Influence of water logging time on the growth of candel seedlings

ActaOceanologicaSinica 2004, Vol. 23, No.1, p. 149-158htp://www.oceanpress.com.cnE-mail:hyxbe@263.netInfluence of water logging time on the growthof Kandelia candel seedlingsCHEN Luzhen1.2, WANG Wenqing)2*, LIN Pengh21. School ofLife Science, Xiamen University, Xiamen 361005, China2. Research Center for Wetlands and Ecological Engineering, Xiamen University, Xiamen 361005, ChinaReceived9 August 2003; accepted 28 December 2003AbstractInfluence of waterlogging time on the growth of Kandetlia cande/ (L) Druce seedlings grown for 70d in the atificialatidal tanks' simulated semidiumal tide under grcenhouse is studied. Sand and soil act as tbe substate and arifcial sea-water with salinity of15 is used in cultivation Shorter waterlogging time (inundated for about2~4 h) promotes thegrowth of K cande1 seedlings, while longer time(inundated more than 8 b) or no waterlogging(0 h) inbibits theirgrowth. The number and length of aerating roots increase with the increase of waterlogging time. Under existing condi-tions, the optimal waterlogging time for the growth ofK candel seedlings is about2 ~ 4h in every tide cycle. Com-pared with other treatmnents, the2 h sanded treatments obtain the highest biomass of sedlings, have the lowest massloss ofhypocotyl and broaden the photosynthetic area by increasing the area per leafafer 70-d cultivation. And the soiltreatments have the similar tendency. However, waterlogging for 8h in every tide cycle is critical for pormal develop-ment ofseedlings. K: cande/ sedlings are highly tlerantto waterlogging and a proper waterlogging is beneficial tothegrowth of K candel seedings.Key words: K candel, growth, optimnal watelogging time, citialatarlogging time1 Introductionnately, at the beginning of 2002, the govermmentdecided to forest 60 000 hm2 of mangroves in theMangroves are a special kind of forest 0C-next 10a. Even though great achievements havecurring in the intertidal zones of tropicalbeen made in mangroves forestation since theand subtropical coastlines. They are impor-1990s, the survival rate is still low. According totant to ecological equilibrium and biodiversi-the investigation report of Fujian Province, thety protection. However, mangroves bave ap-survival rate of mangroves seedlings is less thanproached extinction on the global scale since50%, and it has even dropped to 0% in some areasthe 1950s because of land reclamation, land(Wang and Lin, 2000). Similar phenomena haveenclosure and urban construction from theoccurred in other provinces ofChina(Liao et al.,sea. Total area of mangroves in China is no1996). The mid tidal zones ft for mangroves havemore than 22 000 hm2 now (Zhang et al,been greatly damaged by land enclosure for aqua-2001). Therefore, there is an urgent need to ;culture. And mangroves forestation has to pro-protect mangroves(Mo and Fan, 2001). Fortu-ceed in the mid-to-low tidal zones where the●Corresponding author, E -mail: luzhenc@263.net中国煤化工MYHCNMHGCHEN Luzhen et al. ActaOceanlogicaSinica 2004, Vol.23, No. 1, p. 149-158growth of mangrove seedlings is difficult (Liu,distributions of mangroves in China (Fujian1995). Practice has proved that the waterlog-Province). And it is the only species that hasging time is an important factor of restriction tobeen successfully introduced from South Fujianthe mangove survival rate(Liu, 1995; Chen etto Zhejiang Province(Lin, 1997). Morcover, Kal., 2001; Kitaya et al, 2002), and it is vital tocandel is the major mangrove forestationascertain the critical tidal level fit for man-species in the southeast coastal area of Chinagroves(Fan and Li, 1997; Liaoetal. ，1996;(Lin, 1984). The set of equipments simulatingChen et al,2001).semidiurnal tide and designed by Dr. WangetInfluences of waterlogging on the growthal". is used to study the cyclical waterlogging(Clarke and Hannon, 1970; Naidoo, 1985;tolerance of K. candel seedlings. And the opti-Pezeshki et al. , 1989; Hovenden et al., 1995;mal and critical waterlogging timeof K candelEllison and Farnsworth, 1997), leaf nutritionseedlings have been obtained to provide scien-accumulation(Misra et al, 1984), root develop-tific basis for mangroves forestation.ment(Misra et al, 1984), root anatomy(Hoven-den et al.