Chapter 23 Roots 23:2

adventures primary root Roots – anchors plant into the ground and transports materials to the plants body 2 types Tap – primary root that grows long and thick. Fibrous – branching, where no single root grows longer than the rest, covers a large surface area holding soil in place. fibrous adventures primary root

II. Roots structure and Growth A. 3 Tissue systems 1. Dermal – Epidermis type found on the outside. 2. Vascular – Central cylinder, xylem and Phloem. 3. Ground – Cortex, between dermal and vascular

B. Root system plays a large role in water and mineral transport along with protection and absorption. 1. Root hairs – produce large surface area in soil through which water can enter the plant. 2. Cortex- spongy layer of ground tissue. 3. Endodermis – covers the roots vascular system. 4. Vascular Cylinder – center of the root. 5. Root Cap – covers and protects the apical meristem cells that grow the root in length. It secretes a slippery substance that lubricates the progress of the root through the soil.

Vascular, cortex, endodermis, epidermis

III Root Function A. Functions 1. Anchor 2. Absorb water and travels up the xylem vascular tissue to the plants body. 3. Absorb dissolved nutrients such as carbohydrates from photosynthesis are transport throughout the plants body in the phloem vascular tissue.

Stems

Vascular Tissue Xylem – vascular tissue that transports water and minerals up into the plants body. Phloem – vascular tissue that transports food, mainly sugar throughout the body of the plant moving in many directions.

Stems 23-3 Structure and Function A. 3 Functions 1. Produce Leaves, branches and flowers. 2. Hold leaves up to sunlight. 3. Transport substances between root and leaves.

B. Structure 1. Nodes – where leaves are attached 2. Internode – region between the nodes. 3. Buds – contains under developed tissue that can produce new stem and leaves.

C. Monocot and Dicot Stems 1. Monocot stems – scattered vascular bundles, parallel venation on leaves, herbaceous stems. 2. Dicot stems – vascular bundles are arranged in a cylinder, branched venation on leaves, woody stems.

Monocot cross section

Examples of Monocot plants

Dicot cross section

Dicot versus Monocot

Primary Growth of stems A. Growth only on the tips of roots and stems is called primary growth. 1. This growth is produced by cell division in the apical meristem. This growth takes place in all seed plants.

Secondary growth of stems A. The method of growth in which stems increase in width is called secondary growth. 1. Conifers and dicots secondary growth takes place in the lateral meristematic tissues called the vascular cambium and cork cambium. A. vascular cambium produce vascular tissue and cork cambium produce outer coverings of stems.

Leaves

I. Leaves 23-4 A. Leaves are the main organ of a plant that conducts photosynthesis, making glucose, by capturing sunlight. B. Leaves have special cells (chlorophyll) that allow it to perform this chemical reaction.

A. Structure and Function 1. Mesophyll – leaf ground tissue A. Upper Epidermis - covers top and is sometimes covered with a cuticle. B. Cuticle – waxy covering on the surfaces of some leaves to protect and prevent drying out. 2. Palisade Cell Layer– Under the upper epidermis, closely packed cells, absorb light, lots of chlorophyll.

3. Spongy Cell Layer – below the palisade layer, contains many air spaces for gas exchange. Also where the vascular tissue is found. 4. Stomata – pore like openings underside of the leaf (lower epidermis) that allows carbon dioxide and oxygen to diffuse into and out of the leaf. 5. Guard cells- surround stomata, control the opening and closing of the stomata by responding to changes in water pressure. 6. Lower Epidermis – Bottom of leaf that contains stomata’s

Stomata’s and guard cells