Exam 2 Flashcards
Briefly describe the history of the discovery of cells.
Cells were discovered by Robert Hooke in the 1660s when he looked at cork cells (outer tree bark) through a microscope- called them “cells” bc reminded him of monk’s rooms in the monastery.
How does the structure of a prokaryotic cell differ from that of a eukaryotic cell?
-Prokaryotes have no nucleus, the DNA is unbound in a region known as the nucleoid.
They do not have membrane bound organelles and cytoplasm bound by plasma
membrane.
-Eukaryotic cells have DNA in double-membraned nucleus, have membrane bound
organelles, much larger than prokaryotes
What are the differences between plant and animal cells?
Plants:
-Cell walls
-Cell plate and plasmodesmata
-Plastids and vacuoles
Animals:
-Internal or external skeletons; no cell walls
-Plasma membrane is called a cell membrane.
-Divide by pinching in two; no cell plate nor plasmodesmata
-Centrioles present during cell division.
-No plastids nor vacuoles
Describe the various plant cell organelles and their roles.
Cell Wall
- Mainly composed of cellulose (long glucose chains)
- Matrix of hemicellulose (holds cellulose together), pectin (gives stiffness), and glycoproteins
Plasmodesmata (cell communication)
- Cytoplasmic strands that extend between cells thru small openings, allow for movement of
fluids and dissolved substances
Plasma membrane
- Phospholipid bilayer w/ proteins dispersed throughout- selectively permeable for movement
of subs in/out of cell
Nucleus
- Control center, contains DNA
- Nuclear envelope consists of two membranes
- Pores on surface of envelope, also selectively permeable
Endoplasmic Reticulum
- Flattened sacs and tubes forming channels throughout cytoplasm
- Cell communication, organelle membrane synthesis, protein modification
- Rough ER: ribosomes on outer surface, for protein synthesis/storage
- Smooth ER: lipid secretion
Dictyosomes
- Stacks of flattened discs or vacuoles
- Building blocks of golgi bodies in animals, but don’t pack tightly enough in plants to form
same structure
- Modify carbohydrates, assemblage and collection of polysaccharides
Plastids
- Chloroplasts are the main ones
- Contain grana made of thylakoids
- Thylakoid membranes contain chlorophyll, first steps of PS occur here
- Stroma: matrix of enzymes involved in PS- circular DNA molecule that encodes
production of PS proteins
- Other plastids include chromoplasts (carotenoids) and leucoplasts (starches and oils)
Mitochondria
- Release E from cell resp
- 2 membranes
- Inward membrane forms numerous folds (cristae ) to increase surface area in matrix
which includes DNA and RNA
Vacuoles
- Up to 90% volume in mature cells
- Tonoplasts- vacuolar membranes
- Filled with watery fluid called cell sap containing salts, sugars, proteins, acids, and
anthocyanins
- Help maintain cell pressure and pH, storage of cell metabolites and waste products
Cytoskeleton
- Network of microtubules and microfilaments
- Microtubules control addition of cellulose to cell wall, move flagella and cilia
- Microfilaments: cytoplasmic streaming
Describe plant tissues.
Three or four major groups of organs:
-Roots
-Stems
-Leaves
-Flowers
Each organ is composed of tissues
-A tissue is a group of cells performing a similar function
-There may be more than one tissue per organ
List and describe plant meristems and where they are found.
Meristems are permanent regions of cell growth and differentiation- cells contain very large nuclei and have small/absent vacuoles.
Apical meristems are found at the tips of roots and shoots, allowing them to increase in length
Primary meristems → primary tissues
- Protoderm → epidermis
- Ground meristems → pith (stems), cortex (roots), mesophyll (leaves)
- Procambium → primary xylem and phloem
Secondary meristems → secondary tissues (increase width of roots and stems)
- Not found in all plants
- Cork cambium → periderm
- Lies outside vascular cambium just inside outer bark- produces cork (bark)
- Vascular cambium → secondary xylem and phloem (support and conduction)
Intercalary meristems- found in grasses and plants w no secondary meristems. Located around
nodes along stems, add to stem length
State the difference between simple and complex tissues.
