Exposure to ultraviolet radiation delays photosynthetic recovery in Arctic kelp zoospores

Transcription

1 Photosynth Res (2006) 88: DOI /s y ORIGINAL PAPER Exposure to ultrviolet rdition delys photosyntheti reovery in Arti kelp zoospores Mihel Y. Roled Æ Dieter Hnelt Æ Christin Wienke Reeived: 6 Jnury 2006 / Aepted: 3 Mrh 2006 / Pulished online: 7 June 2006 Ó Springer Siene+Business Medi B.V Astrt Sesonl reprodution in some Arti Lminriles oinides with inresed UV-B rdition due to strtospheri ozone depletion nd reltively high wter tempertures during polr spring. To find out the pity to ope with different spetrl irrdine, the kinetis of photosyntheti reovery ws investigted in zoospores of four Arti speies of the order Lminriles, the kelps Sorhiz dermtode, Alri esulent, Lminri digitt, nd Lminri shrin. The physiology of light hrvesting, hnges in photosyntheti effiieny nd kinetis of photosyntheti reovery were mesured y in vivo fluoresene hnges of Photosystem II (PSII). Sturtion irrdine of freshly relesed spores showed miniml I k vlues (photon fluene rte where initil slope intersets horizontl symptote of the urve) vlues rnging from 13 to 18 lmol photons m )2 s )1 mong speies olleted t different depths, onfirming tht spores re low-light dpted. Exposure to different rdition spetr onsisting of photosynthetilly tive rdition (PAR; nm), PAR+UV-A rdition (UV-A; nm), nd PAR+ UV-A+UV-B rdition (UV-B; nm) showed tht the umultive effets of inresing PAR fluene nd the dditionl effet of UV-A nd UV-B rditions on photoinhiition of photosynthesis re speies speifi. After long exposures, Lminri shrin ws more sensitive to the different light tretments thn the other three speies investigted. Kinetis of reovery in zoospores showed fst phse in S. dermtode, whih indites redution of the photoprotetive proess while slow phse in L. shrin indites reovery from severe photodmge. This first ttempt to study photoinhiition nd kinetis of reovery in zoospores showed tht zoospores re the stge in the life history of seweeds most suseptile to light stress nd tht ultrviolet rdition (UVR) effetively delys photosyntheti reovery. The viility of spores is importnt on the reruitment of the gmetophyti nd sporophyti life stges. The impt of UVR on the zoospores is relted to the vertil depth distriution of the lrge sporophytes in the field. Keywords Alri esulent Æ Kinetis Æ Lminri digitt Æ Lminri shrin Æ Optimum quntum yield Æ P-I urve Æ Photosyntheti reovery Æ Sorhiz dermtode M. Y. Roled (&) Biologishe Anstlt Helgolnd, Alfred Wegener Institute for Polr nd Mrine Reserh, Mrine Sttion, Postfh Helgolnd, Germny E-mil: mroled@wi-remerhven.de D. Hnelt Biozentrum Klein Flottek, University of Hmurg, Ohnhorst- Str. 18, D Hmurg, Germny C. Wienke Alfred Wegener Institute for Polr nd Mrine Reserh, Am Hndelshfen 12, Bremerhven, Germny Arevitions PAR UV-A UV-B PAR+UV-A PAR+UV-A+UV-B I k retr mx PSII photosynthetilly tive rdition (=P) ultrviolet-a ultrviolet-b (=PA) (=PAB) sturting irrdine photosyntheti effiieny mximum reltive eletron trnsport rte Photosystem II

2 312 Photosynth Res (2006) 88: F v /F m P I urve tn h PFR CPDs Introdution mximum potentil quntum yield of PSII photosynthesis-irrdine urve hyperoli tngent photon flux rte yloutne-pyrimidine dimers Supply of spores nd hitt vilility re importnt resoures in mintining kelp ommunities in ostl mrine environments. One propgules re relesed into the wter, plume of spore loud my drift downstrem (Deysher nd Norton 1982) nd n e displed lterlly y urrents nd progressively diluted y turulent mixing (Norton 1992). Zoospores n, therefore, e suspended within the euphoti lyer of the wter olumn for period of time. Settling spores on sustrte t gret depths or under lgl nopies experiene low-light miroenvironment suitle for germintion nd growth. However, sinking veloity of spores is dependent on size, suh tht 55 lm non-motile rpospore of the florideophyte red lg Cryptopleur viole (J. G. Ag.) Kylin relesed from 6 m tll gmetophyte would tke 10 min to reh the sustrte (Coon et l. 1972), while 156 lm non-motile zygote of fuoid rown lg Srgssum mutium (Yendo) Fensholt relesed from 1 m ove the sustrte would tke min (Norton nd Fetter 1981). For kelp zoospores tht re only 3 5 lm in size, the visosity of sewter will dominte nd limit their swimming ility (Purell 1977). The speed of flgellted ells of this size is pproximtely 120 lm s )1 (Kessler 1985). This mens trvel time of out 2 h for distne of 1 m. Therefore, during the trnsitory plnktoni phse, kelp zoospores n e exposed to environmentl stress in prtiulr high photon fluene rtes nd ultrviolet rdition (UVR) within the upper euphoti zone. The potentil for limtion of the photosyntheti pprtus to hnging rdition onditions is n importnt pre-requisite for the eologil suess of lge. Further studies on this spet, espeilly on the erly life stges of mrolge, should e rried out. For exmple, effet of UVR on the photosynthesis of reprodutive ells hs een studied only in few speies of Lminriles (Dring et l. 1996; Wienke et l. 2000; Roled et l. 2005) nd Ulvles (Cordi et l. 2001). Among the three Lminri speies in Helgolnd, photoinhiition of zoospore photosynthesis to different light tretments, onsisting of the whole light spetrum nd exluding UV-B or UV-B+UV-A, nd the pity of reovery of their photosyntheti effiienies ws found to e relted to the depth distriution of dult sporophytes (Roled et l. 2005). Exposure to unnturlly high UVR fluene showed no full reovery in the photosyntheti pities of gmetophytes of the sme speies (Dring et l. 1996). In Arti Lminri digitt (Huds.) Lmour., photosynthesis of zoospores ws signifintly depressed under the whole light spetrum ompred to the sporophytes (Wienke et l. 2000). Most dt on the seweed photosynthesis hve een otined from studies on their mrosopi developmentl stges. Under