Chapter 37 Plant NutritionBiology 102Tri-County Technical CollegePendleton, SC

Macro versus Micronutrients

Macronutrient is nutrient required by plant in large amountsMicronutrient is nutrient required by plant in small amountsMicronutrients:Carbon (CO2)-major component of plant’s organic compoundsOxygen (CO2)-major component of plant’s organic compounds

Macronutrients, cont.

Hydrogen (H2O)-major component of plant’s organic compoundsNitrogen (NO3

-; NH4+)-component

of nucleic acids, proteins, hormones, and coenzymesSulfur (SO4

2-)-component of proteins & coenzymes

Macronutrients, cont.

Phosphorous (H2PO4-; HPO4

2-)-component of nucleic acids, phospholipids, ATP, & several coenzymesPotassium (K+)-cofactor that functions in protein synthesis, major solute functioning in water balance, & operation of stomataCalcium (Ca2+)-formation and stability of cell walls, maintenance of membrane structure and permeability, activates some enzymes, regulates many responses of cells to stimuli

Macro and Micro

Magnesium (Mg2+)-component of chlorophyll, activates many enzymesMICRONUTRIENTS:Chlorine (Cl-)-required for water-splitting step of photosynthesis, functions in water balanceIron (Fe3+; Fe2+)-component of cytochromes, activates some enzymes

Micronutrients, cont.

Boron (H2BO3-)-cofactor in chlorophyll

synthesis, may be involved in carbohydrate transport and nucleic acid synthesisManganese (Mn2+)-active in formation of amino acids, activates some enzymes, required for water-splitting step of photosynthesisZinc (Zn2+)-active in formation of chlorophyll and activates some enzymes

Micronutrients, cont.

Copper (Cu+; Cu2+)-component of many redox and lignin-biosynthetic enzymesMolybdenum (MoO4

2-)-essential in nitrogen fixation and cofactor that functions in nitrate reductionNickel (Ni2+)-cofactor for enzyme functioning in nitrogen metabolism

Micronutrient Why’s?

Most micronutrients function as cofactors of enzymatic reactionsBecause micronutrients generally play catalytic roles that plants need only minute quantities of these elementsExample: only 1 molybdenum atom for each 16 million atoms of hydrogen in dried plant material

Plants and Nitrogen

Plants require nitrogen to produce proteins, nucleic acids, and other organic moleculesThey 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

-)

Plants and Nitrogen, cont.

Nitrate produced in soil by nitrifying bacteria They oxidize ammonia/ammoniumOther species of nitrogen fixing bacteria live in plant roots (mutualistic symbiotic relationship)Nitrogen absorbed by plant is incorporated into organic compounds

Nitrogen Cycle Visual

Miracle Grow or thereabouts…

Ever purchase a bag of triple 13?No, how about triple 10?13-13-13 or 10-10-10 Not brain surgery…is by weight so close Lists contents in order of: Nitrogen, phosphorous, and potassiumN-P-K21-0-0 (Oh yeah…but….)

Nitrogen Fixation

Few species of bacteria possess enzyme that will 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 bacteria nitrogen

fixing

Knowing the Nodes

Nitrogen Fixation Visual

Bits and Pieces…

Mutualistic symbiotic relationshipMycorrhizae is mutualistic relationship between fungus and plant rootsIncreases absorption of water and minerals (especially phosphorus)Can be ECTO or ENDO(This should be a review from Bio 101)

Heterotrophic/Carnivorous 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 haustoriaApproximately 450 plant species are carnivorious

H/C Plants, cont.

Do not live by photosynthesis alone Venus fly trap, sundews, & 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 evolved way to supply their nitrogen (and phosphorous) needs by “eating protein”