Chapter 34

2 systems of the plant body

Root system
Shoot system

Functions of root system

Anchors plant
Absorbs water and nutrients from soil
Conduct ions and water to shoot system
Get energy from shoot system's sugar
Store products of shoot system

Functions of shoot system

Harvest light and carbon dioxide from atmosphere to produce sugar
Conduction

How does surface area vs. volume ratio affect plant absorption?

larger surface area to volume increases absorption efficiency

Taproot

Main root of primary root system, grows vertically down

Lateral roots

Smaller roots that branch out from the taproot

Roots show phenotypic plasticity. What can change? What can determine the change?

Root type and depth can be determined by environment

3 levels of shoot/root diversity

Morphological diversity (among species)
Phenotypic plasticity (within individuals)
Modified shoots/roots (with specialized functions)

Adventitious roots

Grow from shoot system, non-root tissue
Can be used for anchoring/bracing

4 types of modified roots

Anchor roots
Pneumatophores
Prop roots
Storage roots

Anchor roots

Adventitious roots that anchor stems (i.e. ivy)

Prop roots

Adventitious roots stabilize stem (i.e. corn)

Pneumatophores

Roots that allow gas exchange between roots and atmosphere (i.e. Mangroves)

Storage roots

Taproots that store carbohydrates and nutrients (i.e. Beets, carrots)

____ are vertical aboveground structures consisting of ____ where ____ are attached and ____ which are segments between nodes

stems; nodes; leaves; internodes

_____ form at nodes, just above the site of leaf attachment

Axillary/lateral buds

Maxillary bud may grow into a ____

Branch

The tip of each stem and branch contains an ____

Apical bud

_____ and _____ may develop into flowers

Apical and axillary buds

How can plants minimize competition for light?

Various species vary in size and shape

What type of environment favors taller shoot systems?

Lush environment and competition for light

What type of environment favors shorter shoot systems that are more anchored to the soil?

Dry and windblown environments

What can affect phenotypic plasticity in shoot systems?

Temperature, wind exposure, water availability, nutrients, light

5 types of modified stems

Water storage structures
Stolons
Rhizomes
Tubers
Thorns

Water-storage structures of modified stems

stems modified to store water and for photosynthesis (i.e. cactus)

Stolons

stems modified to grow horizontally and produce adventitious roots and leaves at each node aboveground (i.e. strawberries)

Rhizomes

stems that grow horizontally and function in asexual reproduction, nodes belowground (i.e. ginger)

Tubers

underground, swollen rhizomes that store carbohydrates (i.e. potatoes)

Thorns

modified stems that provide protection (i.e. protect from herbivores)

role of surface area of leaf

large surface area for absorbing photons and supporting photosynthesis

a ____ ____ has two main structures, an expanded ____ and a stalk called a _____

simple leaf; blade; petiole

in a ____ ____ the blade is divided into a series of _____

compound leaf; leaflets

how can needlelike leaves reduce water loss

transpiration

how can you differentiate leaves from leaflets

there will be an axillary bud next to the petiole of the leaf, no axillary bud on leaflet

where can plants with small, needlelike leaves thrive? why?

deserts and cold, dry habitats; scarce water supply, less surface area → less water loss

leaves with a large surface area lose large or small amounts of water? Why?

large; transpiration

phyllotaxy

arrangement of leaves on stems

4 types of morphological diversity in leaves (phyllotaxy)

Alternate
Opposite
Whorled
Rosette

alternate leaves

1 leaf per node

opposite leaves

2 leaves per node

whorled leaves

multiple leaves per node

rosette

short internodes with typically alternating basal leaves

leaves do not grow ____, but do show phenotypic plasticity due to environment

continuously

2 types of leaves determined by the amount of sunlight exposed to

Sun leaves
Shade leaves

sun leaves structure and function

relatively small surface area, exposed to higher quality/energy (blue) light.
reduce water loss where light is abundant (typically near top)

shade leaves structure and function

relatively large and broad, exposed to lower quality/energy (red) light.
provide large surface area to maximize photon absorption

5 types of modified leaves

Bulbs
Floral mimics
Succulent leaves
Traps
Tendrils

bulbs

modified leaves that stores nutrients, typically underground (i.e. onion bulbs)

succulent leaves

modified leaves that store water, aboveground (i.e. aloe vera)

floral mimics

modified leaves that look like flowers to attract pollinators (i.e. red leaves of poinsettias)

traps

modified leaves that trap entering insects (use their hood to keep them from exiting, and digest with digestive enzymes or bacteria), typically in areas with low-nutrient soil (ex. lack of nitrogen), plateaus or excessive rain. (i.e. pitcher plant)

tendrils

modified leaves that allow anchoring/climbing, allows for faster growth without wasting resources on fibers (i.e. pea tendrils)

