ROOTS The Hidden Secrets of Plants by John G. Mexal NMSU.

ROOTSROOTSThe Hidden Secrets of PlantsThe Hidden Secrets of Plants

byby

John G. MexalJohn G. MexalNMSUNMSU

Roots --Roots --How Big is the Problem?How Big is the Problem?Rye plant (Rye plant (Secale cerealeSecale cereale))

Type Number Length (m)

Main 143 65

Secondary 35,600 5,181

Tertiary 2,300,000 174,947

Quarternary 11,500,000 441,938

Total 14,000,000 609,570

RootsRoots

StructuresStructuresFate of rootsFate of rootsRole of symbiosisRole of symbiosisTypes of symbiosisTypes of symbiosis InoculationInoculationResponse to inoculationResponse to inoculation

Root StructuresRoot Structures

Radicle Radicle TaprootTaproot: primary root; : primary root;

develops from develops from radicleradicle

Lateral rootsLateral roots: : 11oo develop from taproot. develop from taproot. 22oo develop from 1 develop from 1oo lateral lateral

rootroot Feeder rootsFeeder roots: short roots: short roots Root hairsRoot hairs

Root StructuresRoot Structures

Adventitious RootsAdventitious Roots Roots occurring where Roots occurring where

they are not normally they are not normally found.found.

Example: Anchor roots Example: Anchor roots of corn.of corn.

Important in asexual Important in asexual propagation (rooting)propagation (rooting)

Developing RootDeveloping Root

Stern 2006

Root Cross SectionRoot Cross Section

Fate of Feeder Roots /Fate of Feeder Roots /Wilson 1984Wilson 1984

RootsRoots

Contrary to their image, there are more good germs than bad germs. It’s just that the badgerms get all the publicity.

SymbiosisSymbiosis

DefinitionsDefinitions

SymbiosisSymbiosis: literally; living : literally; living togethertogether

ParasitismParasitism CommensalismCommensalism MutualismMutualism

SymbiosisSymbiosis

DefinitionsDefinitions

SymbiosisSymbiosis: literally; living together: literally; living together ParasitismParasitism: living together where one : living together where one

benefits at the expense of the other.benefits at the expense of the other.

Emroy Shannon

SymbiosisSymbiosis

DefinitionsDefinitions

SymbiosisSymbiosis: literally; living together: literally; living together ParasitismParasitism:: CommensalismCommensalism: living together : living together

where one benefits, but the othwhere one benefits, but the otherer is unaffected, e.g. epiphytes, is unaffected, e.g. epiphytes, bromeliads.bromeliads.

Trudi Schaper

SymbiosisSymbiosis

DefinitionsDefinitions

SymbiosisSymbiosis: literally; living together: literally; living together ParasitismParasitism:: CommensalismCommensalism: : MutualismMutualism: living together : living together

where both parties benefitwhere both parties benefit,,

e.g. lichen.e.g. lichen.

Role of Symbionts in MutualismRole of Symbionts in Mutualism

Function Mycorrhizas N2 fixers Endophyte

Nutrient supply

Yes Yes No

Water uptake

Yes No No

Pest Resistance

Disease ? Insect

Types of MutualismTypes of Mutualism

Mycorrhiza Nitrogen Fixation Common Name

Family Endo- Ecto- Frankia Rhizobium

Legume Fabaceae + + - + Mustards Brassicaceae - - - - Pines Pinaceae - + - - Beech Betulaceae + + + - Willow Salicaceae + + - - Grasses Poaceae + - - -

SymbiosisSymbiosis Plant:Plant InteractionsPlant:Plant Interactions Nitrogen Fixing (certain Nitrogen Fixing (certain

species)species) Mycorrhizas (nearly all Mycorrhizas (nearly all

plants)plants) Endophyte (antifeedant Endophyte (antifeedant

in grasses)in grasses) AcremoniumAcremonium on fescue and on fescue and

ryegrassryegrass

http://www.noble.org/Ag/Research/Articles/TallFescueToxicity/Index.htm

Vegetation TypeVegetation Type Heath/Heath/ Conifer Deciduous Conifer Deciduous GrasslandGrassland

TundraTundra

MycorrhizaMycorrhiza EricoidEricoid Ectomycorrhiza Ectomycorrhiza EndomycorrhizaEndomycorrhiza

