humus Flashcards
what are the other three big categories that humans and earthworms can’t digest
cellulose, hemicellulose, and lignin
too large to dissolve in water
fungi and bacteria have soft or rigid cell walls
rigid
can fungi and bacteria fo phagocytosis
no- they have walls
what is depolymerization in terms of fungi and bacteria and such
digestion
if you chop up polymers and dissolve it in water what will happen
it will be digested
greater nitrogen content leads to faster or slower degredation
faster
which is degraded faster- proteins or carbohydrates
protiens
factors that increase the likelyhood that an enzyme digests a polymer into soluble oligomers
all monomers are the same
backbone within molecule made out of same monomers
linkages between monomers all the same
H bonding between polymers absent
oligopeptide
a little piece of a digested protien
what are the bonds between amino acid monomers that comprimise a protien
CO-NH
do bugs like oligopeptides
yes- they are easy to digest because a protease enzyme cuts the peptide bonds
xyloglucans
most abundant hemicellulose in primary cell wall of plants
backbone of glucose monomers linked by identical linkages
TF if an enzyme can cut through enough identical linkages, the xyloglucan should be soluble
T- breaking down the size due to identical bonds
cellulose properties
All monomers same- glucose
all linkages identical- B1,4
Occurs in bunches
can enzymes easily digest cellulose
no because it occurs in bunches
what keeps cellulose together
H Bonds
what do fungi and bacteria prefer, cellulose or lignin
cellulose
how is lignin polymerized
random linkages
is lignin easy to digest
no- random linkages, linkages can’t be hydrolyzed
how is lignin formed
plant has soup of lignin monomers
free radicals catalyze spontaneously at whatever position the linkage hits
New monomer now has free radical and will now go hunting to pair their unpaired electron, which will result in chain after chain after chain
how is polyethylene created
through ethylene monomers and spontaneous random linkages
how are humic substances created (polymer wise)q
random linkages like polyethylene and lignin
do proteins, starches, and lipids rot fast or slow
fast- worms can digest (people can too!)
do hemicellulose and cellulose decompose fast or slow
slow
who decomposes hemicellulose and cellulose
microbes
What substance is the most degradation resistant
lignin
what type pf enzymes can chop up lignin
peroxidases and white rot fungi
TF how enzymes depolymerize the lignin creates a free radical
T
TF the free radical that enzymes create during lignin depolymerization remain free radicals
F, this will catalyze the repolymerization of lignin monomers + almost anything else organic that happens to be how humic substances are formed
is there more lignin in leafy plant tissue or woody plant tissue
woody
what is typically with lignin in a plant cell (making it nearly undigestable)
cellulose and hemicellulose of woody tissue
TF lignin if wrapped around tube of cellulose
T- defense mechanism
TF humic substances and fresh plant residue is the same thing
F, humic substances are the digested versions of plant residue
how do humic substances form
randomly assembled like lignin
what type of rings are abundant in lignin
benzene rings
two types of things to decompose
greens and browns
greens- nitrogen cellulose lignin
high nitrogen
low cellulose
low lignin
do greens rot fast
yes
do greens leave a lot of humus
no
browns- nitrogen lignin
High lignin
low nitrogen
do browns rot fast
no
As browns are depolymerized, part of their carbon skeletons become randomly assembled and turned into highly desireable humic substances TF
T
If a plant residue has a high C:N ratio, is it a brown or green
brown- low N
If a plant residue has a low C:N ratio, is it a brown or green
green- high N
does humus have a high C:N ratio
no
for annual crops, does the C:N ratio increase or decrease through the growing season
decrease- more lignin over time. More brown mass with more growing
do residues of crops become more or less able to decompose with age
less
if you add straw to your soil, the microebes will suck all of the __ out of the soil and incorporate it into their biomass
Nitrogen
IF you add leafy greens to your soil, it will rot at high speeds and liberate ________– into the soil for the next crop
nitrogen
green stuff will leave more or less humus
less, unless brown is added
TF nematodes eat bacteria and fungi
T
Do nematodes release nitrogen from the bacteria
yes
polyphenols
compounds containing benzene rings with multiple -OH groups attached
what are polyphenols good for for plants
defense against pathogenic fungi and insects
do polyphenols make plants harder to decompose
yes if present at high levels
mineralization*
conversion of any element from an organic to inorganic form
If microbes convert nitrogen in soil to NH4+, is this immobilization
NO mineralization
organic -> inorganic
immobilization
conversion of an element from an inorganic to an organic form
What is the opposite of immobilization
mineralization
immobilization or mineralization : plants take up N from soil and convert it into protiens
immobilization
inorg to org
List some factors that would increase soil organic matter levels
more residues per year
cooler temp
moister soil
more clay
appropriate N fertilization
no till
cover crops
replacing inorganic N sources with organic N sources
how do cooler temps lead to more organic matter
slows microbial destruction of humus
plants are less thirsty- same amt of water supports more biomass
how does moister soil lead to more organic matter
soggy soil has more anerobic volume which means slower destruction of humus
how does more clay lead to more organic matter
clay particles shield humus particles from microbes
how does appropriate levels of N fertilizationa ffect the organic matter
excessive fert- microbes accelerate desctruction
too little- less plant biomass
