Adaptations To Terrestrial Environments Flashcards
Most terrestrial plants obtain nutrients and water from where
Soil
Saturation
Field capacity
Wilting point
Maximum water in soil after raining
Maximum amount of water retained after gravity
Lowest water potential at which plants can get water from soil
Of sand, silt and clay, which has the largest particle size? Which holds most water?
Sand is largest, then silt then clay.
Clay Holds more water because of increased surface area
Can plants extract water easily from clay?
No, too much surface tension
How does water move from roots to leaves?
Water moves into roots by osmosis, and then into xylem. Tension pulls the water upward in the xylem of the root.
Water molecules form a cohesive column in the xylem and the tension pulls the water upward through the stem.
Tension pulls the water coming up and out in the xylem of the lead veins. Water evaporates from the mesophyll cells and diffuses out of the stoma.
In soil with layered types of earth, how do roots differ?
More branched in clay to uptake all the nutrients. Long in sand to pick up water that falls quickly downward.
What wavelength colour do plants not absorb
Green, they reflect it
Extreme temperatures usually _____ the rate of photosynthesis
Reduce
Photosynthesis equation
6CO2+ 12H2O—>C6H12O6+6O2+6H2O
—->=rubisco
Carboxylation pathway
Carbon dioxide is turned into 2 PGA by ribulose biphosphate
Oxygenation pathway of photosynthesis
Oxygen is turned into 1 PGA and phosphoglycolate by ribulose biphosphate
Not as good! Less PGA and now a new byproduct to get rid of
Rubisco/ RUBP carboxylase-oxidase
Enzyme that grabs carbon dioxide and oxygen*
An enzyme involved in photosynthesis that catalyses the reaction of RUBP and CO2 to form two molecules of glyceraldehyde 3-phosphate (G3P)
2 PGA make what?
Sucrose
C3 photosynthesis
Regular photosynthesis in most plants
-carbon dioxide taken up by rubisco and enters the Calvin cycle to produce sugars
-Carbon dioxide is initially assimilated into a 3 carbon compound (G3P). Occurs in mesophyll cells in leaves.
C4 photosynthesis
A photosynthetic pathway in which CO2 is initially assimilated into a 4-carbon compounds, oxaloacetic acid (OAA).
-mesophyll cell using PEP carboxylase to bind to carbon dioxide to produce a four-carbon molecule (OAA). This occurs in the chloroplasts of the mesophyll cells of the leaf. The Calvin cycle takes place in chloroplast of the bundle sheath cells that surround the leaf veins. So plant must move the CO2 that has been assimilated in the mesophyll cells over to the bundle sheath cells.
CO2+PEP=OAA
-efficient and keeps all reactions going by using PEP (more affinity to CO2) to scavenge extra carbon dioxide when it is low.
-allows stomata to remain partially or completely closed for longer periods of time to reduce water loss.
CAM photosynthesis
-mainly in desert and epiphytes (orchid)
-uses PEP carboxylase to store CO2 in acids in tissues to be used in Calvin cycle during the day.
Therefore there is more NADPH and ATP during the day and generate more sugars in the day.
A photosynthetic pathway in which the initial assimilation of carbon into a four-carbon compound occurs at night.
-opens stomata for gas exchange during cool night when transpiration is minimal and conduct photosynthesis during hot day.
-assimilate CO2 with OAA and then conveyed to malic acid and stored at high concentration in vacuoles within the mesophyll cells of the leaf.
-during day, stomata close and stored organic acids are gradually broken down to release CO2 to the Calvin cycle:
-photosynthesis is slowed and so is growing time.
Soil
The layer of chemically and biologically altered material that overlies bedrock or other unaltered material at earths surface
Parent material
The late or bedrock that underlies soil and plays a major role in determining the type of soil that will form above it
What are the distinct layers of soil called
Horizons
Leaching
A process in which groundwater removes some substances by dissolving them and moving them down through the soil to lower layers
Matrix potential
The potential energy generated by the attractive forces between water molecules and soil particles.
How does wilting occur
If a plant cannot counteract the matrix potential with a stronger water potential in the plant, it wilts
The difference between field capacity and wilting point it the amount…..
Of water available to plants
Cation exchange capacity
The ability of a soil to retain cations
-K, Na, Mg, Ca
Older soils have more cations and therefore better fertility
What keeps high solute concentrations in plant roots
-semipermeable membranes prevent larger molecules form leaving plant roots
-cell membranes actively transport ions and small molecules against concentration gradient into the root cells
Soul salinization
The process of repeated irrigation, which causes increased soil salinity
Cohesion tension theory
The mechanism of water movement from roots to leaves due to water cohesion and water tension