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9.1 STRUCTURE AND FUNCTION ARE CORRELATED IN THE XYLEM OF PLANTS
9.2 TRANSPORT IN THE PHLOEM OF PLANTS
9.3 PLANTS ADAPT THEIR GROWTH TO ENVIRONMENTAL CONDITIONS
9.4 REPRODUCTION IN FLOWERING PLANTS IS INFLUENCED BY THE BIOTIC AND ABIOTIC ENVIRONMENT
plants are extremely important, produce oxygen and carbohydrates while absorbing carbon dioxide
removal of carbon dioxide important because of global warming
9.1 TRANSPORT IN THE XYLEM OF PLANTS
UNDERSTANDINGS:
TRANSPIRATION IS THE INEVITABLE CONSEQUENCE OF GAS EXCHANGE IN THE LEAF
PLANTS TRANSPORT WATER FRM THE ROOTS TO THE LEAVES TO REPLACES LOSSES FROM TRANSPIRATION
THE COHESIVE PROPER OF WATER AND THE STRUCTUVE OF THE XYLEM VESSELS ALLOW TRANSPORT UNDER TENSION
THE ADHESIVE PROPERY OF WATER AND EVAPORATION GENERATE TENSION FORCES IN LEAF CELL WALLS
ACTIVE UPTAKE OF MINERAL IONS IN THE ROOTS CAUSES ABSORPTION OF WATER BY OSMOSIS
water is lost in the form of a gas from the leaf through openings called stoamata
transpiration is the term given to the loss of water vapour from leaves and other aerial parts of the plant
water lost from upper structures must be replaced by water absorption
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leaves are main plant organs involved in photosynthesis
consist of flattened portion called blade and stalk called petiole
layer of wax called cuticle as outermost layer, protects plant against WATER LOSS and INSECT INVASION
if no cuticle, outermost layer is EPIDERMIS layer
like stems/roots, leaves have vascular tissue including xylem and phloem
xylem brings water to leaves, and phloem carries products of photosynthesis to rest of lant
xylem and phloem occur together in dense vascular bundles
upper region of leaf has densely packed region of cells, called palisade mesophyll
cells contain large number of chloroplasts for photsynthesis
bottom portion is spongy mesophyll, loosely packed cells with few chloroplasts
air spaces support gas exchange surfaces
stomata occur on bottom surface of leaves
guard cells control opening and closing of stoamata
palisade mesophyll located at surface since lots of light available
veins distributed throughout leaf to transpot materials, occur in middle of leaf so close to all cells
spongy mesophyll near stomata for gas exchange
stomatal pores on bottom so they receive less light, loser temp, less water loss, under epidermis thinner cuticle as a result
transpired water needs to be replaced by intake of water at roots
continuous stream, stream of transpiration
this stream provides minerals as well as water for photosynthesis, water lost is IMPORTANT IN COOLING LEAVES AND STEMS
transport of water is hard (height), thats why xylem is there
xylem SUPPORTS PLANT and CARRIES WATER
xylem composed of many cell types, main ones TRACHEID and VESSEL ELEMENTS
tracheids DEAD CELLS that taper at ends and connect to each other for a continuous column
vessels most important, are dead cells, thick lignified secondary walls
secondary walls often interrupted by primary walls, primary walls include pores that allow water to move laterally
vessel elements attached at ends for continuous columns, like tracheids
ends of vessels have perforations, allowing water to move freely
ancient flowering plants only had tracheids, most modern ones only have vessel elements, they appear to be more efficient in water transport
stomata can only be closed on a short term basis, as CO2 must enter mesophyll region for photosynthesis
stomata open and close because of changes in turgor pressure of guard cells
their thickness is uneven, and taking in water opens the stomata
losing water closes it
transfer of water in guard cells is due to transport of potassium ions
blue part of light triggers ATP to transport potassium into the cell, then osmoses water in
then they passively leave and the water does too
plant hormone abscisic acid causes K ions to diffuse rapidly out, and so stomatas close
hormone produced during water drought
other factors such as CO2 and circadian rhythms affect too
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process of transpiration
spaces in leaf have high conc. of water vapour, it moves to atmosphere where there is a lower gradient
