Plant form, function, and physiology Flashcards
what are land plants?
monophyletic
Where are they descended from?
green algae
land plants are divided into what 2 groups?
- bryophytes
- vascular plants
bryophytes characteristics?
- lack root
- rely on surface water for photosynthesis and reproduction
- many are desiccation tolerant
vascular plants characteristics
- desiccation
- can pull water from soil via transpiration
- ability to control water uptake/loss
what do land plants require?
light, CO2, water, and mineral nutrients
(morphological) Land plants go through adaptations to obtain resources from ______ and ______ the ground.
above and below
3 main plant tissues (leaves)
- epidermis
- mesophyll
- veins
what are the air spaces within leafs connected to air called?
pores, stomata
what is transpiration?
the evaporative loss of water vapour from leaves
how does CO2 move into leaves?
Diffusion
what is diffusion?
excessive loss of water
where does diffusion happen/go through and what is it driven by?
stomata and it is driven by Concentration Gradient
how do plants deal with transpiration?
leaves have a waxy cuticle on the outer surface (epidermis) which helps with limiting water loss and co2 diffusion
Characteristics of stomata
- hydromechanical valve
- each stoma has 2 guard cells surrounding a pore
Guard cells
- shrinks and swells
- ## at resting state, It is closed
solute concentration (guard cells)
- Increase solutes via active
transport to increase water
volume - Decrease solutes to
decrease water volume
CO2 moves from an area of ___ concentration to into an area of ____ concentration
high, low
CO2 moves into photosynthesis and ____come out
O2
Stomata open and close in
response to factors that affect?
CO2 uptake and water loss
light stimulates stomata to?
open
High levels of CO2 inside leaf cause
stomata to?
close
During drought conditions, abscisic
acid is upregulated and causes
stomata to?
close
what does CAM do?
helps prevent water loss
what does temporal pathway do (CAM)
only opens stomata at night
where can CAM be found?
In dry places like deserts and among epiphytes
what are epiphytes
they are plants that grow on other plant branches for support
when is stomata closed CAM
during daytime photosynthesis
when is stomata open CAM
during night time respiration
CO2 converted and stored as (cam)?
4-carbon malic acid in
vacuoles
what is PEP carboxylase?
Enzyme that catalyzes the addition
of bicarbonate (HCO3-) to
phosphoenolpyruvate (PEP)
what does a PEP carboxylase for?
4 carbon organic acid but malic acid when it is in vacuole
What is daytime photosynthesis in cam, explain
- C4 is transferred to chloroplast and decarboxylated for photosynthesis
- PEP is then converted into starch and stored in chloroplast during the day
why is CAM sorta bad?
- slows plants growth
- low competitive ability
- low photosynthetic capacity
- produces carbohydrates slower
(CAM)CO2 substrate –> … —>…
photosynthesis, carbohydrates
(CAM)O2 substrate –> …—>…–>…
photorespiration, net loss of energy, release of
CO2 without carbohydrate
production
why is photorespiration a challenge?
- Rubisco reacts more readily with CO2 but air contains 21% O2 and
only 0.04% CO2 - Rubisco has a hard time distinguishing between CO2 and O2 at high
temperatures; at moderate temperatures O2 is used 25% of the time.
which one gets fixed by rubisco, O2 or CO2 (photorespiration)
CO2
what is photorespiration
a process that occurs when RuBisCO fixes oxygen instead of carbon dioxide, leading to a less efficient pathway that consumes energy and releases CO₂
when does photorespiration usually take place?
- High temperatures: Increase the affinity of RuBisCO for O₂ and decrease its affinity for CO₂.
- High oxygen concentrations: When stomata close to prevent water loss, O₂ levels inside the leaf increase.
- Low CO₂ concentrations: Also a result of stomata closure, reducing CO₂ availability for RuBisCO.
c4 photosynthesis (spatial pathway)
- CO2 capture and the Calvin cycle take place in different cells… happens in mesophyll first then bundle sheath
c4 photosynthesis characteristics
- C4 plants suppress photorespiration
by increasing CO2 concentration
around rubisco - works well during heat
what happens in C4 mesophyll?
- CO2 capture through stomata
- attaches to HCO3
- makes a 4 carbon organic acid through PEP carboxylase
- 1 is taken to bundle sheath and 3 are left to help repeat cycle in mesophyll
what happens in C4 bundle-sheath
- 1 carbon organic acid attaches to CO2 in bundle-sheath
- then goes through rubisco/Calvin cycle
3 transporting water characteristics (trees)
- as height increases, pressure decreases
- no atp needed
- at 10m, there is 1 atm
… Perfect vacuum and water
boils spontaneously
what is parenchyma and what does do?
- Undifferentiated parenchyma
cells - Vascular tissues organized in
a ring near periphery of stem - Continuous pathway from root
tips through stem to veins of
leaves
what is a xylem?
- transports water from roots to leaves
what is a phloem?
- transports carbohydrates from leave to the rest of the plant… roots and etc
what is a sclerenchyma?
- super thick wall
- secondary cell walls made up of cellulose and lignin to provide mechanical strength and support
explain function of a xylem and its characteristics
- during development cell elongates
- has a secondary thick wall containing lignin
- is a hollow tube for conduction
- nucleus, cytoplasm and organelles are lost
- do not extend the length of the plant
- water moves through conduits through pits
what are pits (xylem)
pits allow water to go though conduits
do pits allow water or air to pass through?
water
what are the two types of xylems?
tracheids and vessels
explain a tracheid
- unicellular
- long
- less than 1 cm long
explain a vessel
- multicellular
- severe meters long
- wide
where are tracheids found in?