，1995; Ashord and Allaways, 1995;2 Materials and methodsYoussef and Saenger , 1996; Skelton and All-away, 1996; Koch et al. Snedaker, 1997), oxy-Seven plastic tanks(60 cm tall and 40 cmxgen concentrations at pneumatophores (Skel-60 cm in the bottom)acting as artificial-tidalton and Allaway, 1996), plant-water relationstanks are arranged as shown in Fig. I. It takes 2 h(Naidoo，1985), ion accumulation (Naidoo,to fll each tank with arificial seawater through1985), and gas exchange(Pezeshki et al, 1989;pipes continuously. After Tank A is full of wa-Chui and Chou, 1993; Pezeshki etal.，1997;ter, Tank B is soon flled, and so on. After TankNaidoo et al, 1997)have been studied for someFis full, all water in TanksA, B, C, D, E andFismangrove species. Almost all treatments areunloaded by timer-controlled valves at the bot-soil flooded ，and the seedlings have theirtom of each tank. Therefore, Tank A is full ofleaves exposed to the air in the course of inun-water for 12 h per-tidal-cycle, and the inundateddation. Generally, in the early stage of develop-periods for other treatments are 12, 10,8,6, 4,2ment,seedlings are small and there are fewand 0h, respectively. There are 2 tide cycles ev-chances for them to expose the leaves to the aircry day. The artifial-tidal tanks simulate thewhen the soil surface is flooded in the fieldscrmidiurmal tide. There are 6 pots (20 cm inwhile periods for a one-year-old seedling inun-height and 20cm in diameter, with a small holedated in water or for the soil surface exposedat the bottom to make itself drained quicklytake a long time in every tide cycle. The time forwhile the water in tanks is drained away) in eachinundation depends on the location of thetank. Three pots are flled with washed riverseedlings in the tidal zone. Previous researchessand (D =1 mm) and the other three are flledbave made great achievements in exploring thewith soil collected ftom the Jiulong River Estu-waterlogging tolerant mechanisms of man-ary ofFugong Town, Longhai County，Fujiangroves, but it is still hard to ascertain the opti-Province ofChina(24*29N,117955"E).mal and the critical waterlogging time of man-Healthy and matured hypocotyls of K can-grove seedlings.del are uniform in size and weight [the averageCompared with other mangrove species,weight is(12. 38+3. 00) g]. They are collectedK cande! is the only species that naturally dis-from the Jiulong River Estuary where the soil istributes in the northem boundary of geographiccollected. The yearly average seawater salinity°WengW a, KeL, TamFYNore, t a. Efects of water lggingtme on the growth, rot oxygan reaso r啪end sal blancainKandelia c nelselinge. Aqualt Bolt2003. (ccpad)中国煤化工MYHCNMHGCHEN Luzhen et al. Actu OceanologicaSinica 2004, Vol. 23, No. 1, p. 149-~158151DBtime controlwalue pumpWater containerFig. 1. Arrangement ofartificial- tidaltanks.thereis17 (Lin, 1997). Five hypocotyls arebeing divided by leafarea(cm).planted in each pot. The pots in tanks are sub-All computations are analyzed by one-waymerged with artificial seawater of 15 in salinityANOVA of the statistical software SPSS.(seawater of 22~28 in salinity from the westcoast of Xiamen is diluted by the tap water to 3 Results15) inthe greenhouse (Air temperature rangesfrom 27 to 32 C, sunlight) for 70 d(April 28,3. 