South African Journal of Botany

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1 South Africn Journl of Botny 88 (213) Contents lists ville t SciVerse ScienceDirect South Africn Journl of Botny journl homepge: Photosynthetic dpttion of two semi-rid species of Gethyllis (Kukumkrnk) to drought-nd-shde stress C.W. Dniels,, W.T. Musel, J.L. Mrnewick c, A.J. Vlentine d Deprtment of Horticulturl Sciences, Cpe Peninsul University of Technology, P.O. Box 196, Bellville 7535, South Afric South Africn Herl Science nd Medicine Institute, University of the Western Cpe, Privte Bg X17, Bellville 7535, South Afric c Oxidtive Stress Reserch Centre, Fculty of Helth nd Wellness Sciences, Cpe Peninsul University of Technology, P.O. Box 196, Bellville 7535, South Afric d Deprtment of Botny nd Zoology, University of Stellenosch, Privte Bg X1, Mtielnd 762, Stellenosch, South Afric rticle info strct Article history: Received 2 Novemer 212 Received in revised form 19 Mrch 213 Accepted 25 Mrch 213 Aville online xxxx Edited y J Vn Stden Keywords: Geophytes Specific lef mss Stomtl conductnce Succulent Kroo Trnspirtion rtes Gethyllis multifoli nd Gethyllis villos re winter-growing, summer-looming, deciduous nd ulous geophytes tht grow nturlly in the semi-rid Succulent Kroo Biome of South Afric. G. multifoli is thretened in its nturl hitt nd resides in the Vulnerle ctegory of the Red Dt List of Southern Africn Plnts. Previous investigtions suggested tht G. multifoli is more sensitive to drought stress thn G. villos nd tht oth species dopted certin morphologicl chnges in their leves during shde stress. Current models indicte tht this iome is eing exposed to incresingly drier conditions nd shding from encroching indigenous plnt species. In this study, the photosynthetic gs exchnge responses of oth species to drought nd shde stresses were investigted nd the Vulnerle conservtion sttus of G. multifoli. This investigtion found tht during drought stress G. villos hd more enhnced photosynthetic performnce thn G. multifoli which ppers not to e relted to folir dpttions such s specific lef mss (SLM), ut to the G. villos's leves mintining their stomtl conductnce (G s ), photosynthetic light compenstion (LCP) nd photon yields. Furthermore, during shde stress G. villos lso hd n improved photosynthetic performnce y not ltering its photosynthetic LCP during reduced light conditions. It cn e concluded tht G. multifoli hs lower cpcity thn G. villos to dpt its photosynthetic pprtus to chnging environments such s incresing drought nd shded conditions. This my e contriuting fctor to the thretened conservtion sttus of G. multifoli. 213 SAAB. Pulished y Elsevier B.V. All rights reserved. 1. Introduction The genus Gethyllis (fmily: Amryllidcee), indigenous to South Afric, consists of 37 currently ccepted species nd suspecies (Müller-Dolies, 1986). Gethyllis species hve medicinl properties (Liltved, 1992; Elgorshi nd Vn Stden, 23) nd re chrcterized y four distinct growth phses. The plnts tht thrive under full sun conditions, re winter-growing, summer-looming, deciduous nd ulous geophytes (Du Plessis nd Delpierre, 1973; Mnning et l., 22). Gethyllis multifoli L. Bolus nd Gethyllis villos Thun. grow nturlly in the Succulent Kroo Biome of South Afric, which is primrily chrcterized y low to high winter rinfll nd extreme summer ridity. The rinfll vries etween 2 nd 29 mm per yer nd during summer the tempertures cn e in excess of 4 C. G. multifoli