Chapter 37: Plant Chapter 37: Plant NutritionNutrition
Where does mass come from?Where does mass come from? Mineral nutrientsMineral nutrients-- essential elements-- essential elements
minimal contribution to massminimal contribution to mass Water – 80-85% of herbaceous plants Water – 80-85% of herbaceous plants
over 90% lost via transpirationover 90% lost via transpiration Retained HRetained H22O = solvent, maintain O = solvent, maintain
turgidityturgidity Assimilated COAssimilated CO2 2 makes up most of organic makes up most of organic
molecules mass.molecules mass.
How do plants get How do plants get nutrients?nutrients?
Dry WeightDry Weight 95% organic (carbs, CHO, 95% organic (carbs, CHO,
cellulose).cellulose). 5% inorganics5% inorganics
nitrogen, sulfur, and phosphorusnitrogen, sulfur, and phosphorusFound in many organicsFound in many organics
Plant NutrientsPlant Nutrients Essential nutrientsEssential nutrients-- required for a -- required for a
plant to grow from a seed and plant to grow from a seed and complete the life cycle.complete the life cycle.
Plants require 9 macronutrients and Plants require 9 macronutrients and 8 microsnutrients8 microsnutrientsHydroponic cultures identify Hydroponic cultures identify
essential nutrientsessential nutrients
HydroponicsHydroponics
MacronutrientsMacronutrients Needed in large quantities Needed in large quantities 9 macronutrients 9 macronutrients
carbon, oxygen, hydrogen, carbon, oxygen, hydrogen, nitrogen, sulfur, and phosphorus nitrogen, sulfur, and phosphorus (found in organics)(found in organics)
potassium, calcium, and potassium, calcium, and magnesium (ions)magnesium (ions)
MicronutrientsMicronutrients Needed in very small amounts Needed in very small amounts 8 micronutrients 8 micronutrients
iron, chlorine, copper, zinc, iron, chlorine, copper, zinc, magnanese, molybdenum, boron, magnanese, molybdenum, boron, and nickel.and nickel.
Cofactors of enzymatic reactions.Cofactors of enzymatic reactions. Lacking micronutrients can Lacking micronutrients can
kill/sicken a plant.kill/sicken a plant.
Mineral Deficiencies (ex: Mineral Deficiencies (ex: Chlorosis)Chlorosis) Since Mg and Fe are involved in the production Since Mg and Fe are involved in the production
of chlorophyll, their deficiencies are marked by of chlorophyll, their deficiencies are marked by yellow leaves (chlorosis)yellow leaves (chlorosis)
Mineral DeficienciesMineral Deficiencies Mobile NutrientsMobile Nutrients
symptoms of the deficiency will appear symptoms of the deficiency will appear first in older organs first in older organs
Ex: chlorosis affects older leaves firstEx: chlorosis affects older leaves first Immobile Nutrients Immobile Nutrients
affect young parts of the plant firstaffect young parts of the plant first Older tissue = adequate supplies for Older tissue = adequate supplies for
shortagesshortages
SoilSoil The type of soil (composition/texture) The type of soil (composition/texture)
determines the plants that can survive determines the plants that can survive Originates from weathered rock Originates from weathered rock
(minerals)(minerals) Topsoil (product of weathering)Topsoil (product of weathering) Rich in decaying organic material Rich in decaying organic material
(humus), bacteria and rock(humus), bacteria and rock Horizons Horizons Horizontal layers of soil Horizontal layers of soil
SoilSoil
Soil TextureSoil Texture Depends on the size of its particles Depends on the size of its particles
(coarse sand to microscopic clay)(coarse sand to microscopic clay) LoamsLoams
Most fertile soils (equal silt/sand/clay)Most fertile soils (equal silt/sand/clay) fine particles = large surface area for fine particles = large surface area for
retaining minerals and waterretaining minerals and water course particles = air spaces that supply course particles = air spaces that supply
oxygen to the root (respiration)oxygen to the root (respiration)
Waterlogged Soil Waterlogged Soil Too much Too much HH22OO
Water in air spaces can suffocate a Water in air spaces can suffocate a plantplant
Unfavorable molds can grow and Unfavorable molds can grow and attack plant.attack plant.
Mangroves have long, hollow, tube Mangroves have long, hollow, tube roots that allow them to survive in roots that allow them to survive in marshland.marshland.
