UV-B Radiation, Poplar Phytochemistry & Herbivory

Jeffrey M. WarrenJohn H. Bassman

Washington State University

EPA STAR Graduate Fellowship Program

Ultraviolet Radiation

• Ozone Loss

• UV-B Radiation Increase

• ChromophoresPhenolics, proteins, DNA

• EffectsDirect versus indirect

Effects of UV-B Radiation

UV-B Absorbed

AlteredGrowth

AlteredLitter

AlteredSecondaryChemistry

AlteredCarbonAllocation

AlteredMorphology

Shift inCompetitiveBalance

PathogenRelations

Objectives

• Identify effects of enhanced UV-B radiation on Populus tricocarpa foliar biochemistry:

PS, chlorophylls, flavonoids, nutrients, tannin

• Do these UV-B induced changes affect Chrysomela scripta herbivory:

Growth rate, preference

Methodology - UV-B Lamps

• Enhanced UV-B lamp systemsIndoor non-modulated, Outdoor

modulated

• Indoor Study Design3 treatments (0X, 1X, 2X UV-B for Pullman,

WA)4 blocks4 trees/block

Methodology - Trees

• Harvest ParametersGrowth, leaf area, leaf plastochron index

• ChemistryPhotosynthesis - 14C (30 sec pulse)Chlorophyll a, b - DMF extractionFlavonoids - HPLC (ether, EA purification)Nitrogen, Sulfur, Carbon - CombustionTannins - CBB-BSA binding assay

Methodology - Insects

• Feeding preference trialsSingle beetle in petri dish with leaf disks3 treatments, 30 reps, 24 hours

• Growth rate trialsRecently hatched larva grown on single

leaf3 treatments, 90 reps, 2-3 weeks

3.0

3.2

3.4

3.6

Treatment

SH

OO

T:R

OO

T R

ati

o (

g/g)

0X UVB1X UVB2X UVB

0

2

4

6

8

10

12

14

LPI 1 LPI 7 LPI 13

Leaf Plastochron Index

PH

OTO

SYN

TH

ESIS

(um

ol CO

2 fi

xed m

-2 s

-1)

0X-UVB

1X-UVB

2X-UVB

3.5

5.0

6.5

LPI <2 LPI 4 LPI 6-8 LPI 9-11 LPI 12-14

Leaf Plastochron Index

Foliar

NIT

RO

GEN

(%

) 0X-UVB1X-UVB2X-UVB

6

7

LPI 3 LPI 5 Mean LPI

Leaf Plastochron Index

INSECT B

IOM

ASS (

mg)

0X-UVB1X-UVB2X-UVB

0.17

0.19

0.21

0.23

0.25

0.27

270 280 290 300 310 320

Wavelength (nm)

UV

-B A

bso

rbin

g C

om

pounds

(rel

ati

ve a

bso

rbance

)0X UVB1X UVB2X UVB

13

15

17

LPI <2 LPI =4 LPI 6-8

Leaf Plastochron Index

Foliar

TA

NN

IN(m

g T

AE /

g D

W p

opla

r)1X-UVB2X-UVB

0.004

0.008

0.012

9/ 28/ 99 10/ 13/ 99 Mean

Mass

Eate

n T

issu

e : C

LB m

ass

(g

/h)

0X-UVB

1X-UVB

2X-UVB

Conclusions

• Increased UV-B radiation:

• Increased foliar nitrogen and photosynthesis

• Increased flavonoids but decreased tannins

• Increased CLB preference / CLB growth rate