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Chapter 29-33
Plant Unit
Importance
Evolution to land plants-classification
Plant structure and function
Plant Reproduction
Plant Responses
Plants and People
Tree Man
-Actually, this is believed
to be caused by the Human
Papilloma Virus (HPV)
-Creepy though!
Plants and People (really)
 Plants are used as food
 Plants are used for medicine
 Plants are used for clothing and fabric dyes
 Plants are used as fuels
 Plants are also used for ornamental purposes, improving
erosion, reducing noise, providing habitats for wild
animals, acting as windbreaks, providing shade, and
moderating temperatures
 See page 566, Figure 29-3…good “Nonfood” list of plant
uses
Plants and the Environment
 Plant Ecology – plant interaction in environment
 Photosynthesis
 Provide organisms with inorganic nutrients
 Formation/maintenance of soil
 Plant and animal interactions
 Pollination
 Size, shape, color attract pollinators
 Plant and microbe interactions
 Fungi – Mycorrhizae = symbiotic relationship betw. Plants
and fungi
 Bacteria – nitrogen fixing = take gas and fix so plants can
use
 Plant protection – prevents new plant pests
 Harmful plants – can cause illness, rashes, allergies, and
sometimes death
Evolution of Land Plants
 Changes in Nutrient Absorption
 Vascular Tissue – transports water and dissolved substances
 Xylem-water and inorganic nutrients in one direction
 Phloem- organic compounds in any direction based on need
 Reproduction by spores and seeds – keep reproductive cells
from drying out; can send structures via air
 Prevention of Water Loss – cuticle is waxy; prevents water
loss but also keeps out carbon dioxide
FYI:
*Buoyancy of water provides physical support for algae
Lignin is an evolutionary trait that hardens the cell walls of
plants allowing them to have strength to stand upright
Classification – Page 580, Figure
30-1
 Nonvascular – no true vascular tissue nor true roots,
stems, or leaves
 Vascular, seedless – vascular tissue and true roots,
stems, and leaves (ferns)
 Vascular, seed – vascular tissue and true roots, stems,
and leaves; also produce seeds for reproduction (4 phyla
of gymnosperms, 1 phyla of angiosperms)
Gymnosperms
 Include pine trees
 Produce seeds that are not enclosed in fruits
Angiosperms
 Flowering plants
 Produce seeds within a protective fruit
Alternating Life Cycles
 2 phases
 1st = diploid (2n); sporophyte plant; produces spores
 2nd = haploid (1n); gametophyte plant; produces egg and
sperm
 Alternation of generations = alternates between the
gametophyte phase and sporophyte phase
Nonvascular Plants
 “Bryophytes”
 Do not form true roots, stems, and leaves
 Usually grow on land near streams and rivers
 Seedless; produce spores
 Mostly terrestrial
 Have alternation-of-generations life cycle
 Very small
 Need water to produce sexually (sperm must swim)
 Phyla: Bryophyta, Hepatophyta, and Antherocerophyta
Phylum Bryophyta
 Pioneer plants = mosses; often first species to inhabit a
barren area
 Carpet moss
 Moss gametophytes anchored by non-vascular rhizoids
 Rhizoids anchor moss and absorb water and inorganic nutrients
 Sphagnum (peat moss) – partially decomposed plant
matter; some countries used as fuel; widely used to
enhance the water-retaining ability of potting and
gardening soils.
Phyla Hepatophyta and
Anthocerophyta
 Hepatophyta – liverworts; grow in moist,
shady areas
 Lie close to ground
 Most have thin, transparent leaflike structures
arranged along a stemlike axis.
 Anthocerophyta – hornworts; resemble
liverworts; grow in moist, shady areas.
 Similar characteristic to algae: each cell
usually has a single large chloroplast rather
than numerous small ones
Changes in Nutrient Absorption
 Land Plants
 Algae
 Absorb resources
from surrounding
water
 Vascular Tissue transportation
 Air
 Light and carbon
dioxide
 Shoots/leaves
 Soil
 Water and mineral
nutrients
 Roots
Vascular Plants
 Vascular Seed Plants
 Phylum Cycadophyta
 Cycads
 Seedless Vascular
Plants
 Phylum Psilotophyta
 Whisk Ferns
 Phylum Lycophyta
 Club Mosses
 Phylum Sphenophyta
 Horsetails
 Phylum Pterophyta
 Ferns
 Phylum Ginkgophyta
 Ginkgoes
 Phylum Coniferophyta
 Conifers
 Phylum Gnetophyta
 Gnetophytes like
Ephedra
 Phylum Anthophyta
 Largest phylum of
plants
 Over 240,000 of
flowering plant
Monocots vs Dicots
Specialized Plant Cells – See pg
599
 Parenchyma – loosely packed; cube-shaped
 Involved in many metabolic functions (photosynthesis,
storage of water and nutrients, and healing)
 Bulk of nonwoody plants (ex. Flesh of apple)
 Collenchyma – irregular shape; thick walls
 Usually grouped in strands
 Support regions of plant that are still lengthening (ex.
