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