Stomata w/in epidermis
Jan 11, 2016
Stomata w/in epidermis
LE 36-15a
Cells turgid/Stoma open
Changes in guard cell shape and stomatal opening and closing(surface view)
Radially orientedcellulose microfibrils
Vacuole
Cell wall
Guard cell
Cells flaccid/Stoma closed
May have up to 20K/cm2
Global warming has caused a decrease in
their number
LE 36-15b
• Decreased CO2
• Blue light: triggers H+ pumps (moves H+ out & K+ in)• Circadian rhythms• Temperature
• H2O availability/humidity
• ABA: Abscisic Acid – made in roots in response to H2O deficiency, stress hormone, close stomata
Cells turgid/Stoma open
Role of potassium in stomatal opening and closing
Cells flaccid/Stoma closed
H2O
H2O
H2OH2O
H2O
H2O
H2O
H2O
K+
LE 36-12
Upperepidermis
MesophyllAir
space
Cuticle
Lowerepidermis
Cuticle CO2 O2 CO2Xylem
O2
Stoma
Evaporation
EvaporationWater film
Airspace
Cytoplasm
Cell wall
Vacuole
Air-waterinterface
High rate of transpiration
Low rate of transpiration
= –10.00 MPa = –0.15 MPa
Cell wall
Airspace
Palisade
spongy
phloem
Leaves
• The leaf is the main photosynthetic organ of most vascular plants
• Many leaves are modified for various functions• http://www.arkive.org/venus-flytrap/dionaea-muscipula/video-00.html
http://www.youtube.com/watch?v=trWzDlRvv1M
Xerophytes• Reduced leaves• Thick, waxy cuticle• Decrease # stomata• Stomata in pits surrounded by hairs to reduce air flow/tran• Deep roots• Water storage tissue• Short life cycles,• dormant seeds• Smaller• Pep carboxylase & bundle
sheath cells
LE 36-16
100 µm
Halophytes
• Leaves are reduced to small scaly structures or spines• Shed leaves when water is scarce and stem becomes
green and takes over photosynthesis when leaves are absent
• Water storage structures develop in the leaves• Thick cuticle and multiple layered epidermis• Sunken stomata• Long roots, in search of water• Structures for removing salt build-up
LE 35-10
Shoot apicalmeristems(in buds)
Vascularcambium
Corkcambium
Lateralmeristems
Primaryphloem
Periderm
Corkcambium
Secondaryxylem
Primaryxylem
Pith
Pith
Cortex
Secondary growth in stems
Secondaryphloem
Vascular cambium
Primary phloem
Primary xylem
Cortex
Primary growth in stems
Epidermis
Root apicalmeristems
Tracheids
Spiral bands of lignin for supportXylem is nonliving when plant is mature
Living tissue, membranes maintain sucrose concentrations
LE 35-16
Key
Dermal
Ground
Vascular
Epidermis Cortex
A eudicot (sunflower) stem. Vascular bundles form a ring. Ground tissue toward the inside is called pith, and ground tissue toward the outside is called cortex. (LM of transverse section)
XylemPhloem
Pith
Vascularbundles
Epidermis
Vascularbundles
1 mm
Sclerenchyma(fiber cells)
Ground tissueconnectingpith to cortex
Ground tissue
A monocot (maize) stem. Vascular bundles are scattered throughout the ground tissue. In such an arrangement, ground tissue is not partitioned into pith and cortex. (LM of transverse section)
1 mm
Dicot stem cross section
LE 35-19
Vascular cambium
Types of cell division
Accumulation of secondary growth
LE 35-18aPrimary and secondary growth in a two-year-old stem
Epidermis
Cortex
GrowthXylemray
Vascularcambium
Primaryphloem
Pith
Primaryxylem Phloem ray
EpidermisCortex
Vascular cambiumPrimary phloem
Pith
Primary xylem
Vascular cambium
Primary phloem
Primaryxylem
Secondary phloem
Secondary xylem
First cork cambium Cork
Growth
Vascular cambium
Primary phloem
Secondary phloem
Secondary xylem
Periderm(mainly corkcambiaand cork)
Primary xylem
Pith
Vascular cambium
Secondary phloem
Secondaryxylem (twoyears ofproduction)
Cork
Bark
Layers ofperiderm
Most recentcork cambium
LE 35-18b
0.5 mm
Vascular cambiumSecondary phloem
Secondaryxylem
Transverse sectionof a three-year-old Tilia (linden)stem (LM)
Late woodEarly wood
0.5 mm
Cork cambium
Cork
Periderm
Xylem rayBark
Tree Age
LE 35-20
Growth ring
Vascularray
Secondaryxylem
Heartwood
Sapwood
Vascular cambium
Secondary phloem
Layers of periderm
Bark
No H2O transport
Transport H2O
Heartwood darker due to resins which clog pores to protect from insects
Girdled Trees
Roots
Roots and fungi form mycorrhizae, symbiotic structures consisting of plant roots united with fungal hyphae
Root Hairs
LE 35-12
Key
Dermal
Ground
Vascular
Epidermis
Root hair
Cortex Vascular cylinder
Zone ofmaturation
Zone ofelongation
Zone of celldivision
Apicalmeristem
Root cap
100 µm
Root Growth time lapse
LE 35-13
Key
Dermal
Ground
Vascular
Epidermis
Cortex
Vascular cylinder
Transverse section of a typical root. In the roots of typical gymnosperms and eudicots, as well as some monocots, the stele is a vascular cylinder consisting of a lobed core of xylem with phloem between the lobes.
