theme 4 Flashcards
how many essential elements are there for plants? what are the big ones?
elements that are required for proper functioning of the organism
-N
-P
-K
Ca
Mg
Fe
what are macronutrients
elements and plant needs in large quantities
-C, H, O from air
-N
-P
-K
-S
-Ca
-Mg- all of these are required to be dissolved in water
what are micro nutrients
elements only needed in small quanities
-Cu
Cl
Ni
what is the form of nitrogen that plant prefer to use
NO3-, but then the plant converts it back into NH4
What is the nitrogen cycle
N2 atmos–> NH4 via bacteria in soil or ammonifociation via bac of decaying matter–> NO3- via nitrification via bacteria
why is N important?
allows plant to grow
how is nitrogen taken out of the soil?
harvesting crops (disrupt soil) or the shifting of land for agriculture
how is nitrogen content improved in soil
-crop rotation
fertilizer- domination during the 1940-1970
what are lodging plants
during the 40-70s when fertilizer was surplus, plants grew wayyyy to tall and were prone to falling over and breaking
how much nitrogen from fertilizer used? lost?
only 10% is taken by plants, 90% is lost as runoff
what happens with excess N in water?
Eutrophication (algal blooms). this causes a depletion of O2. the ecosystem is harmed
eutrophication
the enrichment of ecosystems with chemical nutrients such as N and P
what are the grains that are found in soil?
sand 0.02-2mm
silt 0.02-0.002mm
clay <0.002
what is soil solution
a combo of water and its dissolved components that coat particles and fills pore spaces
what do clay and humus particles do to water moles?
negatively charges them- makes it alkiline
what is cholorosis
the yellowing od plant tissues due to a lack of chlorophyll
how are minerals (cations) exchanged between roots/soils
the roots produce H+ ions which will enter the solid, and displace the nutrients (K+, Ca2+ and Mg2+) which in turn are uptaken by the roots
or the roots and CO2 via respiration which are turned into H2CO3 when interacting with H2O, the H+ from this mole displace the cations in the soil and are uptaken by the roots
how are anions exchnaged between soil and roots
anions move freely in the negatively (alkaline) charged soil and easily move into the roots
what is the common pH of soil
8-9
what is alkaline soil
a basic soil whcih can easly leach anions
what is an acidic soil
a soil which cations leach out easily
passive transprt
requires no energy to move a substance. it moves down the [] gradient (with the membrane potential)
-eother moves across the membrane )O2, H2O or CO2) or through a protein
active transport
requires the expenditure of ATP to move a substance (against the gradient)
what are two mechanisms that plants use to increase nutrient uptake
root hairs- greatly increase SA
-Mycorrhizae- a symbiotic relationship with fungus and roots (fungus mobilizes phosphorous)
what is humus?
the top layer of soil (the most important)
what structures are used to transport nutrients over long distances
xylem and phloem
where does short travel distance occure in plants
at roos and in between membrane s
how much water is lost via transpiration
90%
what is water potential
the driving force of water movent
the sum of solute potential and pressure potential
what are aquaporins
chanel protines that promote the movement of water across a hydrophobic membrane
how does water move in relation to water potential
from areas of high potential to areas of low potential
what happens when a solute is added to a water system
the water potential is lowered
what happens when pressure is added to a water system?
the potential is increased (when applying pressure)\
if pressure is removed, then the water potential is lowered
where is water and solutes sorted within a plant cell
the central vacuole
how do things entre the central vacuole
by passing through the tonoplast (the membrane
plasmolysis
wilting when a plant loses water due to dry soil with a low potential
what happens to a plant cell if there is a low water potential in soil
the vacuole will actually take up more solute from the environment to create a lower water potential inside the cell and have water flow into the cell to maintain turgor pressure
what are the two pathways that water and nutrients travel through the roots and into the xylem?
apoplastic and symplastic
what is apoplastic movement
water moves THROUGH cell walls
what is symplastic movement
movement of water through cells via their cytoplasm and plasmodesmata
what are plasmodesmata
connections between cells
what is the casparian stripe? what does it do?
endodermal cells which actively pump ionos across a membrane
a selectively permeable wall/barrier to apoplastic water and solute movement. all intracellular routes are sealed off and all nutrients are pushed into the cell for a ‘screening’. this occurs right before the xylem
is apoplastic or symplastic faster?
apoplastic. this is because nutrients do not need to move through think cytoplasm
why do apoplastic water and solutes into the cell at the endodermis? (strip)
to allow to the plant to regualte its ion uptake and restrcs any solutes from flowing back as its made of a waxy substance
how is water and nut taken into the apoplastic route vs the symplastic route
apo= passive
sympla= generally active, but can be passive depending the plants needs
what is the main mechanical properties of water
cohesion-tension allows for water moles to stick together and be transported up the xylem in one continuous line
transpiration
the mechanism which pulls water up the xylem (application of negative pressure). it evaporates outside the stomatal opening of leaves.
water in the roots 9high P) is pulled to areas of low pressure (higher vasculature)
what is guttation
when the root pressure is so string that enough water is pushed through the xylem so that water droplets from from the stomatal opening
overall the high pressure in root systems contribute to the upward movement of water in a plant
what company is found in the xylem that assists in the maintenance of its structure?
lignin- a heavy organic compound that helps support the xylem from the negative pressure
what does the phloem transport?
long distance of sugar and other nutrients in the form of sap
in what directions does the pholem and xylem transport nutrients?
Xylem is only upwards
phloem is multi-directional
what drives the flow of sap in the phloem?
the presser difference between the sources of sugar and the sinks
what is a source and a sink?
source: where substances are loaded into the phloem
-leaves
sink: where organic substances are unloaded (natural depletion area of substances)
-roots and flower heads
what are sieve tubes and what are they connected to
sieve tube are small tubes that make up the pholem
they undergo partial death and are attached to companion cells which contain all the necessary components for life (to keep the overall phloem body alive)
what is contained in the companion cells?
nucleus
central vacuole
some mitochondria
rough ER (with ribosomes)
golgi bodies
what is retained in the mautre sieve tube?
mitochonria
smooth ER
plastids
plasma membrane
what kind of division occurs that generate the sieve tube and its companion cell from the phloem mother cell
asymetrical: the formation of 2 cells with distinct roles
what is the process of forming the sieve tube and the companion cell?
apoptosis
how does sugar (sucrose)enter the phloem?
via active transportation. generally smaller sugar molecules like sucrose and glucose are transported through plasmodesmata into the companion cells where they are synthesized into larger molecules. the larger molecules then are moved into the sieve tubes
what is pressure flow mechanims
the movement of substances via bulk flow from the source to a sink or from an area of high pressure ([]) to low pressure ([])
where does gas exchange occur?
through the stomata
what leaf layer reducced water loss
the cuticle (a waxy layer)
what challenges does the plant face with gas exchange
getting adequate CO2 but needing to balance the amount of water in its vasculature
-either transpiration (H2O and nutrient uptake ) or phosyn is compromised)
how is to stomatal opening controlled?
by the [K+]. the flow of high [K+] called for water to follow into the guard cells and increases pressure. this opens the pores. low [K+] causes water to flow put, closing the pores;
when is the stomata open vs closed?
open to promote phosyn and when blue light is high
close where the plant is under water stress–> signal initiated by the roots
what is the chemical signal that causes guard cells to close?
mesophyll abosrbs ABA which signals for the closure
what is the mesophyll and its function?
the cells found within a leaf. comprised of the spongy cells and the upper dermis. promotes the evaporation of water
