Delayed greening in theobroma cacao L 2009

8th September 2009

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Delayed greening in Theobroma cacao L.

Leaf and photosynthesis development

| Andrzej Stefan Czech

8th September 2009 Slide 2

INTRODUCTION


What is normal greening

Young leaf is green from the beginnig

Young leaves look like mature ones, but are smaller

Chloroplasts become mature early in the development

Leaf performs photosythesis very early in the development


What is normal greening

Čatský and Šesták 1996


What is delayed greening

Present in 33% of 250 tested tropical species, shade plants

Low chlorophyll content at the beginning of the leaf development

Little chloroplasts

Leaves yellow, thin, transparent, floppy

No cuticle


Delayed greening

Young leaf

Mature leaf

intercellular air space


Etioplast

Mature chloroplast

Young delayed greening chloroplast

Baker, Hardwick, Jones 1975

Baker, Hardwick, Jones 1975

von Sengbusch 2003

PS IPS I granum

thylakoid

Prolamelar bodies mainly with POR protein only

Chloroplast development


Ecological meaning of delayed greening

Masking (defense against herbivores)

Economy (time distribution of energy consuming processes)

Photoprotection (defense against photosensibilization)


Aim

To make a model of development of T. cacao leaves for further research

Motivation

T. cacao can be a model plant for chloroplast development due to tiny chloroplast at the beginning of leaf development. It may be a better model than etioplasts.


RESULTS


Leaf growth and chlorophyll accumulation

Growth preceeds chlorophyll accumulation

Days after reaching 1.5 cm in length0 10 20 30 40

Rel

ativ

e G

row

th R

ate

[% d

-1]

0

20

40

60

80

100C

hlo

rop

hyll [

mo

l m-2]

0

100

200

300

400

500

600

% A

max [%

]

0

20

40

60

80

100

120

Relative Growth Rate Chlorophyll %Amax


Growth of delayed greening versus normal


Leaf growth versus chlorophyll accumulation

Chl [mol m-2]

0 100 200 300 400 500 600

Rel

ativ

e G

row

th R

ate

[% d

-1]

0

20

40

60

80

100

greenhousegrowth chamber

VIVIIIIII

There seems to be a correlation between growth and chlorophyll accumulation in phases II and III


Cell size versus chlorophyll accumulation

Chl [mol m-2]

0 100 200 300 400 500 600

Ep

ider

mal

cel

l siz

e [

m2 ]

0

100

200

300

400

500

VIVIIIIII

Rapid growth in the first phase is due to cell division, in phases II and III only cell expansion happens.


Cell growth of delayed greening versus normal


Spatial leaf growth

Growth pattern different from other dicots

Arabidopsisthaliana

Nicotiana tabacum

Theobromacacao

High growth

Low growth

Wiese et al, 2007 Walter et al, 2005


Photosynthesis development

Chl [mol m-2]

0 100 200 300 400 500 600

Ph

oto

syn

thes

is

[m

ol C

O2

m-2

s-1

]

-2

-1

0

1

2

3

4

VIVIIIIII

Development of CO2 assimilation capacity happens in phase III, when most of the growth is already

accomplished.


Photosystem II efficiency versus chlorophyll content

Chl [mol m-2]

0 100 200 300 400 500 600

Ph

oto

sys

tem

II

eff

icie

nc

y

0.65

0.70

0.75

0.80

0.85

VIVIIIIII

Increase in photosystem II efficiency happens in phase III, when most of the growth is already accomplished.

Bassi, 2009

Bassi, 2009


NPQ versus chlorophyll content

VIVIIIIII

Chl [mol m-2]

0 100 200 300 400 500 600

NP

Q

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

y = 0.0019 x + 1.4317R2 = 0.7639

Protective mechanisms are developed together with chlorophyll accumulation.


VIVIIIIII

Chl [mol m-2]

0 100 200 300 400 500 600

Car

bo

hyd

rate

s

[m

ol

g-1

FW

]

0

10

20

30

40

50

60

70

glucosefructosesucrosestarch

Carbohydrates versus chlorophyll content

Although in phase IV leaf is self-sufficient, it starts to function as active sugars exporter in phase V.


Photosynthesis development of delayed greening versus normal


SUMMARY


LAST (NOT YET PUBLISHED) RESEARCH


In vitro analyses of chloroplast development

Aim: to establish a setup allowing simple and effective modification of growth conditions, to test the influence of sugar, hormones, light, etc. on chloroplast development

Approach: leaf discs, cut from growing or maturing leaves, grown on liquid (or solid) media (Hoagland or MS)


Growth of leaf discs

control HoaglandHoagland

+1% sucrose

Hoagland +3%

sucrose

Hoagland +0.53% mannitol

Hoagland +1.6%

mannitol

maturing leaf160 µmol m-2 Chl

growing leaf100 µmol m-2 Chl

Leaf discs are able to grow if sugars are supplied.

RG

R [

% d

-1]

7 d

ays

aver

age

02468

101214161820

maturing leafgrowing leaf


Growth of leaf discs (dry weight)

Leaf discs are growing, not only swelling.Treatment

Hoagland

Hoagland + 1% sucrose


Hoagland + 0.53% mannitol


DW

[m

g p

er d

isc]

0

1

2

3

4

5

6

7

maturating leafgrowing leaf


Chlorophyll accumulation in leaf discs

Treatment

controlHoagland





Ch

l [

mo

l m

-2]

-50

0

50

100

150

200

maturing leafgrowing leaf


Why chlorophyll accumulation in leaf discs is stopped while growth not?

Maybe growth is internally controlled by cells (e.g. programmed at the very beginning of leaf development) while greening is regulated by plant (via phytohormons) or restricted by nutrient availability.

Further experiments in progress.


Future perspectives

Search for signal(s) for „greening” (chloroplast development).

Comparison of normally developing leaves with leaves where greening is artificially stopped.

Changes in the thylakoid membrane structure and functionality of photosystem II.


Acknowledgements

Forschungszentrum Jülich – Jagiellonian University scholarschip

Ulrich Schurr,ICG-III, Forschungszentrum Jülich, Germany

Shizue Matsubara, ICG-III, Forschungszentrum Jülich, Germany

Kazimierz Strzałka, ZFIBR, WBBiBt, Jagiellonian University, Kraków, Poland

Thank you for your attention.

Delayed greening in theobroma cacao L 2009

Science

Transcript of Delayed greening in theobroma cacao L 2009