water lost is replaced from the vessels in the air spaces of leaf
cohesion is hydrogen bonds between water molecules, adhesion is hydrogen bonds and sides of vessels, adhesion counteracts gravity
tension occurs as cohesion and adhesion maintain columns
main function of roots is to provide mineral ion and water uptake (ALSO ANCHORING THE PLANT)
roots are efficient because of extensive branching pattern, and specialized epidermal structures called ROOT HAIRS
root hairs (villi-esque) increase surface area for water and minerals to be absorbed, by a factor of nearly three
root cap is hella important as it protects apical meristem during primary growth of root through soil
three regions are zone of maturation, zone of elongation, zone of cell division (corresponds with M phase of cell cycle)(edited)
root hairs have higher solute concentration so water moves in
mineral ions are essential, three major processes allow for them to pass from soil to root
diffusion of ions and mass flow of water carrying these ions
action of fungal hyphae
active transport
reasons for atp: too many ions, too big ions
potassium ions specifically move through potassium channels
high concentration of minerals increases osmosis of water
light speeds up transpiration by warming leaf and opening stomata
humidity lowers transpiration because of grandient
wind increases rate of transpiration as it blows away vapour
temperature increases transpiration since more water evaporates
if water intake at roots is low, turgor loss happens and stomata close, transpiration decreases
co2 cause guard cells to lose turgot and close tomata
xerophytes and plants adapted to dry climates, their adaptations include
SMALL THICK LEAVES WHICH REDUCE SURFACE AREA
REDUCED NUMBER OF STOMATA
STOMATA LOCATED IN PITS
THICKENED CUTICLE
HAIR LIKE CELLS TO TRAP WATER VAPOUR
MANY PLANTS BECOME DORMANT IN DRIEST MONTHS
CACTI STORE WATER, CALLED SUCCULENTS
CAN USE ALTERNATIVE PHOTOSYNTHETIC STRATS, CAM PLANTS WHICH CLOSE STOMATA DURING DAY AND TAKE CO2 DURING NIGHT AND C4 THAT TAKE CO2 HELLA FAST
halophytes are plants adapted to salty climates
MANY ARE SUCCULENT, DILUTING SALT CONCENTRATIONS
CAN SECRETE SALT THROUGH GLANDS (E.G. MANGROVE)
CAN COMPARTMENTALIZE NA AND CL IN VACUOLES, TO PREVENT NACL TOXICITY
SUNKEN STOMATA
THICKENED LEAVES
REDUCED SURFACE AREA
BOTH CAN ALSO CLOSE STOMATA USING GUARD CELLS
9.2 TRANSPORT IN THE PHLOEM OF PLANTS
UNDERSTANDINGS:
PLANTS TRANSPORT ORGANIC COMPOUNDS FROM SOURCE TO SINKS
INCOMPRESSIBILITY OF WATER ALLOWS TRANSPORT ALOJNG HYDROSTATIC PRESSURE GRADIENTS
ACTIVE TRANSPORT LOADS ORGANIC COMPOUNDS INTO PHLOEM SIEVE TUBES AT SOURCE
HIGH CONCENTRATIONS OF SOLUTES IN THE PHLOEM AT THE SOURCE LEAD TO WATER UPTAKE BY OSMOSIS
RAISED HYDROSTATIC PRESSURE CAUSES CONTENTS OF PHLOEM TO FLOW TOWARDS SINKS
organic molecules move in plants via phloem
phloem is made up of living cells, xylem is not
phloem is made up of mostly sieve tube members and companionc ells
sieve tube members are connected by sieve plates to form sieve tubes
often referred to as sieve elements
sieve tubes have pores that allow movement of water and dissolved organic molecules
companion cells connected to sieve tube members my plasmodesmata
xylem cells conduct water and minerals only upwards from roots, phloem cells transport in various directions
direction on movement is based on SOURCE TO SINK
a source is an organ that is a net producer of sugar, leaves being primary sources
sink is a plant that uses or stores sugar, so roots, buds, stems ,seeds, fruits
tubers or bulbs can be both structures, as they break down starch to provide sugar but also are sources depending on season
movement of organic molecules is called translocation
organic molecules are dissolved in water and it is referred to as phloem sap
include:
sugars
amino acids
plant hormones
RNA molecules
phloem sap can move as fast as 1mph
process is this
SUGAR LOADED INTO SIEVE TUBE AT SOURCE, REDUCING RELATIVE WATER CONCENTRATION
HYDROSTATIC PRESSURE CAUSES WATER TO OSMOSE ALONG WITH SUGAR
PRESSURE DIMINISHED BY REMOVAL OF SUGAR AT SINK, CHANGED INTO STARCH, INSOLUBLE SO NO OSMOTIC EFFECT
XYLEM RECYCLES RELATIVELY PURE WATER
