O sis,
8:
107-1 19 (1993)
Ecophysiology o a e - i e esp ou s
o
A bu us unedo L.
Robe Sa él, Leono Aleg e2, Ma ia Pe y3 and Jaume Te adas4
1. Depa amen de Tecnologia Ho ícola. Ins i u de Rece ca i Tecnologia Ag oalimen h ia (IRTA),
C a. de Cab ils s/n, 08348 Cab ils
2. Depa amen de Biologia Vege al. Facul a de Biologia. Uni e si a de Ba celona.
A . Diagonal. 645.08028 Ba celona
3. Di ecció Gene al Medi Na u al, DARP. Gene ali a de Ca alunya. Ba celona
4. Cen e de Rece ca Ecolbgica i Aplicacions Fo es als. Uni e si a Au bnoma de Ba celona.
08 193 Bella e a
Key
wo ds:
A bu us unedo,
lea mo phology, osmo ic adjus men , esp ou ecophysiology, wa e
loss a es.
Abs ac .
Plan -wa e ela ionships, lea mo phology and concen a ions o pigmen s, p oline, solu-
ble suga s, an hocyans and nu ien s o a e wild i e esp ou lea es o
A bu us unedo
L.
we e com-
pa ed wi h hose o same age sp ou lea es in unbumed plan s. In sp ing samples, se e al signi ican
di e ences appea : a e - i e esp ou s showed some ju enile cha ac e is ics, such as high issue elas-
ici y, small cells, low speci ic lea weigh , high ChlaIChlb a io and a high an hocyan con en ; on he
o he hand, unbn ned plan s showed d ough ole ance cha ac e is ics by osmo ic adjus men and
lowe issue elas ici y, la ge cells, highe speci ic lea weigh and lowe ChlaíChlb a io. In all sam-
ples, bo h kind o shoo s showed d ough ole ance by osmo ic adjus men , low issue elas ici y, la ge
cells and high speci ic lea weigh . Resul s show ha a e - i e esp ou s ha e, a he beginning o
hei de elopmen , highe mo phological and physiological plas ici y ha he new sp ou s o unbu -
ned plan s.
Resum.
Eco isiologia dels eb o s
d'
A bu us unedo
L.
desp és del oc.
Es compa en les elacions
híd iques, la mo ologia olia i les concen acions de pigmen s, p olina, suc es solubles, an ocians i
nu ien s de les ulles de eb o s
d'd bu us unedo
L.
desp és d'un incendi, amb iguals ca ac e ís i-
ques de les ulles de b o s de plan es no c emades de la ma eixa eda . A les mos es de p ima e a
apa eixen di e ses di e kncies signi ica i es: els eb o s, desp és del oc, p esen en ca ac e ís iques
ju enils, com són al a elas ici a dels eixi s, ci.l.lules pe i es, baix pes especí ic olia , al a elació
ChlaíChlb i un ele a con ingu d'an ocians; d'al a banda, les plan es no c emades p esen en ca ac-
e ís iques de ole bcia a I'eixu pe ajus amen osmb ic i baixa elas ici a dels eixi s, ci.l.lules més
g osses, pes especí ic més al i elació ChlaíChlb in e io . A les mos es de a do els dos ipus de
b o s p esen en ole hncia a I'eixu pe ajus amen osmb ic, baixa elas ici a de eixi s, cbl.lules g os-
ses i pes especí ic olia al . Els esul a s mos en que els eb o s desp és del oc enen, a I'inici del
seu desen olupamen , una plas ici a mo olbgica i isiolbgica supe io que els b o s nous de les plan-
es no c emades.
108
R. SAVE, L. ALEGRE,
M.
PERY
&
J.
TERRADAS
In oduc ion
E e g een scle ophyllous Medi e anean o es s and sh ublands a e la gely do-
mina ed by woody esp ou e s ha egene a e quickly a e dis u bances.
An h opogenic and, o a nino ex en , na u al i es, a e ela i ely equen and i e
has been conside ed as a majo s ess ac o in hese en i onmen s (Rundel 1982).
Changes in communi y plan composi ion a e o mino impo ance (au osucces-
sion, Hanes 1971). P e ious s udies, mos ly in chapa al sh ubs, ha e ound ha
a e - i e esp ou lea es a e mo e mesophy ic han lea es o ma u e plan s.
