Chapter 29: Plant Structure & Function

(of roots, stems, & leaves)Pages 582-607Targets: 18-24

Name: Hour:

Plant Unit Notes 4 of 5

2

Review of Main Plant Cell Parts:• Large fluid-filled vacuole - provide turgor

pressure for support & store water for dry spells

• Plastid: pigment containing organelles

• Thick cell wall - made of cellulose for support, that surrounds the cell membrane

3

Plants are made up of 3 types of cells• Parenchyma Cells

– Thin flexible cell walls, cube-shaped– Large central vacuole– Function: photosynthesis, storage, & healing– Ex: flexible green stems, & fleshy fruit (Apples)

• Collenchyma Cells– Thicker cells walls; irregular shape– Function: support for growing plant parts– Ex: areas still lengthening (Celery stalks)

• Sclerenchyma Cells– Thickest/rigid cell wall– Function: strength & support for non growing

plant parts; usually dies at maturity– Ex: a frame to support the plant (shell on nut)

4

3 Types of Plant Tissue Systems

Location

Function in

Roots

Function in

Stems

Function in

Leaves

Dermal

Tissue(epidermis)

outer most layer

-cuticle-stomata

absorption;

protection

gas exchange

; protecti

on

gas exchange; protection

Ground

Tissue

b/w dermal & vascular

support; storage

support; storage Photosynthe

sis

Vascular

Tissue

Tubes throughou

t plant

transport; support

transport; support

transport; support

5

Vascular Plant Tissue:Xylem:

- Dead at maturity- Transports water- 2 Cell Types

- Tracheid: tapered ends;

pits to allow water to pass through

- Vessel Elements: larger holes at top & bottom

http://www.sirinet.net/~jgjohnso/plants.html

Phloem:- living at maturity-Transports organic material- 2 Cell Types

- Sieve Tube: filters- Companion Cell:

assists in transport along sieve tube

http://www.sirinet.net/~jgjohnso/plants.html

6

• Meristems: where plant growth originates (cells continually divide)

1. Apical Meristems: increase length @ tips• Location: Tips of stem & root

2. Intercalary Meristems: increase length b/w nodes• Location: b/w tip and base of stem & leaves

*why grass can regrow after being mowed

3. Lateral Meristems: increase diameter• Location: outsides of stems & roots• 2 Types:

– Vascular cambium (b/w xylem & phloem)– Cork cambium (outside phloem = makes cork)

• Primary Growth: growth in length (apical & intercalary)• Secondary Growth: growth in width (lateral)

Plant Growth:

7

Concept Check1. What is the function of a plant vacuole?

- provide turgor pressure for support & store water for dry spells

2. Name the 3 types of plant tissues- dermal, vascular, ground

(a 4th could be meristematic)

3. Name the 3 types of cells found in plants- Parenchyma Collenchyma

Sclerenchyma

8

Plant Organs: Roots (typically grow underground)

Function: anchor in place, transport water & mineral nutrients, and storage of water & organic compounds

Types of roots:– Taproot: 1st root is the largest; generally not deep

rooted• Ex: Carrot, radish

– Fibrous Root System: numerous roots develop & branch

• Ex: Grass

– Adventitious: grow roots from above ground parts (stems & leaves); prop roots of corn & aerial roots of vines

9

Root Structures– Root cap : protects apical meristem, produces “oil”

– Root hairs: increase surface area for water absorption (mycorrhizal fungi)

– Cortex: ground tissue just inside of epidermis

– Endodermis: ground tissue found inside the cortex; has a waterproof substance to control water & mineral movement

– Vascular Tissue: innermost core of roots.– Dicot: “X” shaped xylem with pockets of phloem– Monocot: pith in the middle with alternating

xylem & phloem in a ring

– Pericycle: outer layer of vascular tissue; produces lateral roots

10

Plant Organs: Stems (typically above ground, upright & woody or non-

woody)

Function: support leaves, transport material, provide storage

Special Types of stems: (due to adaptations to the environment)

• Stolons: grow along soil to produce new plants

• Tubers: underground; modified for storing energy as starch

• Fleshy stems: store water and carry out photosynthesis

11

Stem Structures–Node: where a leaf is attached to a stem–Internodes: space between the nodes–Bud: where a new shoot can grow (stem or leaf)–Bud scales: cover buds; leave scars after opening

Primary Growth-Pith: forms in center of stem in dicots; separates from cortex-Vascular Tissue:

-Monocots: xylem/phloem in scattered bundles

-Dicots: xylem in/phloem out; form a ring in the cortex

-Look at extra picture handouts!

12

Stem Structures - ContinuedSecondary Growth: stems increase in thickness due to

division of vascular cambium cells (b/w xylem & phloem)

–Wood: secondary xylem–Heartwood: darker wood; older, does not transport water–Sapwood: lighter wood; still transports water

–Bark: phloem near outside of stem; for protection (made of cork, cork cambium, and phloem)

–Springwood: wood cells wide & thin walled; more water present–Summerwood: wood cells small & thick walled; lack of water–Annual Ring: created by difference in appearance (not seen in tropical plants, why?)

13

Transport of sugar through phloem (translocation)• From source to sink by Pressure Flow Hypothesis

– Source: where sugar is made or stored– Sink: where sugar will be stored or used

*sugar mainly made in leaves - moved to rest of plant

Transport water & dissolved minerals through xylem (transpiration)

• Water pulled up by Cohesion-Tension Theory– Water molecules stick together; cohesion– Water molecules stick to xylem; adhesion– Water evaporates through stomata & pulls others along

• Storing water and nutrients– Large amount of parenchyma cells to store:

• Water; cactus / Sucrose; sugar cane / Starch; potatoes

Stem Function: transport, storage, support leaves

14

Plant Organs: Leaves (typically thin & flat)

Function: Capture sunlight for photosynthesis

Types of leaves:- Tendrils: used to support & climb- Spines: protection; non-photosynthetic- Food traps: plants with poor soil nutrients

Structure:– Blade: broad flat portion of leaf– Petiole: stalk-like attachment to stem– Simple leaf: single blade– Compound leaf: blade is divided into leaflets

• Can be doubly compound; leaflets divided

15

• Epidermis: Outside layer of cells– Cuticle: waxy covering; prevent water loss– Hairs: protect against insects & sun– Stomata: tiny air pores, areas for gas exchange;

number & location vary on plants•Guard cells: regulate the size of the stomata

• Mesophyll: Ground tissue; chloroplast-rich– Palisade: under upper-epidermis; tightly packed– Spongy: under palisade layer; loosely packed, air

spaces

• Veins: bundles of vascular tissue (parallel vs. branched)

Leaf Structures

16

Concept Check1. What is the function of the root cap?

- protects apical meristem, produces “oil”

2. What are the main differences b/w xylem & phloem?

- xylem: dead at maturity; transports water; specialized cells: tracheid/vessel elements

- phloem: alive at maturity; transports food; specialized cells: companion/sieve tube

3. What difference b/w the stomata & the guard cells?

- stomata = space; gas (O2/CO2) passes through- guard cells = cells; swell/shrink to control size of

space