Midterm 1 Flashcards
What is the importance of plants?
- Basic human needs: food, clothing, shelter, fuel and clean air
- All are directly or indirectly provided by plants
What is the basic organization of life?
Atoms, Molecules, Cells
Unicellular organisms
One cell performs every life
function: food capture,
photosynthesis, metabolism,
reproduction, etc.
Multicellular organisms
Each cell has a specialized
function. Many similar cells
form tissues, multiple
tissues form organs.
Prokaryotes
Don’t have membrane-bound
organelles
Eukaryotes
Have membrane-bound
organelles
Plants are Eukaryotes. Eukaryotic cells have…
- Membrane-bound organelles (compartments)
- Nucleus - contains the genetic material
Animal cells
- No cell wall
- No large vacuole
- No chloroplasts
Plant Cells
- Cell wall
- Large vacuole
- Chloroplasts
Cell wall
- Made of cellulose
- Function: structure and protection
- Thin, flexible primary cell wall
- Additional thick, rigid secondary cell wall
Plasma membrane
A selectively permeable barrier that regulates the
movement of substances in and out of the cell.
Plasmodesmata
Small channels that connect neighboring cells
together for the exchange of chemical signals
Nucleus
- Control center of the
cell - Stores genetic material
(DNA) - Instructions for making
different enzymes and
other proteins - Bound by a double
membrane—nuclear
membrane
Chloroplast
- Specialized organelle where photosynthesis
occurs - sunlight + water + carbon dioxide = glucose/sugar
- Contains chlorophyll, a green pigment
Variegated plants
some cells acquire
mutations which prevent the production of
chlorophyll
Mitochondria
Site of cellular
respiration
* Sugar and starch is
broken down into
useable energy
* Similar in structure to
chloroplasts (inner
folded membrane)
Vacuole
- Large fluid-filled organelle
- Occupies 90% of the
volume in mature cells - Maintains cell pressure
-
Stores nutrients and breaks
down waste products - Stores water soluble
pigments called
anthocyanins (purple and
red color)
Mitosis
- DNA is duplicated
- Cell is split into two
- Both cells are genetically identical
Plant tissues
Groups of cells that perform the same function
Simple Tissue Types
- Parenchyma (most common)
- Collenchyma
- Sclerenchyma
Three Primary Tissue Systems
- Epidermal Tissue
- Ground Tissue
- Vascular Tissue
Parenchyma Tissue
- Living at maturity
- Most common type of cell
and tissue - Thin primary cell walls
- Large central vacuole
- Can take on many shapes
- Function in photosynthesis,
storage, and transport of
food and water
Amyloplasts
organelles
that store starch
molecules (energy for
the cell)
Collenchyma Tissue
- Composed of living
cells with thickened
primary cell walls -
Flexible support for
organs such as
leaves and
herbaceous stems
Sclerenchyma Tissue
- Dead at maturity
- Thick and rigid secondary
cell walls reinforced with
Lignin - Function in support and
protection
Two cell types of sclerenchyma tissue
- Fibers
- Sclereids
Fibers
- Elongated
sclerenchyma cells - Provide structural
rigidity and stiffening
to leaves, stems, and
roots - Abundant in wood
Sclereids
- Sclereids (stone cells)
form the hard tissues of
nuts, seed coats, etc. - Compact shape
- May be present
together with thin-
walled parenchyma
cells.