Simple tissues have one type of cell, while complex tissues have many types of cells
Identify examples of simple and complex tissues.
Simple tissues- parenchyma, collenchyma, sclerenchyma
Complex tissues: epidermis, periderm, xylem, phloem
Describe three types of simple tissues and where they may be found in the plant.
Parenchyma
collenchyma
sclerenchyma
parenchyma
- Thin, pliable walls (up to 14)
- Cytoplasm has various vacuoles and secretions
- Remain alive for a long period
- Space in between cells
- Found in almost all parts of higher plants
- Edible part of fruits and vegetables
- PS, storage, transfer between cells
- Aerenchyma- parenchyma tissue with extensive connected air spaces (aquatic plants)
- Chlorenchyma- have chloroplasts
- Transfer cells- irregular extensions of cell wall that increase SA of plasma membrane
collenchyma
- Thick cell walls (uneven thickness)
- Pliable and strong, provide flexible support
- Located just below epidermis in leaves, stems, flowers
- Celery string
Sclerenchyma
- Thick, tough secondary walls saturated with lignin
- Dead at functional maturity, function in support
- Sclereids: stone cells scattered in tissue (nuts, seed coats, peach pits, etc)
- Cells as long as they are wide
- Protection, support, prevent drying out
- Fibers: roots, stems, leaves, fruits
- Much longer than wide, provide support
- Have tiny cavities (lumen)
- Used for string, textile, canvas, etc
Explain the structural and functional differences between xylem and phloem.
XYLEM
- Transport water, ions, water-soluble nutrients from roots throughout plant
- Composed of parenchyma cells, fibers, vessels, tracheids, ray cells
- Vessels- long tubes with perforated plate at end
- Tracheids- tapered at end with pairs of pits allowing water to pass from cell to cell,
dead at maturity
- Rays- long lived parenchyma cells function in lateral conduction and food storage
PHLOEM
- Conduct dissolved PS materials throughout plant
- Composed of sieve tube members, companion cells, fibers, parenchyma cells, ray cells
- Sieve tube members: no secondary cell wall or nuclei, lay end to end. Plates with
small pores to allow passage thru sieve tube. Plugged when a cell is injured
- Companion cells: narrow, tapered cells associated w. Sieve tube members
Describe the structure and function of the epidermis, periderm, and secretory tissues.
Epidermis
- The epidermis is a one-cell thick protective layer around all plant organs that consists of
parenchyma cells and some specialized cells
- Cutin: fatty substance on outside of cell wall that forms cuticle, which secretes wax
- Prevents evaporation, resistance to pathogens
- Root epidermal cells → root hairs to increase root surface absorption area
- Leaves have stomata bordered by guard cells
- Some epidermal cells have hairs or secrete
- Secretory cells: flower nectar, citrus oils, latex, resins
Periderm
- Comprises outer bark of woody plants
- Consists mainly of cork cells and some parenchyma cells
- Replaces epidermis when cork cambium begins producing tissue
- Cork cells dead at maturity- suberin injected into cells that waterproofs them
Secretory tissue
-Secretory cells may function individually or as part of a secretory tissue
ex. Flower nectar, Citrus oils, Glandular hair, mucilage, Latex, resins
Describe human uses of different plant tissues.