loading of sugar is thanks to active transport
active transport is chemiosmotic process using pumps and specialized membrane proteins called cotransport proteins that allow for passive and active transport
companion cells are involved too
transprot is passive, loading and removal is all that requires energy
9.3 GROWTH IN PLANTS
UNDERSTANDINGS:
UNDIFFERENTIATED CELLS IN MERISTEMS OF PLANTS ALLOW INDETERMINATE GROWTH
MITOSIS AND CELL DIVISON IN THE SHOOT APEX PROVIDE CELLS NEEDED FOR EXTENSION OF STEM AND DEVELOPMENT OF LEAVES
PLANT HORMONES CONTROL GROWTH IN SHOOT APEX
PLANT SHOOTS RESPOND TO THE ENVIRONMENT BY TROPISMS
AUXIN EFFLUX PUMPS CAN SET UP CONCENTRATION GRADIENTS OF AUXIN IN PLANT TISSUE
AUXIN INFLUENCES PLANT GROWTH RATES BY CHANGING PATTERN OF GENE EXPRESSION
most plants have three types of tissue:
dermal tissue, outer covering that protects against physical agents and prevents water loss
ground tissue, consists of thinwalled cells that store, photosynthesize, support, and secrete
vascular tissue, xylem and phloem that carry out conduction of water and minerals and nutrients and provide support
all derived from meristematic tissue
meristematic tissue is composed of aggregates of small cells that function as stem cells in animals
planths differ from animals as they show growth throughout their life, called indeterminate growth
animals exhibit determinate growth, meaning it ceases after a certain size
apical meristem is at tips of roots and stems, also primary meristem, known as shoot apex
produces new tissue and causes primary growth with mitosis and cell division
growing stem increases exposure to light and CO2
lateral meristems cause growth of thickness
referred to as secondary growth
two types of lateral meristems:(edited)
vascular cambium, produces secondary vascular tissue and lies between xylem and phloem
produces secondary xylem (wood) and phloem
cork cambium, which occurs within bark and produces cork cells
development of plants is affected by:
environmental factors (day length and water)
receptors
genetic makeup
hormones (chemical messengers)
cells affected by hormones are called target cells
tropisms are growth in response to stimuli, positive (towards) negative (away)
gravity, touch, and chemicals
phototropism is positive for stems, negative for roots
AUXIN PRODUCED ON SIDE OF LIGHT
MOVED BY EFFLUX PUMP ACTION TO OTHER CELLS (AUXIN INFLUX)
AUXIN COMBINES WITH RECEPTOR TO TAKE IN H+ IONS
DROP PH
WEAKEN CELL WALLS
ELONGATE
auxins involved in stimulation of meristems, differentiation, development
9.4 REPRODUCTION IN PLANTS
UNDERSTANDINGS:
FLOWERING INVOLVES A CHANGE IN GENE EXPRESSION IN THE SHOOT APEX
THE SWITCH TO FLOWERING IS A RESPONSE TO THE LENGTH OF LIGHT AND DARK PERIODS IN MANY PLANTS
SUCCESS IN PLANT REPRODUCTION DEPENDS ON POLLINATION, FERTILIZATION, AND SEED DISPERSAL
MOST FLOWERING PLANTS USE MUTUALISTIC RELATIONSHIPS WITH POLLINATORS IN SEXUAL REPRODUCTION
any plant with a flower is an angiosperm
most coevolved
two classes of angiosperms:
monocots and dicots
monocots:
parallel venation
flowers in 3s
seeds have one cotyledon (seed leaf)
random vascular bundles
fibrous root system
one opening pollen grain
dicots:
netlike venation
flowers in 4s and 5s
seeds have two cotyledons
ringed vascular bundles
taproot in roots
3 openings in pollen grain
plants alternate generations (gametophyte, haploid) and (sporophyte, diploid)
gametophyte produces plant gametes
sporophyte produces spores, both by meiosis
when pollen hits stigma, it germinates down style and has nucleus in it
forms a zygote
seed structure:
testa is tough outer coat
cotyledons are seed leaves (nutrient storage)
micropyle (scar opening for pollen)
embryo root/shoot (where new plant occurs)
after seed is formed, dehydration occurs, dormancy period, and then gets triggered by water, oxygen, or temperature, or scratches, or fire
germination of a seed:
absorbs water
release of gibberelin
gibberelin produces amylase, hydrolyses starch into maltose
maltose made into glucose, for cellular respiration
glucose also made into cellulose
IN LIGHT PR IS MADE INTO PFR
IN NIGHT, PFR IS SLOWLY MADE INTO PR
REMAINING PFR AT END OF NIGHT DETERMINES FLOWERING