Plants Theme 4 Flashcards
Homeostasis
Dynamic process compensating for changes in the internal and external environment
What are the essential elements for plants?
Nucleic acids (N & P), amino acids (N & S), enzyme cofactors (Ca), photosynthesis (Mg, Fe), regulation of osmosis (K)
How many essential elements are there for plants?
17
What are the essential macronutrients for plants
C, H, O (from water), N, P, K, Ca, Mg (mineral nutrients, must be dissolved in water)
What are the essential micronutrients for plants
Cu, Cl, Ni (trace quantities)
How much of the atmosphere is composed of nitrogen
78%
incorporates atmospheric N into plant available compounds NH4
nitrogen fixation
What happens in ammonification?
Bacteria breaks down decaying organic N into NH4
Which type of N is prefered by plants
NO3, but can take up NH4
What is the process of oxidizing NH4 into NO3
nitrification
Which form of nitrogen is moved via xylem in shoot system
NH4
Who was credited with saving a billion lives from starvation
Borlaug, green revolution
What is Eutrophication?
Enrichment of an ecosystem with chemical nutrients with N & P, caused by fertilizer runnoff
What is chlorosis?
Yellowing of plant tissue due to lack of chlorophyll
What does Humus do?
decomposing organics, holding water and nutrients in the top soil
What is the cation exchange?
mineral cations (Mg, Ca, K) adsorb to negative soil particles
What are the two cation exchange processes?
cellular respiration, where H from carbonic acid replaces mineral cations in soil.
Root hair, where H from the root hairs replaces mineral cations in soil.
Both allow for the uptake of minerals (Ca, K, Mg)
How do plants take in iron
extracted from the soil
What is the rough pH and charge of clay
Alkaline (basic-high pH) and negatively charged
Alkaline soils
anions leach out easily
acidic soils
cations leach out easily
Passive transport
No energy, down/with a concentration gradient
Active transport
requires energy, against gradient
What is Mycorrhizae
The symbiotic association between fungus and plants roots
What increases the plants’ supply of soil nutrients and what is the main nutrient
fungus, P
What do root nodule bacteria do?
nitrogen fixation
What are the conditions required for iron to be taken up by plants?
lower pH and made soluble
What is the water potential of solutes?
always negative
What is the water potential of pure water
0 Mpa
What effect does pushing have on water potential?
increase water potential on side pushed upon
What effect does pulling have on water potential?
negative pressure (tension), reducing the water potential on the side pulled upon
What is wilting?
Low turgor pressure in cells of leaves and stems drops turgor pressure. Plants lose more water than they gain (plasmolysis)
What creates turgor pressure in plants?
osmosis
How does water move through the apoplastic pathway
moves across cortex to endodermis via cell walls and intercellular space until Casparian strip. Never enters plasma membrane
How does water move through the symplastic pathway?
moves from cytoplasm of one cell to the next via plasmodesmata
How does water enter the xylem?
symplastic pathway, casparian strip forces the apoplastic water to enter symplastic
What is the fastest route for water to enter the xylem?
apoplastic
What pathway is water taken up only passively?
apoplastic
Is water taken up actively or passively in the symplastic pathway
both
What allows plants to regulate the ions that pass into the vascular tissue, and restricts solutes from flowing back, and is found in the endodermal layer
Casparian strip
Is the xylem considered apoplastic or symplastic?
Apoplastic
What percentage of water is metabolized by a plant?
10%, the rest is evaporated
What is the driving force of water transport (cohesion-tension) in plants
transpiration
What is the cohesion-tension mechanism
transpiration is the driving force, tension is the resulting pulling force, and cohesion is the replacement of water in the xylem through H-bonds
What factors resist the negative pressure on the water column in cohesion tension?
lignin secondary wall, the weight of the column, and adhesive forces in the xylem
How many stomata are on a leaf
thousands to millions
What is the physical limit of cohesion forces
130m
When root pressure is strong enough to force water out of leaf openeings
Guttation
each squared cm contains _________ of xylem veins
thousands
What does the xylem transport?
water and minerals
what does the phloem transport?
water and organic substances
Translocation occurs in the _______. And is able to flow _________
phloem, multi-directional
What is phloem sap composed of and where does it flow through?
water and organic compounds, sieve tubes
What drives the flow of phloem sap?
pressure differences in source and sink
What is the phloem composed of?
companion cells and sieve tubes
What are 4 characteristics of sieve tubes
alive at maturity, undergo apoptosis, lose organelles to increase sap flow, companion cells are the life support for them
Any region of a plant where organic substances are loaded into the phloem is the _________ and any region where organic substances are unloaded from the phloem is the __________
source, sink
What elements of mature sieve tubes are present?
mitochondria, ER, plasma membrane, plastids (ME-PP)
Sugar loading in the phloem follows which pathway(s)?
apoplastic and symplastic, has to eventually get into symplastic to be transported
How does sugar move into cell walls of phloem cells?
active transport
Sugar unloading in the phloem follows which pathway
symplastic
Load from _____ –> transport to sieve tubes –> unload into _____
source, sink
Bulk flow from source to sink in order
- Sucrose synthesized in the source is actively transported into sieve tubes
- The water potential of sieve tube is lowered, causing water from xylem to follow vis osmosis
- Phloem sap moves in bulk flow towards sink due to lower pressure
- Companion cells take in sucrose via active transport, then sucrose into the sink
- water potential in sieve tubes rise causing some water to move into roots but most of the water into xylem
Where is the stomata located on a leaf?
Epidermis
What type of division do guard cells undergo, and what is their role
symmetric division, controlling the opening and closing of stomata
which type of division do companion cells and sieve tubes undergo
asymmetric division
can transpiration and photosynthesis occur at the same time?
no, one occurs at the cost of the other
What mechanism causes the opening and closing of the stomata
actively transporting K into/out of guard cells
A turgid stomata is ______, while a flaccid stomata is _______
Open, Closed
How does water enter guard cells
Proton pumps H out of guard cells via ATP hydrolysis, creating electrochemical gradient leads to K to enter guard cell, water follows via osmosis
Which state of the stomata increases photosynthesis?
open, allow for CO2 to enter
What is ABA (abscisic acid), and where is it synthesized?
hormonal signal for closure of the stomata, roots
which cells take up ABA from the xylem and release it?
mesophyll cells
In closed stomata what is the K concentration?
low