Epidermal tissue
- Outermost layer of cells,
the epidermis - Complex
tissue:composed of
numerous cell types - Covered with a waxy
cuticle layer to prevent
water loss
Epidermal tissue cell types
Epidermal
cells, root hairs, Guard
cells, trichomes
Epidermal cells
Covered with a waxy cuticle to prevent water
loss
Trichomes
Leaf hairs
Stomata
- Pores (holes) in leaves and stems where
gas exchange occurs and water evaporates - When stomata are open, CO 2 enters the
plant, water and oxygen are released
Ground Tissue
- Present in most organs of the
plant, between the epidermal
tissue and vascular tissue - Photosynthesis, storage,
support
Ground tissue types
- Parenchyma
- Collenchyma
- Sclerenchyma
Vascular tissue
- Continuous tissue
throughout the plant
in which water and
sugar are transported - Composed of
numerous cell types
Vascular Tissue types
- Xylem
- Phloem
Xylem
- Transports water and minerals
- Made of tracheids, vessel elements, fibers, xylem parenchyma
Tracheids
tapered at the ends, water passes between tracheids through thin areas in the cell wall called pits
Vessel elements
long tubular cells
open at both ends, arranged end to end forming vessels that function like water pipes
Phloem
-
Transports sugars and other
organic substances - Composed of sieve tube members, companion cells, phloem fibers, phloem parenchyma
Sieve tube members
long tubular cells with sieve plates in the end walls, arranged end to end, alive but lacking a nucleus
Companion cells
help sieve tube
members function
Primary Growth
- Apical Meristems
- Form primary tissues
- Plant increases in
length - Tips of every branch
(and in leaf axils) - Mitosis creates new
tissues
Phototropism and Auxin
Cell elongation results in the bending of the shoot toward the light
Cook Pine
- Native to New Caledonia
- Grown ornamentally worldwide
- Tree trunk leans toward the equator
(phototropism)
Functions of a stem
-
Transport – water and sugars
through vascular tissue -
Support - holds leaves in
position for efficient
photosynthesis -
Storage– Ground tissue
stores energy and water for
later use
Internal Stem Structure
Vascular Tissue - Conducts water,
minerals, and sugar
Pith- Stem center (storage, support)
Cortex
** Cortex** - Outer portion of ground tissue
** Epidermis** - The outer most layer of cells*
Natural Fibers
- Hemp (Cannabis sativa)
- Grown for rope, paper,
clothing, sailcloth - Strong and resistant to
water and sea water
The typical stem
The pattern of growth is
consistent as the main axis
of the plant develops:
Stem, Leaf, Bud
Modified Stems: Stolons
- Horizontal above- ground stems
- Function:
Vegetative Reproduction
Modified Stems: Rhizomes
- Horizontal below- ground stems
- Function:
Vegetative Reproduction - produce new individuals at nodes below ground
Modified stems: Succulent stems
- round, fleshy, water-storing stems
- Function: Water Storage
Modified Stems: Bulbs
- underground storage stem with fleshy leaves
- Function: water and energy storage
Modified stems: Tuber
- The swollen end of an underground stem.
- Function: Water and
energy storage,
propagation from axillary
buds (”eyes” of a potato)
Modified Stems: Thorn
- Sharp and pointed stem (often a sharp axillary bud)
- Function - Physical protection against
herbivores and frugivores (fruit-eaters)
Root functions
- Anchoring plant in soil
- Absorption
- Conduction
- Storage
- Hormone Production
Root systems: Taproot
- one main root that grows downward
- Carrots, radishes,
turnips, and beets
are examples - Most Eudicots
Root systems: Fibrous roots
- have many branch roots. No single root is more prominent
than others. - Wheat and corn are examples.