strong light, Photosystem II (PSII) is intivted nd this phenomenon is lled photoinhiition. Intivtion of oxygen-evolving omplex is indued y lue light s well s UV light while red light intivtes the photohemil retion enter (Ohnishi et l. 2005). Photoprotetion y inresing therml energy dissiption ontrolled y rotenoids enles the seweeds to reover rpidly fter the offset of the stressful ondition, formerly lled dynmi photoinhiition (Osmond 1994). Photo-oxidtive dmge impirs the funtion of PSII. Photodmge is ontrolled y the stedy-stte oxidtionredution level of the primry quinone eptor (Q A ). Sine the redution stte of Q A linerly inreses with irrdine, the proility of photodmge inreses under strong light (Melis 1999). While light dmges PSII diretly, oxidtive stress during photosynthesis hs een demonstrted to suppress the de novo synthesis of proteins, in prtiulr, the D1 protein, whih is required for the repir of PSII (Nishiym et l. 2004, 2005). Photodmge or hroni photoinhiition minly ours in seweeds growing in the lower sulittorl zone when exposed to high irrdines (Hnelt 1998). These speies hve lower ility to down regulte photosynthesis through photoprotetion or photoregultion proesses (Hnelt et l. 2003). UV-B rdition hs more diret effets on the photosyntheti pprtus. Its sorption y romti nd sulfhydrylontining iomoleules uses diret moleulr dmge (Vss 1997). Prt of the D1/D2 heterodimer; the mjor struturl omplex within PSII re degrded (Rihter et l. 1990), while sorption y DNA uses lesions primrily the formtion of yloutne-pyrimidine dimers (CPDs) (Roled et l. 2004, 2005). UV-A rdition, on the other hnd, ws found to e dmging for PSII y deresing the eletron flow from retion enters to plstoquinone (Grzymski et l. 2001) ffeting eletron trnsport oth t the wter oxidizing omplex nd the inding site of the Q B quinone eletron eptor (Tursányi nd Vss 2002). UV nd lue light were lso found to intivte the oxygen-evolving omplex of the PSII (Ohnishi et l. 2005). So we hve good rguments tht UV rdition impinging on the uniellulr spores of seweeds will inrese their suseptiility to photodmge nd ffet the kinetis of reovery proess fter photoinhiition.

3 Photosynth Res (2006) 88: Kinetis of reovery in photosyntheti effiieny fter high light stress hs een reported in gmetophytes, young nd old sporophytes of Lminri shrin (L.) Lmour. (Hnelt et l. 1997) nd other Arti mrine lge (Hnelt 1998). To our knowledge, no study hs een rried out on the kineti of photosyntheti reovery in kelp zoospores. This study is imed to investigte the impt of exposure to different spetrl irrdines on the photosyntheti effiieny of zoospores fter vrile residene times of zoospores within the light sturting euphoti lyer of the wter olumn. This is simulted here y vrious exposure times to different spetrl omposition nd susequent exposure to dim white light omprle to the onditions on the se ottom or under lgl nopies. It is hypothesized tht the degree of photoinhiition nd reovery of photosynthesis fter exposure to PAR nd UVR of the Lminriles investigted is relted to the upper depth distriution limit of the sporophytes. The results of the present study re of interest to estimte possile effets under senrio of enhned UV-B rdition due to strtospheri ozone depletion (Gthen et l. 1995; Stähelin et l. 2001), s iologilly signifint UV-B rdition (1% UV-B) still penetrtes depths of 4 7 m depending on loud over nd wter turidity in Spitsergen (Wienke et l. 2006). Mterils nd method Algl Mteril Fertile sporophytes of Sorhiz dermtode (Pyl.) J. Ag., Alri esulent (L.) Grev., Lminri digitt nd L. shrin were olleted etween My nd June 2004 y SCUBA divers in Kongsfjorden t Prins Heinrihøy or Blomstrndhlvøy lose to Ny Ålesund (Spitsergen, N, E). Bldes with sori were exised from five different individuls per speies (representing the five replites), lened of epiphytes, lotted with tissue pper nd kept in drkness in moist hmer t 0 C overnight to mximum of 2 dys. To indue rpid relese of zoospores, sori were immersed in 5 10 ml filtered (0.2 lm pore size) sewter t 15 C nd exposed to nturl light lose to window (Wienke et l. 2006). The initil zoospore density ws ounted y use of Neuuer hmer (Brnd, Germny). Stok suspensions were diluted with filtered sewter to give spore densities etween spores ml )1 mong the five replites. Irrdition tretments Photosynthetilly tive rdition (PAR) ws provided y white fluoresent tues (Osrm, L65 Wtt/25S, Munih, Germny). UVR ws generted y UVA-340 fluoresent tues (Q-Pnel, Clevelnd,OH, USA), emitting spetrum similr to solr rdition in the rnge nm. Cell ulture dishes (35 mm 10 mm Corning, Corning In., NY, USA) were overed with one of the following filters to ut off different wvelength rnges from the spetrum emitted y the fluoresent tues: Ultrphn trnsprent (Digefr GmH, Germny); Folnorm (Folex GmH, Germny) or Ultrphn URUV frlos orresponding to the PAR+UV-A+UV-B (PAB), PAR+UV-A (PA), nd PAR (P) tretments, respetively. The spetrl properties of the foils used re pulished elsewhere (Bishof et l. 2002). UVR ws mesured using osine sensor onneted to UV VIS Spetrometer (Mrel Kruse, Bremerhven, Germny) elow the ut-off filters t 5.65 W m )2 UV-A nd 0.47 W m )2 UV-B. PAR ws mesured using osine quntum sensor tthed to LI-COR dt logger (LI-1000, LI-COR Biosienes, Linoln, Nersk, USA) to e 21.8 lmol photons m )2 s )1 (~4.69 W m )2 ). Chlorophyll fluoresene mesurements Photosyntheti effiieny ws mesured s vrile fluoresene of PSII determined using Wter Pulse Amplitude Modultion fluorometer (Wter-PAM) onneted to PC with WinControl softwre (Heinz Wlz GmH, Effeltrih, Germny). Immeditely fter djustment of spore density (not exeeding 1 h fter spore relese), the spore suspension ws filled into 5 ml Qurtz uvettes nd the mximum quntum yield (F v /F m ) ws mesured t time zero (n = 5) s desried y Hnelt (1998) nd