is thretened in its nturl hitt nd is listed in the Vulnerle ctegory of the Red Dt List of Southern Africn Plnts nd World Conservtion Union List of Plnts (Hilton-Tylor, 1996; Corresponding uthor. Tel.: ; fx: E-mil ddress: dnielsc@cput.c.z (C.W. Dniels). IUCN, 1998), while G. villos is not thretened in the sme hitts. In their nturl hitt, oth these species encounter environmentl limittions such s incresing drought stress (Rutherford et l., 1999; Midgeley et l., 22; Von Mltitz et l., 26) nd light restrictions from shding cused y encroching indigenous shrus (Dniels, 27). It hs een oserved tht oth G. multifoli nd G. villos re limited y drought stress nd this phenomenon ppers to hve more significnt effect on G. multifoli (Dniels, 27). According to preliminry work y Dniels (27), G. multifoli hs impired lef nd flower development during the growth nd reproductive phses when exposed to dry conditions. These fetures re prt of survivl strtegy during hrsh environmentl chnges (Du Plessis nd Duncn, 1989). This concurs with other studies tht drought stress increses the rte of pod ortion during the erly stges of pod development in soyens (Liu et l., 23). The success of plnts under stress conditions my e determined y their ility to control crohydrte utiliztion for metolic energy nd their ility to llocte enough mterils to their reproductive phse (Nielsen et l., 21). According to Pelleschi et l. (1997) nd Kim et l. (2), drought stress generlly decreses the photosynthetic rte nd disrupts crohydrte metolism in leves nd therefore could increse the rte of reproductive ortion /$ see front mtter 213 SAAB. Pulished y Elsevier B.V. All rights reserved.

2 C.W. Dniels et l. / South Africn Journl of Botny 88 (213) In ddition to drought stress, Gethyllis plnts my lso encounter light stress in the form of shding from encroching indigenous shrus (Dniels, 27). This encrochment from the invsive shru, Gleni fricn is lso posing growing thret in the nturl hitt of G. multifoli, where mny individul plnts re found growing in the shde of this m tll, shruy species (Dniels, 27; Klsen et l., 29). A previous investigtion (Dniels, 27) reveled tht under controlled shde conditions oth species produced thinner leves with no nturl spirling, which is deprture from the nturl chrcteristic of Gethyllis species (Esler nd Rundel, 1998). The survivl nd growth of Gethyllis species in chnging light environment my e dependent on their shde-tolernce levels, s found for other plnts (Dniels et l., 1979; Lorimer, 1983). This concurs with previous work tht shde stressed plnts cn respond to low irrdince vi ltered lef morphology for more efficient irrdince cpture (Givnish, 1998; Smith nd Huston, 1989; Oliver nd Lrson, 1996) nd enhnced photosynthetic investment (Brouwer, 1962; Poorter nd Ngel, 2). Since oth ulous species occur in semi-rid re, which is eing thretened y progressive ridity due to climte chnge nd incresed shding from invsive species, the im of this work is to therefore investigte the cpcity for photosynthetic dpttion of oth species to these environmentl chnges. 