open stomata: allows for gas exchange: co 2 in and water vapor out atmospheric co 2

Open stomata: allows for gas exchange: CO2 in and water vapor out

Atmospheric CO2


(R): Rubisco: one of the primary enzymesinvolved in photosynthesis



More 12C fixed relative to 13C: light isotopes react faster!




Closed stomata: under water stress plant’s stomata remain closed thus conserving water




Closed stomata: under water stress plant’s stomata remain closed thus conserving waterIncreasing amounts of 13C fixed via rubisco. 13C builds up in concentration due to closed stomata and reduction in 12C concentration




Closed stomata: under water stress plant’s stomata remain closed thus conserving waterIncreasing amounts of 13C fixed via rubisco. 13C builds up in concentration due to closed stomata and reduction in 12C concentration

Plant tissue becomes enriched in 13C.

Less Negative: Becoming enriched in

13C

Relationship between carbon isotope composition (δ13C) from wood cores of Aleppo pine and mean annual

precipitation

Heavier isotopes require more

activation energy

The t-test is used to statistically determine if 2 data sets represent the same population (Fig A) or from 2

different populations (Fig B)

Resp

onse

Var

iabl

e (e

.g. P

lant

gro

wth

rate

)Represented as a distribution

Bar graph with means & standard error

P > 0.05

P < 0.05

-35.00

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00Species A Species B

Normal Precipitation Year

Drought Year

A

B

A A

Questions• Do trees growing during a drought show an isotopic signal that

indicating drought stress?• Do both species respond in the same way to drought? Offer

hypotheses to explain why you observed the pattern you did between species.

• Compare these data to those published in specifically Figure 2: Zhang et al (1997) Carbon isotopic composition, gas exchange, and growth of three populations of ponderosa pine differing in drought tolerance. Tree Physiology 17: 461-466.

• Ask students: to these data show that drought has any effect on plants?

• Ask students to discuss how they would experimentally test to determine if drought actually did have an effect on plants.

• How could understanding carbon isotopes be useful in identifying sources of carbon dioxide emitted to the atmosphere?

What is the effect of exotic fish on the structure of aquatic food webs?The data below are based off of Marks et al. (2010): Effects of flow restoration and exotic species removal on recovery of native fish: lessons from a dam decomissioning. Restoration Ecology 18:934-943Data are delta 15N values

Native Fish Aquatic insect Native Fish Aquatic insect Native Fish Aquatic insectSample # G. robusta Shredder R. osculus Grazer C. clarkii Predator

1 9.5 2.8 8.8 4.2 8.2 5.52 9.9 4 9.2 5 7.8 63 9.8 3.6 9 4.8 8.5 6.24 9.5 3.8 9.2 4.2 9 6.35 9.7 3.5 9.1 4 8.3 5.8

Means 9.68 3.54 9.06 4.44 8.36 5.96Stdev 0.18 0.46 0.17 0.43 0.44 0.32

Exotic Fish Native Fish Aquatic insectNative Fish Aquatic insectNative Fish Aquatic insectExotic FishSample # M. dolemieu G. robusta Shredder R. osculus Grazer C. clarkii Predator L. cyanellus

1 11.2 7.2 2.5 7.9 4.5 7.1 5.8 10.92 11.5 7.3 3.8 7.9 4.8 6.9 5.9 10.53 10.8 7.5 2.9 7.5 5.2 7.2 6.1 10.24 11.7 7.8 3.2 7.3 4.2 7.7 6.2 9.85 11.6 7.2 3.8 7.8 4.1 7.6 5.8 10.3

Means 11.36 7.4 3.24 7.68 4.56 7.3 5.96 10.34Stdev 0.36 0.25 0.57 0.27 0.45 0.34 0.18 0.40Ttest NA NA

0

1

2

3

4

5

6

7

8

9

10

11

12

G. rob

usta

Shre

dder

R. o

scul

us

Graz

er

C. cl

arkii

Pred

ator

Exotic Fish Absent

Exotic Fish Present

11.36: M. dolemieu

10.34: L. cyanellus

Questions• What is the effect of exotic fish on the

structure of stream food webs?• Who does it appear that the exotic fish are

feeding on?• Who would have higher 15N values: a vegan

or a person who consumed meat?• What are some other applications of nitrogen

isotopes? (e.g. diets of human ancestors)

open stomata: allows for gas exchange: co 2 in and water vapor out atmospheric co 2

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