Celery stalk)
 Sclerenchyma – thick, even, rigid cell walls
 Support and strengthen plant
 Usually dies at maturity, providing support (ex. Gritty
texture of pear fruit)
Tissue Systems – Review Table
31-1
 Dermal – outside covering of plants; surrounds ground
tissue
 Ground – consists of all 3 types of cells; surrounds
vascular tissue system; storage, metabolism, and
support
 Vascular – transport and support; xylem and phloem;
Growth in Meristems
 Growth where cells continuously divide
 Apical meristems – located at tips of stems and roots (remember the
onion root tip?)
 Some monocots also have intercalary meristems = above bases of leaves
and stems; allow rapid regrowth from damage
 Lateral meristems – gymnosperms and most dicots have this which
allows roots and stems to increase in diameter
 Vascular cambium – betw. xylem and phloem…produces additional
vascular tissue
 Cork cambium – located outside phloem…produces cork; cork cells
replace epidermis in woody stems and roots; cork cells are dead cells that
provide protection and prevent water loss
 Primary Growth – in length; apical and intercalary
 Secondary Growth - in diameter; lateral
Roots
 Taproot – when first root becomes
the largest root; carrots
 Fibrous root system – numerous
small roots; many monocots…grass
 Adventitious – specialized roots
that grow from stems and leaves;
prop roots of corn (helps keep
stems upright)
Root Structure
 Root cap – covers apical
meristem
 Root hairs - extensions of
epidermal cells (increase
surface area = increase plants
ability to absorb water)
 Most form partnerships with
mycorrhizal fungi = also
increases surface area for
absorption
Just
another
FYI
Cross
section
of
monocot
and
dicot
roots
Stems
 See page 609…
 Shoot system and root system
 Segmented stems = internodes
 At each end of internode = node; contain 1+ leave and
lateral bud (capable of developing into a new shoot)
*Read over page 610 to review primary and secondary growth
in stems
Cross section of mature woody
stem
Bark – protective outer covering
Heartwood – darker wood in
center of tree
Sapwood – lighter wood near
outside
Springwood/Earlywood – When
water is plentiful; vascular cam.
forms new xylem tissue (wide
and thin-walled
Summerwood/Latewood – When
water is more limited; vasc. cam.
forms small, thick cells.
Annual Ring – abrupt change
between small summerwood cells and following year’s large springwood cells.
*Annual rings often do not occur in tropical trees because of their
uniform year-round environment
Stem functions
 Source to sink –
 CHO are “translocated” through the plant
 Source = where CHO are made or stored
 Sink = where the CHO are transported to be stored
 EX. In most plants…CHO from leaves to roots …to the shoot
apical meristems, and to the developing flowers or fruits
PressureFlow
Hypothesis
Page 612
-Movement in phloem
-CHO are actively
transported into the
sieve tubes
-water is also
transported in by
osmosis
-+ pressure builds up
-At “sink”, process
reverses
Cohesiontension
theory
-Water is pulled up the
Stem xylem b/c water
molecules are attracted
to one another
(cohesion)
How roots absorb water and
minerals and then move to
leaves
 Trace the path of water and minerals from the roots to
the leaves with the use of xylem
 Trace the path using a simple concept map, isolating key
points
Types of Leaves
Leaf Tissue
Another
Crosssection
Tissue Systems
 Dermal – epidermis
 Single layer
 Coated by cuticle
 Water, oxygen, and carbon dioxide enter and exit through
stomata
 Mesophyll layers –
 Leaf = ground tissue made of chloroplast-rich parenchyma
cells
 Palisade medophyll
 Spongy mesophyll
 Vascular Tissue
Venation
Moisture Maintenance
 Must maintain a
watery internal
environment
 Developed a cuticle –
waxy coat that does
NOT permit gas
exchange
 Stomata permit gas
exchange during
certain times of the
day
Plants acquire nutrients from
soil and air
 Three sources of a plant’s mass:
 Air – carbon and oxygen = used in photosynthesis =
generates sugar which are the building blocks of other
organic molecules
 Water – absorbed by plant – supplies the hydrogen for
photosynthesis; solvent for transport of other molecules;
makes up about 80-85% of a nonwoody plant’s mass
 Soil – source of inorganic nutrients (minerals)
Mineral requirements of plants
 Most plants need 17 chemical elements to complete
their life cycles:
 3 are not obtained as minerals: C, O, and H
 Mineral nutrients absorbed in ionic form from the soil
 6 of mineral nutrients plants require in greatest abundance:
Nitrogen, Sulfur, Phosphorus, Potassium, Calcium, Magnesium
