plant physiol. 1999 murchie 553 64

8/16/2019 Plant Physiol. 1999 Murchie 553 64

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Plant Physiology , February 1999, Vol. 119, pp. 553±563, www.plantphysiol.org © 1999 American ociety o! "lant "hysiologists

Interactions between Senescence and Leaf OrientationDetermine in Situ Patterns of Photosynthesis and

Photoinhibition in Field-Grown Rice1

Eri !" #urchie$ %i-&hu 'hen$ Stella !ubbart$ Shaobin( Pen($ and Peter !orton)

#obert $ill %nstitute, &epartment o! 'olecular (iology an) (iotechnology, *ni+ersity o! he!!iel), estern (an-,

he!!iel), 1 /0, *nite) 2ing)om 4.$.'., .$., ".$. an) Agronomy, "lant "hysiology an) Agroecology

&i+ision, %nternational #ice #esearch %nstitute, ".7. (o8 933, 199 'anila, "hilippines .:., .".

Photosynthesis and *hotoinhibition in field-(rown rice +Oryza sativa

L", were eamined in relation to leaf a(e and orientation" .wo /arieties

+IR0 and IR23345-11- 67SI829, were (rown in the field in the

Phili**ines durin( the dry season under hi(hly irri(ated$ well-fertili&edconditions" Fla( lea/es were eamined 28 and 188 d after trans*lantin("

7ecause of the u*ri(ht nature of 28-d-old rice lea/es$ *atterns of

*hotosynthesis were determined by solar mo/e-ments: li(ht fallin( on

the e*osed surface in the mornin($ a low incident an(le of irradiance

at midday$ and li(ht striin( the o**o-site side of the leaf blade in the

afternoon" .here was an early mornin( burst of 'O assimilation and

hi(h le/els of saturation of *hotosystem II electron transfer as incident

irradiance reached a maimum le/el" !owe/er$ by midday the

*hotochemical efficiency increased a(ain almost to maimum" Lea/es

that were 188 d old *ossessed a more hori&ontal orientation and were

found to suffer (reater le/els of *hotoinhibition than youn(er lea/es$

and this was accom*anied by increases in the de-e*oidation state of

the an-tho*hyll cycle" Older lea/es had si(nificantly lower chloro*hyll

content but only sli(htly diminished *hotosynthesis ca*acity"

Recent studies show that rice (Oryza sativa L.) yields need toincrease by 70% of current levels by the year 2030 to meet theneeds of a rapidly increasin human population! and this increasemust arise almost e"clusively from e"ist#in hihly irriatedfarmland ($hush and en! &''). o achieve this increase in production! the yield potential needs to be increased and the rateof biomass production improved! particularly durin thereproductive phase (*assman! &''+). ,f the numerous factorsaffectin crop yield! the efficiency with which solar radiation istrans#formed into biomass and the amount of radiation availableare the most important (Russell et al.! &'-').

Liht saturation of photosynthesis leads to a decline inradiation#conversion efficiency. or rice this was estimated to beappro"imately &7% (/urata and /atsushima! &'7) but variesreatly accordin to variety and rowth condi#tions. 1n the tropicaldry season! hih irradiance not only saturates photosynthesis butalso subects the e"posed fla leaf to hih#liht stress. heresponse of rice leaves to hih

& his research was supported by contract no. R04 of the5epartment for 1nternational 5evelopment of the 6.$.

*orrespondin author8 e#mail p.horton9sheffield.ac.u:8 fa" ++ ;&&+

;222;27-7.

irradiance has not been characteriarber! &''). >oth damae to andsustained down#reulation of =11 can be consid#ered to be photoinhibitory (i.e. causin a decrease in the ?uantum efficiencyof photosynthesis8 ,smond! &''+) and potentially could impactthe radiation#conversion effi#ciency of the crop. here is variationamon rice cultivars in both the susceptibility to photoinhibitionand the capac#ity for dissipation of e"cess absorbed liht eneryvia the "anthophyll cycle (>lac: et al.! &'').

1n the rice crop several factors influence the response of leaf photosynthesis to liht. irst! elevated leaf tempera#tures thataccompany hih irradiance have been shown to cause metabolicimbalances (astenes and 4orton! &''b)! deleterious effects onthyla:oid function (astenes and 4orton! &''a)! enhanced photoinhibition (use et al.! &''3)! and enhanced photorespiration(Leeood and @d#wards! &'').