2. Mterils nd methods 2.1. Plnt mterils G. multifoli nd G. villos uls were identified y oth the curtor nd resident horticulturist, nd compred to living collected smples in the Kroo Ntionl Biodiversity Grden (KNBG) (Worcester, Western Cpe, South Afric). The KNBG hs keen interest in the declining numers of G. multifoli, therefore permission ws grnted to collect smples for the reserch project from n re where new rods nd sewerge lines were plnned through the nturl hitt of oth species. Mture uls of oth species were collected fter their winter growth phse (Mrch to mid-august), from their nturl hitt. For conservtion purposes nd due to the thretened sttus of G. multifoli, the exct loction of these species is omitted from this investigtion. The uls of oth species (n = 1 per species per tretment) were potted up in 15 cm nursery pots in sndy, cly soil (ph ) from the nturl hitt. The uls were grown under outdoor conditions for 12 months which included one dormnt phse (6 months spring nd summer) nd one growth phse (6 months utumn nd winter) t the nursery of the Deprtment of Horticulturl Sciences, Cpe Peninsul University of Technology (CPUT), Cpe Town. Tle 1 indictes the verge rinfll nd dily tempertures for the Cpe Town re where plnts were grown nd lso indictes the higher rinfll nd lower tempertures for the growth phse nd lower rinfll nd higher tempertures for the dormnt phse. Wether dt for the Cpe Town re (Tle 1) ws supplied y the South Africn Wether Bureu (Cpe Town WO 21178A3) Environmentl stresses Plnt smples which represented the control (n = 1 per species) were grown under full sun nd irrigted y the mient rinfll of the Western Cpe (Tle 1). The men photosynthetic photon flux density (PPFD) (converted from lux to PPFD) on cloudless dys t 12h ws 1825 ± 63 μmol m 2 s 1. Tempertures round the plnt smples vried from 8 to 24 C nd the reltive humidity from 36 to 1%. The PPFD for ll tretments ws mesured with Toptronic T63 digitl light meter (Sprytech, Bellville, Western Cpe, South Afric) nd the tempertures nd reltive humidity were mesured with Tle 1 The verge rinfll (mm) nd verge dily minimum (min.) nd mximum (mx.) tempertures ( C) for the Cpe Town re (Western Cpe, South Afric). Ech vlue ws otined y clculting the men for two yers ± SE (n = 2). The dt ws provided y the South Africn Wether Bureu nd ws recorded t the Cpe Town wether office (21178A3). Month Men min. temp. ( C) Men mx. temp. ( C) Men rinfll (mm) Jnury 17.3 ± ±.25.3 ±.2 Ferury 16.4 ± ± ± 14.2 Mrch 14.2 ± ± ± 8.2 April 12.4 ± ± ± 33.8 My 9.5 ± ± ± 77. June 8.1 ± 19. ± ± 55.6 July 7.9 ± ± ± 78.8 August 8.1 ± ± ± 55.8 Septemer 9.8 ± ± ± 13.5 Octoer 11.7 ± ± ± 19.8 Novemer 13.4 ± ± ± 27.8 Decemer 15.6 ± ± ± 1.1 Mjortech MT669 digitl reltive humidity/temperture meter (Sprytech, Bellville, Western Cpe, South Afric). Plnt smples which represented the drought stressed smples (n = 1 per species) were grown under full sunlight nd covered with 6 mm cler glss sheet, plced 3 mm ove the plnts. The PPFD, temperture nd reltive humidity environmentl conditions were similr to those of the control. The drought stressed plnts were irrigted t rte of 3% field cpcity once month with de-ionized wter (Mortimer et l., 23). Plnt smples which represented the shde stressed smples (n = 1 per species) were grown under shde structure covered with 8% neutrl lck shde cloth (Alnet, Epping, Western Cpe, South Afric), which hs neutrl effect on light qulity (Ytes, P mx (µmol CO 2.m -2.s -1 ) P mx (µmol CO 2.m -2.s -1 ) G. multifoli G. villos Photosynthetic rte Shde Fig. 1. Lef photosynthetic rtes (P mx )ofg. multifoli nd G. villos during shde () nd drought () stress. Redings were tken t full lef emergence during the pek of the growth phse (June). Different letters indicte significnt differences etween mens ± SE of tretments (P.5, n = 4), comprisons were done for ech species only.