Topsoil OrganismsTopsoil Organisms 1 teaspoon = approx. 5 billion bacteria.1 teaspoon = approx. 5 billion bacteria. Organisms’ alter the physical and Organisms’ alter the physical and
chemical properties of the soil.chemical properties of the soil. Earthworms aerate soil (burrowing) add Earthworms aerate soil (burrowing) add
mucus holds fine particles together.mucus holds fine particles together. Bacteria (ie: nitrogen fixation)Bacteria (ie: nitrogen fixation) Plants extract nutrients, affect soil pH, Plants extract nutrients, affect soil pH,
and reinforce the soiland reinforce the soil
HumusHumus Decomposing organic materialDecomposing organic material Formed by the action of bacteria Formed by the action of bacteria
and fungi on dead organisms, feces, and fungi on dead organisms, feces, leaves, etc.leaves, etc.Crumbly soil -- retains water, Crumbly soil -- retains water,
porous enough for aeration of porous enough for aeration of rootsroots
Rich in minerals from decomp.Rich in minerals from decomp.
How does Soil Hold Water?How does Soil Hold Water?
•Electrostatic attraction between soil particles and water molecules.
•Plants extract the more loosely bound water molecules
•Surface of soil is charged (hydrophilic)
How does Soil Hold MineralsHow does Soil Hold Minerals
Positively charged minerals (KPositively charged minerals (K++, Ca, Ca2+2+, , MgMg2+2+ are not leached out by rain are not leached out by rain because they adhere to negative because they adhere to negative surface of clay (remember origins!)surface of clay (remember origins!)
Negatively charged mineral ions Negatively charged mineral ions (NO(NO33
--, H, H22POPO44--, SO, SO44
2-2-) leach out more ) leach out more
easily.easily.
Cation ExchangeCation Exchange (+) mineral ions are made available to (+) mineral ions are made available to
the plant when Hthe plant when H++ ions in the soil ions in the soil displace the mineral ions from the displace the mineral ions from the clay particles.clay particles.cation exchangecation exchange
roots secrete Hroots secrete H++ and compounds and compounds that form acids in the soil solutionthat form acids in the soil solution
How does Soil Hold Water?How does Soil Hold Water?
Soil MismanagementSoil Mismanagement The Dust Bowl The Dust Bowl
(1930’s)(1930’s) Farmers removed Farmers removed
grasses that held grasses that held soil in place during soil in place during droughtsdroughts
Topsoil was blown Topsoil was blown away and soil away and soil uselessuseless
FertilizersFertilizers Agriculture requires a lot of mineralsAgriculture requires a lot of minerals Fertilizers replace the minerals in Fertilizers replace the minerals in
the soilthe soil ““10-12-8” Fertilizer = 10% nitrogen, 10-12-8” Fertilizer = 10% nitrogen,
12% phosphorus and 8% potassium12% phosphorus and 8% potassium Used to increase crop yieldUsed to increase crop yield Organic Fertilizers (ie: manure)Organic Fertilizers (ie: manure) Too much = pollution of Too much = pollution of
groundwatergroundwater
Water Availability and Water Availability and IrrigationIrrigation Top limiting factor for plant growthTop limiting factor for plant growth Irrigation = bring water to dry Irrigation = bring water to dry
areas (ie desert)areas (ie desert) Irrigated water that evaporates Irrigated water that evaporates
leaves salt behind.leaves salt behind.Lowers soil HLowers soil H22O potentialO potential
plasmolysisplasmolysis
Wind and ErosionWind and Erosion
Wind destroys topsoil of many Wind destroys topsoil of many crops.crops.
Planting trees or other crops Planting trees or other crops (alfalfa) in rows between (alfalfa) in rows between fields.fields.Acts as a windbreak for soilActs as a windbreak for soil
Wind and ErosionWind and Erosion
Sustainable AgricultureSustainable Agriculture
The goal is to eventually The goal is to eventually develop farming techniques develop farming techniques that are maximally that are maximally conservation minded, conservation minded, environmentally friendly, and environmentally friendly, and profitable.profitable.
Human InfluenceHuman Influence Humans have made many areas Humans have made many areas
uninhabitable for both flora and faunauninhabitable for both flora and fauna contamination and/or overdevelopment.contamination and/or overdevelopment.