designted s ontrol. After 3 min drk inution, F o ws mesured with red mesuring light pulse (~0.3 lmol photon m )2 s )1, 650 nm), nd F m ws determined with 600 ms ompletely sturting white light pulse (~275 lmol photon m )2 s )1 ). Photosynthesis (in terms of reltive eletron trnsport rte, retr = PFR DF/Fm ) versus irrdine urves (P I urve) ws lso mesured in the time zero ontrol (n = 3, hosen t rndom from the five replites) s desried y Bishof et l. (1998). The hyperoli tngent model of Jssy nd Pltt (1976) ws used to estimte P I urve prmeters desried s: retr ¼ retr mx tn hði PAR retr 1 mx Þ where retr mx is the mximum reltive eletron trnsport rte, tn h is the hyperoli tngent funtion, is the eletron trnsport effiieny nd I is the photon fluene rte of PAR. The sturtion irrdine for eletron trnsport (I k ) ws lulted s the light intensity t whih the initil slope of the urve () interepts the horizontl symptote (retr mx ). The sturting photosyntheti photon flux density (PPDF) vlue t whih photosynthesis is t 95% of

4 314 Photosynth Res (2006) 88: the mximum vlue (I 0.95 ) is diretly proportionl to I k nd n e derived using the eqution I 0.95 = tn h )1 (0.95) I k (Chlker et l. 1983). Curve fit ws lulted with the Solver Module of MS-Exel using the lest squres method ompring differenes etween mesured nd lulted dt. Controls mesured t time zero were filled into orresponding ulture dishes. To evlute the effet of different rdition tretments nd exposure times, 5 ml of fresh spore suspension were filled into eh 35 mm 10 mm ell ulture dish nd exposed to the three rdition onditions in series of time tretments (1, 4, nd 8 h; n = 5 per tretment omintion) t 7 1 C. After tretments, F v / F m ws determined nd the spore suspension ws returned to the sme ulture dish nd ultivted under dim white light (8 2 lmol photons m )2 s )1 ) t the sme temperture for reovery. Time zero ontrol ws lso mintined t the sme ondition. Mesurements of photosyntheti reovery in time-series were mde fter 2, 4, 8, 24, nd 48 h in dim white light ondition. To eliminte possile hndling effet due to repeted mesurements, F v /F m ws lso mesured in time zero ontrol t time-series in synhrony with reovery of treted smples, nd now designted s distured ontrol. Another set of ontrols in prllel to eh replite ws seprtely prepred nd ultured immeditely in dim white light fter relese designted s undistured ontrol. Photosyntheti effiieny of undistured ontrols ws mesured t the end of the reovery period (48 h) of the experiment. Settled nd germinting spores were slowly resuspended y suking nd jetting the medium ginst the ottom of the ulture dish using Eppendorf pipettes. Time-series reovery in optimum quntum yield of zoospores fter exposure to different spetrl irrdine ws expressed s perent reovery of distured ontrol s: Re t F v=f m ¼ 100 ðct F v=f m ðct F v=f m T t F v=f m ÞÞ=Ct F v=f m where T Fv/Fm is the optimum quntum yield of treted smple fter reovery t time t (2, 4, 8, 24, nd 48 h) nd C Fv/Fm is the orresponding optimum quntum yield of ontrol t time t. Sttistil nlysis Dt were tested for homogeneity (Levene Sttistis) nd normlity (Kolmogorov Smirnov test) of vrine. Corresponding trnsformtions (squre roots) were mde to heteroskedsti nd non-norml dt. Photosyntheti response to vrying irrdine, exposure time nd intertion effet were tested using multiple nlyses of vrine (MANOVA, P < 0.05). Time series mesurements on the kinetis of photosyntheti reovery were sujeted to repeted mesures nlysis of vrine (RMANOVA, P < 0.05) to determine the effet of pre-exposure irrdine tretments of P, PA, nd PAB seprtely mong different exposure times. All nlyses were followed y Dunn s multiple rnge test (DMRT, P = 0.05). Sttistil nlyses were mde using SPSS progrm (SPSS, Chigo, IL, USA). Results The I k vlues of zoospores of ll studied speies were very low. Highest sturting irrdine (I k ) ws mesured in zoospores of the shllow wter speies Sorhiz dermtode t 17.9 lmol photon m )2 s )1 (Fig. 1; Tle 1). Lower I k vlues were mesured in the upper sulittorl speies Alri esulent t 16.2 lmol photon m )2 s )1 nd the mid sulittorl Lminri digitt t 15.4 lmol photon m )2 s )1 nd lowest in the mid- to lower-sulittorl speies L. shrin t 12.6 lmol photon m )2 s )1. The mximum reltive eletron trnsport rte (retr mx ) ws highest in S. dermtode nd in lower, similr rnge in the other speies studied. In L. shrin photoinhiition ws oserved t photon fluene rte ove 80 lmol photon m )2 s )1, ut not in other speies. The vlues of lph were similr in ll speies nd vried etween nd (Tle 1). Mximl quntum yield of the PSII (F v /F m ) in the time zero ontrol ws highest in S. dermtode ( ), ut not signifintly different etween L. digitt ( ), L. shrin ( ) nd A. esulent ( ). Time-series mesurements of the distured ontrols exhiited no signifint hndling effet on the photosyntheti effiieny of zoospores (Tle 2). Comprison etween distured nd undistured ontrol fter 48 h showed no signifint vrition in S. dermtode, A. esulent nd L. digitt. Signifintly higher F v /F m ws, however, oserved in distured ompred to undistured ontrol in L. shrin (T-test, P < 0.001). Exposure to inresing time of PAR signifintly redued optimum quntum yield (F v /F m ) of ll speies investigted (Fig. 2). After 1 h exposure to PAR, photosyntheti effiienies of oth S. dermtode nd A. esulent ws lest ffeted ompred to L. digitt nd L. shrin. Inresing exposure time to PAR hd low dditionl effet on the F v /F m of S. dermtode while L. shrin ws most sensitive to inresing fluene of PAR. A shrp deline in the F v /F m ws oserved in A. esulent ompred to L. digitt (Fig. 2). Light supplemented with UV-A rdition signifintly deresed photosyntheti effiieny y 7% 96% in ll speies

