Plants Flashcards
4 Things Required for Plant Growth
Water (decides plant distribution)
Energy/Light (determines plant architecture)
Gas exchange (photosynthesis during day, respiration at night)
Mineral Nutrition (influences plant health)
Green algae—->land plant progenitors & non-vascular plants—->vascular plants—>seed plants
chlorophyll a and b, stacke membrane in chloroplast, egg and sperm—->cutile, stoma—>vascular tissue for transport and support—> reproduction in dry environments b/c of seeds and pollen
Cell wall
provides structure and protection
Results in lack of mobility of whole organism and seed dispersal
plant adaptive response
growth
so plants need to grow entire life, unlike animals.
Characteristics of Plant Growth
Indeterminate: plant does not grow to a certain size/shape
Reiterative: organized in repeating units
Phyllotaxy
patterns of leaf insertion
opposite/alternate/whorled
Meristems
organized set of undifferentiated cells that divide frequently in an organized fashion.
Define tissue
integrated group of cells with a common structure and form
Differentiated cells
assume specialized structure and function will divide infrequently if at all.
Apical meristems
the topmost meristem
makes avxin which suppressed growth of axillary meristems
controls lengthening/primary growth
SAM
shoot apical meristem
RAM
root apical meristem
New cells below RAM=root cap
New cells above RAM=root; primary lengthening growth
Apical dome
Site of meristem
Has condensed chromosomes
Look for DNA synthesis
Grows upwards and leaves daughter cells behind
Auxiliary Meristems
backup if apical meristem damaged
control secondary/thickening growth
Vascular Cambium
inner ring
makes vascular tissues
New cells inside=xylem
New cells outside=phloem
Cork Cambium
New cells added outside of original cells=periderm (bark)
intercalay/basal meristems
at base of leaves or internodes and add cells in these areas
Advantage of intercalay meristems
safe from grazing animals (not goats though, bastards.)
Dermal layer
outermost layer
“skin”
one cell thick
Cuticle
waxy outer waterproof layer made of cutin
Trichomes
break air motion
prevent water loss
defense
guard cells
surround stomata (breathing holes)
ground tissue
most of cells in plant body
basic cells processes occur (photosynthesis)
3 types: parenchyma, collenchyma, sclerenchyma
Parenchyma
unspecialized
thin walled
soft and fleshy
Collenchyma
thicker but uneven walls
strong flexible tissues like leaf stems (petioles)
example celery stalks
Sclerenchyma
very thick walls
often dead at maturity
example: fibers used in clothing and nut shells/pits
Xylem tissue
contains water conducting cells
dead at maturity
structural support (wood)
Phloem tissues
conducting cells transport food from sources to sinks
Shoots
leaves and stems
autotrophic nutrition
green
dry environments
Roots
heterotrophic nutrition by respiration
moister environments
no cuticle
colorless/no chloroplast
Functions of Roots
anchorage and support
food storage
absorption of water and minerals
Epiphytes
plants that grow on other plants like orchids
examples of tap root systems
carrots potatoes radishes prairie grasses
Root Cap
produces mucilage (slime)-soil lubricant sheds cells that can live in soil
Stele
vascular tissue down center of root
surrounded by meristematic tissue called pericycle
pericycle
meristematic tissue gives rise to root branches which are different from root hairs
root hairs
made of cytoplasm
made of mature cells
die and are replaced quickly
Apoplastic transport
passive transport (diffusion) through cell wall cell walls hydrophilic and filled with pores water, minerals less than 10,000 daltons can easily pass
Apoplasm
all cell walls in a tissue
transport across plasma membrane
via channel
passive or active depending on concentration gradient
required molecular fit with either channel or transporter
symplastic transport
passive
less than 1000 daltons but this is an average
movement in cytoplasm
symplast
all cytoplasm in a tissue
connected through plasmodesmata
monocots
1 seed leaf vascular bundle separated parallel venation no secondary growth flower parts in threes
Dicots
2 seed leaves vascular tissue in rings net venation secondary growth flowering parts in 4s or 5s
Where should cell membrane be?
right before stele for largest capacity of water allowed through
Endodermis
boundary between the cortex and the stele, has casparian strip in it
casparian strip
in the endodermis, waxy barrier that forces stuff to pass through the endodermis plasma membrane
vascular bundle arrangement dicot vs monocot
dicot: cylinder arrangement
monocot: scattered
Purpose vascular system
- thickening, secondary growth
. strengthening-weight bearing (reason for cylindrical arrangement in dicots)
Characteristics xylem conducting cells
- function best when dead
- huge cell walls
- lignin in cell walls-contributes to strength
Parts of the tracheary system
- tracheid
2. vessel elements
Tracheid characteristics
primitive
slanted end walls with pits
gymneosperms have only these
Vessel elements characteristics
evolutionarily newer joined to form vessel end walls dissolve fully or partially through perforation plates form straight tubes more efficient than tracheids
sieve elements
phloem conducting cells
companion cells
provides protiens, ribosomes, metabolic products and other support to sieve tubes
Water potential rule #1
water flows from regions of low solute concentration to regions of high solute concentration (through osmosis0
Water potential rule #2
positive pressure (pushing on solution) can be used to counteract the flow
water potential rule #3
suction/negative pressure can be used to augment/increase the flow (syringe/straw)
water potential equation/components
=pressure contribution (+ or -) –osmotic pressure (always negative but this equation makes up for that)
water potential definition
tendency of water to leave an area so water will always move from high water potential to low water potential
guttation
exudation of xylem sap at tips of vascular plants. happens at night when transpiration does not happen but there is still a push from root pressure
Why is solute potential always negative?