Limiting NutrientLimiting Nutrient N N N/P N/P N/P N/P P P

Increase in latitude or altitude

SymbiosisSymbiosis

Mycorrhiza: ‘Fungus Root’Mycorrhiza: ‘Fungus Root’

After Read 1984

SymbiosisSymbiosis

Mycorrhiza: ‘Fungus Root’Mycorrhiza: ‘Fungus Root’

Coralloid Mycorrhiza

Mycorrhizal RootsUninfected Roots

Live Root Hairs

Dead Root Hairs

Hyphae

EctomycorrhizasEctomycorrhizasSwollen, forked fine rootsSwollen, forked fine rootsFungal mantleFungal mantleHartig netHartig netNo intracellular hyphaeNo intracellular hyphae

RootsRoots

Roots- ectomycorrhizasRoots- ectomycorrhizas

MechanicalBarrier

ChemicalBarrier

Absence of root exudatesrequired by pathogens

Presence of antagonistic rhizospere microoganisms

Absence of root exudatesrequired by pathogens

Ectomycorrhiza developmentEctomycorrhiza development

EndomycorrhizasEndomycorrhizasNo obvious external root modificationNo obvious external root modificationNo mantle or Hartig netNo mantle or Hartig netExtensive intracellular hyphaeExtensive intracellular hyphaePresence of arbuscules, vesicles, & Presence of arbuscules, vesicles, &

chlamydosporeschlamydospores

RootsRoots

EndomycorrhizasEndomycorrhizas

Arbuscules

Spores

Hyphae

Symbiont InoculationSymbiont InoculationSporesSporesMyceliumMyceliumInoculated rootsInoculated roots

RootsRoots

Response to InoculationResponse to Inoculation

IlexCitrus

Nitrogen FixationNitrogen FixationRhizobiumRhizobium + legumes + legumesFrankiaFrankia + various families + various families

Russian oliveRussian oliveAlderAlderMt. mahoganyMt. mahogany

RootsRoots

Globally, 140 billion kg N Globally, 140 billion kg N fixed/ yr by symbiotic fixed/ yr by symbiotic organismsorganisms

Atmosphere = 78% NAtmosphere = 78% N22

Convert NConvert N22 gas into amino acids gas into amino acids Legumes + Bacteria Legumes + Bacteria

((RhizobiumRhizobium)) Alder + ActinomyceteAlder + Actinomycete

((FrankiaFrankia)) Cycads + Blue green algae Cycads + Blue green algae

(Nostoc(Nostoc))

0 lb N/ac 175 lb N/ac

SymbiosisSymbiosis

Nitrogen FixationNitrogen Fixation

0 lb N/ac 175 lb N/ac

Rhizobium on soybeanRhizobium on soybean

FrankiaFrankia on on AlnusAlnus

Roots-- Terms to KnowRoots-- Terms to Know

RadicleRadicle Taproot (primary root)Taproot (primary root) Lateral rootsLateral roots

11oo

22oo

33oo

Root hairsRoot hairs Feeder rootsFeeder roots Adventitious rootsAdventitious roots

SymbiosisSymbiosis MutualismMutualism ParasitismParasitism CommensalismCommensalism

Actinorhiza (Actinorhiza (FrankiaFrankia)) NN22 Fixing ( Fixing (RhizobiumRhizobium)) Endophyte (grasses)Endophyte (grasses) MycorrhizaMycorrhiza

Endo- Endo- --Ecto---Ecto-

Nursery InoculationNursery Inoculation

RootsRoots

Response to InoculationNursery - Increased size

- Increased value- Decreased culls

Field - Improved survival- Improved growth- Altered mycoflora

Response to InoculationResponse to Inoculation

Response to Inoculation /Response to Inoculation /Pinus Pinus radiata)radiata)

Killing TreesKilling TreesMycorrhizal Inoculation + Fertilization/Mycorrhizal Inoculation + Fertilization/

Scott-Lifland 2000Scott-Lifland 2000

0

1

2

3

4

5

10/22/98 2/21/99 6/23/99 10/23/99 2/22/00 6/23/00

Control Trowel Injection

Trunk Diameter (cm) Schinus molleMycorTree Injectable

PHC BioPak

59 g nitrogen

Mycor Tree SaverPHC BioPak

Southwest Trees & Turf 9/’00