chapters 35-39. all plants… multicellular, eukaryotic, autotrophic, alternation of generations
TRANSCRIPT
Plant Structure and Function
Chapters 35-39
Evolution of PlantsAll Plants…• multicellular, eukaryotic, autotrophic, alternation of generations
Alternation of GenerationsSporophyte (diploid)• produces haploid spores via meiosis
Gametophyte (haploid)• produce haploidgametes via mitosis
Fertilization• joins two gametes toform a zygote
Angiosperms
Monocots vs. Dicots• named for the numberof cotyledons present on the embryo of the plant
+ monocots- orchids, corn, lilies, grasses
+ dicots- roses, beans, sunflowers, oaks
Plant MorphologyMorphology (body form)• shoot and root systems + inhabit two environments
- shoot (aerial) + stems, leaves, flowers- root (subterranean) + taproot, lateral roots
• vascular tissues + transport materials between roots and shoots
- xylem/phloem
Plant Anatomy Anatomy (internal structure)• division of labor + cells differing in structure and function
- parenchyma, collenchyma, sclerenchyma (below)- water- and food-conducting cells (next slide)
ParenchymaSt: “typical” plant cellsFu: perform most metabolic functions
CollenchymaSt: unevenly thickened primary wallsFu: provide support but allow growthin young parts of plants
SclerenchymaSt: hardened secondary walls (LIGNIN)Fu: specialized for support; dead
Plant cell types
Parenchyma cells Collenchyma cells
Cell wall
Sclerenchyma cells
Plant cell types• Xylem • Phloem
WATER-CONDUCTING CELLS OF THE XYLEM
Vessel Tracheids
Tracheids and vessels
Vesselelement
Pits
Tracheids
SUGAR-CONDUCTING CELLS OF THE PHLOEM
Companion cell
Sieve-tubemember
Sieve-tube members:longitudinal view
Sieveplate
Nucleus
CytoplasmCompanioncell
Water- and Food-conducting CellsXylem (water)
• dead at functional maturity• tracheids- tapered with pits• vessel elements- regular tubes
Phloem (food)• alive at functional maturity• sieve-tube members-
arranged end to end with sieve plates &Companion cells
Plant TissuesThree Tissue Systems• dermal tissue + epidermis (skin)
- single layer of cells that covers entire body- waxy cuticle/root hairs
• vascular tissue + xylem and phloem
- transport and support• ground tissue + mostly parenchyma
- occupies the space b/n dermal/vascular tissue- photosynthesis, storage, support
Plant GrowthMeristems• perpetually embryonic tissues located at regions of growth + divide to generate additional cells (initials and derivatives)
- apical meristems (primary growth- length) + located at tips of roots and shoots- lateral meristems (secondary growth- girth)
Roots• A root
– Is an organ that anchors the vascular plant– Absorbs minerals and water– Often stores organic nutrients– Taproots found in dicots and gymnosperms– Lateral roots (Branch roots off of the taproot)– Fibrous root system in monocots (e.g. grass)
Figure 35.3
Modified Roots• Many plants have modified roots
(a) Prop roots (b) Storage roots(c) “Strangling” aerial
roots
(d) Buttress roots (e) Pneumatophores
(a) Prop roots (b) Storage roots
Primary Growth of RootsPrimary Growth of Roots• apical meristem + root cap + three overlapping zones
- cell division- elongation- maturation
Stems• A stem is an organ consisting of
– Nodes (could be opposite or alternate)– Internodes
Modified Stems
Rhizomes(d)
Tubers (c)Bulbs
Stolons
(a)
Storage leaves
Stem
Root Node
Rhizome
Root
Buds• An axillary bud
– Is a structure that has the potential to form a lateral shoot, or branch
• A terminal bud– Is located near the shoot tip and causes elongation of a young
shoot
Gardening tip:Removing the terminal bud stimulates growth of axillary buds
Primary Growth in ShootsPrimary Growth in Shoots• apical meristem (1, 7) + cell division occurs + produces primary meristems
- protoderm (4, 8)- procambium (3, 10)- ground meristem (5, 9)
• axillary bud meristems + located at base of leaf primordia • leaf primordium (2, 6) + gives rise to leaves
The leafIs the main photosynthetic organ of most vascular plants
Leaves generally consist ofBlade StalkPetiole
Leaf Morphology• In classifying angiosperms
– Taxonomists may use leaf morphology as a criterion
Petiole
(a) Simple leaf
(b) Compound leaf.
(c) Doubly compound leaf.
Axillary bud
Leaflet
Petiole
Axillary bud
Axillary bud
LeafletPetiole
Modified Leaves
Tendrils
Spines
Storage leaves
Bracts
Reproductive leaves. The leaves of some succulents produce adventitious plantlets, which fall off the leaf and take root in the soil.