5 Photosynth Res (2006) 88: () I 0.0 k = Rel. ETR () I k = Rel. ETR () Rel. ETR I k = (d) I k = Rel. ETR Photon Fluene Rte (µmol photon m -2 s -1 ) Fig. 1 Photosyntheti performne (P-I urve) of zoospores from () Sorhiz dermtode () Alri esulent () Lminri digitt nd (d) Lminri shrin (n = 3) immeditely fter relese from the sori. PFR is the respetive photon fluene rte of tini white light nd retr is the reltive eletron trnsport rte, n index of light hrvesting nd susequent hrge seprtion in PS II nd PS I inititing eletron trnsport nd prodution of NADPH nd ATP. Sturting irrdine (I k ) is estimted s the point t whih the initil slope rosses mximum photosynthesis (retr mx ) using the hyperoli tngent model of Jssy nd Pltt 1976 studied. The dditionl effet of UV-B rdition (PAB tretment) ws only oserved fter 1 h exposure in S. dermtode nd A. esulent. Under longer exposure time, no signifint differene ws oserved etween PA nd PAB tretments (Fig. 2, ). Conversely, in L. digitt nd L. shrin, no signifint differene ws oserved etween PA nd PAB tretments fter 1 h exposure ut signifint dditionl effet of UV-B ws oserved t Tle 1 Photosynthesis-irrdine urve prmeters estimted using the hyperoli tngent eqution of Jssy nd Pltt 1976 nd Chker et l Speies I k (lmol photon m )2 s )1 ) I 0.95 (lmol photon m )2 s )1 ) ETR mx Alph S. dermtode A. esulent L. digitt L. shrin I k is the light intensity t whih the initil slope of the urve () interepts the horizontl symptote, the mximum reltive eletron trnsport rte (retr mx ). I 0.95 is the sturting photosyntheti photon flux density (PPDF) vlue t whih photosynthesis is t 95% of the mximum vlue [I 0.95 = tn h )1 (0.95) I k ] longer exposure time (Fig. 2, d). Multiple nlyses of vrine (MANOVA, P < 0.001) demonstrted signifint effets of irrdine nd exposure time in ll speies investigted (Tle 3). Dunn s multiple rnge test (DMRT, P = 0.05) showed signifintly higher redution in photosyntheti effiienies of zoospores exposed to the whole light spetrum ompred to light without UV-B rdition nd to PAR lone (PAB > PA > P) mong S. dermtode, A. esulent, nd L. shrin. In L. digitt, redution in optimum quntum yield of zoospores exposed to light tretments supplemented with UV-A lone or UV-A+UV-B ws not signifintly different (PAB = PA > P). Fluene s funtion of different exposure times, exhiits signifintly different effet on F v /F m in S. dermtode, A. esulent, L. shrin (8 h > 4 h > 1 h), nd L. digitt (8 h = 4 h > 1 h). The kinetis of photosyntheti reovery in zoospores ws oserved to e different etween speies, spetrl tretments nd exposure times (Fig. 3). In generl, photosyntheti reovery in S. dermtode ws fster under ll light tretments nd exposure times ompred to the three other speies investigted. Regrdless of exposure time, reovery fter exposure to PAR (=P) lone ws lredy 91% 96% fter 2 h nd omplete reovery ws lredy oserved fter 4 h. Reovery in zoospores exposed to light supplemented with UV-A (=PA) ws lower ut not signifintly different ompred to P tretment t 1 h exposure. Photosyntheti reovery of spores pre-exposed for 4 or 8 h to PA ws delyed y 6% 10% during the first 2 h, respetively. A minimum of 8 h post-ultivtion in dim white light ws required for omplete reovery of their photosyntheti effiieny. In light supplemented with UV-A nd UV-B (=PAB), reovery ws signifintly different with P ut not with PA. Pre-exposure for 4 to 8 h PAB further delyed photosyntheti reovery. Complete reovery of photosyntheti effiieny of PAB-treted smples ws oserved only fter 24 h ulture in dim white light. Photosyntheti reovery fter 2 h in A. esulent preexposed to 1 h P tretment ws 87% nd omplete reov-

6 316 Photosynth Res (2006) 88: Tle 2 Men optimum quntum yield (F v /F m ) of untreted zoospores (ontrol) in Sorhiz dermtode, Alri esulent, Lminri digitt, nd Lminri shrin immeditely fter relese nd t different time-series intervls (nd = not determined) Speies Distured ontrol mesurements (h) Undistured ontrol (h) ns 0.04 Sorhiz dermtode nd nd nd ns 0.04 Alri esulent ns nd * 0.02 Lminri digitt Lminri shrin Distured ontrols re mesured t time-series in synhrony with reovery time of treted smples. Undistured ontrols re prllel of eh replite seprtely prepred nd ultured immeditely in dim white light (8 2 lmol photons m )2 s )1 ) fter relese nd photosynthesis ws mesured fter 48-h ultivtion. *refers to signifint nd ns, not signifint differene etween 48-h post-ultivtion men vlues (T-test, P < 0.05) ery ws oserved only fter 8 h in dim white light. This is 4 h more thn the time required for S. dermtode to fully reover its photosynthesis. In smples exposed for 1 h to UVR, photosyntheti reovery fter 2 h ws only 59% nd 37% in PA nd PAB, respetively. Complete reovery ws, however, oserved fter 48 h. Pre-exposure to 4 h of the three rdition ondition (P, PA, PAB) showed liner inrese in photosyntheti reovery within 2 8 h postultivtion. However, only prtil reovery ws oserved in zoospores exposed to P nd lower F v /F m ws lso mesured in PA nd PAB tretments. In L. digitt, reovery of photosyntheti pity fter 1 h pre-exposure to the three rdition onditions ws slower reltive to S. dermtode nd A. esulent. Vlues of photosyntheti effiieny omprle to the ontrol were hieved only fter 24 h post-ultivtion in low white light. After 4 h pre-exposure tretments, photosyntheti reovery ws further deresed in ll tretments. Exposure to 8 h P nd PA tretments did not show further derese in optimum quntum yield suggesting limtion (Fig. 3). Slightly higher photosyntheti reovery ws oserved in 8 h P- nd PA- pre-exposed smples ompred to 4 h P- nd PA- pre-exposed smples (Fig. 3). However, preexposure to 8 h PAB ws found to further dely kinetis of photosyntheti reovery. Photosynthesis of L. shrin ws most sensitive to hnges in spetrl irrdine nd fluene. After 1 h preexposure to P, photosyntheti effiieny reovered to 82% fter 2 h. In the following mesurements, there ws grdul liner inrese ttining full photosyntheti reovery