1 Growth of roots2002-July 4, 2002). Seedlings are fooded at“high tide" to a maximum depth of 60 cm aboveRanging fom2to 12 h, the biomasses ofthe bottom of the tanks, and at“low tide" thethick roots and fine roots decrease with the in-water is slightly below the soil level. Tap watercrease of waterlogging time in sand culture,is added daily to keep the water salinity stable.which are the highest in the 2 h treatmen and areArtificial seawater is replaced every week. Each154.2% and 209.9% higher than those of thetreatment has three replicates.lowest ones(12 h treatment, respectively. AndAfter 70 d culture, biomass partitioning isin soil culture, the highest biomasses of thickdetermined by separating each sample plant in-roots and fine roots occur in the 4 h treatment,to leaf, stem (excluding hypocoty), hypocotyland are 200.8% and 273.8% higher than thoseand root components. Then we find a kind ofof the 12 h treatment. Similarly, mean length ofroots has a larger diameter(D >5 mm) than oth-thick roots is the longest in the 2 h treatment ander roots and is spongy and smooth. This has not125.6% higher than that of the lowest ones(12 hbeen reported previously(Lin，1997) and wetreatment). More than 8 h inundation or no i-name them aerating root provisionally. Hence,nundation has a negative effect on the growth ofroots are separated into three types, which areroots (see Figs 2 and 3), with the symptom ofthick roots(D >l mm), fine roots(D <1 mm),unhealtby growth, reducing their number andand aerating roots. Amount and length of thickshortening their length (see Table 1). Biomassroots and aerating roots are counted and mea-and length of thick roots, and biomass of finesured. Leaves are counted and the suface arearoots are significantly inhibited by waterlog-of mature leaves is measured. Plant material isging time (P= 0.000, P= 0.021, P =0.000, inkilled out at 105 C for10 min and driedat 65 °C.sand culture;P =0.000, P = 0.000, P =0.000,Dry weight of roots, leaves, stem and hypocotylin soil culture; df =6).per plant is recorded. The total biomass perAll treatments show difference in theplant does not include hypocotyl. Calculation oflength and amount of aerating roots in responsesucculence of mature leaves follows the follow-to different waterlogging time. There are noting equation(Wang and Lin, 2000). Succulenceaerating roots in 0 and 2 h treatments. In the 12 h(mg/cm) equals saturated water content: (mg)treatment, only oDe acrating root appears in中国煤化工MYHCNMHGCHEN Luzhen et al. ActaOeeanologicaSinica 2004, Vol. 23, No.1, p. 149-158-公sand-_0←soil- o-sand - 0- - soil0.，0.& 0.410 12Waterlogging time/hFig. 2. Influences of waterlogging timne on thick roots Fig, 3. Influences of waterlogging time on fine roots ofof K. candel seedlings.K cande/ seedlings.Table 1. Influcnces of waterlogging time on the length and number ofthick rootsand aerating roots of K candel seedlingsThick rootsAerating rootsWater-loggingnumber piccelength/cmnumber piecelengh/emtime/hsand80soilsand so22.5+0.921.3+0.4.71.810.1+1.30-22.0+2.119.5+3.714.22.024.8+1.725.010.90.6+1.312.2+1.20.60+0.04.33+3.7226.3+3.122.2+1.010.2+1.610.7+1.76.17+2.902.90+2.69 :23.1+3.024.2+0.910.1+0.50.4+1.72.90+2.323.32+3.2123.4+1.621.3+1.89.1+0.89.3+1.195+1.173.54+2.87199+2.120.6+3.98.6+0.98.1+1.69.30+0.0sand culture, but it is 9.3 cm long, while nonestems(P =0.000, d/'=6) while in the 0and 12 happears in soil culture. The maximum amounttreatments，stems show an unhealthy growth,of aerating roots occurs in the 6 h treatment bothand the biomass in sand culture is 72. 