Stems Students will be able to explain and demonstrate stems of plants

Parts of a Stem Stem –Structural axes Node –Where the leaves or branches grow Internode –Space between two nodes

Apical Bud –Bud at the top of the plant Axillary Buds –Grows at the axel of the Leaf Where Photosynthesis happens

Functions of Stems Support of leaves, flowers, and fruits Conduct water and minerals up from soil Storage of water SOME have a defense (rose bush thorns) SOME are an Anchorage (rhizoid stems like Ivys)

CLASSIFICATION of BUDS Based on ORGANS they CONTAIN –SIMPLE contain a SINGLE flower or leaves Example: Rose –COMPOUND contains SEVERAL flowers or leaves Example: Rhododendrons –MIXED contain BOTH flowers and leaves Example: Apple and Pears

ANATOMY of BUDS APICAL MERISTEM –Division of cells to form new cells REGION OF ELONGATION –Cells elongate to make stem grow LEAF PRIMORDIA –Tissue that differentiates into new leaves AXILLARY BUD PRIMORDIA –Tissue that differentiates into new buds

Specialized Stems Corm Bulb Tuber Crown Spurs Rhizomes Stolon

Corm Solid, fleshly, and scale covered Underground –Examples: Gladiolus Crocus

Bulbs Layers of fleshy scales that overlap each other Underground stem –Examples: Tulips Lilly's Onions

Tubers Food storage area Short, thick underground stem –Examples Potatoes Corn Beets

Crown Closely grouped stems or plantlets Just above ground or just below –Examples African Violets Ferns

Spurs Short stems found on woody plant limbs Increase production of fruit –Examples Pear trees Apple trees

Rhizomes Underground stems that produce roots on the lower surface and extend leaves and flower shoots above the ground –Examples Iris Lily of the Valley

Stolon Stem that grows horizontally above the soil surface –Examples Strawberries Airplane Plant

What questions are there????

Assignment Each person will have all 7 specialized stem You will make a foldable You must have the following: –Stem name –What is your stem (explain it) –Function of stems –Examples (4) –Picture of your stem (hand drawn)

ANATOMY OF STEMS

What does the Xylem do? Transports water and minerals up from the roots. Provides support Stores carbohydrates Protects against disease

What does the phloem do? Food made in the leaves travel up or down the stem. Composed of living cells

STEM TYPES Monocots Dicots

MONOCOTS NO VASCULAR CAMBIUM SCATTERED vascular bundles Growth from increase in PARENCHYMA (pith and cortex) and additional bundles CONSTANT DIAMETER More FLEXIBLE because no real wood Example: Corn, Bamboo, Palms, Grasses

DICOTS- HERBACEOUS PITH - center of stem for food storage CORTEX – beneath epidermis for food storage PITH RAYS – connects pith and cortex for food storage

VASCULAR BUNDLES –XYLEM, PHLOEM, and VASCULAR CAMBIUM Divides 3 ways – INNER xylem, OUTER phloem, and SIDEWAYS to form continuous VASCULAR CAMBIUM layer EPIDERMIS –On YOUNG STEMS before wood forms –PROTECTION for inner tissues –WAXY CUTICLE to prevent water loss LENTICELS – holes in epidermis for gas exchange

DICOTS- WOODY PITH - center of young stem for food storage VASCULAR CAMBIUM XYLEM LAYERS (mostly DEAD TISSUE) –ANNUAL RINGS – one years growth SPRINGWOOD – large cells due to good growing conditions SUMMERWOOD – smaller cells due to drier summers

SAPWOOD - functional xylem –Younger, lighter wood –Conducts WATER and NUTRIENTS HEARTWOOD – non-functional xylem –No longer conducts water –Stronger, heavier wood –RESISTS INSECTS and DECAY VASCULAR RAYS (live parenchyma) –TRANSPORTS WASTE products to heartwood –Lighter in color

BARK Non-functional phloem and cork, a protective material –Bark moderates temperature inside the stem –Protects against pathogens and wounds –Reduces water loss

Live Bark vs. Dead Bark Live Bark Includes phloem, cortex, cork cambium Live cells Dead Break Consists of cork cells Dead cells Filled with suberin

Assignment Coloring pages 73-78