Di e ences ha e been obse ed be ween he mo phology and he physiological
beha iou o e en aged lea es om bo h, esp ou s and ma u e plan s (Oechel and
Has ings 1983, DeSouza e al. 1986, Has ings e al. 1989) and also be ween lea-
es o esp ou s and seedlings (Sa uwa a i and Da is 1989, Thomas and Da is
1989).The aim o his pape is o analyze a la ge numbe o esp ou ea u es as
compa ed o unbu ned plan s o one pe ennial sh ub species,
A bu us unedo
L.,
a lau ophyllous sh ub cha ac e is ic o Medi e anean basin scle ophyllous o es s
and macchia ecosys ems, in o de o es ablish he ela ionship be ween he i e as
an ecological ac o and some esp ou s physiological esponses in an au osucce-
sion con ex .
Ma e ial and me hods
Species and s udy si e
Two expe imen al plo s (400 m2 each), bu ned and unbu ned, we e selec ed in he
Se alada Li o al Ca alana, a he
NE
o he Ibe ian Peninsule. The a ea (3 1TDG
8823 and 3 1TDG 9620) has a subhumid Medi e anean clima e, wi h 745 mm an-
nua1 a e age ain all and 16.7"C a e age annual empe a u e. The subs a e con-
sis s o leucog ani e, suppo ing soils wi h sandy ex u e. The bu ned plo had su -
e ed a wild i e o se e e in ensi y (a e Wells e al. 1979 classi ica ion) ha
a ec ed 105 ha on 17 July 1987. The unbu ned plo has emained so o a leas
i y yea s, acco ding o landowne 's in o ma ion. Measu emen s we e ca ied ou
on
A bu us unedo
L
.,
a equen ly dominan sh ub o small ee in he Medi e anean
macchia and sh ublands and in he unde g ow h o
Que cus ilex, Que cus sube ,
Pinus halepensis
and
Pinus pinea
o es s and woodlands. F om a phy osociolo-
gical poin o iew, ou plo s can be iden i ied as Cis ion mediomedi e aneum
communi ies (Bolbs 1983), wi h
Que cus sube
(co k oak) co e ing 80% o o al
soil su ace.
Sampling me hods
Ten andomly selec ed
A bu us unedo
L. sh ubs we e sampled on each o he bu -
ned and unbu ned plo s. One cu en -yea shoo was aken om he cen al pa
ARBUTUS
UNED0
RESPROUT ECOPHYSIOLOGY
109
on he sou he n side o he c own o each sample sh ub ea ly in he mo ning, once
in la e sp ing (June 6 h 1988) and again in au umn (No embe 9 h 1988). We me-
asu ed he elonga ion o one yea old shoo s, om he node whe e seasonal g ow h
was ini ia ed and om he poin o ini ia ion on he oo c own ( o unbu ned and
bu ned plan s espec i ely).We also measu ed he o al plan heigh in bo h plan
ypes.
Wa e ela ions
Shoo s we e ca ied in sealed plas ic bags con aining some wa e o he labo a-
o y. These shoo s we e ecu unde wa e and placed in beake s con aining some
wa e , enclosed in plas ic bags and s o ed o ehyd a a ion in da kness and a 5OC
o 48 h. Then, i e wa e sa u a ed unbu ned and a e i e shoo s we e used o
measu emen s. They we e weighed and hen allowed o dehyd a e by ee ans-
pi a ion o 4 h a 20°C, 60% R.H., and 50 ~mol.m-~.s-l PPFD. Du ing dehyd a-
ion, wa e po en ial was epea edly measu ed wi h a Schollande p essu e cham-
be (Soilmois u e 3005). F om he sa u a ed weigh , esh weigh s co esponding
o Yx (xylem wa e po en ial) measu es, and d y weigh , we calcula ed he ela i-
e wa e con en (RWC
).
RWC was plo ed agains lIY, ( ype
I1
ans o ma ion,
Ty ee and Rich e 1981, 1982). F om he g aph, he osmo ic po en ial a ull u -
go can be es ima ed. Tu go po en ials (Yp) we e calcula ed om non-linea pa s
o he cu es as he di e ence be ween ac ual da a and he osmo ic (adjus ed) line.
