Plant Structure, Growth, & Development

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

Plant Life Spans Most plants experience indeterminate growth They continue to grow as long as they live The lifespan of plants, however, is genetically determined Annuals – complete their life cycle in 1 year Examples: marigolds, cucumbers (lots of garden plants) Biennials - complete their life cycle in 2 years Year 1: germinate & grow roots Year 2: grow stems & leaves, produce flowers & seeds Examples: evening primrose, celery Perennials – live for more than 2 years Examples: Maple trees, grasses, palm trees

Plant Structure Plants are made up of a root system and a shoot system

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

How do roots grow? There are 3 distinct zones in a plant root where different things are taking place Zone of cell division Includes the apical meristem Produces new cells by mitosis Zone of elongation Cells get longer Zone of maturation The cells differentiate and become specialized The root is protected by a root cap, which protects the apical meristem as the plant grows down into the soil

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

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

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

Flower Structure Flowers are the reproductive structure of angiosperms Sepals: Enclose the bud before it opens Protect flower while it’s developing Petals: Usually brightly colored to attract pollinators

Flower Structure Stamens: The male portion of a flower Made up of an anther and a filament The anther produces haploid pollen grains by meiosis Most flowers have multiple stamens

Flower Structure Carpels/Pistils: The female portion of a flower Stigma: Sticky – to trap pollen Style: Hollow tube which connects stigma and ovary Ovary: Produces female gametes (ovules)

Monoecious and Dioecious Species of Plants “one house” Has both male and female flowers on a single plant Dioecious “two houses” Male and female parts are found on separate plants