Unit 6 review

1
Unit 6 review

• Ch 35
• Root system shoot system
• Fibrous roots- mat of thin roots spreading just
  under the surface
• Taproots- 1 thick vertical root w/many lateral
  roots from it
• Stems- made up of nodes (where leaves attach)
  internodes

2

• Axillary buds- located in the V formed b/w nodes
  and stem, can for a branch
• Terminal buds are at the top end of the stem
  (usually where growth occurs)
• apical dominance- terminal bud prohibits growth
  of axillary buds

3

• Leaves are the site of photosynthesis (palisade
  mesophyll)
• Leafblade petiole (leaf stalk)
• A desert plant would likely have reduced leaves
  to minimize the loss of water through
  transpiration
• Which part of the plant absorbs the most water
  and minerals? (root hairs)

4

• Indeterminate growth- growth occurs throughout a
  plants lifetime
• Most animals and some plant organs stop growing
  once they reach a certain size
• If you pinch back a plant you will make a plant
  that is bushier

5

• 3 cell types in plants
• Parenchymamost common, in all of the plant
  parts, photosynthesis
• Collenchymagrouped in cylinders support
  growing parts of the plant
• Sclerenchymaall parts of the cell that are no
  longer growing tough cell walls

6

• 3 tissue types in plants
• Dermalsingle layer packed cells that covers the
  entire plant protects it (skin)
• VascularXylem Phloem
• Xylem- transports H2O, made of tracheid vessel
  elements
• Phloem- transports minerals, made of sieve
  companion cells
• Ground tissueanything not vascular or dermal
  (pith, cortex)

7

• Based on their life cycle, flowering plants can
  be classified as annuals, biennials, or
  perennials
• Meristems- perpetually embryonic tissues that
  cause indeterminate growth
• Apical meristems are at the tips of roots and in
  buds of shoots, and are where cell division occurs

8

• Primary growth when plant grows at the apical
  meristem (length) roots shoots
• Secondary growth is from lateral meristems
  (width) vascular cambium cork cambium
• Wood- 2ndary xylem
• root cap has cells in 3 stages of growth zone of
  cell division, elongation, maturation

9

• Stomata- small pores flanked by guard cells, that
  are involved in CO2, oxygen, and water exchange
• Lenticels are small bumps on the stem that are
  involved in gas exchange
• Bark- Phloem periderm all tissue outside of
  the vascular cambium

10

• Morphogenesisdevelopment of body form and
  organization
• Pattern formationdevelopment of specific
  structures in specific locations
• Pattern formation is thought to be determined by
  positional information from signals

11
CH 36

• 3 kinds of transport occurs in plants
• 1.) uptake of water and solutes by individual
  cells
• 2.) short-distance from cell to cell (tissues and
  organs)
• 3.) long-distance in xylem and phloem (whole
  plant level)
• The uptake of water across a cell membrane occurs
  by osmosis

12

• The amount direction of movement of water in
  plants can always be predicted by measuring water
  potential
• Air pressure, water-attracting matrices,
  dissolved solutes all have an effect on water
  potential

13

• Water potential solute concentration physical
  pressure
• Turgor pressure is produced by the plasma
  membrane exerting force against the cell wall
• Aquaporins- transport proteins in the plant cell
  pm (more aquaporins means faster osmosis rate)
• tonoplast- membrane of the vacuole (regulates
  molecules in and out)

14

• Osmosis is affected by solute concentration,
  proton pumps, aquaporins, and water potential
• Proton pumps are used to aquire minerals from the
  soil

15

• Cytosols of cells are connected through
  plasmodesmata, this continuum is known as the
  symplast
• Apoplast is the continuum of cell walls
  xtracellular spaces

16

• Water absorption occurs near the root tips
  through root hairs
• Mycorrhizae aid in water mineral absorption
  (they increase the amt the speed at which
  absorption takes)
• plants grow slower w/o mycorrhizae b/c water
  mineral uptake is slower w/o the symbiotic fungi
• Transpiration- main mechanism by which water in
  the xylem moves upward

17

• Transpiration-cohesion-tension mechanism is where
  water is lost through
• transpiration of the leaves b/c of lower water
  potential of the air.
• cohesion of the water molecules is b/c of H-bonds
  adhesion of water to the plant cell
• This enables the water to form a column which is
  drawn up through the xylem as water evaporates
  from the leaves.