P essu e- olume cu es ga e he osmo ic po en ials a ull u go (TloO) and a
ze o u go (Ypo). The olume ic modulus o elas ici y
(E)
a 100% RWC (RWClO0)
was es ima ed assuming linea ela ionship be ween u go po en ial (Yp) and
R WC:
whe e YPlo0 is u go po en ial a RWCIOO and RWCo a e RWC a ull and ze o
u go (Johnson e al. 1984).
Using he same shoo s, s oma al and cu icula wa e loss a es we e measu ed
g a ime ically (by di e ence be ween weigh s a he beginning and he end o
measu emen pe iods) wi h a digi al balance Me le AJ 100, wi h 0.1 mg accu-
acy (Sa é 1986, S eningsson and Liljenbe g 1986). Wa e losses we e e e ed
o d y weigh (DW) and ime uni s. We conside ed as s oma al o cu icula wa e
loss a es he alues ob ained abo e and below he poin o ze o u go espec i-
ely. Ra ios be ween u gid weigh TW and DW, and speci ic lea weigh (SLW)
we e also calcula ed on hese lea es.
Lea mo phology and ana omy
The ou h lea ecen ly expanded om he shoo apex was excised. Pieces om
a cen al a ea o he blades we e hen cu , p ese ed in a o malin-ace ic acid-
110
R. SAVE,
L. ALEGRE,
M.
PERY
&
J.
TERRADAS
e hanol mix u e, clea ed wi h chlo al hyd a e wa e solu ion and insed. Once
moun ed in dis illed wa e hey we e used o e alua e s oma al equency on
abaxial su aces.
Samples o ligh and elec on ansmission mic oscopy we e p epa ed acco -
ding o usual echniques (Pa ke and Fo d 1982). Be ween- ein dis ances, cell pe-
ime e and cell a ea we e calcula ed om a sample o 40 mesophyll cells om
each o h ee lea es. Measu emen s we e pe o med using an In e ac i e Bina y
Analyze Sys em (IBAS Kon on). Mesophyll cell numbe , o al mesophyll cell
pe ime e and o al mesophyll cell a ea we e e e ed o abaxial epide mis wid h.
Mesophyll a eallea a ea and mesophyll olumellea a ea a ios we e measu ed
acco ding o Ju ik e al. (1982). The chlo oplas leng h and wid h and he adaxial
and abaxial cu icle hickness we e also measu ed. The obse a ions we e made
wi h a Philips EM 301 ansmission mic oscope.
Specimens o scanning mic oscopy we e ixed in e hanol, dehyd a ed, ans-
e ed o amyl ace a e, d ied o c i ica1 poin , a ached o specimen s ubs and
coa ed wi h gold. Samples we e examined unde a Camb idge 20 scanning elec-
on mic oscope.
X- ay mic oanalysis
Specimens we e p epa ed as o SEM obse a ion, bu ca bon-coa ed. A Jeol JSM
840 scanning elec on mic oscope, ope a ed a 12 K , o ming images wi h a
10-10 A cu en in ensi y, was used in he obse a ions. The mul ielemen analy-
ses we e ca ied ou wi h a SEM including an ene gy dispe si e X- ay analyze
C6RxAN 10000 (link sys ems), wo king wi h 0.4-0.6
x
10-9 A cu en in ensi y.
An X- ay elemen al mapping was ob ained wi h a highe cu en .
Chemical solu es and pigmen s
Chlo ophyll was ex ac ed in dime hylpho mamid and analyzed acco ding o
Inskeep and Bloom (1985). An hocyans and o he polyphenols we e ex ac ed wi h
3% sulphosalicylic acid and analyzed using a colo ime ic me hod (Ha bo ne
1984). P oline was de e mined acco ding o he colo ime ic me hod desc ibed by
To ecillas e al. (1984), soluble suga s by spec opho ome y, acco ding o W is le
and Wol o m (1962). Ca, K, C1, S, P, Mg and Na we e de e mined by X- ay luo-
escence, wi h a Philips PW 1400 luo ime e . To al ni ogen was ob ained wi h
an au oma ic
N
analyze (Ca 10 E ba AWA 1500).
