ROOTS ROOTS The Hidden Secrets of Plants The Hidden Secrets of Plants by by John G. Mexal John G. Mexal NMSU NMSU
Dec 21, 2015
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