18

• Stomata help regulate the rate of transpiration
• Turgor changes in guard cells control the size of
  the stomata
• Taking up water makes the guard cells swell and
  buckle, increasing the size of the pore.
• Water loss causes the stomata to close
• Guard cells help balance the photosynthesis-trans
  piration compromise
• Root pressure can cause guttation- exudation of
  water drops on tips of grass blades or leaf
  margins

19

• Transpiration requires
• Adhesion of water molecules to cellulose
• Cohesion b/w water molecules
• Evaporation of water molecules
• Transport through the tracheids
• most water taken up by a plant is lost by
  transpiration

20

• In the roots the casparian strip forces water
  solutes to pass through the pms of the
  endodermis cells before entering the xylem

21

• Phloem transports organic products of
  photosynthesis from leaves to the rest of the
  plant
• Sieve tubes always carry sugars from a sugar
  source to a sugar sink.
• Sugar sourceorgan that is a net producer of
  sugar
• Sugar sinkorgan that is a net consumer or storer
  of sugar
• Example late spring phloem would transport
  sugars from the leaf source to the apical
  meristem sink

22
CH 37

• Plants need macromnutrients in lg amts.
• C, O, H, N, S, P, K, Ca, magnesium (K does not
  have a direct role in photosynthesis)
• Micronutrients needed Cl, Fe, Bo, Mn, Zn, Cu,
  Ni, molybdenum
• 90 of the dry weight of plants is from oxygen
  carbon
• micronutrients act as cofactors in
  enzyme-catalyzed rxns

23

• Chlorosis- refers to the yellowing of leaves b/c
  of reduced chlorophyll production
• Topsoil is a mix of rock particles, living
  organisms, humus (partly decayed)
• The most fertile soil is a mix of humus loam

24

• To be available to roots the minerals must be
  released from the soil particles.
• Anions arent bound tight are released w/ease
• Cations are involved in cation exchange roots
  add H ions to soil this displaces cation
  minerals from soil particles into the soil soln

25

• In hydroponic cultures plants are grown in
  mineral solns w/o soil. The soln is aerated to
  provide the roots w/oxygen
• For plants to absorb N it must be changed to NH4
  or NO3.
• N-fixing bacteria convert N2 to NH3 (ammonia),
  then ammnionifying bacteria convert NH3 to NH4.
• Nitrogen fixation- bacteria converting N2 gas
  into ammonia
• NO3 is the form of N that is mainly absorbed by
  plants
• Denitrifying bacteria convert nitrates to N gas

26

• Plant roots of legumes others have nodules that
  are plant cells w/N-fixing bacteria
• Mycorrihizae- symbiotic relationship b/w plants
  and fungi.. It gets sugar from the plant and the
  fungus in return increases the surface area for
  water and mineral uptake and secretes chemicals
  that stimulate root growth and antibiotics for
  protection from bacteria
• The earliest vascular plants did not have roots
  so it is likely that symbiotic fungi aided in
  water mineral absorption

27

• Epiphytes are not parasitic, they just use other
  plants as support they do not get nutrients from
  the host
• Carnivorous plants- photosynthetic but get some N
  other minerals by digesting small animals
• mainly to supplement for low levels of N in the
  soil
• Sustainable agriculture- farming practice that
  uses conservation minded methods

28
CH 38

• Angiosperms other plants undergo an alteration
  of generations in their life cycle, in which the
  diploid plant (sporophyte), produces haploid
  spores by MEIOSIS
• spores develop into male female gametophytes,
  gametophytes develop make gametes (by MITOSIS),
  which may undergo fertilization form new
  sporophytes
• Sporophyte-meiosis-gametophyte-gametes-fertilizati
  on-diploid zygote

29

• In angiosperms, the sporophyte is called the
  dominant generation b/c this is the form of the
  plant that we see.
• The gametophyte is the pollen embryo sac of the
  flower
• Flowers have the gametophytes
• Sepalsprotect flower bud b-4 opening
• petalsattract insects and other pollinators
  w/color and smell

30

• Stamenmale reproductive organs (anther-where
  pollen is released, filament)
• Carpelsfemale reproductive organs (ovary,
  stigma, style)
• Completeall basic sex organs
• Incompletestaminate, carpellate
• Monoecious staminatecarpellate on same flower
• Dioeciousstaminate carpellate flowers on
  separate plants so cannot self-pollinate

31
LE 38-2a
Stigma
Anther
Carpel
Stamen
Style
Filament
Ovary
Sepal
Petal
Key
Receptacle
Haploid (n)
Diploid (2n)
An idealized flower
32

• Sporangia (spore house) of an anther there are
  many diploid microsporocytes, each of which
  undergoes MEIOSIS to produce 4 haploid
  microspores, which become haploid male
  gametophytes
• In the ovary, ovules form, each w/a single
  sporangium. Inside is a single cell
  (megosporophyte) that grows undergoes MEIOSIS
  to make 4 haploid megaspores. (usually only 1
  survives to produce an embryo sac)
• The products of meiosis are spores

33
LE 38-4
Development of a male gametophyte (pollen grain)
Development of a female gametophyte (embryo sac)
Pollen sac (microsporangium)
Mega- sporangium
Micro- sporocyte
Ovule
Mega- sporocyte
MEIOSIS
Integuments
Micropyle
Micro- spores (4)
Surviving megaspore
Each of 4 microspores
Female gametophyte (embryo sac)
MITOSIS
Antipodal cells (3)
Ovule
Generative cell (will form 2 sperm)
Male gametophyte (pollen grain)
Polar nuclei (2)
Egg (1)
Synergids (2)
Integuments
Nucleus of tube cell
20 µm
Key to labels
Ragweed pollen grain (colorized SEM)
Embryo sac
75 µm
Haploid (n)
100 µm
(LM)
Diploid (2n)
(LM)
34