1% andin sand and soil culture . And the maximum64.8% lower than that of8 h treatment(the max-mean length occurs in 6 and 4 h in sand and soil,imum); and is 77.7% and 45.5% lower than thatrespectively. Rclatively, the amount and meanof8 h(the maximum) in soil culture, respective-length are higher in the 6, 8 and 10 h treatmentsly(sce Fig.4).as shown in Table I. Proper waterlogging pro-3.3 Growth of leavesmotes the increase in amount and the elongationofaerating roots.The maximum leaves biomass and surfacearea of mature leaves also occur in 2 h in sand3.2 Growth ofstemsculture, and are 595.5% and 435.3% bigher thanBiomass of stems is the highest in the 8 h .those of 12 h treatrnent(the minimum), respec-treatment fllowed by 10, 6, 4 and2 h, showingtively. And they occur in 4 h in soil culture.a tendency towards longer waterlogging timThere is approximately negative linear correla-wbich significanty promotes the growth oftion betwen biomas and waterlogging time,中国煤化工MYHCNMHGCHEN Luzhen et al. Acta0ceunologicaSinica 2004, Vol. 23, No.1, p. 149~158一心sand-o- - soil. -女-sand -0- soil1.0「).80.150).60.1000.40.0500.2 t0.0000.031012024681012Waterlogging time/hFig. 4. Infuences of waterlogging time on stemsFig s. Influences of waterlogging time on matureofK cande! sedlings.leaves of K. candel seedlings.|一0- sand - o-soil- sand --- soil40.0 「4.0r豆30.03.5-复20.0个元女要真合重10.0 t.0Watrlgging time/hFig. 6. Infuences of waterlogging time on mature lcafFig. 7. Influenccs ofwaterlogging timne on mature leafaera of K candel seedlings.suculence of K. cande! seedlings.and between surface area of mature leaves andfor the growth of seedlings, and generally losewaterlogging time from 2 to 12 h in sand cul-weight when they grow into seedlings. After 10ture(P =0.000, df=6).(Figs 5 and 6). Similarweeks’cultivation, the mean dry weight pertendency occurs in soil cultrure from 4 to 12hhypocotyl in each treatment is significantly lower(P= 0.000，df =6)while succulence of ma-than 5.60 g per hypocotyl before culture. Theture leaves increases with the prolonging ofmaximal weight loss occurs in the 6 and 8 h treat-waterlogging time from0to 10h (P =0.005,ments, and is approximately two times that of thein sand culture; P =0.031, in soil culture; dfslightest one (2 h treatment) in sand culture.=6)， and declines rather abruptly in the 12 hWeight loss of hypocotyls increases signifcantlytreatment(Fig. 7).from 2 to 8 h of waterlogging and then declines3.4 Effect on total biomass and weight loss ofabruptly after 8 h inundation as shown in Table 2(P -0.005, P =0.001). while, in soil culture,hypocotyls of K candel seedlingsweight loss of bypocotyls is lower in short timeBefore the seeds of viviparous K andelwaterlogging (0 ~2 bh), and higher in the4~ 8 hfall down from the matemal plants，theytreatments, although it is not significant withinhave germinated into hypocotyls. And they4~8 h treatments(P =0.640, P =0.695).supply a large amount of nutrient and energyAfter 10 weeks' culture, changes of total中国煤化工MYHCNMHG154CHEN Luzhen etal. Acta OeeanologicaSinica 2004, Vol, 23, No. 1, p. 149-158maximum total biomass in soil culture occurs in- o-sand - o- soilthe 4 h treatment, and it has the same tendencyas the sand culture.2.0004 Discussion1.5001.0004.1 Influence on the growth of K.candelseedlings0.500024610 1by waterlogging timeWaterlogging time/hPrevious studies on other plants indicate thatFig. 8. Influences of waterlogging time on the totalthe growth of plants is sensitive to water submer-biomass of K cande! seedlings.gence and is greatly slowed down in the case ofTable 2. Influences of waterlogging timne on the masssubmergence, but root tllering, adventitious rootsloss of K candel hypocotyl after cultivationgrowing and aerenchyma formation are greatlypromoted by waterlogging (Liu， 1992; Guan,1996). When the soil is flooded, the total biomassWaterloggingMass lss'g.time/hand root biomass of A nicennia maring signifi-01.241士0.2741.245 士0.165cantly decline (Hovendenetal. ，1995)and the1.109 +0.3151.863 +0.075growth of roots and leaves is greatly restrained in1.292+0.2792.290 +0.033other mangrove species, such as A vicennia ger-2.219+ 