photosynthesis and nutrition Flashcards
reactants and products
reactants: CO2, water, and light
products: sugar
two stages
light reaction (take place in thylakoid membrane)
Calvin cycle (take place in stroma)
light reactions
convert light energy to chemical energy of ATP and NADPH
Split H2O into O2
Calvin Cycle
uses ATP and NADPH to convert CO2 to sugar G3P
returns ADP, inorganic phosphate, and NADP+ to light reactions
cycle goes around three times
function of chloroplast pigments
absorb light
types of photosynthetic pigments
essential pigment: chlorophyll a
accessory pigments: chlorophyll b, carotenoids, phycobillins
the pigments absorb different wavelengths of light
what contributes to yellowing and reddening of leaves
carotenoids
what creates green color of leaves
chlorophyll
C3 pathway
most typical photosynthetic pathway, produces three carbon molecule G3P, three phases: carbon fixation, reduction, regeneration of RuBP
starts with RuBP and ends with RuBP
CO2, ATP, and NADPH needed
catalyzed by rubsico
photorespiration
rubsico fixes O2 instead of CO2, causing CO2 to be released and using ATP
no sugar produced
occurs in hot and dry conditions when stomata is closed
C4 and CAM pathways
first carbon fixation involves PEP carboxylase instead of rubisco
CO2 is stores as malate or aspartate
4 C molecules of produced
2nd carbon fixation is the calvin cycle
how are carbon fixations separated in C4 and CAM
separated spatially in C4: mesophyll and bundle sheath cell
CAM: stomata opens at night and closes during the day
night: CO2 incorporated into organic acid
Day: Calvin cycle occurs
C4 advantages
higher opitmal temperature, more photosynthesis, conservation of water, used 1/3 to 1/6 less rubisco, less water loss due to nitrogen efficiency
C4 disadvantages
more ATP needed
CAM features
high water use efficiency, facultative use of CAM pathway (can be switched into), used by ferns, aquatic plants, succulents, and epiphytes
types of nutrients
micronutrients and macronutrients
macronutrients
sulfure, phosphate, magnesium, calcium, potassium, nitrogen
beneficial elements
other nutrients that are essential for only limited groups of plants
nutrient deficiency symptoms
necrosis (dying of cells), chlorosis (not enough chlorophylls)
magnesium property
it is phloem mobile, meaning it can move through the phloem
soil function
provides most nutrients, mixture of inorganic material and dead organism, some living organisms
where do plants grow into
the topsoil
layers of soil
O horizon (humus) at top, A horizon (topsoil), E, B, C, less organic matter found as you go down to R (bedrock)
grassland soil layers
has a lot of topsoil compared to forests
three main textures
clay, sand, silt
sand
many macropores, allowing for movement of water
clay
very small particles, mostly micropores, water doesn’t move that well
ideal soil texture for plant growth
loamy soil
silt
less macropores than sand but more than clay
saturated soil
pore spaces are filled with water
wilting point
not enough water
field capacity
ideal point where water and air pockets are both present
clay needs more water than sand to reach field capacity
micelle
soil particles, cations are held on, anions moved out of soil, especially sand
root hair function
secrete CO2 from respiration and H+, allows plants to pick up nutrients
Do anions or cations leach more from soil?
Anions, because they are readily available
what is soil mostly likely to bind
H+ ions
limiting essential nutrients
nitrogen and phosphorous
Nitrogen requirement
plants require it, acquire it as NH4+ or NO3-, only done through prokaryotes
nitrogen cycle
NO3- is easily leached out of soils, nitrogen fixing bacteria and ammonifying bacteria turn nitrogen to ammonia
nitrogenase funciton
converts N2 to organic nitrogen, found only in prokaryotes, inhibited by O2, NH4+ and NO4
cyanobacteria
function as nitrogen fixers
nitrogen fixing symbioses
nodulated legumes, nodulated non legumes, non nodulated nitrogen fixers, plant cyanobacteria assocation
nodulated legumes
symbiotic relaitonship with nitrogen fixing bacteria
fabaceae family (beans, peas, etc), provide N to soil, are also nutritious to wildlife as high protein food
one non leguminous species
leghemoglobin
lowers O2 conc in nodules and gives them their red color
white nodules are parasitic, green nodules are senesced, red is good
how do bacteria enter root
through the root hair, pericycle divides, forming the root nodule which provides habitat for bacteria
Vascular tissue forms symbiotic relationship with bacterial colony
non nodulated nitrogen fixers
barley, maize, rice, wheat, sorghum, intercellular spaces and xylem vessels
obtain 60% or more of their N needed
plant cyanobacteria association
external to root cell, cyanobacteria located in pockets within its fronds
carnivorous plants
use non nitrogen fixing uptake methods
include venus flytrap, pitcher plants, and sundews
parasitic plants
non N fixing, can also be photosynthetic, produce haustorium that penetrates into host secondary xylem
mycorrhizas
directly break down proteins in soils
phosphorous
leaches less than N, most available in rhizosphere (cluster roots), bound and unavailable to plants, support nitrogen fixers
root fungi association
allows plants to get phosphorous
some mycorrhizal associations are almost obligate
types of mycorrhizae
ecto, endo, ericoid, orchidaeous, ectendo
most plant families are endo
ecto are visibly seen
endo are not
glomeromycota
reproduce spores underground, fungi hard to see
history of mycorrhizae
fossilized fungal spores, found from the arctic to the tropics, 90 percent of all plant families
fungi function
increase surface area of plant roots, increase resistance to pathogens, decrease susceptibility to soil toxins, stimulate nitrogen fixation, improve soil structure
ectomycorrhizae structure
fungal layers found outside of root (mantle)
hartignet - sites of exchange
endomycorrhizae
pentrates the roots
monotropoid mycorrhizae
tripartite relationship, link between fungus, an autotrophic plant, and the heterotrophic plant
how does water move
from higher to lower potential
what causes opening and closing of stomata
solute concentrations, stomata most open at midday when K+ and sucrose concentrations are peaking
cavitation and embolism
breakage of cells that forces water to move laterally
embolism - water hits air pocket
how does water enter
root hairs
guttation
water is getting pushed up into the plant and out the pores
hydathodes
specialized stomata responsible for guttation
phloem transport
waters move into high solute areas and push sugars to next area via osmosis
source (photosynthetic areas) to sink (areas of growth)
apoplastic vs symplastic loading
apoplastic - sugars move through plasmodesmata and are then uploaded into sieve tube cell, cell wall movement
symplastic - no movement though cell wall, cell to cell movement all the way to sieve tube