- Use sclerenchyma fibers for rope, textiles, string, canvas
- Use wood for construction
Describe the organization of the shoot system
Leaves
Buds
Stems
Flowers
Fruits
- Leaves arranged for optimal sun exposure
- Fruits and flowers positioned for optimal seed dispersal and pollination
Describe the roles of the stems
Stems transport water, minerals, and food between roots and leaves
Describe the primary growth and stem anatomy
Apical meristem is at the stem tip; dormant before growing season, protected by bud scales/ leaf primordia
GO LOOK AT CROSS SECTION
Know the difference between dicot and monocot stems
Monocot stems
- No secondary meristems- no secondary vascular tissue or cork growth
- Primary xylem and phloem scattered throughout stem in bundles, surrounded by
sclerenchyma cells
- Vascular bundle consists of:
- Two large vessels, several small vessels
- Xylem cells stretch and then collapse leaving air space
- Phloem has sieve tubes and companion cells
Dicot stems
- Vascular bundles arranged in cylinder
- Vascular cambium arises btw primary xylem/phloem
Understand the secondary growth and anatomy of wood
- Woody plants show secondary growth during their second year, which continues for many
years (100+ in some cases)
- Most monocots, some dicots do not have
secondary growth - Vascular and cork cambium active all year
- Vascular cambium is narrow band between xylem and phloem- those facing the center of the plant become secondary xylem, those facing outside of the plant secondary phloem
- Cork cambium produces suberin and phelloderm cells that reduce water loss, protect stem
- Lenticels: exchange gases
seasonal production of wood
- Springwood: large vessel elements of xylem
- Summerwood: fewer, smaller vessel elements compared to sclereids and fibers
Springwood and summerwood alternate as light and dark rings, combining to make one annual ring
(light + dark) - Environment affects size of rings
Sapwood: lighter xylem closer to cambium; still alive
Heartwood: older wood in center darkened by resins, gums, tannins - Supports tree but not involved in conduction; can be removed without killing tree
Softwood: comes from conifers, no fibers or vessel elements
Hardwood: comes from dicot trees, has fibers and vessel elements
Know the several different types of modified stems
Rhizomes
- Horizontal stems below ground
- Found in grasses and ferns
Tubers
- Below ground, grow in different directions
- Potatoes
Bulbs
- Numerous fleshy leaves with small stem at lower end (think about what an onion looks like)
- Stores food that plant uses when it is first growing
- Onions, lilies, tulips, hyacinths
Corms
- Short, thick underground stem with papery leaves, used for food storage
Cladophylls
- Resemble leaves, play primary role in PS in plants that have them
- Asparagus, cacti
Thorns
- Originate from leaf axils, help protect plant from predators
- NOT prickles or spines
Stolon
- AKA runners; function as horizontal stems
- Asexual reproduction in plants (strawberry plants, weeds)
Describe some examples of human uses of stems
the primary use of stem products is wood
- ½ US and Canada wood production → lumber for construction
- Pulp is second largest use- made from sawdust and wood waste
- Creates paper, synthetic fibers, plastic, linoleum
- Veneer- thin sheet of desirable wood over cheap lumber
- Developing countries use wood as significant fuel source
- Maple syrup- yum!
Describe the various functions of leaves.
Leaves capture light energy through photosynthesis
Have stomata (tiny pores) that allow CO2 to enter and O2 to
diffuse out
- Water vapor also escapes via stomata
- Water loss controlled by guard cells that open/close
stomata
Waste accumulate in leaves and are disposed of when leaves
are shed
Play major role in movement of water absorption by roots
- Transpiration → water evaporation from
leaf surface
- Guttation → root pressure forces water
out of hydathodes @ tips of leaf veins
Describe the structure and the different components of leaves.
Leaves originate as Primordia in buds
Petiole: attaches leaf to stem
- Leaves are immobile if lacking petiole
Lamina: flattened blade
Vascular bundles: network of veins
Stipules: at base of petiole
Deciduous trees shed leaves after one growing season
Distinguish between simple and compound leaves, the various phyllotaxis, venations and
distinguish between monocot and dicot leaves.
Simple leaves- with single blade
Compound leaves- blade divided into leaflets
Phyllotaxy: arrangement of leaves on stems
Alternate- one leaf per node
Opposite- two leaves per node
Whorled- three of more leaves at the
node
Venation: arrangement of veins in a leaf or leaflet blade
-Pinneatley veined leaves- main midvein
included within enlarged midrib
-Secondary veins bench from midvein
Palmaetley veined leaves- several primary veins fan out from base of blade
Monocot - primary veins parallel= parallel venation
Dicots- primary veins divergent in various ways= netted or retiuclate venatiom
Dichotomous ventilation- veins fork evenly
and progressively from base of blade
Know the different structures of leaves.
