ROOTSROOTS

►Absorb water and nutrientsAbsorb water and nutrients►Anchor plant in soilAnchor plant in soil►Store carbohydrates/starchStore carbohydrates/starch

Types:Types:

► Taproot systemTaproot system ► Fibrous root systemFibrous root system

Root AdaptationsRoot Adaptations

►Need to adapt to soil env.Need to adapt to soil env.►Root capRoot cap

ProtectsProtects Covers apical meristemCovers apical meristem Involved in gravitropismInvolved in gravitropism

►Root hairsRoot hairs NumerousNumerous Increase surface areaIncrease surface area

Structure of rootsStructure of roots

►EpidermisEpidermis No cuticle in area of root hairsNo cuticle in area of root hairs

►CortexCortex Loose parenchyma cells, some Loose parenchyma cells, some

sclerenchymasclerenchyma Main function is storageMain function is storage Large intercelluar spaces Large intercelluar spaces

► aeration and water uptakeaeration and water uptake

Structure of roots cont.Structure of roots cont.

►EndodermisEndodermis Inner layer of cortexInner layer of cortex Snug fitSnug fit Casparian stripCasparian strip

►SteleStele Vascular cylinder in centerVascular cylinder in center Outermost layer is pericycleOutermost layer is pericycle

►Parenchyma cells give rise to lateral rootsParenchyma cells give rise to lateral roots

Movement of Water into the Movement of Water into the RootRoot

►Root hairsRoot hairs Difference in water potentialDifference in water potential

►2 pathways water can take:2 pathways water can take: SymplastSymplast ApoplastApoplast

Movement of water cont.Movement of water cont.

►Most water moves along cell walls, Most water moves along cell walls, does not enter the celldoes not enter the cell Cellulose absorbs water like spongeCellulose absorbs water like sponge Apoplastic routeApoplastic route Water and mineral ion diffuse across Water and mineral ion diffuse across

cortexcortex

►When endodermis reached, waterproof When endodermis reached, waterproof Casparian strip prevents further Casparian strip prevents further movement along cell wallsmovement along cell walls

►http://plantandsoil.unl.edu/croptechnology2005/pages/animationOut.cgi?anim_name=water_movement_roots.swf

Movement of Water cont.Movement of Water cont.

►Endodermis regulates movement of Endodermis regulates movement of minerals from soil into vascular tissue minerals from soil into vascular tissue and throughout the plantand throughout the plant

►Water enters by osmosisWater enters by osmosis►Dissolved minerals are actively Dissolved minerals are actively

transported against concentration transported against concentration gradientgradient

►Once though endodermal cells, Once though endodermal cells, water/minerals enter xylemwater/minerals enter xylem

MUTUALISTIC MUTUALISTIC RELATIONSHIPSRELATIONSHIPS

►MycorrhizaeMycorrhizae Soil fungiSoil fungi Hyphae increase surface areaHyphae increase surface area Fungi provide essential nutrientsFungi provide essential nutrients

►Root nodulesRoot nodules Roots of legumesRoots of legumes Nitrogen-fixing bacteriaNitrogen-fixing bacteria Atmospheric nitrogen converted to Atmospheric nitrogen converted to ammoniaammonia

Soil EnvironmentSoil Environment

►4 main components:4 main components: Inorganic mineral particlesInorganic mineral particles Organic matterOrganic matter WaterWater AirAir

►3 sizes of inorganic particles:3 sizes of inorganic particles: SandSand SiltSilt ClayClay

Soil EnvironmentSoil Environment

►Clay particlesClay particles Negative chargeNegative charge Attract positive cationsAttract positive cations

►Roots pump out HRoots pump out H++

►Cation exhange occurs at clayCation exhange occurs at clay►Positive minerals can be absorbed by Positive minerals can be absorbed by

rootsroots►Negative anions tend to wash out of soilNegative anions tend to wash out of soil

Soil Properties affect PlantsSoil Properties affect Plants

►Pore Space Pore Space Equals roughly 50%Equals roughly 50% Allows air and water to diffuseAllows air and water to diffuse

►AcidityAcidity Determines solubility of nutrientsDetermines solubility of nutrients May lead to leaching of mineralsMay lead to leaching of minerals

►Erosion = lost fertilityErosion = lost fertility