3 38 C.W. Dniels et l. / South Africn Journl of Botny 88 (213) ; Dun et l., 25). During the experimentl period, the men PPFD on cloudless dys t 12h ws 365 ± 26 μmol m 2 s 1 nd ws pproximtely 2% of full sunlight. The temperture round the shde stressed plnt smples ws ~1 2 C lower thn tht of the control, nd the reltive humidity 2 4% higher thn tht of the control. The plnt smples under shde stress tretment were lso irrigted y the mient rinfll of the Western Cpe (Tle 1). The redings of ll the environmentl conditions under ll tretments were tken dily t the following time intervls: 9h, 12h nd 15h Physiologicl responses An infr-red gs nlyzer (Licor, Li-64 Portle photosynthesis system, Lincoln, Nersk, USA) coupled to lef chmer, ws used to mesure the photosynthetic rtes (P mx ), lef drk respirtion rtes (D r ), stomtl conductnce (G s ) nd trnspirtion rtes (E) of the plnt smples during the growth phse. The redings were tken on fully expnded leves t the pek of the growth seson during the month of June. G. villos plnts hve flt leves (±5 mm in dimeter) nd section of one lef lde per plnt ws used for the redings. G. multifoli plnts consist of thin needle-like leves (±1 2 mm in dimeter) nd 6 8 lef sections per plnt were used for the redings. The infr-red gs nlyzer ws set to tke the net photosynthetic rte redings t the following light photosynthetic photon flux densities (PPFD):, 5, 15, 35, 5, 75, 95, 12 nd 15 μmol m 2 s 1. Six redings were tken per PPFD nd redings were recorded from four plnts per specie per tretment. The corresponding temperture for the photosynthetic rte redings in the lef chmer ws set t 25 C nd the reltive humidity 55 75%. Liner regression nlysis ws performed on dt within the G s (mmol -2.s -1 ) G s (mmol -2.s -1 ) G. multifoli G. villos Shde Stomtl conductnce Fig. 2. Stomtl conductnce (G s )ofg. multifoli nd G. villos during shde () nd drought () stress. Redings were tken t full lef emergence during the pek of the growth phse (June). Different letters indicte significnt differences etween mens ± SE of tretments (P.5, n = 4), comprisons were done for ech species only. E (mmol H 2 O.m -2.s -1 ) E (mmol H 2 O.m -2.s -1 ) G. multifoli G. villos Shde Trnspirtion rte Fig. 3. Trnspirtion rtes (E) of G. multifoli nd G. villos during shde () nd drought () stress. Redings were tken t full lef emergence during the pek of the growth phse (June). Different letters indicte significnt differences etween mens ± SE of tretments (P.5, n = 4), comprisons were done for ech species only. PWUE (µmol CO 2.mmol -1 H 2 O) PWUE (µmol CO2.mmol-1H2O) G. multifoli G. villos Shde Photosynthetic wter-use efficiency Fig. 4. Wter-use efficiency (PWUE) of G. multifoli nd G. villos during shde () nd drought () stress. Redings were tken t full lef emergence during the pek of the growth phse (June). Different letters indicte significnt differences etween mens ± SE of tretments (P.5, n = 4), comprisons were done for ech species only.

4 C.W. Dniels et l. / South Africn Journl of Botny 88 (213) light-limited prt of the light response curve to clculte the pprent photon yield. Photosynthetic wter-use efficiency (PWUE) ws clculted s P mx /E Sttisticl nlysis Significnt differences of the mens for ech species, were seprtely tested under drought nd shde stress. The mens were seprted using post hoc Fisher's Protected LSD, multiple comprison test (SuperANOVA, version for Mcintosh Acus Concepts, USA). Different letters indicte significnt differences etween tretments (P.5, n = 4), nd superscript numers indicte the comprisons for ech species only (1 = G. multifoli; 2 = G. villos). 