Resul s
Da a ob ained on wa e ela ionships, mo phology and chemical composi ion pa-
ame e s a e shown in ables 1-4. Unbu ned plan s we e alle (5 m heigh in a e-
age) and he canopy diame e was 3 k0.5 m, wi h
3
shoo s pe b anch on a e a-
ARBUTUS
UNED0
RESPROUT ECOPHYSIOLOGY
11 1
ge. A e - i e esp ou s we e 1.5 m all and had 20 esp ou s pe plan in a e age.
In he sp ing samples, du ing he ea ly s ages o he a e - i e egene a ion p o-
cess, we assume ha unbu ned and bu ned plan s ound a mo e o less simila soil
wa e a ailabili y, because hey we e in e y simila and neighbou ing locali ies.
Unknown di e ences can, ne e heless, exis due o i e-induced en i onmen al
modi ica ions.
The new shoo leng h inc ease in June was nea 10 imes highe in a e - i e
han in unbu ned plan s. Unbu ned plan s in la e sp ing showed a highe con en
o s a ch g anules (Pe y e al. 1989) and p oline, highe alues o modulus o elas-
ici y (210% o a e - i e esp ou s), la ge cells, 90-124% hicke cu icles on ada-
xial and abaxial su aces espec i ely, la ge chlo oplas sizes,
39%
mo e
K,
and
highe o al nu ien con en (see able 4). On he o he hand,
Yploo
and
YpO
we e
lowe in unbu ned plan s and he same was ue o s oma al and cu icula ans-
pi a ion a es, o calcium concen a ion and o ChldChlb (10% highe in a e -
i e esp ou s). Unbu ned plan s showed highe SLW and lowe TWIDW a io
han a e - i e esp ou s (see able 1).
In he No embe sampling, a e he summe d ough , hyd ic pa ame e s sho-
wed simila alues in he wo plo s. Xe omo phy was inc eased in a e - i e es-
p ou s: he elas ici y modulus inc eased by 124%, osmo ic alues 103% and SLW
64%,
whe eas cell osmo ic olume and TWDW a io dec eased (see ables 1 and
2)
.
Mesophyll c oss-sec ion a ea, mesophyll cell a ea lea su ace, mesophyll cell
olume/lea su ace, hickness o lea , mesophyll and abaxial cu icle, chlo oplas
size and nu ien concen a ion we e all nea ly he same in a e - i e and unbu -
ned lea es. Adaxial cu icle was 42% hicke in a e - i e han in unbu ned lea es.
In addi ion, mean lea a ea was
56%
highe
in
a e - i e ( his di e ence was only
5%
in June) . ChldChlb a io was 18% highe in a e - i e lea es and an hocyans
Table
1.
Wa e ela ions (Yxloo, Yxo,
E
max), s oma al and cu icula wa e loss a es
(TRmax, TRc), p oline, soluble suga s, speci ic lea weigh (SLW) and u gid weigh Jd y
weigh a io
(TWIDW)
o lea es o
A bu us
unedo
L. in wo expe imen al plo s (bu ned
and unbu ned) du ing la e sp ing and au umn. A e age alues a e gi en
SD.
La e sp ing
(716188)
Au umn
(9113188)
Unbu ned Bu ned Unbu ned Bu ned
Y,loo (MPa)
-1.56 k0.32 -0.74
0.15 -1.49
0.13 -1.50 0.33
Y,o (MPa)
-1.80k0.17 -1.36 0.13 -2.02 0.08 -2.09 0.28
E
max (MPa)
14.95
3.19 4.82
2.28 12.64
2.69 10.81
1.65
TRmax(mg.g-1.DW.min-1)
3.08k1.52 3.80 2.01 3.42, 1.30 3.37 1.10
TRcu
(mg.gl.DW.min-1)
1.11 k 0.30 1.82k0.33 0.97 0.25 1.12 0.23
P oline
( ng.gl.DW)
39.60 k 4.60 27.20
4.20 108.60
20.00 79.20
16.00
Soluble suga s
(%)
9.20
0.50 8.70
+
0.30 11.70
0.50 18.20
0.60
SLW
(mg.
cm-2)
14.50
0.60 10.50
0.44 15.04 k 0.73 17.20 k 0.60
TWDIDW
2.80 0.09 3.90 0.30 2.36 0.02 2.40k 0.06

112
R.
SAVE,
L.
ALEGRE,
M.
PERY
&
J.
TERRADAS
showed a g ea e inc ease (125%). S a ch accumula ion, on he con a y, was al-
ways highe in unbu ned plan s.