• After fertilization ovules develop into seeds
  ovaries into fruit
• A pollen grain lands on the stigma, germinates
  makes a pollen tube that extends towards the
  ovary.
• 1 sperm fertilizes the egg 2n embryo
• Other sperm combine w/2 polar nuclei to form
  endosperm
• This is double fertilizationresult is a diploid
  embryo triploid endosperm are formed
• pollination brings gametophytes together so
  fertilization can occur

35

• Following fertilization is germination (if the
  seed lands in a good spot to start its new life)
• 1st step in germination is imbibition of water
• pollen grain is to male gametophyte as embryo
  sac is to female gametophyte

36

• Transgenic plants have genes from more than one
  species
• concerns about GM crops are
• allergies,
• effects on non-target organisms,
• hybridization w/wild species,
• long term effects

37
CH 39

• -Signal transduction consists of the plants
  realization of stimuli to its response
• Tropism- plant growth response that causes a
  plant to grow to or away from a stimulus
• Phototropism- growth in response to light
• Gravitropism- growth in response to gravity
• Plants bend toward light b/c of cell expansion
  on the DARK SIDE of the stem

38

• Hormones- chemical messengers
• Hormones make their effect by changing gene
  expression, changing the permeability of the pm
• Animal plant hormones work diff b/c
• Animals move away fast from negative stimuli
  most plants dont
• Plants are much more variable in their morphology
  development than animals

39

• its much more difficult to study plant hormones
  b/c
• The effect are usually b/c of interaction b/w
  hormones
• They are found in small amounts in the plant
• We probably havent found them all yet
• They can cause diff responses in diff plants

40

• proton pumps- lower the pH in the cell wall,
  activating expansins, enzymes that loosen the
  walls fabric then w/cellulose loosened, the cell
  can elongate

41

• Cytokinins
• made in roots travel to other parts of plant
• stimulate cell division growth,
• stimulate germination
• Abscisic acid
• inhibits growth,
• seed dormancy,
• closes stomata during drought
• Gibberellins
• stem elongation,
• fruiting,
• promote seed bud germination,
• flowering leaf growth

42

• Auxins
• promote cell elongation (stem elongation),
• stimulates proton pumps in the pm,
• enhances fruiting (seedless tomatos)
• Brassinosteroids
• inhibit root growth,
• retard leaf abscission
• Ethylene
• fruit ripening,
• apoptosis,
• growth development of plant organs

43

• Photomorphogenesis-describes light effects on
  plant morphology
• Blue red light have greatest effects
• Both are involved in stem elongation
• Phytochromes are pigments that are involved in
  many of the plants responses to light

44

• Circadian rhythms are physiological cycles w/a
  frequency of 24 hours arnt paced by
  environmental variables
• Short day plants need a night that is longer than
  a certain length to flower
• Long-day plants require the most daylight to
  flower
• Day-neutral plants can flower at any time
• It is night length that actually controls it.

45

• Florigen is a flowing signal found in leaves is
  not yet fully understood
• Plants respond to herbivores by
• Attracting predatory animals
• Chemical defenses (toxins)
• Physical defenses (thorns)
• Production of volatile molecules

46

• Plant defenses
• Cells near infection area destroy themselves so
  infection doesnt spread
• Making chemicals to kill pathogens
• Aquiring gene-for-gene recognition to turn on
  proteins to make defenses
• Waxy cuticle that pathogens cant get through
• Cold stress is dealt w/by altering membrane
  composition
• Heat stress-used heat shock proteins, prevent
  denaturing of proteins etc

47

• Essay
• Hormones play important roles in regulating the
  lives of many living organisms.
• a.) For 2 of the following physiological
  responses, Explain how hormones cause the
  response in plants.
• --Increase in height
• --adjustment to change in light
• --adjustment to lack of water
• b.) Describe 2 different mechanisms by which
  hormones cause the effects at the cellular level.

48

• The movement of water through vascular plants in
  important to their survival.
• a.) Explain the mechanism of water movement
  through vascular plants during transpiration.
  Include a discussion of how the anatomy of
  vascular plants the properties of water
  contribute to this process.
• b.) Explain how gas exchange affects
  transpiration
• c.) Describe 2 adaptations that affect the rate
  of transpiration in desert plants.

49

• Flowering plants have evolved various strategies
  for fertilization.
• a.) Describe the process of fertilization in
  flowering plants
• b.) Discuss 2 mechanisms of pollen transfer the
  adaptations that facilitate each mechanism.
• Some species of flowering plants have evolved
  mechanisms to prevent self-fertilization.
• c.) Discuss an evolutionary advantage of
  preventing self-fertilization.
• d.) Describe 2 mechanisms that prevent
  self-fertilization.

50

• Angiosperms (flowering plants) have wide
  distribution in the biosphere and the largest
  number of species in the plant kingdom.
• a.) Discuss the function of 4 structures for
  reproduction found in angiosperms the adaptive
  (evolutionary) significance of each.
• b.) Explain how alternation of generations occurs
  in angiosperms.
• c.) Explain how both male female gametophytes
  are developed in angiosperms

51

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