Epidermis → single layer of cells covering the entire surface of the leaf
- Devoid of chloroplasts
- Coated with cuticle (with cutin)
- May secrete other waxy substances
- Protects tissues inside leaves
- Waste materials accumulate in epidermal cells
- Different types of glands may also be present in the epidermis
- Lower epidermis has thin layer of cutin and has numerous stomata
Stomata:
- Bordered by two guard cells
- Regulate gas exchange between leaf interior and atmosphere
- Regulate water evaporation
Guard cells
- Originate from the same parent cell and contain chloroplasts
- Changes in amount of water in guard cells cause them to inflate or deflate
- Inflate = stomata open
- Deflate = stomata close
Mesophyll → between two epidermal layers
- Where photosynthesis takes place
- Palisade mesophyll
● Compactly stacked, barrel-shaped parenchyma cells, commonly two rows
● Contains most of leafs chloroplasts
- Spongy Mesophyll
● Loosely arranged parenchyma cells with abundant air space
Veins → vascular bundles
- Scattered throughout mesophyll
- Consist of xylem and phloem tissues surrounded by bundle sheath of thicker-walled
parenchyma
Monocot mesophyll and veins
- Do not have mesophyll differentiated into palisade & spongy layers
- Have bulliform cells on either side of central vein
- Bulliform cells: causes leaf to fold or roll, reducing transpiration
● Partly collapses under dry conditions
List various leaf modifications.
Shade leaves
- Receive less total light than sun leaves
- Larger and thinner than sun leaves
- Fewer well defined mesophyll layers and fewer chloroplasts
- Fewer hairs
Leaves of Arid regions (aloe vera)
- Arid regions = less water, wide range of temperatures, high intensity of
light
- Leaves reduce water loss by
● Thick, leathery leaves
● Fewer stomata or sunken stomata
● Succulent, water-retaining leaves, or no leaves
● Dense, hairy coverings
Leaves of Aquatic areas:
- Less xylem and phloem
- Transpiration does not work here
- Mesophyll not differentiated into palisade and spongy layers
- Large air spaces
Tendrils and Spines
- Tendrils → modified leaves that curl around more rigid objects, allowing
plants to climb or support weak stems
● Garden peas
- Spines → reduce leaf surface, water loss, and protect from herbivory
● Cacti
● Leaf tissue replaced with sclerenchyma
● Photosynthesis occurs in stems
Storage Leaves
- Succulent leaves modified for water storage
● Have parenchyma cells with large vacuoles
● Desert plants
- Fleshy Leaves store carbohydrate
● Onions, lily
Window Leaves
- In succulent desert plants of Africa
- Leave buried in the ground, except for exposed end
- End has transparent, thick epidermis and transparent water storage cells
underneath
- Allows light into leaf, buried leaves prevent plant from drying out
Reproductive leaves
- Walking fern - new plants at leaf tips
- Air plant - tiny plantlets along leaf margins
Floral leaves (bracts)
- At bases of flowers or flower stalks
- Poinsettia - flowers do not have petals, instead brightly colored bracts
surround flowers
- Clary’s sage - colorful bracts are at top of flowering stalks above flowers
Insect-Trapping Leaves
- Grow in swampy areas and bogs
- Various types
- Nitrogen and other elements are deficient in soil
- Specialized leaves traps and digest insects
Pitcher Plants
- Insects trapped and digested inside cone-shaped leaves
- Leaves have nectar-secreting glands around the rim that attracts insects
- Leaves collect water which drowns insects that fall in
- Bacteria and enzymes secreted by plant digest the insects
Sundews
- Round oval leaves
- Leaves are covered with glandular hairs that have a sticky fluid of
digestive enzymes at tip
- Insects get stuck in fluid
- Leaves bend inward and surround the insect
Venus’s flytraps
- Two have of blade are hinged along midrib
- If trigger hairs are touched, blade halves snap together and trap insects
List some human and ecological importance of leaves.
