Aspects of photoadaptation in the intertidal red alga Gracilaria chilensis

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Frontispiece

Gracilaria chilensis growing on intertidal rnud flats. Blockhouse Bav.

Manukau Harbour, Auckland. New Zealand.

Aspects of Photoadaptation in the

fnhrtidal Red Alga Gracilaria chilensis

Michelle Lisa Glogau Stevens

A thesis submitted for the degree of Doctor of Philosophy in Botany

Universiry of Auckland

February 1992

INn/ERsITY OF AUCKLANO TIBMRY BICLC3Y

Tl{ESIS

;,

Abstract

The intertidal red alga, Gracilaria chilensis Bird, Mclachlan er Oliveira

(Rhodophyta, Gracilariales), lives

in

an environment

in

which

light

is

highly

variable

in terms of both amplitude and duration. A laboratory investigation of

the

photophysiology of G. chilensis was conducted to

assess

the

response

of

the photosynthetic _apparatus to

light variability

characteristic of the natural environmenr

Freshly collected

Gracilaria

chilensis was found to

exhibit

an endogenous rhythm

of

photosynthesis

in

conditions

of

constant

limiting light

and temperarue. However,

such a phenomenon was not obscrved in saturating light. Rhythms of

phycobiliprotein

concentration and dark respiration were also observed but were not as well-defined and could nor account

for

the photosynthetic rhythm.

The photosynthetic

response

of G. chilensis to light fluctuations of various

durations (0.25 to 900 seconds) and

light

levels was compared

to

that

in

static light.

G. chilensis was able to

utilise rapidly

fluctuating

light (< I

second) more

cfficiently

than fluctuations

of

longer duration (60-900 second). Mean photosynthetic rates werc enhanced

by

uP

to

l50Vo

in fluctuating light of

less than

60

sec duration

over

that predicted

from

steady-state.

The photosynthetic _appararus

of freshly

collected

G.

chilercis was

found to

have

many low-light "shade" acclimation characteristics. These included a low compensation point (5 pmolm-2 s-l) and onset of saturation (80 }rmolm-2 s-l;

suggesting sensitivity to

photoinhibition.

However, (laboratory)

low-light

acclimated

G.

chilensis was able to tolerate periods of constant high

light

(2000 lrmolm-2

r-l; for

periods

of

six hours

without

detectable detrimental effect on photosynthetic _capacity, although photosynthetic

cfficiency

was

significantly inhibited

after

two

hours

of

this treatment.

The time

course and

characteristics of photoacclimation were determined by culturing G.

chilersis

in low-

(15

pmol

_m-2

s-l)

and

high-

⁽¹⁸⁰

pmol .-2 r-l; [ghr and high- and low-nitrogen regimes. The observed change in photosynthetic

characteristics and

pigment

concentration indicated

that acclimation

began

after

a

time

lag

of l-2

days, was complete

aftcr

approximately a week and was reversible.

Acclimation to growth light

included _changes

in growth

rate,

P-I

response curves,

pigment concentration

and

composition

and

other biochemical

components (e.g.

carbon/nitrogen ratio). The nitrogen regime significantly affected pigment

concentration

in

the

high-light

grown plants and the rcsponse suggesrs pigments play

a role in nitrogen storage as

well

as

light

harvesting.

These various

physiological

characteristics described above were interpreted as

important

mechanisms that enable

G.

chilensis

to

optimise photosynthetic response

in

the

highly

dynamic and stressful zone

of

the

intenidal

environment.

Page v

Acknowledgments

Special thanks

go to my

supcrvisor, Frank Dromgoole,

for his

enthusiastic suppon and guidance throughout this project, and his patience

in

waiting

for

0re end

"pncduct'.

David

Chapman

provided me with helpful

advice and

wcnt far out of his way

to solve my pigment analysis dilemma.

I would

also

like to

thank the many people

who

assisted me, proffened advice and

kept me cheerful during

the

projecc Linda

Vy'orkman,

Brian Sorrell,

Paula

Kenrick, Terry and Dara Robinson, Brian wilson, Richard Serra, Ewan Cameron, Iain McDonald, Nicola watson, Erika Little, Anne wilson, Brian McArdle, rohn

Cole,

Flavia Clifford-White, Dianne Brunton, Margaret Gordon, Bill vant,

John

Brown, Alwyn

Rees,

Tim Pickering, Peter &

Pat

Lovell, John Christeller, William Laing,

Wendy Nelson, Chris and Claire

White, David

_and

Lynn

Lambert

&

the rogues

from

the Evolutionary _Genetics Laboratory, Marie Taylor,

Larry

Jensen, Maureen Thompson and Douglas Rogan.

