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