Discussion
Wa e ela ionships
Di e ences in hyd ic s a us be ween a e - i e esp ou s and unbu ned plan s ha e
been no ed p e iously in o he s udies: xylem wa e po en ials ha e been compa-
ed on di e en chapa al species by Has ings e al. (1989) and Rundel (1982);
s oma al conduc ance a midday has been also conside ed by DeSouza e al. (1986)
and Has ings e al. (1989). Thei esul s sugges a g ea e wa e a ailabili y o es-
p ou lea es: esp ou s ha e la ge indi idual lea es bu a educed LAI (because
he e a e less lea es), wi hou a p opo ional dec ease in he oo sys em and in
he capaci y o wa e abso p ion. Ou da a suppo hese obse a ions. In unbu -
ned au umn plan s, a highe anspi ing o al lea a ea (LAI) can cause empo a y
Table 2. Some s uc u al cha ac e is ics o he
A buus
unedo
L. lea es in wo expe i-
men al plo s (bu ned and unbu ned) du ing la e sp ing and au umn. A e age alues a e
gi en
SD.
La e sp ing (716188) Au umn (911 3188)
Unbu ned Bu ned Unbu ned Bu ned
Lea a ea (cm2) 9.53k 0.53 11.85k 0.72 7.67 0.72 11.60 1.61
Lea
hickness (pm) 219.16k 2.86 209.20 0.72 217.68 3.04 340.48 4.12
Mesophyll
hickness (pm) 188.44 1.90 176.48 0.72 177.10 2.70 31 1.28 2.87
Adaxial cu icle
hickness (pm) 6.16 0.70 3.24 0.07 8.03 0.16 11.39+ 0.81
Abaxial cu icle
hickness (pm) 7.14 0.14 3.20k 0.46 8.18+ 0.27 8.19 0.30
Dis ance be ween
eins (pm) 787.80 10.90 716.60 11.50 1138.00k16.30 722.80k14.50
S oma al ecuency
(numbe .mm-2, 321.30 18.10 570.60 25.80
-
-
Mesophyll cell
c oss-sec ional
size (pm2) 262.80 21.80 172.28 15.30 260.51 20.14 419.00 39.60
Chlo oplas leng h
(~m) 5.23 0.90 3.12 0.30 5.89k 0.25 5.22 0.40
Chlo oplas wid h
(CLm) 1.92k0.17 1.18 0.23 2.46 0.34 2.07 0.40
ARBUTUS
UNED0
RESPROUT ECOPHYSIOLOGY
113
o sus ained wa e de ici s. We can he e o e expec educed suga ansloca ion
and an inc ease o s a ch g anules (Acke son 1981, Riazi e al. 1985). Tha in-
c ease o s a ch g anules is obse ed in ou samples (Pe y e al. 1989). As a e-
sul , ca bon is mo e a ailable han ni ogen and p oline accumula es (as obse ed
p e iously by Tully e al. 1979, Aspinall and Paleg 198 1, Handa e al. 1986)
.
The
ac i e solu e accumula ion and solu e concen a ion induced by dec ease in ce-
llula olume due o s a ch g anules (Acke son and Hebe 1981) may p omo e a
decline in
Yploo
and
Ypo
(as shown by ou esul s on Table 1). High alues o
modulus o elas ici y and he la ge cells indica e ha in ma u e plan s a small con-
ibu ion om hese cha ac e is ics can be expec ed o osmo ic adjus men (Mye s
and Neals 1986, Robichaux e al. 1986). On he o he hand, i is known ha he
osmo ic adjus men is a ou ed by a high
K
concen a ion (Fo d and Wilson 1981),
and ou unbu ned plan s ha e mo e
K
han he a e - i e esp ou s (Table 3)
.
The highe
Yploo
and
Ypo
o esp ou s could be he esul o a g ea e wa e
a ailabili y pe uni o anspi ing su ace and o a low con en o osmo ical so-
lu es such as p oline.This is due o lack o s ess andlo lack o soluble suga s as
a esul o as e g ow h (Radose ich e al. 1977, Oechel and Has ings 1983). The
low alue o he modulus o elas ici y and he small cells indica e ha elas ici y
plays an impo an ole in cellula u go main enance (B ad o d and Hsiao 1982,
Mye s and Neales 1986).