fter 8 h. Pre-exposure to P for 4 nd 8 h resulted in stronger photoinhiition nd steeper liner inrese in photosyntheti effiieny. No full reovery ws oserved fter 24 h post-ulture in zoospores preexposed to 8 h PAR. Exposure to light supplemented with UVR showed different trends in reovery kinetis etween exposure tretments. After 1 h pre-exposure to PA nd PAB, there ws steep liner inrese in photosyntheti reovery etween 2 h nd 8 h post-ultivtion. However, no further reovery ws oserved fter 24 h post-ultivtion. In 4-h PA nd PAB pre-exposed smples, steep liner inrese in photosyntheti effiieny ws oserved etween 1 h nd 24 h post-ulture ut men reovery ws lower ompred to zoospores exposed only to 1 h pre-tretment. Zoospore exposed to 8 h PAB ws only le to reover 31% of its photosyntheti pity fter 24 h post-ultivtion. Repeted mesures nlysis of vrine (RMANOVA, P < 0.01) showed signifint effets of irrdine on the kinetis of photosyntheti reovery of ll speies investigted. Dunn s multiple rnge test (DMRT, P = 0.05) demonstrtes fster reovery in spores pre-treted with different fluene of PAR lone (Fig. 3). Supplement of

7 Photosynth Res (2006) 88: Fig. 2 Men optimum quntum yield (F v /F m ) of zoospores during tretment to photosynthetilly tive rdition (PAR = P), PAR + UV-A (PA), nd PAR + UV-A + UV-B (PAB) t different exposure times in () Sorhiz dermtode () Alri esulent () Lminri digitt nd (d) Lminri shrin. Vertil rs re stndrd devitions (SD, n = 5). Multiple nlysis of vrine (MANOVA) is presented in Tle 3 () F v /F m () F v /F m () P PA PAB (d) Time (h) Time (h) Tle 3 Multiple nlysis of vrine (MANOVA) nd signifine vlues for the min effets nd intertions of light tretment (spetrl irrdine ompose of P, PA, nd PAB) nd exposure time on photosyntheti effiieny of zoospores in four speies of Lminriles from Spitsergen (*signifint; ns, not signifint) Speies Soure of vrition df F-vlue P-vlue S. dermtode Spetrl irrdine (A) < 0.001* Exposure time (B) < 0.001* A*B ns A. esulent Spetrl irrdine (A) < 0.001* Exposure time (B) < 0.001* A*B < 0.001* L. digitt Spetrl irrdine (A) < 0.001* Exposure time (B < 0.001* A*B ns L. shrin Spetrl irrdine (A) < 0.001* Exposure time (B) < 0.001* A*B * UV-A rdition delyed photosyntheti reovery in ll speies exept in S. dermtode zoospores pre-exposed to 1 h PA, where photosyntheti reovery is not signifintly different with P tretment. Exposure to light supplemented with the whole UV spetrum (PAB) signifintly delyed photosyntheti reovery. Zoospores exposed to PAB hd signifintly lower reovery rte ompred to P in ll speies nd exposure time nd to PA in ll speies exept in 4 h-exposed A. esulent nd 1 h-exposed L. digitt where no signifint differene ws oserved etween PA nd PAB tretments (Fig. 3). Disussion This study onfirms tht photosynthesis of kelp zoospores is shde dpted nd tht UVR uses muh stronger photoinhiition of photosynthesis ompred to dult sporophytes. Moreover, it is the first report on the kinetis of photosyntheti reovery of kelp zoospores whih is dependent on spetrl qulity, exposure time nd speies, nd whih reflets the depth distriution of the dult sporophytes. The I k estimtes derived from retr mx s minimum sturting inident irrdine (I o ) points to the shde dpttion of photosynthesis in kelp zoospores. The vlues etween 13 nd 18 lmol photons m )2 s )1 re muh lower ompred to old temperte Lminri speies, whih re hrterized y I k vlues rnging from 20 to 40 lmol photons m )2 s )1 (Roled et l. 2005). Spores of sutropil (wrm temperte) kelp speies showed even higher I k vlues rnging from 41 to 77 lmol photons m )2 s )1 (Amsler nd Neushul 1991). The deresing I k from the mid- to high-ltitudes orresponds to the deresing solr irrdine from the equtor to the polr region. A similr reltion hs een demonstrted in dult mrothlli of seweeds from polr to tropil regions (Lüning 1990; Wienke et l. 1993; Weykm et l. 1996). The photosynthesis-irrdine prmeters determined here reflet the depth distriution of the dult sporophytes. The shllow wter speies S. dermtode hs retr mx nd I k vlues onsiderly ove the vlues of the other three

8 318 Photosynth Res (2006) 88: Fig. 3 Time-series reovery in the men optimum quntum yield (F v /F m ) of zoospores fter exposure to photosynthetilly tive rdition (PAR = P), PAR + UV-A (PA), nd PAR + UV- A + UV-B (PAB) t different exposure times (vertil olumns) in () Sorhiz dermtode () Alri esulent () Lminri digitt nd (d) Lminri shrin (horizontl olumns) expressed s perent reovery of distured ontrol. Controls were untreted smples ultured t dim white light (8 2 lmol photons m )2 s )1 ). Vertil rs re stndrd devitions (SD, n = 5). Repeted mesures nlysis of vrine (RMANOVA, P < 0.01) showed signifint differene etween tretments. Letters on grph show result of Dunn s multiple rnge test (DMRT, P = 0.05); different letters refer to signifint differene etween tretments () F v /F m (% reovery) () F v /F m (% reovery) () F v /F m (% reovery) (d) Control F v /F m = ± 0.03 Control F v /F m = ± 0.04 Control F v /F m = ± Exposure time of tretment (h) P PA PAB F v /F m (% reovery) Control F v /F m = ± Time-series reovery (h) speies from deeper wters. The strongest shde dpttion is present in the mid- to lower-sulittorl speies L. shrin. This speies is hrterized y very low I k vlue nd is the only speies photoinhiited t tini light levels 68 lmol photons m )2 s )1. A similr trend ws oserved in the P I urve prmeters mong zoospores of Helgolndi Lminri speies (Roled et l. 2005) nd in dult mrothlli of numerous speies (Lüning 1990; Weykm et l. 1996). Depression in mximum quntum yield (F v /F m ) of PSII ws lower in Sorhiz dermtode nd Alri esulent ompred to the two Lminri speies. Redution of photosyntheti pity nd quntum effiieny in plnts exposed to high fluene rtes of PAR is protetive