100 µm
Endodermis
Core ofparenchymacells
Pericycle
Xylem
Phloem
Endodermis
Pericycle
Xylem
Phloem
50 µm
100 µm
Transverse section of a root with parenchyma in the center. The stele of many monocot roots is a vascular cylinder with a core of parenchyma surrounded by a ring of alternating xylem and phloem.
Active Transport of Minerals in Roots
• Solutes in roots greater than in soil due to active transport
• Protein pumps for different ions
• Mycorrhizae of fungus help absorb minerals from soil particles to root (mutualistic)
LE 36-8b
Transmembrane route
Key
Symplast
Apoplast
Symplastic route
Transport routes between cells
Apoplastic route
Apoplast
Symplast
Symplastic route: via the continuum of cytosolApoplastic route: via the the cell walls and extracellular spaces
LE 36-9Casparian strip
Endodermal cellPathway alongapoplast
Pathway throughsymplast
Casparian strip
Plasmamembrane
Apoplasticroute
Symplasticroute
Roothair
Vessels(xylem)
Cortex
EndodermisEpidermis Vascular cylinder
Media
Transport in root
Minerals from soil
LE 36-18
Vessel(xylem)
Sieve tube(phloem)
Sucrose
Source cell(leaf)
H2O
H2O
Sucrose
Sink cell(storageroot)
H2O
Pre
ssu
refl
ow
Tra
nsp
irat
ion
stre
am
Companion cell
Media: Phloem transport spring/
summer
Sucrose is carb transported because it isn’t easily metabolized by plant during transport
Osmotic pressure: bulk flow
Using the apoplastic route to load sucrose into the phloem seive- tubes with the help of companion cells. Concentration gradient of sucrose is established by active transport. H+ is transported out of companion cells using ATP, build-up of H+ flows down concentration gradient through a co-transport protein which carries the sucrose in
Some plants just use symplastic route
What organelle is common in companion cells? Why?Lots of in folding of plasma membrane of companion cell into sieve tube cell, why?For symplastic route, there must be many of these between companion and sieve tube cells?Rigid cell walls of sieve tube cells allow for establishment of pressure necessary to achieve flow of phloem
Aphids & whitefly have special stylets that can penetrate plant tissues to reach phloem. Experiment anaesthetized aphid and stylet is severed (b). Phloem continues to flow out of stylet (e) and both rate of flow and composition of sap can be analyzed by looking at radioactively labelled CO2. The closer to the sink, the slower the rate of phloem flow.
Phototropism
Sumanas animation
Auxin• Discovered indirectly in the study of phototropism• Produced in apical meristem; moves downward• Influences cell growth by changing pattern of gene
expression to produce PIN3 transporter proteins which transport auxin to where growth is needed
• Promotes:– Stem elongation through acid growth hypothesis cell
expansion– Root growth and development: used w/ cuttings– Fruit development: stimulates seedless tomato plants
w/o fertilzation
LE 39-8a
Cross-linkingcell wallpolysaccharides
Cell wallenzymes
Microfibril
Expansin
CELL WALL
Plasma membrane
CYTOPLASM
ATP
Acid Growth Hypothesis:Auxin stimulates movement of H+ into cell wall which breaks down cellulose, increases osmosis, cells expand
Gravitropism
• Gravity causes statoliths to accumulate on lower side of cells.
• PIN3 transporter proteins direct auxin to bottom of cells
• High auxin inhibits root cell elongation so top cells elongate at higher rate than bottom cells, so root bends downward
Micropropagation of plants using tissue from shoot apex, nutrient agar
gels & growth hormones.• In vitro• Identify stock plant w/
desirable traits• Sterilize plant tissue from
stock plant, cut into explants• Explant placed into sterilized
growth media w plant hormones
• Equal amts of auxin & cytokinins form undifferentiated mass = callus
Depends on totipotency of plants: ability to differentiate into any plant part
Growth medium w/ 10X more auxin than - cytokinins – promotes rooting
If ratio of auxin to cytokinin is less than 10:1 – promotes shoots
Once both develop cloned plant is transferred to soil.
Micropropagation for rapid bulking up of new varieties, production of virus-free strains of existing
varieties and propagation or orchids and other rare species
• Apical meristem usually free of viruses
• Fast process, takes up less space
• Orchid seeds are hard to germinate
• Plantlets can be stored in liquid nitrogen
• Propagate rare species and plant in wild habitat