Phytoremediation – Phytoremediation – Use of plants that Use of plants that utilize toxic contaminants to clean up our utilize toxic contaminants to clean up our messmess Ex: alpine pennycress (Ex: alpine pennycress (Thlaspi Thlaspi
caerulescenscaerulescens) accumulates zinc in its ) accumulates zinc in its shootsshoots
Nitrogen FixationNitrogen Fixation Atmosphere = 80% nitrogen, yet Atmosphere = 80% nitrogen, yet
plants suffer from deficienciesplants suffer from deficiencies Plants cant use NPlants cant use N22 (g) directly (g) directly
Must be taken as NHMust be taken as NH44++ or NO or NO33
--
Decomp. of humus by microbes Decomp. of humus by microbes releases usable nitrogen into the releases usable nitrogen into the soilsoil
Denitrifying BacteriaDenitrifying Bacteria
Convert NOConvert NO33-- (usable) into N (usable) into N22
(not usable) which diffuses (not usable) which diffuses into atmosphereinto atmosphere
Denitrifying bacteria remove Denitrifying bacteria remove usable nitrogen from the soilusable nitrogen from the soil
Nitrogen-Fixing BacteriaNitrogen-Fixing Bacteria Nitrogen FixationNitrogen Fixation
Soil microbes convert NSoil microbes convert N22 (not usable) (not usable)
into NHinto NH33 (will be usable) (will be usable)
Nitrogen fixation restocks the soil Nitrogen fixation restocks the soil with usable forms of nitrogen with usable forms of nitrogen (specifically ammonia)(specifically ammonia)
Nitrogenase complex of enzymes Nitrogenase complex of enzymes catalyze rxnscatalyze rxns
Nitrogen Cycle in the SoilNitrogen Cycle in the Soil
Nitrogen FixationNitrogen Fixation Once bacteria release NHOnce bacteria release NH33, it picks up , it picks up
extra Hextra H++ to become NH to become NH44++ which plants which plants
can assimilate directlycan assimilate directly Much NHMuch NH44
++ oxidized to NO oxidized to NO33- - (also (also
absorbed) absorbed) Once absorbed, plants incorporate Once absorbed, plants incorporate
nitrogen into amino acids and nitrogen into amino acids and organicsorganics
SymbiosisSymbiosis When a species participates in a When a species participates in a
direct relationship with an direct relationship with an individual of another species.individual of another species.
Often involve microorganisms.Often involve microorganisms. Can be good, bad, or neutral for Can be good, bad, or neutral for
one or both of the organisms.one or both of the organisms.
Nitrogen-Fixing Root Nitrogen-Fixing Root NodulesNodules
RhizobiumRhizobium bacteria exist in specialized bacteria exist in specialized projections in roots of legumesprojections in roots of legumes
The bacteria fix nitrogen into usable The bacteria fix nitrogen into usable forms. forms.
The plant supplies nutrients to the The plant supplies nutrients to the nodule through xylem and phloem.nodule through xylem and phloem.
Relationship is good for both.Relationship is good for both. Plant gets nitrogen, the bacteria Plant gets nitrogen, the bacteria
obtains nutrients.obtains nutrients.
Root NodulesRoot Nodules
Root NodulesRoot Nodules
MycorrhizaeMycorrhizae Symbiosis b/t fungi and root of nearly Symbiosis b/t fungi and root of nearly all plantsall plants..
Early evolutionary adaptation??Early evolutionary adaptation?? Fungi gets a good (protected) environment with Fungi gets a good (protected) environment with
nutrients from plantnutrients from plant Plant Benefits:Plant Benefits:
FungusFungus surface area and absorbs surface area and absorbs minerals in the soil and supplies them to the minerals in the soil and supplies them to the plant.plant.
Fungi secretes growth factors that stimulate Fungi secretes growth factors that stimulate root growth.root growth.
Fungi produce antibioticsFungi produce antibiotics
Plant ModificationsPlant Modifications Parasites – Plants Parasites – Plants
that steal nutrients that steal nutrients from other plants (ie: from other plants (ie: tap into vascular tap into vascular tubes)tubes)
Carnivores – Plants Carnivores – Plants that eat meat (ex: that eat meat (ex: venus fly trap)venus fly trap)