AMF Enhancement of Plant Water Relations - Aggie Horticulture ...

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Vesicular Arbuscular Mycorrhiza

Arbuscular Mycorrhizal Enhancement of Plant Water RelationsAMF enhancement of drought resistance may be response to better host nutrition—particularlyPhosphorus (Safir & Nelson, 1985); Nitrogen (Subramanian, 2003)Phosphorus AMF affect mechanisms that control plant water relations such as: aLeaf gas exchange (Hardie 1985; Davies et al. 1993; Koide 1993)Generally higher stomatal conductance and transpiration (Augé 2001)Turgor maintenance- osmotic adjustment (Augé et al 1986)Phytohormone production (Duan et al 1995, Nikolaou et al. 2003, Estrada-Luna &Davies, 2003)Nonhydraulic root to shoot communication of soil drying (Augé & Dunn 1991)Root hydraulic conductivity (Sweatt & Davies 1984; Nelson 1987; Cui & Nobel 1992;Syvertsen & Graham 1990)

AMF Enhancement of Plant Water Relations (con.)•Extraradical hyphae development-improved root/soil contact (30 to 100 m /g soil)(Benthlenfalvay et al, 1988, Davies et al, 1992)•Enhancement of soil structure, aggregate stability and subsequent t available soil water(Augé et al. 2001)•Greater carbon allocation (sink-regulated) to roots (Wright et al. 1998)Morphological ChangesHigher root-shoot ratio, greater lateral root formation, leaf abscission (Henderson &Davies, 1990);Leaf expansion (Koide, 1985) Better drought-acclimated AMF plants (greater plant fitness).Drought can enhance colonization & extraradical hyphae formation of AMF.

Plant Water Relations• Plant Acclimation to Drought•Acclimatization of TC produced plantlets

Drought Resistance [Levitt, 1980;Augé 2001](low external H 2 O potential)Drought Tolerance(Survival at low internal H 2 O potential)Drought Avoidance(Maintain high internal H 2 O pot.)Dehydration ToleranceDehydration Avoidance(Survival at low internal H 2 O content) (Maintain high internal H 2 O content)

APPROACH :Compare AMF and Non-AMF plants of comparable sizeand tissue nutritional status.Acclimate plants to drought via repetitive droughtcycles(bell pepper, Rosa hybrida), or a slowlydeveloping drought cycle (chile ancho peppers,neem tree seedlings).

Capsicum annuum(Bell peppers)Glomus deserticola

Bell Pepper: : Capsicum annuum L. ‘Early Bountiful’AMF:Glomus deserticolaFertilization: LANS 22 µg g P ml - 1 AMF; NonAMF 44 µg g P ml-1Drought Acclimated (DA) –PredawnΨ leaf-0.9 MPa; Ψ soil -0.5 MPaNondrought Acclimated (Non-DA)–PredawnΨleaf-0.2 MPa;1/2 plants subjected to four DA cyclesDA and Nondrought acclimated plants subjected to droughtDA and NDA given a 3-day 3recovery cycle.

Leaf water potential (Ψ(leaf ) of bell pepperduring peak drought & recovery

Leaf osmotic potential (Ψ(π ) of bell pepperduring peak drought & recovery

Net photosynthesis (A) of bell pepperduring peak drought & recovery

AMF Enhancement of Drought Stress-Bell PepperAMF Peppers have: Leaf Chlorophyll Stomatal Conductance Photosynthesis Osmotic Adjustment Faster Drought Recovery Phosphorus & plant size notthe limiting factor

AMF Pepper Plants have:•Greater Extraradical Hyphae formation•Greater Soil Aggregation•Improved Soil Tilth•Glomalin – hydrophobicprotein

→ Not all mycorrhiza respond equally to droughtChile ancho pepper:•Glomus fasciculatum(Trappe, Oregon)•ZAC-19: mixed Glomus species: G. albidium, G. claroides,G. diaphamum(Zacatecas, Mexico; 450 mm annual Precipitation;Chamizo, Ferrera-Cerrato, 1998)