- Most Monocots (e.g. corn, wheat, rice, palms, onions)
Roots have
- a root cap that
protects the apical
meristem - no nodes
- root hairs for H 2 O
absorption
Root cap
- Protects the root tip
- Produces lubricating mucigel
- Constantly sloughed off and
regenerated by apical
meristem
Root epidermis
- Provides protection
- Absorbs water and minerals from
the soil - Absorption is facilitated by root
hairs
Examples of Monocots
- Lilies
- Orchids
- Irises
- Onions
- Bananas
- Ginger
- Grasses
- Agaves
Eudicots
- Roses
- Tomatoes
- Sunflowers
- Poppies
- Apples
- Oranges
- Avocados
Monocots vs. Eudicots (Stem)
- Monocots: vascular bundles are scattered throughout stem
- Eudicots: vascular bundles are arranged in a ** ring** around stem
Endodermis in roots
- Ring of cells surrounding
vascular cylinder - Each cell of the
endodermis is surrounded
by a Casparian strip
impregnated with suberin
and lignin - The Casparian strip is
impermeable to water
and solutes
Casparian Strip
- Substances entering or
leaving the vascular
cylinder must pass
through a plasma
membrane of the
endodermis cells - Function: Regulation of
what enters and leaves
the vascular cylinder - Effectively acts like a filter
for the root
Pericycle
- Layer of
meristematic cells
where lateral roots
develop - Outer boundary of
vascular tissue, just
inside the endodermis
Lateral Roots
- emerges from the
pericycle inside of the
primary root - maintains its connection with the vascular tissue
Root ground tissue
- Greatest volume of
most roots - Function: storage of
starch
Root Symbiosis with Bacteria
Plant gets nitrogen,
bacteria gets sugar from
the plant
Root Symbiosis with Fungi
- Plant provides sugar for
fungi - Fungi provide water and
nutrients with plants
Adventitious roots
Roots that arise from a tissue other than the pericycle
Prop Roots
Adventitious roots that stabilize the plant, like
stilts or lateral braces.
Aerial Roots
Above-ground adventitious roots that absorb
water or reach the soil and function as prop roots
Sugar Beet
- Artificially selected for a
high concentration of
sucrose - Same species as chard,
and red beets (varieties) - Beet sugar accounts for
40% of the world’s sugar
production
Haustoria
- Penetrating roots of
parasitic plants - Connect to vascular tissue of
host plant and steal water
and nutrients - Mistletoes, wildflowers, etc.
Annuals
- most herbaceous plants that demonstrate only
primary growth - entire life cycle takes place in one growing season.
Biennials: two seasons, germination to seed
- First season - energy storage in roots/stems
- Second season – stored energy used to produce
flowers and fruits
Perennials: plants that live for several years
- soft-stemmed plants that die back each
year, re-sprout each year from underground roots/stems - Woody plants (shrubs and trees) that display secondary
growth in their stems and roots - Monocots DO NOT display secondary growth
What happens to perennial plants after years of growth?
After several years of growth, perennial plants start to form secondary tissues
Secondary growth
Formation
of wood and bark
and widening of
stems and roots
Meristem
where growth occurs
Lateral meristems
- Vascular cambium
- Cork cambium
Cork
- Produced by the cork
cambium, which develops
from parenchyma cells in
the cortex - Replaces the epidermis
- Cork cells are dead and
impregnated with suberin
wax (waterproof) - Protective outer coating
- Constantly regenerated to
protect vascular cambium
Coast Redwood
- California’s state tree
- Redwood lumber is
the most
commercially
valuable softwood
(gymnosperm wood) - Coast redwoods are
the tallest trees on
Earth
What are the two state trees
- Coast Redwood
- Giant Sequoia
The Functions of Leaves
- Photosynthesis
- Regulate water loss - transpiration
- Many specialized functions
- Storage
- Protection
- Attraction
- Propagation
- Climbing
Early Development of a Leaf
Apical meristem forms leaf primordia (immature leaves) and axillary buds during primary
growth
Morphology of a Leaf
-
Blade – expanded
portion of the leaf - Petiole – leaf stalk
-
Stipule – appendage
at the base of the
petiole
Leaf Venation
Vein: vascular bundles
in the leaves
Simple Leaves
The leaf blades are not divided
into separate parts (may be
deeply lobed)
Compound Leaves
Leaf blades are
divided into leaflets
Pinnately compound
leaflets arise from either side
of the rachi
Palmately compound
leaflets diverge from the
petiole tip (no rachis)
Rachis
an extension of the petiole
Bracts
leaves associated with
flowers. They help attract
pollinators