0.0282.348 +0.172minans,Laguncularia racemasa and Rhizophora2.218+0.1122.300 +0.257mangle (Pezeshki et al. 1989). Wang et al". study101.696+0.2382.182 +0.055also suggests the inhibition on the growth of K.121.539土0.1261.565 +0.143candel seedlings, while there is not significantdifference between 0 and 2 h treatments. Currentbiomass are shown in Fig. 8. Total biomass ofresearch indicates that the prolonging waterlog-2 h treatment in sand culture, including roots,ging time has a native effect on growth, while nostems and leaves, is the largest, and 232.2%waterlogging and long-time waterlogging (morehigher than that of 12 h treatment (the lowestthan 8 h) significantly inhibit the growth ofone). But total biomass of 0 h treatment isseedlings. Data of the maximal growth of K. can-38.5% lower than that of2h treatment. Fromdel seedlings excluding leaf succulence, stem2 to 8 h treatments, there is a slight decrease inbiomass and length of thick roots OCcur in the 2 htotal biomass, although the difference is nottreatment in sand culture. And tbey occur in thesignificant(P =0.037, P =0.249, P= 0.469).4 h treatment in soil culture. Biomass of thickBut abrupt descents occur in the 10 and 12 hroots and fine roots, which are closely related totreatments, which have the total biomass ofnutrient absorption, declines abruptly with the20.8% and 52.6% lower than that of8 h treat-increase of waterlogging time . Similarly, the de-ment, respectively (P =0.000，P =0.000).crease of biomass and surface area of matureThis indicates that the waterlogging inhibitsleaves results in the reduction of photosynthesisthe nutrient accumulation of seedlings whenand assimilation.the waterlogging exceeds 8 h. Total biomassIt has been found that the growth of stemsof no waterlogging(0 h) is 38.5% lower thanand leaves is speeded up by increasing the secre-that of the2 h treatment (P =0.000).. The tion of endogenous bormone under, flooded con-中国煤化工MYHCNMHGCHEN Luzhen et al. Acta OceanologicaSinica 2004, Vol. 23, No.1, p. 149~158155ditions in rice(Guan, 1996). Similar phenom-Mangroves are the woody plant communityena occur in K cande! seedlings that theoccurring in the intertidal zones and need naturalbiomass of stem remains high in the long-timetidal wave during the growth(Lin, 1997). Zhangetwaterlogging treatments (6~10h). We sup-al.(1997) and Zhang et al.( 2001) found that man-pose it to be another mechanism of moderat-groves distribute in the tidal zoDe between the av-ing roots anoxia under inundation. Oxygen iserage sea level and the spring tide level in theinhaled by the leaves above the water surfacesemidiumal tide. Ellison and Farnsworth (1997)and delivered to the roots. Succulence of ma-planted mangrove seedlings in simulated semidi-ture leaves is expressed by saturated waterurnal sea level, and found that the seedlings plant-content per leaf area. In order to reduce dehy-ed in mid tide grew the best. Reports ofKomiya-dration under inundation ，leaves mayma et al.(1996) suggested that the survival rate isclose pores to keep the tougor pressure stablesignifcantly influenced by elevation. It is(Liu，1992). Current studies have provedknown that K candel distributes in the mid-tidalthat tougor pressure of leaves may be in-zone naturally (Lin, 1997) and is inundated forcreased and the leaves succulence may be pro-about 2~4 h every tide cycle generally.moted by appropriate waterlogging.The longer the waterlogging time is, the4.2 Influence on aerating roots by waterlog-worse the growth of the seedlings is. Our resultshave showed that biomass of thick roots, fineging timeroots, mature leaves and total biomass are thePlants always promote the numbers ofhighest in the 2 h treatment in sand culture. Andaerating roots to mitigate oxygen deficit underunder this condition，the number of thick