PL ANT STRUCTURE &

FUNCTIONS C . 9 1 2 . L . 1 4 . 7

ROOT SYSTEMS VS. SHOOT SYSTEMS

• Root System:– Part of the plant normally found below the ground

– Functions to anchor the plant to the ground

– Absorbs water & minerals from the ground and moves them to the stem

– Some are food storage sites for the plant

• Example: carrot, sweet potato, beet, turnip (edible forms)

Shoot System

Root System

ROOT STRUCTURE

2. Apical Meristem: produces cells that increase the roots length

–Develop into numerous types of root tissues that perform different functions

1. Root Cap: located at the very tip of the root

–Protects the growth point (meristem) of the root

–Secretes a slime that helps the root move through the soil

–Causes the root to grow downward

PRIMARY TISSUES IN ROOTS (PRIMARILY YOUNG ROOTS)1. Epidermis:

–Outer most cell layer

–Absorbs water & minerals

–Protects inner layers

–May have root hairs projecting from it that help absorb water and anchor it

2. Ground Tissues: A. Cortex• Layer below the epidermis • Made of parenchyma cells• Help to transport and store plant substancesB. Endodermis• Inner boundary of the cortex • Regulates the material that enters vascular tissues

through “Caspian strip”C. Pericycle• Layer of cells next to endodermis, towards center of

root• Produces lateral roots

3. Vascular Tissues: –Xylem: water-carrying vascular tissue composed of vessel

elements and tracheids (cylindrical cells that transport material)

–Phloem: transports dissolved sugars and other organic compounds throughout a plant

Root Structure Video

SHOOT SYSTEM (3 MAIN PARTS)1. Stems:

–Support leaves & lift them towards the sun

–Tissues of the stem transport water & minerals from the roots to the leaves and food from the leaves to the roots

–Green stems can photosynthesize

2. Leaves:–Produce food–Exchange gases between plant & leaves

3. Flowers:–Reproductive organs–Produce seeds

STEMS•Monocot Stem (Herbaceous) Example: Grass

–Vascular bundles made of xylem and phloem are scattered

• (Eu)Dicot Stem (Woody) Example: Oak Tree

–Vascular bundles made of xylem and phloem are found in rings (ex. Tree rings)

LEAVESA.Structures

1.Epidermis

–The outermost layer that is covered by the waxy cuticle

–Has openings called stomata that are pores that regulate the passage of gases and water vapor to and from a leaf

2. Petiole

– Attached blade of leaf to the stem

–Some plants (like grass) may not have one

2. Mesophyll

–Middle layer of the leaf

–Two cell layers thick

• Palisade Mesophyll: Most photosynthesis occurs here and contains many chloroplasts

• Spongy Mesophyll: Irregularly shaped, loosely packed cells where oxygen, carbon dioxide, and water vapor can pass through; contains fewer chloroplasts

Leaf Structure Video

B. Functions of Leaves1. Produce food through

photosynthesis

2. 2. Release oxygen and take in carbon dioxide

3. Release water vapor

C. Specialized Leaves

1. Needles of conifers

2. Spines of cactus

• Small to prevent water loss

• Protects the plant from being eaten

TRANSPIRATION•Transpiration: Water evaporates from the inside of a

leaf to the outside through stomata

–Stomata usually located on underside of leaves

–Carbon dioxide and oxygen diffuse through the stomata that open close because of guard cells

PLANT TRANSPIRATION

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