9 Photosynth Res (2006) 88: strtegy to dissipte exess energy sored y the PSII s het to void photodmge. This photoprotetion proess, lso known s dynmi photoinhiition, is regulted to dissipte exessive rdition (Osmond 1994). This proess my lso e modulted y n inrese in the zexnthin ontent of the PSII ntenn (Adms nd Demming-Adms 1992) nd/or y inresing the mount of intive PSII enters therey proteting the photosynthetilly tive enters (Öquist nd Chow 1992). In ontrst, impirment of PSII retion enter D1 protein, the mjor trget of oxidtive dmge in PSII (Aro et l. 1993) indues photointivtion. This ours in seweeds or propgules of seweeds growing in the lower sulittorl zone when exposed to high irrdines. These speimens hve lower ility to down regulte photosynthesis through photoprotetion (Frnklin et l. 2003). After photoinhiition, reovery of photosynthesis often requires dim white light onditions (Hnelt et l. 1992). If low-light dpttion is the generl feture of rown lgl zoospores, s presented here, exessive light my exert signifint effet on their survivl in the wter olumn. UVR exerts n dditionl stress on the photosyntheti pprtus of zoospores. Although the mesurle effets of oth PAR nd UVR in the redution of photosyntheti effiieny re similr, the mehnisms ehind PAR- nd UVR-indued inhiition of photosynthesis re different (Hnelt et l. 2003). UV rdition depresses photosyntheti performne y dmging the oxidizing site nd retion enter of PSII (Frnklin et l. 2003; Tursányi nd Vss 2002; Grzymski et l. 2001). Both UV nd visile light ws, however, found to indue photoinhiition when Mngnese (Mn) ion is relesed into the thylkoid lumen. Mn-depleted oxygen-evolving omplex indues oxidtive dmge to the PSII retion enter euse P nnot e redued normlly (Hkl et l. 2005). Other more diret impts of UVR on photosynthesis inludes its sorption y romti nd sulfhydryl-ontining iomoleules using diret moleulr dmge (Vss 1997) nd, y proteins nd DNA forming yloutne-pyrimidine dimers (CPDs, Setlow 1974). Effiient DNA dmge repir nd reovery of PSII dmge ontriuted to higher germintion suess in spores of the upper sulittorl L. digitt ompred to the lower sulittorl L. hyperore from Helgolnd (Roled et l. 2005). In S. dermtode, n inrese in numer nd size of phlorotnnin-ontining physodes ws oserved fter UV exposure whih ontriuted protetion ginst ellulr dmge, whih enhned germintion rte (Wienke et l. 2004). The differene in the reovery of photosyntheti pity fter photoprotetion nd photodmge hs een defined within time frme vguely desried s within severl minutes nd severl hours, respetively (Frnklin et l. 2003; Hnelt et l. 2003). This definition is dependent on hlorophyll ntenn size nd numer of hloroplst in different life stges of mrolge. In uniellulr hlorophytes Dunliell slin Teod., ells with lrger Chl ntenn ws found to inur signifintly higher rte of photodmge (Broli nd Melis 1998). Zoospores with only one hloroplst per ell (Henry nd Cole 1982) re more suseptile to photodmge ompred to multi-ellulr life history stges. Inident UV-B rdition n esily penetrte through the thin plsmlemm of zoospores dmging the hloroplst. Intrellulr self-shding in mrolgl thlli nd the nonuniformly shped nd unevenly sped ells use multiple sttering (Grzymski et l. 1997), whih n ttenute up to 95% of the inident UV-B rdition nd yet trnsmit etween 70% nd 80% of the visile rdition (Roereht nd Cldwell 1983). Thus rdition is seletively filtered to effetively remove the short UV wvelengths efore rehing the hloroplsts. With severl vriles to onsider in our experimentl setup, we were onstrined to mesure photosyntheti reovery only fter 2 h post-ultivtion in low white light to void prllel mesurements. Despite this limittion, we suggest tht redution in photosyntheti effiieny in PARexposed S. dermtode zoospores is due to photoprotetion while in PAR-exposed L. shrin is due to photointivtion. Zoospores of S. dermtode were le to down regulte photosynthesis through dynmi photoinhiition while inomplete reovery in zoospores of L. shrin results from the longer time required for de novo synthesis nd replement of dmged D1 protein in the thylkoid memrne. Future studies on D1 protein nd zexnthin synthesis (Adms nd Demming-Adms 1992; Andersson et l. 1992; Bishof et l. 2002) re neessry to onfirm this hypothesis. Dmge to retion enters of PSII ffeting the wter-oxidizing omplex (Tursányi nd Vss 2002) might e responsile for the lower nd delyed photosyntheti reovery in UVR-exposed zoospores. The life stge-dependent photodmge nd synthesis of new D1 protein n e investigted using linomyin, whih inhiits plstidil protein synthesis, to mp plstid trnsripts tht re extensively nd rpidly proessed (Frnklin nd Lrkum 1997; Bergo et l. 2003; Ykndwl et l. 2003). Bsed on the result of this lortory study, spore viility nd eventul suessful reruitment is dependent on the residene time of zoospores within the euphoti zone where they might e exposed to exessive rdition. The residene time in the euphoti zone is ffeted y severl vriles suh s the position of the spore produing tissue, swimming speed nd sedimenttion rte, phototxis nd hydrodynmi onditions. For exmple, Sorhiz polyshides (Lightfoot) Btters nd Nereoystis speies relese spores from the upper prt of the thllus whih is lose to the wter surfe, while Mroystis C. Agrdh

