delayed greening in theobroma cacao l 2009
TRANSCRIPT
8th September 2009
Mit
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d d
er
Helm
holt
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sch
aft
Delayed greening in Theobroma cacao L.
Leaf and photosynthesis development
| Andrzej Stefan Czech
8th September 2009 Slide 3
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
8th September 2009 Slide 5
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
8th September 2009 Slide 7
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
8th September 2009 Slide 8
Ecological meaning of delayed greening
Masking (defense against herbivores)
Economy (time distribution of energy consuming processes)
Photoprotection (defense against photosensibilization)
8th September 2009 Slide 9
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.
8th September 2009 Slide 11
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
8th September 2009 Slide 14
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
8th September 2009 Slide 15
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.
8th September 2009 Slide 17
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
8th September 2009 Slide 18
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.
8th September 2009 Slide 19
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
8th September 2009 Slide 20
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.
8th September 2009 Slide 21
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.
8th September 2009 Slide 25
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)
8th September 2009 Slide 26
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
8th September 2009 Slide 27
Growth of leaf discs (dry weight)
Leaf discs are growing, not only swelling.Treatment
Hoagland
Hoagland + 1% sucrose
Hoagland + 3% sucrose
Hoagland + 0.53% mannitol
Hoagland + 1.6% mannitol
DW
[m
g p
er d
isc]
0
1
2
3
4
5
6
7
maturating leafgrowing leaf
8th September 2009 Slide 28
Chlorophyll accumulation in leaf discs
Treatment
controlHoagland
Hoagland + 1% sucrose
Hoagland + 3% sucrose
Hoagland + 0.53% mannitol
Hoagland + 1.6% mannitol
Ch
l [
mo
l m
-2]
-50
0
50
100
150
200
maturing leafgrowing leaf
8th September 2009 Slide 29
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.
8th September 2009 Slide 30
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.
8th September 2009 Slide 31
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.