Sun and Shade Acclimation of the Photosynthetic Apparatus in Gymnostomum aeruginosum

Adam Yock2003-04

http://www.scibridge.sdsu.edu/coursemats/introsci/diversity/chlorobionta/chlorobionta_cladogram.jpg

Chloroplast

ChloroplastGranum (stack of thylakoids)

Thylakoid

ChloroplastGranum (stack of thylakoids)

LHCRC

electron transport pathwaySun

Photons

Thylakoid

NADPHNADP+

ADP + P

ATP

PSIPSII

Light-Harvesting Complexes (LHC)• Photosystematic antennas• Contain chl a and b

Reaction Centers (RC)• Beginning of electron transport chain• Contain chl a

Introduction

Lower-order Plants(bryophytes)

Higher-order Plants

Sun-acclimated Specimen• More RC• Less LHC• Higher Chl a/b

Shade-acclimated Specimen

• Constant RC, LHC, and Chl a/b

• Less RC• More LHC• Lower Chl a/b

Reactions of Light-acclimated Specimens

LHCchl a/b

chl a/b

chl a/b

• Post and Vesk analyzed light adaptability in moss using chl a/b

Previous Studies

Analyze light adaptability in moss (Gymnostomum aeruginosum) using both a chlorophyll ratio (chl a/b) and a protein ratio (LHCp/RCp).

Purpose

Peas:• Both chl a/b and LHCp/RCp would significantly change

Moss: • Neither chl a/b nor LHCp/RCp would significantly change

Hypotheses

1:

p = 6. 2464 x 10-5p = 0.8868

Table 1: Average Chlorophyll/gram of Fresh Weight

Ave µg Chl a+Chl b/gFw SD t-testSun-acclimated Moss 559.6 105.8 p = 0.0050Shade-acclimated Moss 2259 776.6

Tris-Tricine 10-16% gradient Electrophoresis gel

2:

3:

Table 2: Thylakoid Protein Ratios (LHCp/RCp) in Peas

Table 3: Thylakoid Protein Ratios (LHCp/RCp) in Moss

•Explore the apparent discrepancy between the change in chlorophyll ratios and the change in the protein ratios

•Use at least three thylakoid isolations per specimen

Further Study

• Dr. Verhoeven

• Ms. Fruen

• Breck Team Research 2003-04

Acknowledgements

Sun and Shade Acclimation of the Photosynthetic Apparatus in Gymnostomum aeruginosum

Adam Yock2003-04

• Chl a = 12.25 x A663.6 – 2.55 x A646.6

• Chl b = 20.31 x A646.6 – 4.91 x A663.6

• Chl a + Chl b = 17.76 x A646.6 + 7.34 x A663.6

Absorbance readings entered into the equations:

Analysis

Chlorophyll Ratios: • Pea chl a/b changed significantly (p = 6. 2464 x 10-5)

• Agrees with hypothesis

• Moss chl a/b did not change significantly (p = 0.8868 )•Agrees with hypothesis

Discussion

Protein Ratios: • Pea LHCp/RCp changed significantly (p = 1.44 x 10-5)

• Agrees with hypothesis

• Moss LHCp/RCp changed with marginal significance (p = 7.00 x 10-2)

•Does not agree with hypothesis

Discussion

Methods: Collecting Moss/pea Samples

Peas:• Grown from seed

Moss:• Harvested from the banks of a small rivulet in St. Paul, MN

•Prepared-Moss ground in liquid nitrogen-Peas blended in a blended

•Vortexed and spun in centrifuge (moss twice, peas three times) •Aliquoted

Isolating Moss/pea Thylakoids

•Mixed with acetone-Moss ground in acetone-Peas diluted with acetone and vortexed

•Spun in centrifuge (moss twice, peas once)•Read supernatant in spectrophotometer at 663.6 nm and 646.6 nm

Measuring Moss Chlorophyll Content

• Spun in centrifuge• Boiled

Moss/pea SampleElectrophoresis Preparation

Results