3. Results During shde (Fig. 1) nd drought (Fig. 1) stress, G. multifoli hd reduction in its light sturted photosynthetic rtes (P mx ), while the P mx for G. villos remined unchnged. These photosynthetic ptterns of oth species, concur with their respective stomtl conductnce (G s )(Fig. 2, ) nd trnspirtion rtes (E) (Fig. 3, ). In spite of the differences in photosynthetic shde responses in G. multifoli nd G. villos, the photosynthetic wter-use efficiencies (PWUE) remined unchnged in oth species during shde stress (Fig. 4). However, G. multifoli hd n increse in PWUE under drought stress, while G. villos remined unchnged (Fig. 4). The decline in the P mx of G. multifoli in response to drought nd shde stress, is not relted to lef morphologicl dpttions such s specific lef mss (SLM) (Fig. 5, ), ut rther to lef photochemistry nd the ssocited pigments. In this regrd, the G. multifoli plnts hd n increse in the lef compenstion point (LCP) under drought nd shde stress, wheres the LCP of G. villos remined unchnged (Fig. 6, ). Furthermore, the pprent photon yield of G. multifoli G. multifoli G. villos LCP (µmol m -2.s -1 ) LCP (µmol m -2.s -1 ) G. multifoli G. villos Light compenstion point Shde Fig. 6. Light compenstion points (LCP) of G. multifoli nd G. villos during shde () nd drought () stress. Redings were tken t full lef emergence during the pek of the growth phse (June). Different letters indicte significnt differences etween mens ± SE of tretments (P.5, n = 4), comprisons were done for ech species only. G. multifoli G. villos SLM (g.m-2) Shde (mol CO2.mol-1) (mol CO 2.mol -1 ) Shde SLM (g.m -2 ) Specific lef mss Fig. 5. Specific lef mss (SLM) of G. multifoli nd G. villos during shde () nd drought () stress. Redings were tken t full lef emergence during the pek of the growth phse (June). Different letters indicte significnt differences etween mens ± SE of tretments (P.5, n = 4), comprisons were done for ech species only. Fig. 7. Lef photon yield of G. multifoli nd G. villos during shde () nd drought () stress. Redings were tken t full lef emergence during the pek of the growth phse (June). Different letters indicte significnt differences etween mens ± SE of tretments (P.5, n = 4), comprisons were done for ech species only.

5 4 C.W. Dniels et l. / South Africn Journl of Botny 88 (213) declined shrply during shde nd drought stress, while G. villos remined unffected (Fig. 7, ). These responses were not ssocited with n ltertion in the drk respirtory costs of G. multifoli nd G. villos leves (Fig. 8, ). However, the rtio of photosynthesis to drk respirtion indictes tht lthough there ws no chnge in G. villos, tht there is significnt decline in G. multifoli during shde nd drought stress (Fig. 8c, d). 4. Discussion During drought stress, the ility of lef photosynthesis to dpt to dry conditions depends on suite of ltertions relting to lef morphology, stomtl control nd photochemistry. Under drought stress, G. villos hd etter photosynthetic performnce thn G. multifoli, which ppers not to e relted to folir dpttions such s specific lef mss (SLM), ut to G. villos's leves mintining their stomtl conductnce (G s ), photosynthetic light compenstion (LCP) nd photon yields during the dry periods. Stomtl control of photosynthesis is well-known dpttion in previous work from vrious ecosystems (Winter nd Schrmm, 1986; Dun et l., 25; Vlliyodn nd Nguyen, 26; Musil et l., 29). In contrst, the inility of G. multifoli plnts to mintin their photosynthetic performnce under drought conditions is underpinned y oth stomtl nd photochemicl fctors. In G. multifoli plnts, the increse in photosynthetic LCP nd the decline in pprent photon yield under drought conditions indicte tht these leves re not le to efficiently utilize light energy for photosynthesis. Similr photosynthetic responses were reported for other spring geophytes, Scill ifoli nd Podophyllum pelttum (Popovic et l., 26; Constle et l., 27). -induced responses in plnt cells re chrcterized y reduction in photosynthetic ctivity due to series of fctors, including the reduced ctivity of photosynthetic enzymes (Teizdeh, 1998; Iern nd Muromicle, 26). In G. multifoli, the LCP nd photon yields indicte tht the efficiencies of the pigment-relted photochemicl rections my hve een impired. The decline in G s, concurs with previous findings to tht of