I would like to acknowledge the financial

assistance

of the University

Grants Committee

for

the Post-Graduate scholarship that

provided

_three years

of

support

for

my Ph.D.

To

my families

(Glogau, Stevens and

Harris),

especially

Omi, Linda

and Trevor, a special thank you

for your

love, encouragement, support and

for

having the conviction that

I

would get thcre

in

the end.

Finally, I wish to

thank you, Peter,

for your love,

friendship, and help

-

especially those endless hours spent at the computer

ryping in my

references and perfecting _the thesis layout. Most

of

all, thank you

for

being there when

I

needed you.

Page

vi

Thble of Contents

Abstract

Ackttowledgments

Table

of

Contents

Teblc

of

Figures andTables

List of

Ahhreviations Generd Intm&tction

chapter 1

Endogenous _Rhythms

of

photosynthesis

and Respbdion in Gracilaria

ehilensis,

Innoduction

Methods

Plant Material and Collcction Apparatus

Experirnental _Procodure Calculations

Satistical

Analysis

Results

Light

Responses Dark Responses

Discussion

v

vi

vii

xl

xvl

I

7

8

I

9 9 13

l3

13 20

u

Pagevii

Table of Contents

Chapter

2

Chapter 3

Sbdy

State and

Dynantic

Plntosynthcsis

iz Gracilaria

chilensis.

Inuoduction

₃₅

Methods

Plant Material Apparatus Treatrncnt Calculations Statistical Analysis

Results

Steady-State Reqponses Flucnrating

Light

Responses

Mean Photosynthctic Reqponse to Fluctuating

Light of

Various Periods and

ppFD

Discussion

Adjustnrent Responses Fluctuating

Light

Photoinhibifion

of P hoto sy

ntlu

sis

in

Low

-Light

occlimote

d Gracilaria

chilensis.

Introduction

Methods

Plant Material, Collection and

Culturc

Apparatus

Erperimental Procedure Calculations

Statistical Analysis

Results

36 36 36 38 42 43

43 43 46

53 53 56

68 68 68 69 70 70

Page

viii

Table of Contents

P-I

Curve

Conuol

P-I

Curves

High UghtTreatment

Discussion

Introduction

Methods

Plant Material, Collection and Culturc Experimental

hocedure

Measurements and Calculations Statistical Analysis

Results Part

I

Specific Growth Rates

Pigment C-oncennations and Ratios

Photosynthetic and Respiration Responses

Acclimation

_{Kinetics and Time}

Dry

Weight/Fresh Weight Ratio

Carbon Contenq Nitrogen Content and Carbon/t litrogen Ratio

Pan2

Photoacclimation _to

High Light

Photoacclimation _to

l,ow Light

Discussion

70

7l 7l

73 Chapter

4 Time

scales

and chuocteristics

of

photoacclimation in Gracilaria

chilensis

83

84 86 87 89

89

89 90 99

ll3

l16

r16

118

ll8

r20

r20

Conclading

Discassion

t4l

Table of Contents

Appendix

1 collection

site ond

Hfrit o/Gracilaria

chilensis. 148

Appendix2 WoundRespnse of Gracilaria

chilensis

:Tln

Effect of

Woanding

on

Plwtorynthesis and

respiration.

Appendix

3

^Pigment

Extraction

andAnalysis

in Gracilaria chilensis.

153

Appendix

4 LishtUariobility

at

Blacklnuse

Bay. ₁₅₆

Appendix

5 Modifud

Provssolirs Nutrient

Mediunt

Appendix

6 hrodifwd Kjeldahl

Method

of

Nitrogen

Determination 16l

Literature Cited

150

160

163

Page

x

List of Figures and Thbles

chapter 1 Endogercus

_Rhythms

of

phonsynthesis

andRespiration in Gracilaria

chilensis

Figure I

Apparatus

for

oxygen exchange

nreasurements. l0

Figure 2

Oxygen electrode

chamber. lI

Figure 3

^P-I curve

for

freshly collected

G. chilewis.

¹²

Figure 4

^Rhythm

of

photosynthetic

activity

in _constant

limiting light

and

temperature.

