Biology 102 Chapter 37
Plant Nutrition
1. Distinguish between macronutrient and micronutrient and
describe their role in plant structure and metabolism.
---macronutrient is a nutrient required by the plant in
large amounts
---micronutrient is a nutrient required by the plant in
small amounts
MACRONUTRIENTS:
---carbon (CO2); major component of plant’s organic
compounds
---oxygen (CO2); major component of plant’s organic
compounds
---hydrogen (H2O); major component of plant’s organic
compounds
---nitrogen (NO3-, NH4+); component of nucleic acids,
proteins, hormones, and coenzymes
---sulfur (SO42-); component of proteins, coenzymes
---phosphorus (H2PO4-, HPO42-); component of nucleic acids,
phospholipids, ATP, several coenzymes
---potassium (K+); cofactor that functions in protein
synthesis, major solute functioning in water balance,
operation of stomata
---calcium (Ca2+); important in formation and stability of
cell walls and in maintenance of membrane structure and
permeability; activates some enzymes; regulates many
responses of cells to stimuli
---magnesium (Mg2+); component of chlorophyll; activates
many enzymes
---chlorine (Cl-); required for water-splitting step of
photosynthesis; functions in water balance
---iron (Fe3+, Fe2+); component of cytochromes; activates
some enzymes
---boron (H2BO3-); cofactor in chlorophyll synthesis; may be
involved in carbohydrate transport and nucleic acid
synthesis
---manganese (Mn2+); active in formation of amino acids;
activates some enzymes; required for water-splitting
step of photosynthesis
---zinc (Zn2+); active in formation of chlorophyll;
activates some enzymes
---copper (Cu+, Cu2+); component of many redox and ligninbiosynthetic enzymes
---molybdenum (MoO42-); essential in nitrogen fixation;
cofactor that functions in nitrate reduction
---nickel (Ni2+); cofactor for an enzyme functioning in
nitrogen metabolism
---these elements function mostly as cofactors of
enzymatic reactions
---it is because micronutrients generally play catalytic
roles that plants need only minute quantities of these
elements
---example: only 1 molybdenum for each 16 million atoms
of hydrogen in dried plant material
2. Recall the forms of nitrogen that plant can absorb and
describe how they are used by plants.
---plants require nitrogen to produce proteins, nucleic
acids, & other organic molecules
---plants CANNOT use nitrogen in gaseous form (N2)
---to be used, must be in form of ammonium (NH4+) or
nitrate (NO3-)
---plants acquire most of their nitrogen in the form of nitrate
(NO3-)
--produced in soil by nitrifying bacteria
-oxide ammonium
--other species of nitrogen fixing bacteria live in
plant roots (symbiotic relationship)
---nitrogen absorbed by the plant is incorporated into
organic compounds
3. List the three elements most commonly added to agricultural
soils.
---ever buy a bag of triple 13 (13-13-13)?
---nitrogen, phosphorus, and potassium
---N-P-K
4. Explain the role of nitrogen-fixing bacteria and mycorrhizae
in the nutrition of some plants.
---few species of bacteria possess enzyme that enables them to
convert nitrogen gas to ammonia (N2-->NH3)
--essential to life on this planet
--cyanobacteria and Rhizobium
---Rhizobium “infects” roots of plants causing nodulation
--these nodes are site of bacterial nitrogen fixing’
---symbiosis and mutualism
---REVEIW from Biology 101 on mycorrhizae
---symbiosis and mutualism between plant roots and a fungus
---ecto and endo
---increases absorption of water and minerals (especially
phosphorus) by plant
5. Explain how the nutrition of heterotrophic plants and
carnivorous plants differ from that of typical (autotrophic)
plants.
---some plants have lost ability to sustain themselves by
photosynthesis
--mistletoes, dodders, and Indian pipe
--kind of ify for mistletoe, but....
--extract nutrients from hosts by absorptive organs called
haustoria
---approximately 450 plants species are carnivorous
--do not live by photosynthesis alone
--Venus flytrap, sundews, and pitcher plants
---most live in acidic environments
--difficult for decay-causing organisms to break down bodies
of dead organisms
--hence not much “recycling”
---these plants have evolved way to supply their nitrogen needs
by “eating protein”