Unit 7 Plants

Part 2: Tissues, Roots, Stems & Leaves

Plant Tissues – 1. Dermal Tissue

• Outer covering

• Made of epidermal cells

• Waxy coating: cuticle

• Accessories: – Trichomes (“fuzz”)– Root hairs (absorption)– Guard cells (regulate water/gas

movement at surface)

Plant Tissues – 2. Vascular Tissue

• Transport system – Moves water/nutrients

• Xylem: water-conducting tissue– Tracheids– Vessel elements

• Phloem: food-conducting tissue– Sieve tube elements– Companion cells

Plant Tissues – 3. Ground Tissue

• Everything else• Three types– Parenchyma (majority) Thin cell walls; functions

include storage & photosynthesis

– Collenchyma Strong, flexible cell walls; functions include support

– Sclerenchyma Extremely thick/rigid; extra support/toughness

Plant Growth• Indeterminate (never stop)

• Meristem Tissue clusters where new growth occurs via mitosis

• Cells produced in meristem = undifferentiated (not yet specialized)

• Apical meristem = at end of root or stem; responsible for increased length

• Cells gradually differentiate

Plant Roots: 1. Types

• Taproots Long, thick primary root; mainly in dicots

• Fibrous roots Branching system, no primary; mainly in monocots

Plant Roots: 2.

Structure/Growth

Plant Roots: 3. Functions• Anchor

• Uptake nutrients from soil (N, P, K, Mg, Ca)

• Active transport of mineral ions Leads to osmosis of water

• One-way movement into vascular cylinder and up (capillary action)

• Generates root pressure to move water/nutrients from roots all the way up plant

Stems: 1. Structure/Function

• Three functions:– Produce

leaves/branches/flowers– Hold leaves up to sun– Transport substances

between roots + leaves

Stems: 2. Primary Growth

• Primary growth: New cells only produced at root + shoot tips (ends)

• Cell division in apical meristem

Stems: 3. Secondary Growth

• Stems grow thicker/wider• Dicots and conifers• Division of the vascular cambium (a different

kind of meristem)– Produces more xylem + phloem

• Grows from inside - outward• Protected by cork cambium

Stems: 3. Secondary Growth

• Leads to formation of wood• Wood = layers of xylem• Center = oldest, eventually non-functional

xylem (heartwood)• Exterior layer = sapwood (active)

Leaves: 1. Structure

• Blades: flattened; collect sunlight

• Petiole: stem

Leaves: 2. Function

• A. Photosynthesis– Special ground tissue: mesophyll palisade +

spongy)– Stomata (pores; gas movement)– Guard cells (regulation)

Leaves: 2. Function

• B. Transpiration– Loss of water– Replaced by water drawn up from roots

• C. Gas exchange– Take in CO2, give off O2

– Guard cells regulate movement in response to environment