Path of N from atmosphere to
plant’s roots
 N is often in limited supply
 Used to produce proteins, nucleic acids, and hormones
 Makes up 80% of atmosphere, however atmospheric
Nitrogen is a gaseous form of nitrogen that plants can’t
use
 Plants must absorb from the soil in the form of mineral
ions
Path of N from the
atmosphere to plant’s roots
 N must first be converted to ammonium ions or
nitrate ions
 Certain species of soil bacteria convert atmospheric
nitrogen to ammonia (nitrogen fixation)
 Ammonifying bacteria contribute ammonia to the soil by
breaking down feces and dead leaves
 Nitrifying bacteria convert ammonium ions to nitrate ions
 Nitrogen-fixing bacteria live freely in the soil,
however, some plants house their own (legumes)
 Bacteria found in lumps on the legumes’ roots (root
nodules)
 Relationship benefits legumes and nitrogen-fixing bacteria
 Bacteria fix nitrogen
 Plant provides CHO and other organic nutrients to bacteria
Fertilizer contents
 Comercially produced; contain minerals
 Usually enriched in nitrogen, phosphorus, and
potassium (3 most deficient in farm and
garden soils)
 “10-12-8” three-number code in fertilizer; 10%
Nitrogen, 12% phosphorus, and 8 % potassium
 Not stored in soil for later use, though
 Usually wasted; taken from soil by rainwater
and irrigation = may pollute groundwater,
streams, and lakes
 Rotate crops reduces N fertilizer use
 Mulch and manure release minerals more
gradually
Plant Reproduction
 Life cycle of mosses
 Life cycle of ferns
 Life cycle of conifers
Life cycle of mosses
Production of one type of spore = homospory
Life cycle of mosses = homosporous alternation of
generations
Male Reproductive
structure
Dominant generation = gametophyte
Female Reproductive
Structure
Life cycle of ferns
Dominant Generation = Sporophyte
Similar to moss…most are homosporous
Life cycle
of
conifers
Microspores = male
grow into male
gametophytes
Megaspores = female
grow into female
gametophytes
Heterospory = production
of different types of
spores…
Heterosporous alternation
of generation
Male cones of a pine release huge numbers of pollen grains
Flower Parts
Male reproductive
structure =
stamens…made up of an
anther and filament
Female reproductive
structure = pistil…made
up of a stigma, style, and
ovary
Flower
pollination
Fruit and seed dispersal
 Dispersed by animals, wind, water forcible discharge,
and gravity
 Fruit = a matured ovary
 Simple = formed from one pistil of a single flower
 Aggregate = formed from several pistils of a single flower
 Multiple = formed from several flowers growing together
 Seed coat = protective coat surrounding
embryo of seed
 Cotyledon = seed leaf (part of
embryo)…dicot = 2 cotyledons
 Embryo
 Radicle = embryonic root
 Hypocotyl = stem between the cotyledons
and radicle
 Epicotyl = stem above the cotyledons
Structure of seeds
Conditions for seed germination
Water
Oxygen
Temperature
Vegetative
propagation
Use of vegetative structures to
produce new plants
Rhizomes, bulbs, and tubers
Plant Horomones – see Page 648,
Table 33-1
 Auxins = involved in plant-cell elongation, apical
dominance, and rooting
 Gibberellins = stimulates elongation growth
 Ethylene = responsible for ripening of fruit (hang green
bananas above apples on counter…bananas ripen; ripen
peaches in brown paper bag b/c they release ethylene
and stimulate ripening)
 Cytokinins = promote cell division in plants (remember
“cytokinesis”)
 Abscisic Acid = inhibits other hormones (causes closure
of plant’s stomata in response to drought)
Plant Movement
Also referred to as
“gravitropism”
Chemotropism = a plant’s growth response to a
chemical change (growth of pollen tube)
Nastic Movements
Photoperiodism
 Plants response to changes in the length of days and
nights
 Critical Night Length = plant’s specific requirement for
darkness; regulates flowering
 SDP = short-day plants; flowers when the days are short
and the nights are longer
 LDP = long-day plants; flowers when the days are long and
the nights are shorter
 DNP = day-neutral plants; not affected by day length
Phytochrome = bluish, light sensitive pigment that allows
plants to monitor changes in day length
Vernalization
 Low-temperature stimulation of flowering
 Important for fall-sewn grain crops
 Farmers often use this to grow and harvest their crops
before a summer drought sets in
Fall colors
Caused by photoperiodic response and by temperature response
Longer nights = leaves stop producing chlorophyll…chlorophyll
degrades and carotenoids become more visible (hidden by more
abundant chlorophyll