G ea e s oma al and cu icula wa e loss a e in a e - i e esp ou s may be
explained by g ea e wa e a ailabili y (Oechel and Has ings 1983) and by mo -
phological cha ac e is ics, such as s oma al densi y and cu icle hickness (Table 2)
(Le i 1980, Mo gan 1984). The highe anspi a ion low can p omo e high pas-
si e calcium abso p ion a es, hus explaining a la ge Ca accumula ion in a e -
i e esp ou s.
High TWIDW a io obse ed in sp ing o esp ou s can be explained by low
apoplas ic wa e con en and hin cell walls (Jensen and Henson 1989). The low
SLW and he high anspi a ion a e measu ed ( able 1) a e in ag eemen wi h his
in e p e a ion. TWDW a ios sugges ha ju enile cha ac e is ics (Mesegue 1990)
Table
3.
Solu e concen a ion o
A buus
unedo
L. lea es in wo expe imen al plo s (bu -
ned and unbu ned) du ing la e sp ing and au umn. A e age alues a e gi en
SD.
La e sp ing
(716188)
Au umn
(911 3/88)
Unbu ned Bu ned Unbu ned Bu ned
N (%DW)
2.08
+
0.07 1.49
+
0.05 1.58
+
0.10 1.40
+
0.03
K
(%DW)
2.23 k0.04 1.60 k0.04 1.43
+
0.03 1.39 k0.02
Ca (%DW)
1.07
+
0.07 1.77
+
0.07 2.07
+
0.00 2.47
+
0.03
Mg (%DW)
0.15
+
0.00 0.15
+
0.01 0.20
+
0.01 0.22
+
0.02
Na (%DW)
0.015
+
0.01 0.009
0.00 0.15
0.00 0.012
+
0.00
C1 (%DW)
0.008
+
0.00 0.038
+
0.00 0.010
+
0.00 0.032
0.03
S (%DW)
0.190
+
0.03 0.138
0.06 0.160
+
0.01 0.130
+
0.03
P
(%DW)
0.28
+
0.01 0.17
+
0.01 0.16
+
0.00 0.12
+
0.01
114
R. SAVE, L. ALEGRE,
M.
PERY
&
J.
TERRADAS
shown in a e - i e esp ou s and d ough s ess can bo h play a ole in he adap-
a ion o esp ou s o en i onmen al ac o s.
The dec ease o soil wa e a ailabili y and high e apo a i e demand du ing
he summe d ough , oge he wi h he inc ease in he lea a ea o esp ou s, can
explain he change o he esp ou s hyd ic beha iou o a wa e conse a ion be-
ha iou mo e like ha o ma u e plan s. Lea es o esp ou s became mo e xe o-
mo phic as a esul o an inc ease in he modulus o elas ici y, he osmo ic solu e
con en and he SLW (Tu ne and Jones 1980, Mo gan 1984, Bowman and Robe s
1985) and a dec ease in cellula osmo ic olume (Acke son and Hebe 198 1) and
TWIDW a io (Jensen and Henson 1989).
S uc u al cha ac e is ics
Smalle size o lea mesophyll and epide mal cells, closely dis ibu ed eins and
inc eased s oma al equency in la e sp ing esp ou s can be ela ed o highe pho-
osyn he ic a es (Mo gan e al. 1987). Enhanced pho osyn hesis du ing he i s
yea a e he i e in
A bu us unedo
has been desc ibed by Fleck e al. (1990).
Resul s o mesophyll c oss-sec ional a ea show a ela ion be ween he size o lea
cells and he modulus o elas ici y. Lowe alues o he modulus o elas ici y a e
associa ed wi h small cells (Robichaux e al. 1986). Lea cells and he modulus o
elas ici y inc eased in he esp ou s be ween he wo samplings o app oach he
ma u e plan s alues, as p e iously desc ibed.
Nu ien concen a ion
Highe o al nu ien concen a ion (as a pe cen age o d y weigh ) ound in ma-
u e plan s can be ela ed o hei low
YpIOO
alues (Mo gan 1984). Whe eas ends
in he accumula ion o solu e nu ien s we e simila o hose o o al ionic con-
cen a ion, Ca showed highe concen a ion in esp ou s. Ca was loca ed on he
abaxial side o he epide mis. Solu es wi hin he anspi a ion s eam accumula e
wi hin o nea he s oma al complex (Mans ield 1990). The accumula ion o Ca
could he e o e be ela ed o high anspi a ion a es in he esp ou s.