Leaf AnatomyEpidermal Tissue• upper/lower epidermis• guard cells (stomata)
Ground Tissue• mesophyll +palisade/spongy parenchyma
Vascular Tissue• veins + xylem and phloem
Keyto labels
DermalGround
Vascular
Guardcells
Stomatal pore
Epidermalcell
50 µm
Surface view of a spiderwort(Tradescantia) leaf (LM)
(b)Cuticle
Sclerenchymafibers
Stoma
Upperepidermis
Palisademesophyll
Spongymesophyll
Lowerepidermis
Cuticle
Vein
Guard cells
Xylem
Phloem
Guard cells
Bundle-sheathcell
Cutaway drawing of leaf tissues(a)
Vein Air spaces Guard cells
100 µmTransverse section of a lilac(Syringa) leaf (LM)
(c)
Leaf Anatomy
Dermaltissue
Groundtissue Vascular
tissue
The Three Tissue Systems: Dermal, Vascular, and Ground
Dermal Tissue
– Protects plant from: • Physical damage• Pathogens
• H2O loss (Cuticle)
Vascular tissue– Carries out long-distance transport of materials
between roots and shoots– Consists of two tissues, xylem and phloem
Ground Tissue– Includes various cells specialized for functions such as
storage, photosynthesis, and support
– Pith = ground tissue internal to the vascular tissue– Cortex = ground tissue external to the vascular tissue
Secondary Growth
Lateral Meristems• vascular cambium + produces secondary xylem/phloem (vascular tissue)• cork cambium + produces tough, thick covering (replaces epidermis)• secondary growth + occurs in all gymnosperms; most dicot angiosperms
The Vascular Cambium and Secondary Vascular Tissue
• The vascular cambium– Is a cylinder of meristematic cells one cell thick– Develops from parenchyma cells
2° Growth
• As a tree or woody shrub ages– The older layers of secondary xylem, the
heartwood, no longer transport water and minerals
• The outer layers, known as sapwood– Still transport materials through the xylem
Cork CambiumPeriderm• protective coat of secondary plant body + cork cambium and dead cork cells
- bark
• cork cambium producescork cells
CHAPTER 36
Plant Transport
MineralsH2O CO2
O2
CO2 O2
H2O Sugar
Light
• A variety of physical processes– Are involved in the different types of transport
Sugars are produced byphotosynthesis in the leaves.5
Sugars are transported asphloem sap to roots and otherparts of the plant.
6
Through stomata, leaves take in CO2 and expel O2. The CO2 provides carbon forphotosynthesis. Some O2 produced by photosynthesis is used in cellular respiration.
4
Transpiration, the loss of waterfrom leaves (mostly through
stomata), creates a force withinleaves that pulls xylem sap upward.
3
Water and minerals aretransported upward from
roots to shoots as xylem sap.
2
Roots absorb waterand dissolved minerals
from the soil.
1 Roots exchange gases with the air spaces of soil, taking in O2 and discharging CO2. In cellular respiration, O2 supports the breakdown of sugars.
7
The Central Role of Proton Pumps
• Proton pumps in plant cells– Create a hydrogen ion gradient– Contribute to membrane potential
CYTOPLASM EXTRACELLULAR FLUID
ATP
H+
H+ H+
H+
H+
H+H+
H+
Proton pump generates membrane potentialand H+ gradient.
–
––
–
– +
+
+
+
+
• Plant cells use energy stored in the proton gradient and membrane potential– To drive the transport of many different cations
+CYTOPLASM EXTRACELLULAR FLUID
Cations ( , for example) are driven into the cell by themembrane potential.
Transport protein
K+
K+
K+
K+
K+ K+
K+
K+
–
–
– +
+
(Membrane potential and cation uptake
–
–
+
+
Figure 37.6b
(b) Cation exchange in soil. Hydrogen ions (H+) help make nutrients available by displacing positively charged minerals (cations such as Ca2+) that were bound tightly to the surface of negatively charged soil particles. Plants contribute H+ by secreting it from root hairsand also by cellular respiration, which releases CO2 into the soil solution, where it reacts with H2O to form carbonic acid (H2CO3). Dissociation of this acid adds H+ to the soil solution.
H2O + CO2 H2CO3 HCO3– +
Root hair
K+
Cu2+
Ca2+
Mg2+
K+
K+
H+
H+
Soil particle
–
–– –
– – ––
–
• Cotransport– A transport protein couples the passage of H+ to
anions
H+
H+
H+
H+
H+
H+
H+H+
H+
H+
H+
H+
NO3–
NO 3 –
NO3
–
NO 3–
NO3
–
NO3 –
–
–
– +
+
+
–
–
– +
+
+
NO3–
Cotransport of anions
H+of through a
cotransporter.
