Herbicide effectiveness under elevated CO2
Authors:• Prof. Michelle Leishman
(NSW)• Dr Paul Downey (ACT)• Dr Tanja Lenz (SA)• @PWaryszak
(WA)
Predicted level of CO2
Ambient CO2 in 2100 = 700 ppm(IPCC 2001)
Ambient CO2 in 2016 = 403 ppmAmbient CO2 in 2012=
380 ppm
Plant responses to the elevated CO2
• Biomass 5• Leaf thickness 5• Wax deposition 5
Source: http://evolution.berkeley.edu/evolibrary/article/mcelwain_02
• Stomatal density 6• Stomatal conductance 6
Effect of Glyphosate on Plants
Our Question:How do Plants Respond to the
Herbicide under Elevated CO2 ?
Glyphosate
Enzyme Immobilization
Starvation
CO2 x Herbicide Effect
• Biomass 5• Leaf thickness 5• Wax deposition 5• Stomatal density 6• Stomatal conductance 6
• Effectiveness of herbicide goes down (dilution?) 6
Source: http://www.sarinalandcare.org.au/plants-database/anredera-cordifolia
single speciesfocusso far
(Anredera)
Plant Species List in Our StudySpecies (15) Family Form (5) Propagation
Avena barbata Poaceae grass seed
Bromus catharticus Poaceae grass seed
Chloris gayana Poaceae grass seed
Ehrharta erecta Poaceae grass seed
Pennisetum clandestinum Poaceae grass seed
Ageratina adenophora Asteraceae herb seed
Tradescantia fluminensis Commelinaceae herb cutting
Verbena bonariensis Verbenaceae herb seed
Asparagus aethiopicus Asparagaceae shrub seed
Cotoneaster glaucophyllus Asteraceae shrub seed
Lantana camara Verbenaceae shrub cutting
Senna pendula Fabaceae shrub seed
Olea europaea Oleaceae tree seed
Anredera cordifoli Basellaceae vine aerial tuber
Ipomoea indica Convolvulaceae vine cutting
Fully FactorialDesign
DESIGN:Herbici
delevel
CO2Ambien
t(380 ppm)
CO2Elevate
d(550 ppm)
Control(none) n≈10 n≈10
Recommended
n≈10 n≈10
Double recommende
dn≈10 n≈10
DESIGN:Herbici
delevel
CO2ambien
t
CO2elevate
dControl(none) n≈10 n≈10
Recommended
n≈10 n≈10
Double recommende
dn≈10 n≈10
10 ml/plant
Measuring the Response:• Biomass ~ CO2 level
• Survival ~ Herbicide Dose + CO2 level
Biomass (g)
Response to CO2 (light)
Source: http://www.nzflora.info/factsheet/Weed/Cotoneaster_glaucophyllus.html
Biomass Response ( g)to CO2 (heavy)
Kikuyu Grass
Survival (%)
Response to
Glyphosate (n≈10)
put in Tanja survival curves
Recommended
Dose
Double Recommend
ed
Surv
ival
Surv
ival
Surv
ival
Week since Spray
Week since Spray
Ambient CO2
Elevated CO2
Survival (%) Response to Glyphosate (n≈10)
Image Source: https://en.wikipedia.org/wiki/Glyphosate#/media/File:Glyphosate-3D-balls.png
Overall Survival
Response (%) to All
Herbicides
Image from: http://www.wikiwand.com/en/Tradescantia_fluminensis
Image from: http://www.wikiwand.com/en/Ipomoea_indica
Survival ~ CO2 + Herbicide
?
Effect on Survival (P<0.001)
Herbicide (-) none
CO2 (+) low
Grass (-) low
Vine (+) High ***
Shrub (+) High***
Herb (+) low
Tree (+) low
Survival in CO2 & Herbicide by Species (low %)
Ambient CO2Elevated CO2
Survival in CO2 & Herbicide by
Species (high %)
Elevated CO2 Ambient CO2
CO2 - Conclusions
Slight but consistent CO2 fertilizing effect
(550 ppm)
Invasive Shrubs and Vines survive best.Species-specific
response to herbicide under elevated CO2
THANK YOU
@PWaryszak
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