=econd! leaf anle has been identified as influencin the dereeof liht saturation of upper leaves (Aoshida! &'-&b). t the 1RR1in the hilippines! new rice varieties have been developed that possess a series of ideal traits! includin riid! upriht leaves.

hese varieties are called B. 6p#riht leaves were introduced tothese new varieties to increase the penetration of sunliht throuhto lower leaves! thus optimi


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55< 'urchie et al. "lant "hysiol. Vol. 119, 1999

available cross#sectional area (4e et al.! &''8 Falladares andearcy! &''7). he upriht leaf anle therefore pro#foundlyinfluences the chanes in liht absorption occur#rin durin thediurnal cycle. Liht saturation of photo#synthesis may not bereached! or may be short#lived! and the period of e"posure tohih#liht stress reduced. n upriht leaf anle is not e"pected toreatly alter the diur#nal chanes in leaf temperature! suestinthat there will be periods of low liht absorption and hihtemperature.

hird! the liht responses of leaves are predicted to be alteredwith rowth of the crop. Ge have observed that! as the canopymatures and the rain#fillin stae proresses! more than 0% of B fla leaves adopt a more horianHos in the hilippines. he site was (&+I&&9 B! &2I &9 @! altitude 2& m). he rice (Oryza sativa L.)varieties used were 1R72 and 1R'-#&&2#2 (>=120) (referredto hereafter as 1R). he former is a commonly used 1ndicavariety and the latter a ropical Japonica of the B class.=eedlins were transplanted in January and plants were hihlyirriated throuhout the study. /aa#has clay soil was used(nda?ueptic 4apla?uoll). Butri#ents were supplied so as to be

plentiful throuhout.

nalysis too: place at two staes of rowthC before flow#erinat appro"imately 0 d after transplantin! and ap#pro"imately &00d after transplantin! when rains were halfway throuh the fillinstae (the yellow#ripe stae8 Aoshida! &'-&b) and the fla leaveshad beun to senesce (as assessed by a decreasin *hl content).

Gas Echan(e

Leaf as#e"chane measurements were made usin a 1R asanaly

Leaf samples were ta:en at various points durin the day and

immediately fro


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"hotosynthesis, "hotoinhibition, an) enescence in #ice 555

'hl ;ssay

he *hl content of leaves in the field was measured usin ahand#held *hl meter (model =5#02! /inolta! Ramsey! BJ) asdescribed previously (/ar:well et al.! &''). =everalmeasurements were ta:en on each leaf and averaed. en leaves

were used to find an averae value. Falues from the *hl meter (=5 values) were converted into *hl per unit leaf area usincalibration curves devel#oped for each variety. calibration curvewas constructed for =5#values versus *hl per unit leaf area (asestimated by e"traction and assay in -0% acetone).

E*erimental Protocols

1t was important that photosynthesis be assessed in situ (i.e. thatall conditions were :ept as close as possible to those e"perienced by the leaf). herefore! the leaf was :ept at its natural anle of

posture. or youn leaves of 1R this was a vertical position. or 1R72 there was more variation in leaf anle! althouh fla leaveswere mostly upriht. 1t was also observed that the most common position for either variety was with the ada"ial surface at '0Irelative to the risin sun8 we shall refer to this leaf surface as face&. he opposite side of the blade! which received the after#noonsun! will be called face 2. Leaves were taed beforemeasurements were ta:en! and the same position on the leaf wasmeasured each time (appro"imately &0 and cm from the tip of the blade for 1R and 1R72! respectively).

he older fla leaves of both varieties had a more hori#


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556 'urchie et al. "lant "hysiol. Vol. 119, 1999

Fi(ure " @ight;saturation cur+es ta-en in the

!iel) !or %#65 a an) %#=/ b at 35 mg m@/1

@ an) 9 mg m@/1 ' :7/. 'easurementswere ma)e 6 ) !ollowing transplanting.

ison with iure &a it may be concluded that photosynthe#sis wassaturated for a sinificant part of the day (at least + h). t '00 mmL/& *,2! the photosynthesis rate was more than double thatobserved at ambient *,2 levels.

iure 3 shows diurnal courses of *,2 e"chane for 0#and '0#d leaves of 1R. Falues for photosynthesis and stomatalconductance were comparable to those of previ#ous e"perimentsusin the same varieties and carried out durin the dry season at1RR1 (=. en! unpublished data). or 0#d leaves of 1R! direct photosynthesis measured for face & increased dramatically from 7to ' / as photon flu" density increased! and by this time photosynthesis was liht saturated. 4owever! between ' and &0/ there was an une"pectedly early (>lac: et al.! &'') decline in photo#synthesis capacity ( P ma") to 70% of this ma"imum rate andthis was maintained for the rest of the mornin. Falues of

Fi(ure >" &aily pro!iles o! photosynthesis a an) b an) stomatal

con)uctance c an) ) !or %#65 lea+es 6 ) a an) c an) 1 ) b

an) ) !ollowing transplanting. @, , Face 1 )irect ', !ace 1 in situ

P, !ace / )irect Q, !ace / in situ. 4rror bars represent 4 o! at leastse+en replicates. ee te8t !or )etails.