10 320 Photosynth Res (2006) 88: nd Alri hve their reprodutive sporophylls situted slly, just ove the holdfst (Norton 1992). Negtive phototxis in Sorhiz polyshides my id downwrd settlement to low-light environment under the nopy of dult kelp nd undergrowths while positive phototxis in Etorpus Lyngye my ompenste for the low relese height resulting from the plnt s smll stture to pture required light for photosynthesis to llow suffiient net prodution. On the other hnd, sporophylls of Alri esulent (L.) Grev. relese more zoospores with wter motion ompred to lm ondition (Gordon nd Brwley 2004). Fertile plnt prts n lso drift wy, survive for long period nd relese propgules within the euphoti zone. Exessive turulene ould not only hinder sedimenttion of spores to the low-light miroenvironment t depths ut ould lso diffuse gmetophytes t distne hindering settlement of opposite sex within reh tht ould entil filure of sporophyte development (Norton 1992). To estimte the eologil impt of enhned UVR, reprodutive sesonlity s well s diel periodiity in zoospore relese mong different kelp speies should e onsidered. For exmple, formtion of sporogeni tissue in Lminriles hve een reported to e either sesonl (Roled et l. 2005; Wienke et l. 2006) or perennil (Chpmn 1984, Josk nd Bolton 1987). Mximum spore prodution nd relese in Ekloni mxim (Osek) Ppenf. ours in spring nd erly summer (Josk nd Bolton 1987). Winter reprodution in the lower sulittorl Lminri hyperore in Helgolnd is thought to e strtegy to void reprodutive filure due to the reltive sensitivity of their zoospores to PAR nd UVR (Roled et l. 2005). Spore relese of Nereoystis luetken (Mertens) Postels et Rupreht t dwn is suggested to e mehnism to mximize photosyntheti potentil of the spores (Amsler nd Neushul 1989). Despite the higher UVR: PAR rtio pplied in this lortory experiment, results otined on kinetis of photosyntheti reovery support the results on field germintion experiments performed on S. dermtode, A. esulent, nd L. digitt. In these experiments, zoospores were exposed to mient solr rdition t different wter depth nd ultivted in the lortory t low-light ondition, simulting low-light miroenvironment upon settlement (Wienke et l. 2006). In ll speies, germintion rtes of zoospores exposed to PAR were similr t ll depths investigted. However, UV rdition ffeted germintion rtes in different wys, depending on the speies nd the wter depth. Zoospores of S. dermtode germinted in ll wter depth while germintion of zoospores of A. esulent ws strongly inhiited in 0.5 m wter depth. The most suseptile speies ws L. digitt, whose zoospores filed to germinte in 0.5 nd 1.0 m-wter depths. This pttern is t lest prtly sed on the differentil photosyntheti reovery of the zoospores fter UV exposure, shown in the present study. The degree of UV exposure depends on severl vriles suh s the wether ondition, the ontent of UV soring ozone in the tmosphere nd the optil properties of the wter olumn. Strtospheri ozone depletion is highest in spring, t the sme time the sewter is very ler (Hnelt et l. 2001). So the risk to e exposed to the dmging UV rdition is highest during this time of the yer. Aknowledgements We thnk A. Gruer for tehnil help, the diving tem of Spitsergen 2004 field mpign espeilly M. Shwnitz for olleting fertile plnt mteril nd the Ny- Ålesund Interntionl Arti Environmentl Reserh nd Monitoring Fility for support. Referenes Adms III WW, Demming-Adms B (1992) Opertion of xnthophyll yle in higher plnts in response to diurnl hnges in inident sunlight. Plnt 186: Amsler CD, Neushul M (1989) Diel periodiity of spore relese from kelp Nereoystis luetken (Mertens) Postels et Rupreht. J Exp Mr Biol Eol 134: Amsler CD, Neushul M (1991) Photosyntheti physiology nd hemil omposition of spores of the kelps Mroystis pyrifer, Nereoystis luetken, Lminri frlowii, nd Pterygophor liforni (Pheophyee). J Phyol 27:26 34 Andersson B, Slter AH, Virgin I, Vss I, Styring S (1992) Photodmge to Photosystem II- primry nd seondry events. J Photohem Photoiol B: Biol 15: Aro EM, Virgin I, Andersson B (1993) Photoinhiition of photosystem II: intivtion, protein dmge nd turnover. Biohim Biophys At 1143: Broli I, Melis A (1998) Photoinhiitory dmge is modulted y the rte of photosynthesis nd y the photosystem II light-hrvesting hlorophyll ntenn size. Plnt 295: Bergo E, Segll A, Giometti GM, Trntino D, Sove C, Andreui F, Brto R (2003) Role of visile light in the reovery of photosystem II struture nd funtion from ultrviolet-b stress in higher plnts. J Exp Bot 54: Bishof K, Hnelt D, Tüg H, Krsten U, Brouwer PEM, Wienke C (1998) Alimtion of rown lgl photosynthesis to ultrviolet rdition in Arti ostl wters (Spitsergen, Norwy). Polr Biol 20: Bishof K, Kräs G, Wienke C, Hnelt D (2002) Solr ultrviolet rdition ffets the tivity of riulose-1,5-iphosphte roxylse-oxygense nd the omposition of photosyntheti nd xnthophyll yle pigments in the intertidl green lg Ulv ltu L. Plnt 215: Chlker BE, Dunlp WC, Oliver JK (1983) Bthymetri dpttions of reef-uilding orls t Dvies Reef, Gret Brrier Reef, Austrli. II. Light sturtion urves for photosynthesis nd respirtion. J Exp Mr Biol Eol 73:37 56 Chpmn ARO (1984) Reprodution, reruitment nd mortlity in two speies of Lminri in southwest Nov Soti. J Exp Mr Biol Eol 78: Coon DA, Neushul M, Chrters AC (1972) The settling ehviour of mrine lgl spores. In: Nisizw K (ed) Proeedings 7th Interntionl Seweed Symposium, University of Tokyo Press, Tokyo, pp

11 Photosynth Res (2006) 88: Cordi B, Donkin ME, Peloquin J, Prie DN, Depledge MH (2001) The influene of UV-B rdition on the reprodutive ells of the intertidl mrolg, Enteromorph intestinlis. Aqut Toxiol 56:1 11 Deysher L, Norton TA (1982) Dispersl nd oloniztion in Srgssum mutium (Yendo) Fensholt. J Exp Mr Biol Eol 56: Dring MJ, Mkrov V, Shoshin E, Lorenz M, Lüning K (1996) Influene of ultrviolet-rdition on hlorophyll fluoresene nd growth in different life-history stges of three speies of Lminri (Pheophyt). Mr Biol 126: Frnklin LA, Lrkum AWD (1997) Multiple strtegies for high light existene in tropil mrine mrolg. Photosyn Res 53: Frnklin LA, Osmond CB, Lrkum AWD (2003) Photoinhiition, UV-B nd lgl photosynthesis. In: Lrkum AW, Dougls SE, Rven JA (eds) Photosynthesis in Alge. Kluwer Ademi Pulishers, The Netherlnds, pp Gthen P von der, Rex M, Hrris NRP, Lui D, Knudsen BM, Brthen GO, De Bker H, Fin R, Fst H, Gil M, Kyrö E, Mikkelsen IS, Rummukinen