Chile Ancho pepper plants during peak drought stress (day 20).AMF Drought SoilMoist.(%)ψ leaf(-Mpa)g s(mmol m -2s -1 )RWC(%)Whole PlantTranspiration(mg H 2Om -2 s -1 )WUE(10 -3 . g.kg -1 )Control No 17.0±1.4 0.1±0 268±14 92.6±1.4 48.2±1.4 5.34 18.9G. fasc. 18.3±0.4 0.1±0 257±13 88.9±1.1 48.1±1.4 5.29 18.7ZAC-19 18.8±0.2 0.1±0 233±19 93.0±1.9 46.7±2.1 5.09 18.8∆(‰)Control Yes 3.9±0.1 0.7±0.1 57±7 80.2±3.4 30.1±1.7 5.55 19.1G. fasc. 3.8±0.1 0.8±0.1 46±4 79.3±1.0 27.1±1.6 5.68 19.2ZAC-19. 4.1± 0.4 0.2±0 51±4 84.4±1.9 25.4±1.9 5.58 19.2SignificanceAMF NS 0.0001 NS NS NS NS NSDrought (D) 0.0001 0.0001 0.0001 0.0001 0.0001 NS NSAMF X (D) NS 0.0001 NS NS NS NS NS

Wilting of Chile Ancho pepper plants -- peak drought stress (day 20).AMF Drought % Plantsnot wilted% Plantsmoderatelywilted% PlantsseverelywiltedControl Yes 0±0 47±12. 53±12G. fasc. 0±0 26±10 74±10ZAC-19. 0±0 79±10 21±11SignificanceAMF NS 0.0026 0.0089Drought (D) 0.0001 0.0001 0.0001AMF x D NS 0.0026 0.0089

Effect of Drought Stress on Colonization of Chile Ancho pepperControlGlomusfasciculatumZac-19% ArbusculeFormation% VesicleFormationDroughtNo 0 56.4a 37.5bYes 0 21.6b 43.0a(Pr>F)NS 0.0001 NSDroughtNo 0 81.4a 29.9Yes 0 42.8b 26.1(Pr>F)NS 0.0001 NS% Total RootColonizationDroughtNo 0 90.2a 51.9bYes 0 62.7b 59.9a(Pr>F)NS 0.0001 0.003

VesiclesGlomus intraradiciesNeem (Azadirachta indica)Appressorium

Table 2. Growth parameters of mycorrhizal (AMF) and Non-VAMneem plants at the end of the drought stress cycle(23 days of drought followed by a 1 day recovery).AMFDroughtacclimationLeafNo.LeafareaPlant dry mass (g)Root/shootratio(m 2 )Leaf(g)Stem(g)Root(g)(g.g - 1 )NonAMFAMFNoYesNoYes29±221±229±223±20.20±0.010.010.14±0.010.010.20±0.010.010.14±0.010.0118±111±118±112±111±18±111±09±111±19±012±19±00.38±0.030.030.47±0.030.030.40±0.020.020.43±0.030.03SignificanceAMFDroughtAMF x DNS**NSNS**NSNS**NSNS**NSNS**NSNS**NS

AMF Effects on Neem Tree Seedlings ± AMF neem trees of similar size and nutrition respond to droughtsimilarly.Neem drought response: decrease in leaf area, gas exchange rate and waterrelations parameters.Rapid recovery after rehydration with an acclimation of stomatal conductance.

