Research Article Effects of Salt-Drought Stress on Growth and Physiobiochemical Characteristics of Tamarix chinensis Seedlings

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1 e Sientifi World Journal, rtile ID , 7 pages Researh rtile Effets of Salt-Drought Stress on Growth and Physioiohemial Charateristis of Tamarix hinensis Seedlings Junhua Liu, 1,2 Jiangao Xia, 2 Yanming Fang, 1 Tian Li, 2 and Jingtao Liu 2 1 College of iologial and Environmental Sienes, Nanjing Forest University, Nanjing , China 2 Shandong Provinial Key Laoratory of Eo-Environmental Siene for Yellow River Delta, inzhou University, inzhou , China Correspondene should e addressed to Jiangao Xia; xiajiangao2012@126.om and Yanming Fang; jwu4@njfu.edu.n Reeived 9 June 2014; Revised 3 July 2014; epted 3 July 2014; Pulished 22 July 2014 ademi Editor: Hongo Shao Copyright 2014 Junhua Liu et al. This is an open aess artile distriuted under the Creative Commons ttriution Liense, whih permits unrestrited use, distriution, and reprodution in any medium, provided the original work is properly ited. The present study was designed to larify the effets of salinity and water interross stresses on the growth and physioiohemial harateristis of Tamarix hinensis seedlings y pots ulture under the artifiial simulated onditions. The growth, ativities of SOD, POD, and ontents of MD and osmoti adjusting sustanes of three years old seedlings of T. hinensis were studied under different salt-drought interross stress. Results showed that the influene of salt stress on growth was greater than drought stress, the oxidation resistane of SOD and POD weakened gradually with salt and drought stresses intensified, and the ontent of MD was higher under severe drought and mild and moderate salt stresses. The proline ontents inreased with the stress intensified ut only signifiantly higher than ontrol under the interross stresses of severe salt-severe drought. It implied that T. hinensis ould improve its stress resistane y adjusted self-growth and physioiohemial harateristis, and the interross ompatiility of T. hinensis to salt and drought stresses an enhane the salt resistane under appropriate drought stress, ut the dominant fators influening the physiologial iohemial harateristis of T. hinensis were various with the hanging of salt-drought interross stresses gradients. 1. Introdution Tamarix hinensis elongs to the Tamarix family (Tamariaeae), whih are mainly xerophytes. It is native to China andkorea,anditisknowninmanyotherpartsoftheworld as an introdued speies and sometimes an invasive noxious weed. It easily inhaits moist haitat with saline soils. T. hinensis as an ornamental plant was introdued into North meria at the eginning of nineteenth Century and later into the southwest merian desert regions for windreak and sand fixation. Tamarix hinensis reeives more attention amongst different Tamarix speies [1]. eause of its strong adaptaility to the loal environment, T. hinensis replaed the native speies, and as the rapid invasion to many rivers and desert edges results in the loss of iodiversity in arid area, water onsumption inreased and a series of related prolems are listed as US ten alien invasive speies [2, 3]. s a nativespeies in China, T. hinensis is mainly distriuted in the northwest arid area of Xinjiang, Inner Mongolia and Gansu, and it is also the main speies for vegetation restoration of eologial restoration and protetion for the oastal wetlands of ohai Gulf. The Yellow River Delta is the most onentrated distriution area of T. hinensis [4], ut this area is eing threatened y hydrologial hanges [1]. In reent years, due to the large amount of groundwater exploitation of loal area, seawater intrusion led to soil salinity and the evaporation to preipitation ratio inreased. Due to the lak of freshwater resoures, the salt and drought stress eame the two major effet fators on loal T. hinensis seedlings growth [4, 5]. s known, soil is an essential omponent of wetland eosystem, whih an support, hold, and regulate water and