14

Figure 5

Rhythms of photosynthetic activity, pigment

concentration and pigment

ratios.

16

Figure 6

Rhythms of photosynthetic activity, pigment

concentration and pigment

ratios.

17

Figure 7

Rhythms of photosynthetic

activity

reploned _on

phycoerythrin

basis. Zl

Figure I

Photosynthetic

activity

in constant saturating

light

and

temperature.

₂₂

Figure 9

Rhythms of dark respiration rate in constant

darkness and

temperature.

₂₃

Thbfe

I

characteristics

of

rhythms in

Gracilaria chilewis.lS

Thble

2

Comparisons of pigment concentration and

ratios.lg

Thble

3

c-omparisons of pigment concentration and

ratios.lg

Thble

4

Species

of

algae

in

which tnre endogenous

rhythms have been

recorded.

27 Thble

5

Species

of

macroalgae in which true endogenous

rhythms _{were not}

observed.

2g

Page

xi

List of Figures andTables

Chapter

2

^Steady State and

Dynamic

Photosynthesis

in Gracilaria chilensis

Figure l0

Figure ll

Figure

12

Figure

13

Figure

14

Figure

15

Figure

16

Figure

17

Figure

18

Figure

19

Apparatus used

in

CO2 exchangc

measu€ments.

32 Apparatus used to crEate

fluctuating light.

39 Idealised P-I rcsponse

curve.

4() P-I curve for

Gracilaia chilersis. M

Panerns of photosynthetic adjustment to constant

light following

a dark or

low light pretreaunenr.

46 Panern of photosynthetic adjusuncnt to

fluctuating light following

_dark

prctreatrnenr.

47 Example

of

the time course

of differential

CO2 in constant and fluctuating

light.

49 Mean photosynthetic rate as a function

of

phase

period.

₅₀

Time course

of differential

CO2

in fluctuating

lightof300

and 900 secondphase

period.

59 Effect of

light

fluctuations on photosynthetic rate.60

Table 6 Table 7

Table 8

Table 9

Table l0

Table

1l

Thble 12

Table 13

Light

treatments used

in

experiments.

Photosynthetic parameters

of Gracilaria

chilensis in the emersed state.

Adjusnnent times, dominant patterns and photosynthetic rates

of

G

racilaria

c hile nsis.

Adjushnent times and photosynthetic rates

in

response to fluctuating

light.

Water loss

in

the

IRGA.

4l

43

45

47 51 Ratio

of

mean photosynthetic rate

in

fluctuating

light

and PPFD to the theorctical value of

pr.

₅₂

Ratio of mean photosynthetic rate

in fluctuating light

and PPFD to the theoretical value of

pp.

₅₂

Plants in which an enhancement

of

photosynthetic rates in fluctuating

light

have becn

recorded.

57

Page

xii

List of Figures andTables

Chapter

3 Photoinhibition of

Photosynthcsis

in Low-LightAcclimated Gracilaria

chilensis.

Figure 20

Spectral

disribution of

the metal halide

light

used

in

high

light

treatments.

Figure 2l

^Effects

of

exposue to high

light

on photosynthetic parameters.

Thble

14

photosynthetic parameters from

initial

and frnat

p-l

curves measured without a high

light

treatrnent

control. 7l

Thble

15

comparisons of photosynthetic pararneters

before and after exposure to high

light

72 Table

16

^Algae

in

which photoinhibition

of

photosynthesis has been

observed.

76 Table

17

carotenoid _to chlorophyll ratio

of

natural,

low

and high

light

grown

Gracilaria chilensis.

^g0

Chapter

4 Time

Scales and

Charrcteristics

_of

Photoacclimation in Gracilaria

chilensis

Figure 22

Cultivation

tank.

^g5

Figure 23

^Time course

of

specific growth

rate.

90

Figure 24

^Time course

of

specific growth _{rate at}

low

and high nitrogen

concentrations.

^gz

Figurc 25

Time course

of

pigment

concentrations.

93

Figure 26

Time course of phycoerythrin concentration

at

low

and high ninogen

concentrations.

95

Figure 27

^Time course of phycocyanin concentration

at

low

and high nitrogen

concentrations.

96

Figure 28

Time coune of

chlorophyll

a concentration

at

low

and high nitrrogen

concenkations.