rootswaterlogging(Liu, 1992; Guan, 1996). Aerat-and leaf area of mature leaves reaches the highest,ing roots of other mangrove species also havewhich benefits nutrient absorption and materi -the same function(Lin, 1997). But aeratingal accumulation. In the 2 h treatment, seedlingsroots in K candel bas not been reporteddo not exhibit any menace features and developyet(Lin, 1984, 1997). Current research findsin a balanced way. Excluding the stem biomass,that a kind of spongy and smooth roots has adata of the growth almost reach the top in the4 hhigher atached region on the hypocotyls thaninundation in soil culture, and have the same ten-thick roots and fine roots. Mean diameter ofdency as the sand culture. After 10 weeks 'cul-them is larger than 5 mm. Anatomical ob-ture, all hypocotyls lose weight and hypocotylsservations indicate that they generally havelose the least in the 2 h treatment in sand cultureabundant large cortical gas spaces, which weand in 0 h treatment in soil culture. This showssuppose to have the ability of oxygen storagethat the growth of seedlings under short time(2~ 4and transportation. They do not grow out ofh) inundation could maintain normal photosyn-soil surface in the course of culture. Changesthesis and nutrition absorption.of aerating roots among different treatmentsOver 8 h ofinundation, the total biomass ofhave showed that they could moderate oxygenK candel seedlings descends rapidly. And oth-deficit if they could maintain a normaler data related to the growth , such as length,growth. Further researches are being carriedbiomass of thick roots, leaves biomass, leaves ar-oreas and stern biomass, also bave significantly de-4.3 Optimal waterlogging time and criticalwa-scending (see Figs2 ~8). It is concluded that thegrowth of K. candel seedlings is significanty in-terlogging time of K.candel seedlingshibited, and the rate of photosynthesis and nutri-中国煤化工MYHCNMHG156CHEN Luzhen et al. Acta OceanologicaSinica 2004, VoL. 23, No.1, p. 149-158tion absorption has descended.According to this result, we conclude30200031, the Key lterm of Science and Technology ofXi-that the optimal waterlogging time of K can-amen under contract No 30220021046, and the Doctor-del sedlings under artificial tidal conditionsate Vesting Point Foundation of the Minstry of Educationis 2~4 h inundation every tidal cycle, and theofChina under contract No.20030384007. We apreciatecritical waterlogging time is over 8 h inunda-Dr. Zhang Yihui and Dr. Chen Changping for their kindlytion in every tidal cycle. When the waterlog-help in this work.ging time exceeds this critical value， thegrowth of R candel seedlings is distinctlyRefcrencesinhibited. Because inundation used in our re-search is different from that in former studiesAshord A E, Allaways W G.1995. There is a continuum of(Komiyama et al. , 1996; Zhang et al. , 1997;gas space in young plants of Avicennia maria9，MarEllison and Farnsworth, 1997; Zhang et al. ,Ecol Progr Ser,295:5~112001 )which seedlings are soil flooded, theChen YJ,Chen W P, Zheng SF, etal.2001. Researches ontidal flat under curent conditions is higherthe mangrove plantation in Panyu, Guangdong. Ecolog-than that in former studies, which has led to aica Sciencecin Chinese),20(,2):25 -31longer time of waterlogging in our resuts.ChuiC Y, Chou C H.1993. Oxidation in the RhizosphereThe results ofWang et al'?. suggested that theofmangrove Kandelia cande! seding. Soil Sci Plantcritical time of being exposed to air for KNutr, 39(4):725~-731candel seedlings is at least 6 h in every tidalClarke L D, Hannon NJ.1970. The mangrove and marshcycle, which is similar to our results.communities of the Sydney district. I. Plant growth inGenerally, the optimal and critical wa-relation to salinity and waterlogging. 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