P ma" for face 2 were at a similar level. /easurements of stomatal

conductance indicated that this reduction in P ma" was associatedwith closure of stomata. hotosynthesis rates in situ were lower than direct rates after -C30 /! and this disparity was further enhanced by midday. he de#cline of in situ photosynthesis was probably due to a com#bination of the decline in P ma" and adecreased 1R. t midday in situ photosynthesis was 3% of P ma". >roadly similar behavior was shown by 0#d leaves of 1R72(data not shown).

t the rain#fillin stae only face & was measured in 1R because of the loss of an erect leaf posture. hotosyn#thesis ratesafter &0 / were liht saturated (compare with i. 2). 1n contrast

to the youn leaves! there was no midmornin decrease in P ma"!and! in fact! photosynthesis rates were the same as those found inthe late mornin and beyond in the youner leaves (i. 3).hotosynthesis re#mained constant for a lare part of the day!declinin as the irradiance decreased after 2 /. t & / adramatic decline in stomatal conductance occurred! while

photosynthesis rates remained hih. low internal *,2concentration was also recorded at this time (data not shown). nalmost identical pattern was noted for 1R72 leaves (not shown).

Gith the e"ception of the early mornin burst of *,2assimilation! direct rates of photosynthesis for 1R were similar at 0 and &00 d. 1n situ rates for the &00#d leaves were hiher thanfor 0#d leaves because of the more favorable leaf anle! and totaldaily carbon ain! as as#sessed from the area under the curves in

iure 3! indicated appro"imately 30% more photosynthesis in the&00#d fla leaves. here was a small decrease in the liht# and

*,2#

saturated P ma" (from + to +0 mmol *,2 m/2 s/&)! suest#in

that the onset of senescence and *hl content in the&00#d leaves was appro"imately 3+% below the youner leaves(able 1). or 1R72 there was no statistically sinifi#cant

difference in P ma" at '00 m mL/& *,2 between youn and old

leaves! althouh the *hl content had decreased by 2% in theolder leaves.

*hl fluorescence was used to more fully e"plore the effect of leaf posture and ae on photosynthesis. or face & of youn leaves

of 1R! F=11 declined steeply as the irradiance level increased!

reachin a minimum value of appro"imately 0.2 at - to &0 /(i. +a). =uch a low value


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"hotosynthesis, "hotoinhibition, an) enescence in #ice 55=

.able I" Photosynthetic capacity and Chl contents of leaves of

IR65 and IR72

&ata are shown !or lea+es 6 an) 1 ) !ollowing transplanting.For :hl the +alues represent the means 6 4 o! between = an) 1lea+es. Fi+e measurements were ta-en !rom each lea! an)

a+erage). P ma8 represents light;saturate) ./ mmol uanta m/3

s/1 an) :7/;saturate) 9 mg m@/1 :7/ photosynthesis

measure) in the !iel) as in Figure /. All +alues are signi!icantly)i!!erent to a 1B le+el when comparing 6; an) 1;) plants,e8cept those mar-e) with an asteris-.

"lant :hl :ontentP

ma8

mmol m/2

mmol m/2 s

/1

%#65

6 ) 3C5.5 6 /5.1


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55C 'urchie et al. "lant "hysiol. Vol. 119, 1999

reached a ma"imum value of appro"imately 20 to 2 atappro"imately - /! after which time there was a decline before afurther increase in the afternoon. hese :inetics were the result of the contribution of the illumination of the two leaf surfaces.Leaves that had been maintained hori#


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Fi(ure 0" &aily pro!iles o! )ar-;a)apte) !luorescence parameters

!or %#65 lea+es le!t in a +ertical position @ or place) in a horiEontalposition at C A' an) maintaine) there !or se+eral )ays therea!ter.