97

Figure 29

Trme course

of

pigment

ratios.

9g 74

Page

xiii

List of Figures andTables

Figure 30

^Time course

of

pigment ratios at

low

and

high nitrogen

concentrations.

100

Figure 31 fime

^course

of

P-I curve

pammeters.

102

Figure 32

Timc coune

of

phoosynthetic

efficiency

at

low

and high nitrogen

concenrrations.

106

Figure 33

^{T'rme course}

of

maximum photosynthesis

at

low

and high nitrogen

conccntrations.

107

Figure 34

^{Time course}

of

dark respiration rate

at

low

and high nitrogen

concentrations. l0g Figure 35

^{Time course}

of

compensation point

of

at

low

and high nitrogen

concentrations. l0g Figure 36

^{Time course}

of

onset

of

saturation

at

low

and high nitnogen

concentrations. ll0

Figure 37

^{Time course} of phoosynthetic

efficiency

at

low

and high nitrogen

concentrations. lll

Figure 38

^{Time course}

of

maximum photosynthesis

at

low

and high

nirogen concentrations. lIz

Figure 39

^{Time course}

plot of

the change

in

phycoerythrinconcentrarion. ll4

Figure 40

^{Time course} of pigment concentrations and

photosynthetic

parameters. ll9

Figure 4l

^{Timc course}

of

pigment concentrations and

photosynthetic

pararneters. Lzl

Table

l8 Experimenul

procedures used

in timc

course experiments.

Table

19

Specific growth rate under

differcnt light

and nitrogen enrichment regimes.

Table

20

Steady state values of pigment concentrations and ratios.

Thble

2l

Steady state photosynthetic _and respiration pariameters under different

light

and niuogen enrichment rregimes.

Table

22

^First order rate constants

for

acclimation

of

pigment concenrations and photosynthetic

86

9l

94

Page xiv

104

List of

Figwes

andTables

Table 23

Table 24

Thble 25

Table 26

Table2T

Table 28

Concluding

Discussion

Figure

42

efficiency.

Steady state values

of

biochemical components

underdifferent light

and nitrogen

enrichment regimes.

Rate constants

for

acclimation

in

phytoplankton _and

Gracilaria

c hilensis.

Times

for

complete acclimation

in

phytoplankton _{and algae.}

Photoacclimation _changes in red algae.

Range

of

^growth rates

in Gracilaria

species.

Photosynthetic characteristics of

intenidal

and subtidal red algae.

115

tt7

124

t26 r28

134

r37

Reqponses

of

the photosynthetic apparails.

t45

Appendices

Figurc

43

Figure

44

Figure

45

Figure

46

Figure

47

Table 29

Thble 30 Thble

3l

C-ollection site and habit detail.

Absorption _spectrum of pigments.

Timc _course

of

light

variability.

Light variability

at Blockhouse Bay.

Light variabiliry

ar Blockhousc Bay.

Effect

of

wounding on photosynthesis and respiration.

Yeild of pigments from a second extracdon.

Comparison

of Chlorophyll

yeild.

148

t54

156 158 159

15l

153

t54

List of Abbreviations

A

0(

c

Chl c CT DW FW HL Hr

+

It

IRGA

+

q

LL Min

N

P.I Curve

.Absorbance, eg. A.656 = absorbance at 656nm

Photosynthesis effi ciency Carbon

Chlorophyll a

Circatidal

Dry

weight Fresh weight

Iligh Light Hour

Compensation PPFD Onset

of

saturation PPFD krfra-red gas uralyser Saturating PPFD

Fint-order

rate constant

Low Light

Minute

Nitrogen

Photoslmthesis-Irradiance Response

Cun'c

Page

mi

List of

Abbratiatiotrs

PC PE

Pg

P,oo

P.oo

PPFD

PS Ps

PSU

R

Sec

tr

Phycocyanin Phycoerythrin

Rate of photosynthesis

in

a specific fluctuating PPFD calculated

from aP-I

curve assuming integration of PPFD

Photosynthetic rate at saturation PPIID Mean photosynthetic rate

Photosynthctic photon

flux

density Photosystem

Rate of photosynthesis

in

a specific

fluctuatingppFD

calculated

from

a P-I curve assuming integration of phoosynthate Photosynthetic

Unit

Dark regpiration rate.

Second

Specific growth nate