Cell accumulates anions ( , for example) by coupling their transport to theinward diffusion
H+
H+
H+
H+
H+H+
H+
H+ H+
H+
SS
S
S
SPlant cells canalso accumulate a neutral solute,such as sucrose
( ), bycotransporting
down the
steep protongradient.
S
H+
–
–
–
+
+
+
–
–
++–
H+ H+S+
–Contransport of a neutral solute
• Cotransport– Is also responsible for the uptake of sucrose by plant
cells
• Water potential– Is a measurement that combines the effects of solute
concentration and pressure– Determines the direction of movement of water
• Water– Flows from regions of high water potential to regions
of low water potential
Quantitative Analysis of Water Potential• The addition of solutes
– Reduces water potential
0.1 Msolution
H2O
Purewater
(a)
• Negative pressure– Decreases water potential
H2O
(d)
• Application of physical pressure– Increases water potential
H2O
(b)
H2O
(c)
Aquaporin Proteins and Water Transport
• Aquaporins– Are transport proteins in the cell membrane that
allow the passage of water
– Do not affect water potential
Movement of fluid in the xylem & phloem is driven by pressure differences at opposite ends of the xylem vessels and sieve tubes
Fluid Movement
• Water and minerals ascend from roots to shoots through the xylem
• Plants lose an enormous amount of water through transpiration, the loss of water vapor from leaves and other aerial parts of the plant
• The transpired water must be replaced by water transported up from the roots
Pushing Xylem Sap: Root Pressure
• At night, when transpiration is very low– Root cells continue pumping mineral ions into the
xylem of the vascular cylinder, lowering the water potential
• Water flows in from the root cortex– Generating root pressure
• Root pressure sometimes results in guttation
Transpiration produces negative pressure (tension) in the leaf
Which exerts a pulling force on water in the xylem, pulling water into the leaf
The transpirational pull on xylem sapIs transmitted all the way from the leaves to the root tips and even into the soil solutionIs facilitated by cohesion and adhesion
• The stomata of xerophytes– Are concentrated on the lower leaf surface– Are often located in depressions that shelter the
pores from the dry wind
Lower epidermaltissue
Trichomes(“hairs”)
Cuticle Upper epidermal tissue
Stomata 100 m
TranslocationIs the transport of organic nutrients in the plant
Phloem sapIs an aqueous solution that is mostly sucroseTravels from a sugar source to a sugar sink
Translocation through Phloem
A sugar sourceIs a plant organ that is a net producer of sugar, such as mature leaves
A sugar sinkIs an organ that is a net consumer or storer of sugar, such as a tuber or bulb
Sugar Source & Sink
TranspirationLab
Control of TranspirationPhotosynthesis-Transpiration Compromise• guard cells help balance plant’s
need to conserve water with its requirement for photosynthesis
Stomatal closing • 1. Potassium ions move out of the vacuole and out of the cells. • 2. Water moves out of the vacuoles, following potassium ions. • 3. The guard cells shrink in size. • 4. The stoma closes.
Stomatal opening
1. Potassium ions move into the vacuoles.
2. Water moves into the vacuoles, following potassium ions.
3. The guard cells expand.
4. The stoma opens.
Plant nutrition
• Chapter 37
Plant NutritionWhat does a plant need to survive?• 9 macronutrients, 8 micronutrients + macro- required in large quantities
- C, H, N, O, P, S, K, Ca, Mg + micro- required in small quantities
- Fe, Cl, Cu, Mn, Zn, Mo, B, Ni + usually serve as cofactors of enzymatic reactions
• The most common deficiencies– Are those of nitrogen, potassium, and phosphorus
Phosphate-deficient
Healthy
Potassium-deficient
Nitrogen-deficient
Hydroponics
• Remove only one macronutrient to see effects on plant
SoilTexture and Composition• texture depends on size of particles + sand-silt-clay
- loams: equal amounts of sand, silt, clay
• composition + horizons
- living organic matter- A horizon: topsoil, living organisms, humus- B horizon: less organic, less weathering than A horizon- C Horizon: “parent” material for upper layers
• soil conservation issues + fertilizers, irrigation, erosion
Soil
• A mixture of mineral particles, decaying organic material, living organisms, air, and water, which together support the growth of plants
Aeration
Soil Bacteria and Nitrogen Availability• Nitrogen-fixing bacteria convert atmospheric N2
– plants absorb ammonium (NH4+), nitrate (NO3
-)
Atmosphere
N2
Soil
N2 N2
Nitrogen-fixingbacteria
Organicmaterial (humus)
NH3
(ammonia)
NH4+
(ammonium)
H+
(From soil)
NO3–
(nitrate)Nitrifyingbacteria
Denitrifyingbacteria