'easurements were ta-en on the )ay o! changing lea! orientationr or a!ter 5 ) in that position @. "oints represent means o! at

least eight replicates.

notes the ?uantum efficiency of open =11 centers! declines as aresult of BE. here were considerably reater overall levels of BE in the &00#d leaves compared with youner leaves! with F v9D F m9 reachin values of 0.3 to 0.+! which is consistent with

the hiher 5@= in these leaves. he :inetics of F v9D F m9 weredifferent between old and youn leaves. 1n youner leaves F v9D F m9 decreased rapidly on leaf face &! as seen previously! butunli:e ? (i. +)! it rela"ed only slowly after &0 / (i. -! c andd). 1n older leaves BE developed proressively between 7 /and midday (i. -! d and f) and matched the increase in 5@=.

here were sinificant differences in the carotenoid con#tent of youn and older leaves. he main difference was the dramaticincrease in the carotenoid to *hl ratio (able 11). he increase inthis ratio was reater than the decrease in *hl content per unit leaf area (see able 1)! indicatin net synthesis of carotenoid on a leaf#area basis. he two culti#vars behaved somewhat differently. 1n1R the carotenoid to *hl ratio doubled but there were no laredifferences in the relative content of different carotenoids. he"antho#phyll cycle pool si


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56 'urchie et al. "lant "hysiol. Vol. 119, 1999

.able II" Carotenoid composition of leaves of IR65 and IR72

&ata are shown !or lea+es 6 an) 1 ) !ollowing transplanting an) !or 6;) lea+es that ha) been

-ept in a horiEontal position !or 5 ) hor. Values o! lutein, b;carotene, an) neo8anthin represent the

amount o! each carotenoi) as a percentage o! the total carotenoi) pool. Ganthophyll cycle represents

the total o! all 8anthophyll cycle constituents +iola8anthin 1 anthera8anthin 1 Eea8anthin as a

percentage o! the total carotenoi) pool. :ar:hl is the molar ratio o! total carotenoi) to total :hl.

Values are means 6 4 o! at least 1/ replicates.

"lant @utein b;:arotene eo8anthinGanthophyll

:ar:hl:ycle

%

%#65

6 ) 33./ 6 .< /C.6 6 .5 9.6 6 ./ /C.1 6 1.1 ./9 6 ./

1 ) 3=.3 6 .6 /6.3 6 .= 9.C 6 ./ /C.< 6 1. .5C 6 .6

6 ) hor 31.6 6 .= 3. 6 1.3 9.< 6 .3 /C.1 6 .9 .31 6 .1

%#=/

6 ) 33.< 6 .3 /9./ 6 .3 1.5 6 .1 /6.6 6 .< ./9 6 ./

1 ) 35. 6 .9 /


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the ideal techni?ue for e"plorin the relationship between leaf anle and photosynthesis. Ge have established clearly that =11 issaturated on one surface of the leaf in the mornin and the other surface in the afternoon. he values of ? recorded durin these periods indicate a hih level of liht stress! but because thee"posure was brief (a few hours)! the amount of chronic photoinhibition was small. hotoinhibition is a time#dependent process that depends on accumulated photon dose (ar: et al.!&'')8 it is not ust the level of illumination but the period over which this occurs. his view was confirmed by the observationthat leaves of 1R forced into a hori


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56/ 'urchie et al. "lant "hysiol. Vol. 119, 1999

&''-). *learly! further wor: is needed to elucidate the reasons for fla leaf senescence durin the rain#fillin period.

'Orit#ish plantspecies. lant *ell @nviron 2$% -&;-

&ar !, )reb P, 3er)9ig B, Feierabend J (&''3) =ensitivity to photodamae increases durin senescence in e"cised leaves. J lanthysiol 2#2% 3-;++

&(us( ', Peng (&'') >rea:in the yield frontier of rice. In /

Reynolds! = Raaram! = /cBab! eds! 1ncreasin Aield o#tential inGheatC >rea:in the >arriers. 1nternational *enter for 5evelopment of /ai


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*ussell ', Jaris P', !on)ei)( J+ (&'-') bsorption of radiation bycanopies and stand rowth. In K Russell! > /arshall! K Jarvis! eds!lant *anopiesC heir Krowth! orm and unction. *ambride6niversity ress! *ambride! 6$! pp 2&;3'

T(omas 3, )oddar) J+ (&'-0) Leaf senescence. nnu Rev lant hysiol:2% -3;&&&

8alladares F, Pearc7 *0 (&''7) 1nteractions between water stress! sun#shade acclimation! heat tolerance and photoinhibtion in the sclerophyll Heteromeles arbutifolia. lant *ell @nviron .6% 2;3 8an &oo)en O,

nel JF3 (&''0) he use of *hl fluorescence nomenclature in plant stress physioloy. hotosynth Res .