unique plant cell features

primary cell wall, secondary cell wall, plasmodesmata, chloroplasts, central vacuole

cell wall structure and function

cellulose-rich and surround plant cells (some may have a rigid secondary wall as well), used for structural support and maintain cell integrity under internal pressure

plasmodesmata

intercellular connections that connect cytoplasm of adjacent cells that allow things to be transferred from one cell to another

chloroplast

pigment that convert light into sugar, site of photosynthesis,

central vacuole

storage, cell sap (aq soln) inside with water, nutrient, waste (since plants can’t excrete like human)

non-photosynthetic cells may have organelles similar to chloroplasts but modified for ___

storage of pigments, starch, oil, proteins

simple tissues consist of ______ and complex tissues consist of ____

a single cell type; several cell types

3 tissue systems are found in plants

dermal tissue system
ground tissue system
vascular tissue system

dermal tissue system consists of

complex tissue, epidermal cells, stomata

epidermal cells: function

protect plant surface, secrete waxy cuticle to reduce water loss and protect against pathogens

stomata: function

regulate gas exchange and water loss by opening and closing

guard cells: locale, function

2 surround each stoma, change shape to open and close stoma

trichomes

hairlike appendages made up of specialized epidermal cells

trichomes: functions

reflect sunlight to keep plant surface cool
limit transpiration to reduce water loss
protect from herbivores by providing barbs/toxins
trap and digest insects

ground tissue system consists of

parenchyma, collenchyma, sclerenchyma

parenchyma: structure and functions

simple tissue, relatively thin primary cell walls
in leaves: primary site of photosynthesis
in roots: store starch granules

totipotent

capacity to divide and develop into a complete plant

benefits of cells being totipotent

allows wound healing and asexual reproduction (ex. can be cloned by making cuttings)

callus

mass of undifferentiated parenchyma cells that roots can develop from and be planted

collenchyma: structure, functions, locale

simple tissue, unevenly thickened primary cell walls
provide flexible structural support to parts actively growing
under epidermis of stems outside vascular bundles

sclerenchyma: structure

complex tissue: long fibers and short protective sclereids, thin primary and thick rigid secondary cell wall

sclerenchyma secondary cell walls contain

tough, rigid lignin
cellulose

difference between sclerenchyma and collenchyma

collenchyma have expandable primary cell walls and support growing tissue in stems
sclerenchyma are dead at maturity and provide support after growth

most abundant and versatile plant cells

parenchyma

vascular tissue system consists of

2 complex tissues: xylem and phloem

xylem: structure, functions

complex tissue: water-conducting cells, parenchyma cells, fibers
conducts water and dissolved nutrients from root to shoot

2 types of water-conducting cells in xylem: functions

tracheids with pits for water to move through, in all vascular plants
vessel elements with perforations for water transport in angiosperms

phloem: structure, functions

complex tissue: sieve-tube elements/sieve plates, companion cells
conducts sugars, amino acids, hormones, and other substances between roots and shoots

sieve-tube elements

long, thin cells with perforated ends (sieve plates), lack nuclei, directly connected to companion cells via plasmodesmata

companion cells

maintain cytoplasm and plasma membrane of sieve-tube elements

meristems

populations of undifferentiated cells that retain ability to undergo mitosis

how can plants grow throughout their lives?

they have many meristems

apical meristems: locales, function

found at tip of each root and shoot, responsible for primary growth

cells and tissues derived from _______ make up the primary plant body

apical meristems

3 distinct primary meristems that apical meristems give rise to

protoderm
ground meristem
procambium

protoderm gives rise to

the dermal tissue system

ground meristem gives rise to

the ground tissue system

procambium gives rise to

the vascular tissue system

organization of primary root system from superior to inferior

zone of cellular maturation
zone of cellular elongation
zone of cellular division
root apical meristem
root cap

organization of primary root system from deep to superficial

vascular tissue (xylem, phloem)
pericycle
ground tissue
endodermis
cortex
epidermal tissue
root hairs
apical meristem
root cap

root cap: functions

produced and replenished by meristem, protects, senses gravity to determine direction of growth, secretes lubricant

zone of cellular division contains

apical meristem, protoderm, ground meristem, procambium

zone of cellular elongation contains

cells increasing in length

zone of cellular maturation contains

cells that differential into dermal, vascular, or ground tissue that absorbs water and nutrients thru root hairs

organization of primary shoot system in eudicots from deep to superficial

ground tissue: central pith and outer cortex
vascular bundles (arranged in ring near perimeter)
xylem
phloem
fibers
epidermis

organization of primary shoot system in monocots from deep to superficial

ground tissue with scattered vascular bundles
epidermis

secondary growth: products, where it occurs, functions

produces wood
in species that have a cambium and apical meristems
increases width of roots and shoots, increase structural support, increase amount of conducting tissue available