dicots

Primary growth Roots root cap: protection of meristem and pushes through soil zone of cell division: primary (apical) meristem where new root cells are produced zone of elongation: cells elongate; pushes root tip into soil zone of maturation: complete maturation and differentiate to become tissues

The Shoot System The shoot system consists of: vegetative shoots (which bear leaves) floral shoots (which bear flowers) Stems have 3 important functions: Producing leaves, flowers, branches Holding leaves up to the sunlight Transporting substances between roots and leaves

Primary Tissues of Stems Vascular bundles (xylem and phloem) Surrounded by ground tissue (xylem faces pith (central core of plant) and phloem faces cortex (tissue between the vascular tissue and the dermis). . . See diagram below)

How do stems grow? Primary growth Secondary growth Increase in length Occurs by cell divisions in apical meristem (at top of shoot) Secondary growth Increase in width Occurs by cell divisions in the lateral meristems (also known as vascular cambium)

Apical Meristems

The Shoot System: Leaves Leaves are attached to stems at nodes The area between 2 nodes is called an internode

The Shoot System: Leaves Leaves are the primary photosynthetic organs of most vascular plants Most leaves have a flattened blade and a petiole, which is the stalk that attaches the leaf to the stem

Primary Tissues of Leaves Epidermis/cuticle (protection; desiccation) Stomata (tiny pores for gas exchange and transpiration): surrounded by guard cells which open and close stomata Mesophyll: ground tissue between upper and lower epidermis ; site where photosynthesis takes place

Secondary Growth This type of growth produces thickness in stems and roots in woody plants Two lateral meristems vascular cambium: produces secondary xylem (wood) and secondary phloem (diameter increase; annual growth rings) cork cambium: produces thick covering that replaces the epidermis; produces cork cells; cork plus cork cambium make up the periderm (outer, protective coat) Bark: all tissues external to vascular cambium (phloem plus periderm)

The formation of “bark”

Tissue Systems in Plants All 3 plant organs (root/stem/leaf) have dermal, vascular, and ground tissue systems Dermal Tissue System Outer protective covering, similar to our skin  Protects the plant from water loss and disease The cuticle is a waxy coating that helps to prevent water loss

Tissue Systems in Plants Vascular Tissue System Carries out long-distance transport of materials within the plant Xylem and phloem are examples of vascular tissues Ground Tissue System Pith (inside vascular tissue) and cortex (outside vascular tissue) are examples of ground tissue Includes cells specialized for storage, photosynthesis, and support

Summary of primary & secondary growth in a woody a stem PRIMARY PRIMARY LATERAL SECONDARY MERISTEMS TISSUES MERISTEM TISSUES Protoderm Epidermis Secondary phloem Primary phloem Vascular Procambium cambium Secondary Primary xylem xylem Ground meristem Ground Pith & tissue: Cortex Cork cambium Cork Apical meristem of stem Periderm

Microscope Activity You will be examining various slides of plants In your lab notebooks, I want you to draw what you see at the 100X and 400X powers and label as many parts as you can You may use your textbooks for aid (look at the diagrams in Ch. 35) pp. 721 - 726