8/7/2019 CAM lab write up

http://slidepdf.com/reader/full/cam-lab-write-up 1/4

Malic Acid Concentrations, Energy Dissipation Levels, and Pigment Ratios in CAM

Pathway Full Light and Shade Acclimated Plants

Adam Karl

Crassulacean acid metabolism (CAM) is an effective alternative means for plants

to store carbon dioxide to use in the Calvin Cycle in water stressed environments.

However, because CAM plants have finite malic acid stores, light saturated CAM plants

may deplete their malic acid stores before the day is over. Three jade plants (Crassula

ovata) were exposed to high light (350-400 μmol photons/sec meter 2) and three to low

light (32-40 μmol photons/sec meter 

2

) for ten hours to measure how titrateable acidity

levels, photosystem II efficiency, and xanthophylls cycle pigment pools are affected as

malic acid stores are depleted. High light treatment plants had significantly lower 

titrateable acidity levels than low light plants, and had significantly lower acid levels at

the end of the day than at the beginning (Figure 1). High light plants also had

significantly lower photosystem II efficiencies than low light plants, and had significantly

lower PSII efficiencies at the end of the day than at the beginning (Figure 2). There was a

significant relationship between titrateable acid level and photosystem II efficiencies in

high light plants (Figure 3). In high light plants, there was a strong relationship between

the proportion of xanthophylls cycle pigments as zeaxanthin and antheraxanthin and the

length of light exposure (Figure 4). There is also a strong inverse relationship in high

light plants of the proportion of xanthophyll pigments as zeathanthin and PSII efficiency

(Figure 5). We argue that as malic acid stores in high light plants became depleted,

photosystem II became less efficient due to a lack of ADP and NADP+ to reduce because

they were already reduced as ATP and NADPH and unable to become oxidized in order 

8/7/2019 CAM lab write up

http://slidepdf.com/reader/full/cam-lab-write-up 2/4

to fuel the Calvin Cycle because there was no malic acid as a carbon source for the

process. A higher proportion of xanthophylls cycle pigments were in the forms of 

antheraxanthin and zeathanthin in order to dissipate the excess energy the saturated and

eventually nonfunctional photosystems were not able to utilize.

High

Low

Light Treatment

Error Bars show Mean +/- 1.0 SE

Bars show Means

0.0 2.5 5.0 7.5 10.0

Length of 

Light Exposure (hr)

0.00

50.00

100.00

150.00

Titrateable A

cidity

 (µequ acid g

FW-1)

Figure 1: Mean titrateable acidity levels of leaf tissue from high and low light treatmentsover a day of radiation exposure (N=3 for each measurement). A 1-way ANOVA reveals

a significant difference between high and low light plants (p<0.001). High light

titrateable acid levels from 0 and 2 hours of light exposure were significantly higher thanthe acid levels for the rest of the day (tukey p< 0.019). There was no significant

difference in acid levels within the low light treatment.

8/7/2019 CAM lab write up

http://slidepdf.com/reader/full/cam-lab-write-up 3/4

High Low

 

0.0 2.5 5.0 7.5 10.0

Length of 

Light Exposure (hr)

0.000

0.200

0.400

0.600

0.800

PSII Efficien

cy

0.0 2.5 5.0 7.5 10.0

Length of 

Light Exposure (hr)

Figure 2: Mean photosystem II efficiencies from high and low light treatments over a dayof radiation exposure (N=3 for each measurement). A 1-way ANOVA reveals a

significant difference between high and low light PSII efficiencies (p<0.001). High lightPSII efficiencies from 0 hours of light exposure were significantly higher than theefficiencies for the last three measurements of the day (tukey p<0.009) and PSII

efficiencies from 2 hours of light exposure were significantly higher than those of the last

two measurements (tukey p<0.022). There was so significant differences in low light PSIIefficiencies.

High Low

 

0.00 50.00 100.00 150.00

Titrateable Acidity

(µequ acid gFW-1)

0.200

0.400

0.600

0.800

PSII Efficiency

PSII Efficiency = 0.26 + 0.00 * TitrateableAcidityµequacidgFW1

R-Square = 0.58

0.00 50.00 100.00 150.00

Titrateable Acidity

(µequ acid gFW-1)

PSII Efficiency = 0.79 + -0.00 * TitrateableAcidityµequacidgFW1

R-Square = 0.02

Figure 3: PSII efficiency in relation to titrateable acidity levels for high and low lighttreatments. High light had a strong relationship between PSII efficiency and titrateable

acidity levels (R 2=0.585). There was not a strong relationship with low light (R 2=0.154).

8/7/2019 CAM lab write up

http://slidepdf.com/reader/full/cam-lab-write-up 4/4

High Low

 

0.0 2.5 5.0 7.5 10.0

Length of 

Light Exposure (hr)

0.3

0.4

0.5

0.6

0.7

0.8

ZA per VAZ

ZA per VAZ = 0.31 + 0.05 * LengthofLightExposurehr 

R-Square = 0.67

0.0 2.5 5.0 7.5 10.0

Length of 

Light Exposure (hr)

ZA per VAZ = 0.30 + 0.00 * LengthofLightExposurehr 

R-Square = 0.07

Figure 4: Proportion of xanthophyll cycle pigments as zeaxanthin and antheraxanthin in

relationship to length of light exposure for high and low light treatments. There was astrong relationship for high light plants (R 2=0.669), but not low light plants (R 2=0.066).

High Low

 

0.200 0.400 0.600 0.800

PSII Efficiency

0.00

0.20

0.40

0.60

Z per VAZ

Z per VAZ = 0.62 + -0.73 * PSIIEfficiency

R-Square = 0.49

0.200 0.400 0.600 0.800

PSII Efficiency

Z per VAZ = 0.04 + 0.03 * PSIIEfficiency

R-Square = 0.00

Figure 5: Proportion of xanthophyll cycle pigments as zeaxanthin in relationto PSII

efficiency in highand low light treatments. There is a strong inverse relationship for high

light treatments (R 2

=0.585), but not for low light treatments (R 2

=0.024).