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Ulasan : Nama : Aris CahyonoNPM : 1525010145Kelas : C25

Dalam tanaman padi ada penurunan gelapdisesuaikan v ! m dan karena itu dapat disimpulkan"ah#a tanaman padi un$dergo "entuk photoinhi"itionkronis di lapangan% se&auh mana yang tergantung pada"er"agai diteliti. Ber"agai 'ndica digunakan (')*+,adalah le"ih sensitif daripada -ropical aponica (')/0,.perco"aan la"oratorium dilakukan denganmenggunakan kondisi pertum"uhan yang sama denganyang di lapangan telah menun&ukkan "ah#a penurunanv ! m diamati pada varietas terse"ut di"utuhkan &amuntuk pulih sepenuhnya (. Chen dan 2.3. 4urchie% datatidak dipu"likasikan,. Penurunan hasil kuantum karena

itu akan men&adi penting ketika tingkat cahayakemudian menurun dan fotosintesis tidak lagi cahaya &enuh. 3al ini akan ter&adi pada de$lipatan di 'A) menu&utengah hari dan selama Shading dise"a"kan olehpergeseran pola cahaya$5ek atau dengan a#an. Ada$kedepan% #aktu yang di"utuhkan untuk pulih daridepresi "erkelan&utan di v ! m "erpotensi pentingdalam menentukan keuntungan kar"on sehari$haridalam daun tegak karena 5uktuasi situ di PA) le"ihmendadak daripada di daun hori6ontal. Datamenun&ukkan peru"ahan yang relatif kecil di v ! m%khususnya di ')/0% tetapi harus menun&ukkan "ah#a"eras sering tum"uh di "a#ah kondisi kurangmenguntungkan daripada yang digunakan di sini7 8lehkarena itu% tanggapan photoinhi"itory le"ih "esardiperkirakan.

otosintesis dan Photoinhi"itionerakan daun di cahaya yang tinggi adalah

strategi yang ditetapkan untuk menghindari cahayastres pada tanaman yang le"ih tinggi (B&o:rkman danDemmig$Adams% 199;,.


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daun dari ')/0 dipaksa ke posisi horisontal sehinggasaturasi cahaya dipertahankan selama "agian utamadari hari dipamerkan photoinhi"ition le"ih "esardaripada ketika dalam posisi vertikal.

-elah ter"ukti "ah#a daun dalam posisihori6ontal menerima le"ih "esar total penyinaran harian(Duncan% 19*1,% tapi ini "elum pernah dipertim"angkandalam hal tingkat stres ringan. 2fek menguntungkan

dari postur daun vertikal &elas ditun&ukkan dalampengamatan nilai minimum dekat >P pada tengah hari@meskipun PA) maksimum% potensi stres ringan adalahminimal.


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dengan daun muda% >P adalah maintained pada nilaisedikit le"ih tinggi.

Bukti lain dari paparan "erkelan&utan terhadapstres cahaya datang dari dua kali lipat dari rasio siklusFanto?l karotenoid untuk Chl dalam daun yang le"ihtua. Dalam ')*+ ini &uga dikaitkan dengan peru"ahankomposisi karotenoid dalam mendukung siklus Fanto?l.

mumnya% tanaman terkena stres ringan memilikiFanto?l tinggi ukuran siklus renang (Demmig$Adams danAdams% 199/,. Biasanya ini akan men&adi +0E sampaiG0E dari total karotenoid7 di ')*+ dan ')/0 nilai$nilai iniadalah G+E dan +E% masing$masing% dalam daun 1$d. ntuk ')*+ tapi tidak ')/0% peningkatan total kolamrenang siklus Fanto?l di daun pikun di"andingkandengan daun muda terlihat% menun&ukkan "ah#a "entukaklimatisasi untuk meningkatkan fotoproteksi itu ter&adidi daun ini. elas% ada "e"erapa per"edaan dalamaklimatisasi -ropis aponica dan varietas padi 'ndicauntuk radiasi sehu"ungan dengan siklus Fanto?l.

=erugian Chl dari daun dapat tim"ul darise&umlah penye"a"% termasuk aklimatisasi denganradiasi tinggi% stres oksidatif% kar"ohidrat penumpukan%atau hormon diatur "reak$do#n dari kloroplas untukmempromosikan < resirkulasi untuk tenggelam. Ada"ukti yang menun&ukkan "ah#a "eras sum"er rendahuntuk tenggelam rasio (yaitu ukuran #astafel "esar,menginduksi penuaan di daun "endera (Hada et al%199G7.


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mengisi dan ini cenderung daun untuk periode"erkelan&utan ke&enuhan cahaya photosyn$tesis danphotoinhi"ition le"ih "esar. Secara kualitatif% semuakarakteristik ini ditemukan "aik dalam

plant physiol. 1999 murchie 553 64

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