M, Stähelin J, Vrotsos C (1995) Oservtionl evidene for hemil ozone depletion over the Arti in winter Nture 375: Gordon R, Brwley SH (2004) Effets of wter motion on propgule relese from lge with omplex life histories. Mr Biol 145:21 29 Grzymski J, Johnsen G, Skshug E (1997) The signifine of intrellulr self-shding on the iooptil properties of rown, red, nd green mrolge. J Phyol 33: Grzymski J, Orrio C, Shofield OM (2001) Monohromti ultrviolet light indued dmge to Photosystem II effiieny nd ron fixtion in the mrine ditom Thlssiosir pseudonn (3H). Photosynth Res 68: Hkl M, Tuominen I, Kernen M, Tyystjrvi T, Tyystjrvi E (2005) Evidene for the role of the oxygen-evolving mngnese omplex in photoinhiition of photosystem II. Biohim Biophys At 1706:68 80 Hnelt D (1998) Cpility of dynmi photoinhiition in Arti mrolge is relted to their depth distriution. Mr Biol 131: Hnelt D, Huppertz K, Nultsh W (1992) Photoinhiition of photosynthesis nd its reovery in red lge. Bot At 105: Hnelt D, Wienke C, Krsten U, Nultsh W (1997) Photoinhiition nd reovery fter high light stress in different developmentl nd life-history stges of Lminri shrin (Pheophyt). J Phyol 33: Hnelt D, Tüg GH, Bishof K, Groß C, Lippert H, Swll T, Wienke C (2001) Light regime in n Arti fjord: study relted to strtospheri ozone depletion s sis for determintion of UV effets on lgl growth. Mr Biol 138: Hnelt D, Wienke C, Bishof K (2003) Photosynthesis in mrine mrolge. In: Lrkum AW, Dougls SE, Rven JA (eds) Photosynthesis in Alge. Kluwer Ademi Pulishers, The Netherlnds, pp Henry EC, Cole KM (1982) Ultrstruture of swrmers in the Lminriles (Pheophyee), I. Zoospores. J Phyol 18: Jssy AD, Pltt T (1976) Mthemtil formultion of the reltionship etween photosynthesis nd light for phytoplnkton. Limnol Oenogr 21: Josk MAP, Bolton JJ (1987) In situ mesurement of zoospore relese nd sesonlity of reprodution in Ekloni mxim (Alriee, Lminriles). Br Phyol J 22: Kessler JO (1985) Hydrodynmi fousing of motile lgl ells. Nture 313: Lüning K (1990) Seweeds. Their environment, iogeogrphy nd eophysiology. Wiley-Intersiene, New York Melis A (1999) Photosystem-II dmge nd repir yle in hloroplsts: wht modultes the rte of photodmge in vivo? Trends Plnt Si 4: Nishiym Y, Allkhverdiev SI, Ymmoto H, Hyshi H, Murt N (2004) Singlet oxygen inhiits the repir of photosystem II y suppressing the trnsltion elongtion of the D1 protein in Synehoystis sp. PCC Biohemistry 43: Nishiym Y, Allkhverdiev SI, Murt N (2005) Inhiition of the repir of photosystem II y oxidtive stress in ynoteri. Photosyn Res 84:1 7 Norton TA (1992) Dispersl y mrolge. Br Phyol J 27: Norton TA, Fetter R (1981) The settlement of Srgssum mutium propgules in sttionry nd flowing wter. J Mr Biol Ass UK 61: Ohnishi N, Allkhverdiev SI, Tkhshi S, Higshi S, Wtne M, Nishiym Y, Murt N (2005) Two-step mehnism of photodmge to photosystem II: step 1 ours t the oxygen-evolving omplex nd step 2 ours t the photohemil retion enter. Biohemistry 44: Öquist G, Chow WS (1992) On the reltionship etween the quntum yield of Photosystem II eletron trnsport, s determined y hlorophyll fluoresene, nd the quntum yield of CO 2 -dependent O 2 evolution. Photosynth Res 33:51 62 Osmond CB (1994) Wht is photoinhiition? Some insights from omprisons of shde nd sun plnt. In: Bker NR, Bowyer JR (eds) Photoinhiition of photosynthesis, from the moleulr mehnisms to the field. BIOS Sientifi Pul., Oxford, pp 1 24 Purell EM (1977) Life t low Reynolds numer. Am J Phys 45:3 11 Rihter M, Rühle W, Wild A (1990) Studies on the mehnism of Photosystem II photoinhiition I. A two-step degrdtion of D1- protein. Photosynth Res 24: Roereht R, Cldwell MM (1983) Protetive mehnisms nd limtion to solr ultrviolet-b rdition in Oenother strit. Plnt Cell Environ 6: Roled MY, vn de Poll WH, Hnelt D, Wienke C (2004) PAR nd UVBR effets on photosynthesis, viility, growth nd DNA in different life stges of two oexisting Gigrtinles: implitions for reruitment nd zontion pttern. Mr Eol Prog Ser 281:37 50 Roled MY, Wienke C, Hnelt D, vn de Poll WH, Gruer A (2005) Sensitivity of Lminriles zoospores from Helgolnd (North Se) to ultrviolet nd photosynthetilly tive rdition: implitions for depth distriution nd sesonl reprodution. Plnt Cell Environ 28: Setlow RB (1974) The wvelengths in sunlight effetive in produing skin ner: theoretil nlysis. Pro Ntl Ad Si USA 71: Stähelin J, Hrris NRP, Appenzeller C, Eerhrd J (2001) Ozone trends: review. Rev Geophy 39: Tursányi E, Vss I (2002) Effet of UV-A rdition on photosyntheti eletron trnsport. At Biol Szeged 46: Vss I (1997) Adverse effets of UV-B light on the struture nd funtion of the photosyntheti pprtus. In: Pessrkli M (eds) Hndook of photosynthesis. Mrel Dekker In., New York, pp Weykm G, Gómez I, Wienke C, Iken K, Klöser H (1996) Photosyntheti hrteristis nd C:N rtios of mrolge from King George Islnd (Antrti). J Exp Mr Biol Eol 204:1 22 Wienke C, Rhmel J, Krsten U, Weykm G, Kirst GO (1993) Photosynthesis of mrine mrolge from Antrti: light nd temperture requirements. Bot At 106:78 87 Wienke C, Gómez I, Pkker H, Flores-Moy A, Altmirno M, Hnelt D, Bishof K, Figuero FL (2000) Impt of UV rdition on viility, photosyntheti hrteristis nd DNA of rown lgl zoospores: implitions for depth zontion. Mr Eol Prog Ser 197:

12 322 Photosynth Res (2006) 88: Wienke C, Clyton MN, Shoenwelder M (2004) Sensitivity nd limtion to UV rdition of zoospores from five speies of Lminriles from the Arti. Mr Biol 145:31 39 Wienke C, Roled MY, Gruer A, Clyton MN, Bishof K (2006) Suseptiility of zoospores to UV rdition determines upper depth distriution limit of Arti kelps: evidene through field experiments. J Eol 94: Ykndwl N, Lupi C, Bilng R, Potrykus I (2003) Linomyin tretment: simple method to differentite primry nd proessed trnsripts in rie (Oryz stiv L.) hloroplst. Plnt Mol Biol Rep 21: