Photoprotection in an ecological context: the remarkable complexity of thermal energy dissipation
PRESENTATION: Photoprotection in avocado leaves in ... · Fotoprotección en las hojas de avocado...
6
Fotoprotección en las hojas de avocado en relación con el manejo del canopeo Photoprotection in avocado leaves in relation to canopy management Barry Osmond 1,2 Britta Förster 2 and John Leonardi 3 1 University of Wollongong 2 Australian National University 3 Avocados Australia Abstract: avocado retains a deep canopy of shade leaves with high photosynthetic efficiency. They are doubly photoprotected by 2 pigment systems and do well in diffuse light and long sun- flecks, achieving 20-50% photosynthesis rates of sun leaves at the same light intensity. Depending on pruning style shade leaves suffer light stress for >3 days, but re-invent the pigment systems of sun leaves in ~10 days; simply amazing!! Proceedings VII World Avocado Congress 2011 (Actas VII Congreso Mundial del Aguacate 2011). Cairns, Australia. 5 – 9 September 2011
Transcript of PRESENTATION: Photoprotection in avocado leaves in ... · Fotoprotección en las hojas de avocado...
Fotoprotección en las hojas de avocado enrelación con el manejo del canopeo
Photoprotection in avocado leaves inrelation to canopy management
Barry Osmond 1,2 Britta Förster 2
and John Leonardi 3
1 University of Wollongong2 Australian National University
3 Avocados Australia
Abstract: avocado retains a deep canopy ofshade leaves with high photosynthetic efficiency.
They are doubly photoprotected by 2 pigmentsystems and do well in diffuse light and long sun-flecks, achieving 20-50% photosynthesis rates ofsun leaves at the same light intensity. Dependingon pruning style shade leaves suffer light stress
for >3 days, but re-invent the pigment systems ofsun leaves in ~10 days; simply amazing!!
Proceedings VII World Avocado Congress 2011 (Actas VII Congreso Mundial del Aguacate 2011). Cairns, Australia. 5 – 9 September 2011
One hundred-fold range in photosynthesis within aSouthern Hemisphere avocado canopy at noon
N
S
EW
0.19
114
0.79
ØPSII = efficiency of light use
ETR = capacity to fix carbon
DS = protection against excess light
0.68
52
0.28
0.76
21
0.13
0.43
134
0.56
0.83
1
0.06
Orchard at Goodwood Qld; at noon 23 July 2010
• why do avocados keep deeply shadedinner canopies with high efficiency, low
capacity leaves seemingly poorlyprotected against excess light?
• how do these leaves tolerate extremecanopy management regimes?
Differential effects of pruning strategy on shadeleaf photosynthesis
0
20
40
60
80
100
120
140
160
0 200 400 600 800 1000
Light intensity; PFD, μmol m-2 s-1
Ca
pa
city
tofix
CO
2;
ET
R,
μm
olm
-2s
-1
shade (Fv/Fm 0.75±0.02)
sun 4.5 h (Fv/Fm 0.76±0.01)
sun 3 d (Fv/Fm 0.70±0.02)
dark 3 d (Fv/Fm 0.77±0.03)
sun (Fv/Fm 0.73±0.02)
Selectivebranchremoval
0
20
40
60
80
100
120
140
160
0 200 400 600 800 1000
Light intensity; PFD, μmol m-2 s-1
Po
ten
tia
lC
O2 f
ixa
tio
n;
ET
R,
μm
ol m
-2s
-1
shade (Fv/Fm 0.82±0.01)
1 d sun (Fv/Fm 0.47±0.03)
3 d sun (Fv/Fm 0.43±0.01)
3 d dark (Fv/Fm 0.78±0.01)
sun (Fv/Fm 0.73±0.02)
"V" pruning
of upper
canopy
Lu
tein
ep
oxid
ec
ycle
Lx-c
ycle
Vio
laxan
thin
cycle
V-c
ycle
Two pigment cycles in avocado shade leaves:both may stabilize photoprotection (NPQ)
Rabinowitchet al (1975)
in greentomatoes
Yamamotoet al (1962)
in lettuceleaves
Reversal of Lx-cycle is 10-100 x slower than V-cycle in
avocado shade leaves
L
Lx
Z
A
V
Photoprotection 1: ΔL “locks-in” high NPQ for 72h in shade leaves
0
10
20
30
40
50
60
70
Lx L* V A Z
Pig
men
ts,
mm
olm
olC
hl
-1
cont (Fv/Fm=0.81; DS=0.01)
exp 1h (Fv/Fm=0.78, DS=0.33)
cont 24h (Fv/Fm=0.78, DS=0.02)
rec 24h (Fv/Fm=0.78, DS=0.09)
0
0.5
1
1.5
0 120 240
0
0.5
1
1.5
0 100 200 300 400 500
NP
Q,
a.u
.
0
5
10
15
20
25
0 100 200 300 400 500
ET
R,
µm
olm
-2s
-1
cont
exp 1h
0
5
10
15
20
25
0 100 200 300 400 500E
TR
,µ
mo
lm
-2s
-1 cont 24h
rec 24h
0
0.5
1
1.5
0 100 200 300 400 500
PFD, µmol m-2
s-1
NP
Q,
a.u
.
0
0.5
1
1.5
0 120 240
Time, s
A
B C
D E
Lx VL
A Z
NPQΔL
NPQΔLAZ
NPQΔL
New science from avocado:shade leaves prove that
LUTEIN has one, possiblytwo, roles in photoprotection
AZcost
After just 1 h in 10 %sun Lx→ ∆L and ∆L
replaces A+Zovernight to sustain
high NPQ
Lutein first to decreaseon shade-sun transfer:photoxidative protection
(as in retina?)
0
10
20
30
40
50
60
70
80
90
cont 0830 exp 0830 exp 1630
Pig
ments
,m
molm
ol
-1C
hl
Lx
L* (-100)
no∆L
cost
∆L
Photoprotection 2: huge new synthesis of ΔL and A+Z from carotenes
0
20
40
60
80
100
120
1.0 1.3 2.0 10.0 10.3 11.0 19.0 19.3 20.0 39.0 39.3 40.0
Days after transfer to sun
Pig
me
nts
,m
mo
lm
ol
-1C
hl
Lx
ΔL
0
20
40
60
80
100
120
0.0 0.3 1.0 10.0 10.3 11.0 19.0 19.3 20.0 39.0 39.3 40.0
Days after transfer to sun
Pig
me
nts
,m
mo
lm
ol
-1C
hl
V
A+Z
Surprising science: oldavocado shade leaves are
able to reinvent themselvesas sun leaves in ~10 days
0
50
100
150
200
Lx L* (-100) V A+Z
Pig
me
nts
mm
olm
ol-1
Ch
l
inner
outer N
avocado pigments, Goodwood
