Secret Life of Plants

Plant Anatomy

Terms

• Node – place where leaf petiole attaches

• Internode – stem between nodes

• Terminal bud – at the end of a branch

• Axillary bud – at the base of a leaf

• Tap root – large central, vertical root

• Lateral root – branches off the taproot

• Fibrous roots – all roots about the same size, no central tap root

Root Diversity

Prop Root – support tall, top heavy plants

Storage roots – store food and water

Pneumatophores – air roots, enable root system to obtain oxygen

Stem Diversity

Bulbs – vertical, underground shoots consisting of enlarged bases of leaves that store food

TuberEnlarged ends of rhizomes specialized for storing food

Eyes – clusters of axillary buds

RhizomeHorizontal stem that grows below surface

Leaf DiversityTendrils – modified leaves, used to cling to support

Spines – leaves, but photosynthesis is carried out in green flesh

Storage leaves – stores water

Brachts – leaves that surround group of flowers, attracts pollinators

Reproductive leaves – produce adventitious plantlets, fall off and take root in soil

Tissue Types• Dermal Tissue – outer protective

covering– Epidermis – nonwoody plants– Periderm – woody plants

• Ground Tissue – neither dermal nor vascular– Pith – internal to vascular tissue– Cortex – external to vascular tissue

• Vascular Tissue – long distance transport of materials between roots and shoots– Xylem – water and minerals upward– Phloem – sugars downward

Xylem – Tracheids & Vessels

Water transporting system

Phloem – Sieve tubesSugar transporting system

Plant Growth

• Primary Growth– Growth in length of roots or shoots– Growth at the apical meristem (tips of roots and

shoots)• Secondary Growth (will do later)– Growth in diameter of stem or root– Growth at the vascular cambium– Growth at the cork cambium

Root Structure

Tissues in Dicot Root• Epidermis – no cuticle• Cortex – parenchyma, food storage• Endodermis – inner layer of cortex, sealed• Pericycle – outer rim of vasc. bundle, lateral roots• Phloem – sugar transport• Cambium – area of potential new xylem &

phloem growth• Xylem – water & mineral transport

Lateral Root Growth

Dicot & Monocot Stem

Tissues in Dicot Stem

• Epidermis• Cortex• Vascular Bundles

PhloemCambiumXylem

• Pith ( more storage)

Tissues in Monocot Stem

• Epidermis• Ground tissue• Scattered vascular bundles in the ground

tissue – Only phloem and xylem, no cambium

Leaf Anatomy

Tissues in mesophytic leaf• Upper epidermis• Palisade mesophyll• Vein – Xylem– Phloem– Bundle sheath cells surround the X and P

• Spongy mesophyll with air spaces• Lower epidermis

Epidermis details

• Cuticle (Wax) layer on outside of epidermis• Ordinary Epidermal cells have no chloroplasts• Stoma – opening in the leaf for gas exchange• Guard cells (with chloroplasts) are on either

side of the stoma• Usually more stoma on the bottom of the leaf

Mesophyll Region

• Photosynthetic cells– Palisade cells maximize exposure to light– Spongy cells allow accumulation of gases

• Veins – Xylem delivers water and minerals– Phloem transports photosynthetic products for

metabolic needs of cells or storage– Bundle sheath cells surround vein & protect

Secondary Growth

• Growth in Girth

• Vascular cambium produces secondary xylem and phloem

• Cork Cambium produces periderm and cork