Root
NH4+
Soil
Atmosphere
Nitrate and nitrogenous
organiccompoundsexported in
xylem toshoot system
Ammonifyingbacteria
Nutritional AdaptationsSymbiotic Relationships• symbiotic nitrogen fixation + Legume root nodules contain bacteroids (Rhizobium bacteria)
- mutualistic relationship - Crop rotation (Legumes • mycorrhizae + symbiotic associations of fungi and roots
- mutualistic relationship
• parasitic plants + plants that supplement their nutrition from host
- mistletoe, dodder plant, Indian pipe• carnivorous plants + supplement nutrition by digesting animals
Mycorrhizae and Plant Nutrition• Mycorrhizae
– Are modified roots consisting of mutualistic associations of fungi and roots
• The fungus– Benefits from a steady supply of sugar donated
by the host plant
• In return, the fungus– Increases the surface area of water uptake and
mineral absorption and supplies water and minerals to the host plant
• Unusual nutritional adaptations in plants
Staghorn fern, an epiphyte
EPIPHYTES
PARASITIC PLANTS
CARNIVOROUS PLANTS
Mistletoe, a photosynthetic parasite Dodder, a nonphotosynthetic parasite
Host’s phloem
Haustoria
Indian pipe, a nonphotosynthetic parasite
Venus’ flytrapPitcher plants Sundews
Dodder
Phytoremediation
• Poplars remove nitrates• Mustard removes uranium
Pesticide Levels (ppb) inGround Water Before & After Phytoremediation Activities
Wetlands
Uptake of Soil SolutionSymplastic Route• continuum of cytosol basedon plasmodesmata
Apoplastic Route• continuum of cell walls andextracellular spaces
Lateral transport of soilsolution alternates betweenapoplastic and symplastic routes until it reaches theCasparian strip
Casparian StripA belt of suberin (purple) that blocks the passage of water and dissolved minerals.
PLANT REPRODUCTIONChapter 38
Plant ReproductionSporophyte (diploid)• produces haploid spores via meiosis
Gametophyte (haploid)• produce haploidgametes via mitosis
Fertilization• joins two gametes toform a zygote
• An overview of angiosperm reproductionAnther attip of stamen
Filament
AntherStamen
Pollen tube
Germinated pollen grain(n) (male gametophyte)on stigma of carpel
Ovary (base of carpel)
Ovule
Embryo sac (n)(female gametophyte)
FERTILIZATIONEgg (n)
Sperm (n)
Petal
Receptacle
Sepal
Style
Ovary
Key
Haploid (n)
Diploid (2n)
(a) An idealized flower.
(b) Simplified angiosperm life cycle.See Figure 30.10 for a more detailedversion of the life cycle, including meiosis.
Mature sporophyteplant (2n) withflowers
Seed(developsfrom ovule)
Zygote(2n)
Embryo (2n)(sporophyte)
Simple fruit(develops from ovary)
Germinatingseed
Seed
CarpelStigma
Mechanisms That Prevent Self-Fertilization
Stigma
Antherwith
pollen
Stigma
Pin flower Thrum flower
The most common anti-selfing mechanism in flowering plantsIs known as self-incompatibility, the ability of a plant to reject its own pollen
Preventative Selfing
• Some plants– Reject pollen that has an S-gene matching an
allele in the stigma cells
• Recognition of self pollen– Triggers a signal transduction pathway leading
to a block in growth of a pollen tube
Double FertilizationDouble Fertilization• pollen grain lands on stigma + pollen tube toward ovule + both sperm discharged down the tube
- egg and one of the sperm produce zygote
- 2 polar nuclei and sperm cell produce endosperm
+ ovule becomes the seed coat + ovary becomes the fruit
Seed Structure and Development
Foliage leaves
Cotyledon
Hypocotyl
Radicle
Epicotyl
Seed coat
Cotyledon
Hypocotyl Cotyledon
Hypocotyl
• The radicle– Is the first organ to emerge from the germinating seed
• In many eudicots– A hook forms in the hypocotyl, and growth pushes the
hook above ground
• Monocots– Use a different method for breaking ground when they
germinate
• The coleoptile– Pushes upward through the soil and into the air
Foliage leaves
ColeoptileColeoptile
Radicle
PLANT RESPONSES TO INTERNAL AND EXTERNAL SIGNALS
Chapter 39
Tropisms
• Growth toward or away from a stimulus
• Gravitropism (Gravity)• Phototropism (Light)• Thigmotropism (Touch)
Etiolation
• The stems of plants raised in the dark elongate much more rapidly than normal, a phenomenon called etiolation.
Figure 39.3
CELLWALL
CYTOPLASM
1 Reception 2 Transduction 3 Response
Receptor
Relay molecules
Activationof cellularresponses
Hormone orenvironmentalstimulus
Plasma membrane
Signal Transduction Pathway
Plant hormones help coordinate growth, development, and responses to stimuli
• Hormones– Are chemical signals that coordinate the different parts of
an organism
Photoperiod, the relative lengths of night and day+ Is the environmental stimulus plants use most often to detect the time of year