- horsetails and ferns
- lycophytes
- gymnosperms
where are vessels found?
- angiosperms
- gymnosperms
(xylem) water flows faster through?
longer/wider conduits
(xylem) passing through pits is?
flow resistance
(xylem) plants with ____ can achieve greater rates of water transport
vessels
(xylem) explain Tension
- hydrogen bonds connect to other hydrogen bonds
- usually stick to the sides of the xylem to go up better against pressure
- Tensile force whereby molecules are pulling on one another
- negative pressure is created by water modules pulling upwards as water evaporates from transpiration
(xylem) steps of tension/from root to leaves
- Water evaporates from cells
lining leaf air spaces while
stomata are open - Pull water molecules to occupy
these spaces
1. the evaporation of water from leaf causes pressure from xylem to decrease
2. hydrogen bond that form between water molecules helps water to move through xylem
3. the negative tension pressure in xylem must overcome the surface tension of air-water interfaces of soil.
(xylem) what is cavitation?
when water is replaced by water vapour.
- like air/gas from being frozen
(xylem) how to deal with cavitation?
- pts help by only allowing water transfer to another conduit.
- Pits protect the system so that only water passes through –
cavitation/embolism can be contained to one conduit
(xylem) what does it mean when a xylem collapses?
when negative pressure causes conduit wall to move inwards
what is a phloem sap
it is a sugar rich solution that flows through lumen
Source-to-sink transport of
carbohydrates
phloem
what is a multicellular sieve tube?
- they are modified cells called side elements
- connected end to end
what things do phloem transport besides carbohydrates? (6)
- inorganic forms of nitrogen
- amino acids
- ions
- hormones
- protein signals
- RNA
where are resource regions located?
- leaves
- tubers
- stems
what are the resource regions?
where glucose or sucrose is made
what are sink regions?
where the source regions go/develope
where are sink regions located?
- developing fruits
- roots
- young leaves
turgor pressure in ___ phloem is ___ because water is drawn by ____ as sugars added to the phloem
source, high, osmosis
phloem steps
- starts at source region
- sucrose goes through companion cell
- pressure difference between source and sink drives the movement of phleom sap
- then goes into companion cell
- then into sink (ex root)
Transports material in one direction only (from roots to leaves):
xylem
Transports dissolved nutrients
phloem
Transportation is driven by differences in concentrations (source-sink dynamics)
phloem
The cells that make up this tissue type are alive at maturity
phloem
This type of tissue is often deliberately damaged by herbivores seeking the carbohydrates it transports
phloem
where do vascular plants obtain resources from?
soil via roots
plants are ___ water and ___ dry matter
85, 15
root hairs
outgrowth from epidermal cells near root tips that greatly increase surface area
what is a cation exchange capacity (CEC) of soils?
it is where negatively charged ion replace the floating + charged ions in the soil particle (which is -)
lower pH =
higher availability
higher pH =
lower availability
root structure
- water soluble nutrients enter the roots and then travel through xylem to the rest of the plant
- xylem conduits are not in direct contact with soil
cortex (root)
parenchyma cells in root interior
endodermis (root)
layer of cells surrounding root vascular tissues,
- basically selects which materials enter the xylem
steps of entering roots
- ions that enter cytoplasm of a root cell can move to the xylem through plasmodesmata
- or they can move water-filled spaces of cell walls
- at the endodermis, the caesarean strip prevents ions and water from moving in the walls, which forces them into passing through cell membrane
casparian strip
it is a band of hydrophobic material that encircles each endodermal cell
water can only enter xylem by passing through ____ of ____ cells
cytoplasm of endodermal
does water pass through epidermis and cortex easily?
yes
what are fungi good for?
mobilizing P and decomposing organic matter in soils to release N
what are bacterias good for?
some convert gaseous N2 into chemical forms that are more easily taken up and used by plants
What is Mycorrhizae
- Fungus + root (greek)
- symbiotic association between plant and fungus colonizing root cortex during periods of active plant growth
symbiotic movement (2)
- plant carbohydrates –> fungus
- plants <— inorganic jungle nutrients
how much carbohydrates does fungi consume?
4-20%
what do fungi provide?
nutrients
what do fungi secrete which helps make soil nutrients more
enzyme
endomycorrhizae
- jungle networks within root cells
- enhance plant’s uptake of phosphorus
- 80% of plants
what is endomycorrhizae good for?
they penetrate inside root cells and enhance carbon and nutrient exchange
ectomycorrhizae
- thick sheath of fungal cells + filaments that surround root tip
- provide plant with nitrogen
- 10% of plants
what is function of ectomycorrhizae?
- surrounds root but do not penetrate
- carbon and nutrients are exchanged through plasma membrane
Rhizobia
- N2 is not bio-accessible; needs to e converted to NH3
- plant mutualism with bacteria to gain access to nitrogen
rhizobium bacteria role and steps
- multiple outside of the root in response to chemical signals
- then enter through root hair or break into epidermis
- then the bacteria take up residence in a root nodule formed by dividing root cells
where does bacteria fix nitrogen and what does it provide?
root nodule and provides access to Nitrogen
rhizobium –>
N to plant –> N incorporated into seeds –> plant protein