Landscaping - shade trees
food - cabbage, lettuce, celery, spices
Dyes - bearberry, henna
Fuel - yareta plants
Oils - eucalyptus, pennyroyal
Perfumes - lavender, oils of orange tree
Ropes and twine - agave
Drugs - narcotics, tobacco, marijuana
Beverages - tea
Insecticides - rotenone
Waxes - carnauba and caussu waxes
Aesthetics - floral arrangements, gardens
Explain the functions of roots.
Important underground aspect of all vascular plants
Anchor plants into soil
Absorb water and minerals
Store food or water
Other specialized functions
Differentiate between dicot and monocot roots and how each type develops.
Dicot roots:
- Taproot: single thick root with smaller lateral branches
● Development: upon germination, embryos radicle grows and develops into
thick taproot with thinner branches
● Rose, Oak, Carrots
Monocot roots:
- Fibrous roots: wide network of thin roots
● Development: large number of fine roots of similar diameter grow out of the
base of the plant
● Corn, Grass, Palm trees
Describe and identify the different regions of roots.
- Root Cap:
- Thimble-shaped mass of parenchyma cells covering each root tip
- Protects tissues from damage as root grows
- Secretes mucilage that acts as lubricant
- Functions in perception of gravity
- Region of cell division:
- Composed of apical meristem in the center of root tip
- Region of cell elongation:
- Cells become several times their original length: vacuoles merge
- Region of maturation:
- Cells differentiate into various distinctive cell types
Describe and identify the different tissues of roots.
Epidermis:
- Composed mostly of long epidermal cells
- Some cells develop into root hairs
- Root hairs: form at the region of maturation
● Tubular extensions of specialized epidermal cells
● Function in water and mineral absorption
Cortex:
- Parenchyma cells between epidermis and vascular cylinder
- Mostly stores food
Endodermis:
- Inner boundary of cortex consisting of a single-layered cylinder of compact cells
Vascular Cylinder:
- Most of cells of vascular cylinder are primary xylem or primary phloem
List various modifications of roots.
Food Storage Roots:
- Certain plants store large amounts of starch (amyloplasts) and other carbs
- Sweet potatoes and yams and some pumpkins
Propagative roots:
- Adventitious buds on roots develop into suckers (aerial stems)
Pneumatophores:
- Found in plants with roots growing in water
- Spongy roots that extend above the water’s surface and enhance gas exchange
between atmosphere and subsurface roots
Buttress roots:
- Some tropical trees growing in shallow soil produce big roots to stabilize trees (fig
tree)
Parasitic roots:
- Produced by parasitic plants
- Most have no chlorophyll and are dependent on chlorophyll-bearing plants for
nutrition
Aerial roots:
- Velamen roots → several thick epidermis layers to reduce water loss (orchids)
- Prop roots → support plants in high wind (corn)
- Ivies → aid plants in climbing (english ivy, virginia creeper)
Describe mycorrhizae and how this association benefits the plants.
Mycorrhizae:
- Fungi that form mutualistic association with plant roots
- 95% of land plants have mycorrhizae
- Mutualistic association: both fungus and root benefit and are dependent upon
association for normal development
- Fungi facilitate absorption and concentration of nutrients, especially phosphorus for
roots
- Plant furnishes sugars and amino acids to fungus
- Plants with mycorrhizae develop few roots hairs compared with those growing
without an associated fungus
List some human uses of roots.
Food source:
- Carrots, sugar beets, turnips, horseradishes, cassava (tapioca), yams, sweet
potatoes
Spices:
- Sassafras (main ingredient in traditional root beer), licorice
Dyes
Drugs
- Aconite, ipecac, gentian, reserpine
Insecticide
- rotenone