stomtl closure in order to conserve wter (Teizdeh, 1998; Dun et l., 25). In G. multifoli, theg s declined y 7% of the control, wheres P mx only declined y 62%, indicting tht G s my serve s mjor dptive mesure for leves under drought stress. This reltionship etween G s nd photosynthesis is congruent with previous work (Winter nd Schrmm, 1986; Dun et l., 25; Vlliyodn nd Nguyen, 26) nd in prticulr with findings from Mediterrnen-type climtes where the decrese in stomtl conductnce, cused the stomtl limittion on photosynthesis to increse s much s 7% (Glmés et l., 27). In spite of the decrese in photosynthesis for G. multifoli under drought stress, the increse in photosynthetic wter-use efficiency (PWUE) ws consequence of greter decline in trnspirtion rte thn photosynthesis. Similr responses were reported in Cstne dentt plnts where n increse in irrdince nd not necessrily drought, resulted in n increse in the PWUE (Wng et l., 26). During shde stress, lef photosynthesis cn dpt to low light conditions vi suite of ltertions relting to lef morphology nd photochemistry. G. villos hd etter photosynthetic performnce in low light, compred to G. multifoli. Compred to the P mx decline of G. multifoli, G. villos mintined its photosynthetic rte under low light. This ws possile in the G. villos, y not chnging the photosynthetic LCP in the shde. Furthermore, the decline in the rtio of photosynthesis to drk respirtion in G. multifoli, indictes tht there is significnt decline in G. multifoli's cpcity to mintin.3 G. multifoli G. villos c G. multifoli G. villos D r (µmol CO 2 m -2.s -1 ).1.5 P mx : D r Shde. Shde D r (µmol CO 2 m -2.s -1 ) d P mx : D r Lef drk respirtion rte. Tretment Fig. 8. Lef drk respirtion rtes (D r )ofg. multifoli nd G. villos during shde () nd drought () stress nd rtio of photosynthesis (P mx ) to drk respirtion (D r ) under shde (c) nd drought (d) stress. Redings were tken t full lef emergence during the pek of the growth phse (June). Different letters indicte significnt differences etween mens ± SE of tretments (P.5, n = 4), comprisons were done for ech species only.

6 C.W. Dniels et l. / South Africn Journl of Botny 88 (213) higher net cron gin during shde. These findings indicte tht G. multifoli's inility to cclimte to shde is drsticlly compounded y the lower net gin in cron during shde. Similrly, in Trdescnti liflor, reduction in the photosynthetic rte during low light environments, resulted in lower net cron gin (Chow et l., 1991). 5. Conclusion These findings indicte tht G. villos plnts re etter le to dpt their P mx to drought nd shde conditions, compred to G. multifoli. The reduced ility of G. multifoli to dpt to wider rnge of environmentl extremes such s drought nd shde conditions my contriute to its thretened conservtion sttus in this environment. These findings indicte tht G. villos plnts re etter le to dpt their P mx to drought nd shde conditions, compred to G. multifoli. The reduced ility of G. multifoli to dpt to wider rnge of environmentl extremes such s drought nd shde conditions my contriute to its thretened conservtion sttus in this environment. Acknowledgments The uthors cknowledge the Cpe Peninsul University of Technology (CPUT) nd the Deprtment of Horticulturl Sciences (CPUT) for finncil ssistnce nd use of the nursery nd lortory fcilities. Grtitude is expressed to Nomi Dniels for the preprtion of the plnt smples. References Brouwer, R., Distriution of dry mtter in the plnt. Netherlnds Journl of Agriculturl Science 1, Chow, W.S., Admson, H.Y., Anderson, J.M., Photosynthetic cclimtion of Trdescnti liflor to growth irrdince: lck of djustment of light-hrvesting components nd its consequences. Physiologi Plntrum 81, Constle, J.V.H., Peffer, B.J., De Nicol, D.M., 27. Temporl nd light-sed chnges in cron uptke nd storge in the spring ephemerl Podophyllum pelttum (Bereridcee). Environmentl nd Experimentl Botny 6, Dniels, C.W., 27. 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