because water flows from high water potential to low water potential. When solute concentration increases, you want the water potential to decrease so water goes there
Why does long distance xylem transport require negative pressure?
there needs to be an additional force pulling water/stuff up tree besides adhesion/cohesion and pressure from the roots. Because the air has a much lower water potential than all parts of the plant, stuff is pulled/sucked up/out of the tree.
Properties of water that facilitate xylem transport
- adhesion: water sticking to hydrophilic surfaces
2. cohesion: tendency of water molecules to stick together
Phloem transport entails what?
Requires positive pressure
drives sugars from source tissues to sink tissues
Low surface area/volume ratio photosynthetic organ set up
used in deserts
minimizes transpiration and water loss
High surface area/volume ration photosynthetic organ set up
in places with good water access
temperate zones
maximum light exposure
Mid surface area/volume ratio photosynthetic organ set up
used in succulent plants
Stomata
breathing holes in cell epidermis
Guard cells control how open and closed stomata are
Palisade mesophyll
densely packed parenchyma
houses chloroplast and receives light
Spongy mesophyll
loosely arranged parenchyma cells
has lots of pockets for gas exchange to occur
Lower epidermis
thinner than upper epidermis
has lots of guard cells and stomata
Two characteristics of guard cells
- radial hoops of cellulose
2. thickening of inside wall (towards stomata)
Stomata in high water conditions
stomata open because water potential inside cell is less than water potential outside
Stomata in low water conditions
stomata close
water potential inside greater than outside
Guard cell mechanisms
change concentration of K+.
- to open stomata, [K+] increased so solute potential decreases and so does total water potential**
- to close stomata, [K+] decreased inside cell so solute potential increased as does total water potential
Leaf water content
if high, stomata open (low [ABA])
if low, stomata close (high [ABA})
happens by hormone signalling of “drought” horomone ABA
[CO2]
stomata open if low
stomata close if high
Effect of light on stomata opening/closing
If perceive blue light, open
if dark, close
Hierarchy of plant needs
water
high low
CO2 closes
high low
light opens
high low
open close
sugar to starch. water potential?
water potential increases
morphological adaptations to dry environments
cactus: leaves are spines
succulents: low SA/volume ratio
trichomes: break air speed, move air away from stomata
Pines: needles, stomata sunken into pites with trichomes
behavioral adaptations to dry environments
desert trees: flip day/night cycles
prairie plants: turn leaves relative to sun
deciduous habit
Biochemical adaptations to dry environments
C4 and CAM plants
C4 photosynthesis
calvin cycle in bundle sheath less water lost when converting carbon dioxide stomata closed for majority of day use lower levels of CO2 tropical grasses, sugar cane, corn
CAM
day/night cycles flipped
stomata open at night, collect CO2
closed during day to restrict water loss
desert plants/plants under severe water stress
Macronutrients
Carbon hydrogen oxygen phosphorus nitrogen sulfur K+: osmotic balance Mg2+: in chlorophyll and for enzymatic activity Ca2+:cellular glue and signalling molecule
Commercial fertilizers
Nitrogen phosphorus potassium
Soil-Mineral-Root relationship
soil is basic, holds acidic minerals
roots acidify soil, neutralizing it
roots absorb freed minerals
Mobile elements
move readily through vascular system
Mg2+
older leaves gives minerals to younger ones
old yellow, new green if difficient
Immobile elements
cells hold on to elements once they are to final destination
FE2+
old leaves green, new yellow if deficiency in plant
Nitrogen Fixation
extremely expensive
turns atmospheric N2 into NH3
done by cyanobacteria and Rhizobium
bacteria legume symbiosis
plant-rhizobium signalling leads to root hair curling
infection thread
bacteria colony
differentiation into bacteriods
O2 is poisonous to bacteria so O2 levels kept low by leg hemoglobin
carnivory
plants eat animals
live in bogs–>acidic, nitrogen deprived environments
Life History Patterns
- annuals: grow and reproduce in single season
- Biennials: grow in one season and reproduce in the next (tap root plants)
- Perennials: live multiple years, spend a fraction of a given year on reproduction (bulbs, trees, shrubs)
Masting
production of massive amounts of fruits/seeds in a season (oaks-acorns, bamboo)
Asexual Reproduction
suitable for stable environments/ones with competition for resources
no meiosis gametes, or sexual fusion
offspring produced by mitosis=clones
examples: strawberries, banyan trees, aspen
totipotent cells
unrestricted developmental potential
can assume any differentiated cell type
Sexual Reproduction
alternation of generations
evolutionarily smarter
two generations of sexual reproduction
- diploid: sporophyte generation (plants produce spores)
2. haploid: gametophyte generation (plants produce gametes