In he all sampling, simila nu ien concen a ions we e ound in esp ou s
and ma u e plan s. Ca and Mg inc eased as compa ed o sp ing samples, whe eas
N,
P,
S and
K
dec eased. This is a esul o he di e en mobili y o he elemen s,
and is usually obse ed in all lea aging p ocesses (Mengel and Ki by 1982).
Chlo ophyll and polyphenol con en s
Highe alues o ChlaJChlb a io obse ed in esp ou s on bo h sampling da es
(Table 4) can indica e a highe po en ial o pho osyn he ic ac i i y (Boa dman
1977, Edwa ds and Walke 1983). In ac , highe pho osyn he ic a es ha e al-
ways been measu ed in esp ou s (Oechel and Has ings 1983, DeSouza 1986,
Has ings e al. 1989, Fleck e al. 1990).
ARBUTUS
UNED0
RESPROUT ECOPHYSIOLOGY
115
Table 4. Lea chlo ophyll and an hocianins con en and a io ChldChlb om wo expe i-
men al plo s (bu ned and unbu ned) o
A bu us
unedo
L.
A e age alues a e gi en
SD.
La e sp ing (716188) Au umn (911 3/88)
Unbu ned Bu ned Unbu ned Bu ned
Chla (yg.cm-2) 29.4
4.0 13.3
+
1.0 46.1
2.6 45.4
10.3
Chlb (yg.cm-2) 10.0
1.4 4.1
0.4 12.4
2.5 11.4
5.0
Chl (pg.cm-2) 39.4
5.3 17.4
1.1 59.1
3.2 56.6
14.6
ChldChlb 2.9
k
0.2 3.2
0.4 3.9
0.9 4.6
+
1.6
An hocianins
(a a 573 nm)
- -
0.61 1.37
Unde na u al condi ions, pho osyn he ic pho on lux densi y (PPFD) is
highe in mos adaxial mesophylls, and dec eases wi h he dep h om he adaxial
su ace. Phenolic subs ances may se e o sc een ou damaging adia ion om he
unde lying issues (A aus e al. 1986), and his can help o explain he g ea ole-
ance o hin sun lea es o high PPFD. An hocyan inc ease in esp ou s can play
his p o ec i e ole. Fu he , i can be ela ed o ju enile cha ac e is ics o la e al
axilla y buds in esp ou s (Hacke e al. 1989, Mesegue 1990).
Conclusions
A he beginning o he g ow h pe iod, esp ou s showed a mechanism o d ough
ole ance due o issue elas ici y (Le i 1980, Mo gan 1984)
.
Elas ici y does
no in luence u go -media ed p ocesses, such a e elonga i e g ow h and pho-
osyn hesis (B ad o d and Hsiao 1982), and allows a g ea e alloca ion o assi-
mila es and nu ien s o he plan g ow h (Munns 1988). A he same ime, un-
bu ned plan s showed d ough ole ance by ac i e osmo ic accumula ion, osmo ic
adjus men wi h osmo ic concen a ion due o educed cell olume caused by
s a ch g anules p esence (Acke son and Hebe 1981, Mo gan 1984), oge he
wi h low elas ici y. This allowed lowe wa e po en ial o be eached o a gi en
change in wa e olume, and so con inuous wa e up ake om d ying soils was
possible. Low issue elas ici y may be an impo an cha ac e is ic allowing low
wa e po en ials o be eached wi hou de elopmen o de imen al wa e de i-
ci s (Bowman and Robe s 1985). Mo eo e , unbu ned plan s ha e o he me-
chanisms o d ough a oidance, such as hicke cu icle and low cu icula ans-
pi a ion a es (Le i 1980).
In he all, he wo plan ypes showed simila mechanisms o d ough ole-
ance, osmo ic adjus men and low issue elas ici y, oge he wi h mechanisms o
d ough a oidance, hicke lea es and cu icles and low wa e loss a es. The de-
elopmen o hese wo wa e s ess esis ance mechanisms p esumably esul ed
om summe d ough s ess (Mo gan 1984), bu di e ences due o lea on ogeny