Plant Tissue Systems

Plant Structure and GrowthVascular Plant Body Shoot System – Root System –Growth Determinate and Indeterminate Growth – Primary and Secondary Growth –

Classes of Flowering Plants Monocots and Eudicots Compared – Lifespans –

Plant Tissue Ground Tissue - Vascular Tissue - Dermal Tissue -

Primary Shoot Systems Features – Functions – Stems – Leaves –

Secondary Shoot Systems Growth –Woody Stem Structure –

Root Systems Features – Types of Roots – Zones of Primary Root Growth – Root Tissues –

Unit IIPlants

Learning Goal 2Describe the three main tissue

systems in the plant body.

Plant Structure and Growth

The Vascular Plant Body• Shoot system– Stems– Leaves– Flowers/Fruits

• Root system– Roots– Root Hairs– Root Cap

Growth

• Determinate growth common in animalsgrowth stops at a certain age

• Indeterminate growth – Plant grows throughout life– Meristems give rise to plant body– Increase in number of cells– Increase in size of cells

Primary Growth

• Apical meristems at root and shoot tips – Increases height of

shoot, length of roots

Secondary Growth

• Lateral meristems at root and shoot tips – Self-perpetuating cylinder of tissue– Increases diameter of stems and roots

Classes of Flowering PlantsEudicots and Monocots Compared

Lifespans

• Annual (one growing season)– Herbaceous

• Biennial (two growing seasons)– Roots, stems, and leaves first season– Flowers, fruits, and seeds second season

• Perennial (growth continues year after year)

Plant TissuesGround TissueParenchyma• Soft primary tissues– Thin primary cell

walls, pliable and permeable

– Specialized for storage, secretion, photosynthesis

CollenchymaFlexible support– Thicker primary cell

walls– Elongated cells in

strands or sheathlike cylinder

Sclerenchyma• Rigid support and

protection– Thick secondary cell

walls– Sclerids (protective

casings) and fibers (support)

Vascular Tissues• Xylem – Conducts water and dissolved minerals– Thick, lignified secondary walls– Dead when functional

• Tracheids– Elongated, tapered, overlapping ends– Lateral connections through pits

• Vessel members– Shorter, tubelike columns– Lateral connections through pits and perforations

Tracheids and Vessel Members

• Phloem– Conduct sugars and other solutes – Living when functional

• Sieve tube members– Joined end to end in sieve tubes– Sieve tube cells assisted by companion cells– End walls (sieve plates) studded with pores

Sieve Tube Members

Dermal Tissue

• Epidermis covers primary plant body – Waxy cuticle layer restricts water loss– Pairs of guard cells in leaf epidermis create

stomata (openings) for gas exchange

• Epidermal specializations– Trichomes (hairs) – Absorbent root hairs

Epidermal Tissue

Primary Shoot Systems• Features• Stems are adapted to provide support, routes

for vascular tissues, storage, and new growth

• Leaves carry out photosynthesis and gas exchange

• Plant shoots may have juvenile and adult forms

• Consists of main stem, leaves, and buds– Plus any attached flowers and fruits

• Functions:– Mechanical support– House vascular tissues– May store food and water– Buds and meristems for growth

Stems

• Organized into modular segments– Nodes: Where leaves and buds are attached– Internodes: Between nodes– Terminal bud: At apex of main shoot – Lateral buds: In leaf axils, produce branches

Stem Structure

Eudicot Vascular Bundles

• Form a stele (cylinder)– Outer cortex, inner pith

Monocot Vascular Bundles

• Scattered throughout ground tissue of stem

Modified Stems

Leaves

• Blade– Large surface area for photosynthesis and gas

exchange

• Petiole (in eudicots)– Attaches leaf to stem

Fig. 31.15, p. 725

b. Simple leaves (eudicot)

Poplar(Populus)

Oak(Quercus)

Maple(Acer)

Leaf Forms

Fig. 31.15, p. 725

Petiolule

c. Compound leaves (eudicot)

Red Buckeye(Aesculus)

Honey Locust(Gleditsia)

Black Locust(Robinia)

Leaflets

Leaf Adaptations

• Responses to environmental and herbivore pressures

Leaf Internal Structure

Secondary Shoot Systems

Growth• Vascular cambium gives rise to secondary

growth in stems

• Secondary growth can also occur in roots

• Secondary growth is an adaptive response

• Increases girth of roots and stems

• Vascular cambium– Produces secondary xylem and phloem

• Cork cambium– Produces cork, part of protective bark

Woody Stem Structure• Vascular cambium produces wood

• Cork cambium produces cork

• Bark– Living and nonliving tissue outside vascular cambium

(secondary phloem and periderm)

• Periderm – Cork, cork cambium, and secondary cortex

• Heartwood, sapwood

Root Systems

Features• Taproot and fibrous root systems are

specialized for particular functions

• Root structure is specialized for underground growth

• Absorb water and dissolved minerals

• Conduct water and minerals to aerial plant parts

• Anchor and support aboveground parts

• Often store food

Types of Roots

Zones of Primary Root Growth

• Zone of cell division– Root cap– Quiescent center

• Zone of elongation • Zone of maturation

Fig. 31.21, p. 730

Endodermis

a. Eudicot root

Root cortex

Pericycle

Primaryxylem

Primaryphloem

Stele(vascular cylinder)

Epidermis

Fig. 31.21, p. 730

Primaryphloem

b. Monocot root

Pith

Root cortex

Epidermis

Stele

Primaryxylem

Root Tissues

• Exodermis – Outer layer of root cortex

• Endodermis– Inner layer of root cortex

• Pericycle • Between stele and endodermis• Can function as meristem

LG 2 Vocabulary Terms

1. Apical/Lateral Meristems -2. Parenchyma -3. Collenchyma -4. Sclerenchyma -5. Cambium -6. Trachied -7. Nodes -8. Pith -9. Sieve Tube -10. Root Cortex -