Sexual Plant life cycle
diploid (2N) meiosis produces haploid spores (1N) mitosis to form gametophyte (1N) gametes produces through mitosis sexual fusion to form zygote (2N) diploid adult again
Three parts of flowering plant reproduction
- flower
- double fertilization
- fruits
Flowers
modified shoot for reproduction
product of SAM
Flower development
receptacle: base formed by first cells
sepals: leaf-like. protective covering for bud
Petals: attract pollinators
stamen: functionally male
carpels: functionally female
Complete/incomplete flower
has all 4 flower parts
does not have all 4 flowering parts
Perfect flower/imperfect flower
stamen and carpels
one or the other
Inflorescence
collection of all flowers on a plant
example: corn: tassel flowers have stamen only, ear flowers have carpels only
Parts of Stamen and function if applicable
Filament
anther: under goes meiosis and mitosis to produce pollen
Parts of carpels and function is given
Stigma: receives pollen
Style: transports pollen to ovary
Ovary
Pistel
consists of stigma style and ovary
Ovule
undergoes meiosis and mitosis
houses embryo sac which is multicelluar haploid and produces female gametes (egg)
Pollination
delivery of pollen from anthers to stigma
NOT fertilization
Physical problems of plant reproductions
- dispersal: pollen is non-motile
2. selfing
Solution to dispersal problem
- wind transport
2. pollinator transporters. Food rewards given. Flowers attract them.
Solution to Selfing
- in perfect flowers, pollen and eggs mature at different times
- spacing solution: separate male and female flowers (monecious) or imperfect flowers (diecious)
- biochemical/genetic solution: self-incompatibility
Pollen production
DO NOT UNDERSTAND. LOOK IN YOUR BOOK.
Double fertilization
in flowering angiosperms
consists of 2 fertilization events
1. egg and sperm make zygote (2N) which forms the embryo
2. central cell +sperm–> endosperm (3N)
Whats a seed and whats in it?
fertilized ovule. in angio and gymneosperms
have embryo, nutritive tissue and seed coat
seed functions
dispersal
establishment of seedling
seed features
- produced in large quantities b/c of high death rates
- tissues have low water content (2-10%)
- full of highly concentrated food materials
Angiosperm seeds
- embryo: 2N of new gene combination
- endosperm: 3N of 2 maternal, 1 paternal
- seed coat: 2N of maternal genes
Gymneosperm seeds
embryo: 2N of new gene combination
2. seed coat: 2N of maternal DNA
3. nutritive tissue: 1N
Why are gymniosperm less successful than angiosperm
- fewer protective coverings: ovule on outside of pine cone
- wind pollinated: tons of pollen produced, high cost of production
- one fertilization event: egg+sperm=zygote
- long period from pollination to seed dispersal: up to two years
gymniosperm embryo development process
- pollination
- development of nutritive tissue
- fertilization
- embryo development
angiosperm embryo development process
- pollination
- double fertilization
- embryo and nutritive tissue develop simultaneously.
Endosperm
contributes no cells or genes to new generation
an accessory and nutritive tissue
3N: 2 egg, 1 sperm gene donations
Persistent endosperm
gives nutrients to embryo after germination
example: corn, starch forming plants
Transient endosperm
gives nutrients to embryo before seed shed
in protein forming plants
Fruit development specifically how carpel changes into fruit
ovary wall–>fruit wall
ovule–>seed
egg (fertilized)–>embryo
style–>style
Gravitropism
response to gravity in direction and degrees via directional growth
*positively gravitropic=grows towards gravity (roots)
FUNCTION OF ROOT CAP
*negatively gravitropic=grows away from gravity (shoots)
Phototropic
response to light direction, intensity, and color
+=shoots
-=roots
Thigmotropic
growth response to touch
+=vining, climbing plants (grapes, peas, ivies)
-=roots to avoid obstacles in soil
Statoliths
plastid organelles in root cap with large starch granules that give weight to cell.
believed to be involved in gravitropism
Experiments Touch sensing
seeds on hardened petri dish
incline dish
get wavy roots (wave assay)
Light sensing
involves pigment protein complexes in cytoplasm
blue light and red far red photoreceptors
blue light photoreceptors
reflect yellow
absorb blue
phototropins and cryptochromes
also in guard cells to regulate stomata opening and closing for day-night cycles.
Red-far-red photoreceptors
photochromes
control seed germination, greening of seedlings, flowering response
Inactive (closed kinases) are sensitive to red light
Active (open kinases) are far red sensitive
Classic plant hormones and transport methods
- auxin
- cytokinins
- gibberellins
- abscisic acid
- ethylene
small and travel apoplastically and symplastically.
peptide hormones
defense
brassinosteroids
steroid hormone
cell elongation
dwarf plants don’t have them
oligosaccharins
carbohydrates
in cell wall as a defense response
jasmonic acid
gas
defense response
can signal to surrounding plants
florigen
flowering hormones
maybe small protein that travels through phloem