Water Use Efficiency Dry Mass gain per total water usage –(g Carbon/kg H 2 O) [Long Term] Gas Exchange: net Photosynthesis/ stomatalconductance (A)) / (g(s ) [Instantaneous]

Table 1. Wager Use Efficiency (WUE) in leaves of well-watered watered and droughtstressed AMF and Non-AMF neem plants during 23 days of drought followedby a 1 day recovery (day 24).Mycorrhiza(AMF)DroughtstressWater Use Efficiency(g DM/ kg H 2O)NoninoculatedInoculatedSignificanceAMFDroughtInteractionNoYesNoYes2.50.92.41.2NS**NS

Water Use Efficiency (con)Stable Isotope Discrimination (C(C 13 /C 12 ) WUE not greater in AMF plants

Table 1. Carbon isotope discrimination (∆)() in leaves of well-watered watered anddrought stressed AMF and Non-AMF neem plants during 23 days ofdrought followed by a 1 day recovery (day 24).MycorrhizaDroughtstress∆ (‰)(AMF) Day 0 Day 24NoninoculatedInoculatedNoYesNoYesMature leaves20.71±0.170.1720.54±0.420.4220.32±0.260.2620.30±0.370.37Expanding leaves21.67±0.2618.66±0.2321.47±0.1219.03±0.590.59Mature leaves20.81±0.240.2420.35±0.510.5121.22±0.2820.18±0.350.35SignificanceAMFDroughtInteractionNSNSNSNS**NSNSNSNS

AMF --MICROPROPAGATED CHILE ANCHO PEPPER PLANTLETSDURING ACCLIMATIZATION AND POST-ACCLIMATIZATIONInoculation TechniqueSpore Slurry Solution:AMF Banding

Transplantation of Chile AnchoExplantGrowth Chamber 5 daysDay 1 — Near 100 % RHDay 2 — Near 100 %Day 3 — 80 %Day 4 — 70 %Day 5 — 60 %Day 6: Transfer to GHRooted Explant5-Day Growth ChamberTransplant

Development of mycorrhiza in micropropagated chile ancho pepper(Capsicum annuum L. cv. San Luis) plantlets during acclimatizationand post-acclimatization(Estrada-Luna & Davies, 2003).

Relative watercontent [RWC]Transpiration [E][Stomatal conductanceNoncolonized (NonAMF)and AMF micropropagatedchile ancho pepper(Capsicum annuum L. cv.San Luis) plantlets duringacclimatization and post-acclimatization(Estrada-Luna & Davies, 2003).Photosynthesis [A][

Leaf chlorophyll of noncolonized (NonAMF) and AMF micropropagatedchile ancho pepper (Capsicum(annuum L. cv. San Luis) plantlets duringacclimatization and post-acclimatization.(Estrada-Luna & Davies, 2003).

Leaf ABAStem ABAAbscisic acid (ABA) innoncolonized (NonAMF)and AMF micropropagatedchile ancho pepper(Capsicum annuum L. cv.San Luis) plantlets duringacclimatization(Estrada-Luna & Davies, 2003).Root ABA

Summary AMF can enhance plant water relations independent of tissue P. Differences among AMF isolates in plant water relations. AMF not more Water Use Efficient Decreased ABA. Drought stress can enhance AMF symbiosis. AMF plants are better acclimated to drought (greater plant fitness) Importance of Extraradical Hyphae-associated associated soil characteristics-soil moisture retention Mechanistic understanding of AMF & Water relations is incomplete(Safir et. al, 1972; Reid, 1979; Augé 2001, 2003)

L. Aguilera-GomezM.J. AlvaradoA. AlarconM. A. ArnoldS.H. BoT.W. BouttonC. CalderónC.A. CallL. Amaya de CarpioA. CartmillCollaboratorsM.C. DrewS.A. DurayJ.N. EgillaA. Estrada-LunaR.C. Ferrera-CerratoY-C C HeJ.C. Henderson-ColeZ. HuamanR.G. LindermanJ.C. Miller, Jr.S.E. NewmanR.J. NewtonL. PhavuphutanonJ.R. PotterV. Olalde-PortugalJ.D. PuryearJ.A. Saraiva GrossiM.E. StrongS.E. SvensonM.E. Sweatt