PRESENTATION: Photoprotection in avocado leaves in ... · Fotoprotección en las hojas de avocado...
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
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0.43
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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
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Light intensity; PFD, μmol m-2 s-1
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pa
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tofix
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ET
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olm
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-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
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Light intensity; PFD, μmol m-2 s-1
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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
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Pig
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ts,
mm
olm
olC
hl
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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)
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rec 24h
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Time, s
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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?)
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cont 0830 exp 0830 exp 1630
Pig
ments
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ol
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hl
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∆L
Photoprotection 2: huge new synthesis of ΔL and A+Z from carotenes
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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
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,m
mo
lm
ol
-1C
hl
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ΔL
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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
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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
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Lx L* (-100) V A+Z
Pig
me
nts
mm
olm
ol-1
Ch
l
inner
outer N
avocado pigments, Goodwood