2 2 The Sientifi World Journal nutrients [6]. However, the effets of drought stress and salt stress on the growth and development of plants are oupled together, y reduing the soil solution water potential. Many of the previous studies are foused on the interation etweensaltanddroughtanditseffetonplantgrowth and physiologial and iohemial harateristis [7 10]. The effets of salt and drought stress on plant physiologial and iohemial properties are mainly onentrated in the mmodendron ifolium [7, 10], Gleditsia sinensis [8], and Ceris hinensis unge seedlings [9]. ut the stress physiology researhes of T. hinensis mainly onentrated on single salt stress [11 14] or drought stress [15, 16], suh as salt stress on the growth of T. hinensis [11], physiologial and iohemial harateristis during the leaf expansion period [17], photosynthesis and osmoti adjustment sustanes [12], and salt seretion harateristis and influene fator under saline haitats [13]. Furthermore, the drought resistane mehanism under different stress levels [15] and physiologial and eologial harateristis [16] under different environment had een arried out. ut the physiologial and iohemial harateristis response of T. hinensis to the saltdrought interross stress onditions has not een reported. This study was aimed at analyzing the hange dynami of iomass, superoxide dismutase (SOD), peroxidase (POD), malondialdehyde (MD), and osmoti adjusting sustanes under different gradients of salinity stress-drought interross stresses treatment, simulating the soil moisture and soil salinity onditions of sea-side and land-side and larifying the growth and physioiohemial harateristis of T. hinensis under different salt-drought stresses onditions. 2. Materials and Methods 2.1. Plants. Three-year-old Tamarix hinensis seedlings were seleted from National Marine Eologial Conservation Region at Changyi ounty in Shandong Provine, China. Previous works indiated that these seedlings had homogenesis traits in physiologial and morphologial aspets Experimental Setup. The experiments were arried out in a greenhouse at inzhou University, inzhou, China, from Marh 21, 2013, to June 15, T. hinensis seedlings of 3a old hadeentransplantedtoresearhgreenhouse,oultivated using pots diameter 30 m, high 50 m, 1 plants per pot, a totalof24plants,pottedmatrixforsandyloamsoil(salt ontent 0.02%). T. hinensis seedlings normal growth after pril20th2013tosaltanddroughtstresstreatment.drought stress treatment using Hsiao [14] moisture gradient design method, inludes high soil moisture (mild drought stress) and low soil moisture (serve drought stress); the soil relative water ontent was 55% 60% and 30% 35%. Salinity (soil salinity/soil dry weight) y NaCl solution onfiguration of different gradient times irrigation to ontrol, set up 2 levels, the salt onentrations were 0.4%, 1.2% and 2.5%, and the saltontentof0.02%asontrol.thepotottomisprovided with a tray whose depth is 8 m, the leakage water into the pot and the leaning tray, lean water is poured into the pot to prevent salt loss [18]. The experiment onsists of 8 (2 4) salt-drought treatments. Eah treatment was repeated 3 times and was designed y randomized lok arrangement. Salt and drought stress treatment for 8 weeks (From pril 20th to June 15th), determination of sample indexes Plant Sampling and nalysis. The same position of T. hinensis seedlings mature leaves was olleted and dried, groundandsievedthrougha120meshsieve,andsealedwith plastiagstoemeasured Physiologial and iohemial Indexes. The SOD ativity was determined y nitro lue tetrazolium [19, 20] four photohemial redution method; the ativity of POD [21] was measured using guaiaol olorimetri method; MD was measured y T olorimetri method [19] Determination of Proline Content. Take 0.05 g of dry sample into a entrifuge tue, sulfosaliyli aid with 10 ml 3%, sealing ag seal affixed after oiling water ath extration for 30 min; after ooling entrifugal (3000 r/min, 10 min), 1 ml supernatant fluid, 1 ml 3% sulfosaliyli aid, aeti aid, and 2 ml 2.5% aid indene ketone were added to three glass test tues (tue with glass alls) in oiling water ath for 60 min hromogeni reation; then we ool them to room temperature to join the 4 ml toluene and shake extrated red material, still taking the toluene layer, in the 520 nm asorane (OD) [19] Statistial nalysis. ll statistial tests were performed using SPSS Two-way NOV was used to determine the signifiane of different salt and drought treatment effets on growth and the physiologial harateristis. Mean treatment differenes were separated y the LSD test (P < 0.05 and P< 0.01)ifF-tests were signifiant. 3. Results 3.1.EffetofSaltandDroughtStressesontheGrowthTraitsof T. hinensis. s an e seen from Tale 1, T. hinensis plant height inreased more signifiantly (P < 0.05) in the salt ontent at 0.4% level, respetively, 34.7% and 15.0%, than CK under high and low soil moisture, ut the plants died under the stress ondition with salinity 2.5% and high soil moisture (see Figure 2). The main root length of T. hinensis showed no signifiant differene (P > 0.05) etween 0.4% salt stress treatment and CK under high soil moisture level, ut the main root length of 1.2% salt stress treatment was shorter oviously than CK (P < 0.05). Under low soil moisture ondition, the main root length inreased first and then dereased, and the main root length of 1.2% salt stress treatment was signifiantly longer than CK (P < 0.05). The asal diameter of T. hinensis inreased first and then dereased with the inrease of the salt ontent in the two kinds of soil moisture onditions and reahed the maximum at 0.4%, and the salt ontent of 1.2% was signifiantly dereased (P < 0.05). Under the mild and severe drought stress, aoveground parts and underground parts dry weight of T. hinensis was oth inreased first and then dereased with the salt

3 The Sientifi World Journal 3 Water ondition High soil moisture (mild drought) Low soil moisture (severe drought) Tale 1: Effets of Tamarix hinensis growth and iomass onditions with different salt and drought stresses treatment. Treatment Salinityontent Plant height (m) Main root length (m) Stem asal diameter (m) Overground iomass (g) Underground iomass (g) CK ± ± 1.25 a 0.51 ± 0.12 a ± ± % ± a ± 1.67 a 0.63 ± 0.26 a ± 3.35 a 9.52 ± 2.71 a 1.2% ± ± ± ± ± % CK ± ± ± 0.14 a ± ± % ± 4.72 a ± ± 0.22 a ± 1.37 a 7.03 ± 1.15 a 1.2% ± ± 1.67 a 0.35 ± ± ± % ± ± ± ± ± 0.76 The different letters within the same row indiate the signifiant differene at 0.05 level. stands for plant individual death. stress inrease, and reahed the maximum value at the salt ontent of 0.4%. In addition, plant individuals of T. hinensis still alive under the severe drought stress, while died in mild drought under severe salt stress, it may e appropriate drought stress an improved T. hinensis to a ertain extent of salt tolerane to water logging and saline haitats. The aove results showed that the effets of salt stress on the growth of T. hinensis were more than drought stress, although there are ertain inhiitory effets of drought stress on T. hinensis. In the meanwhile, the variation degree of aoveground dry weight was higher than those of the underground parts under the drought stress and salt stress treatments Effets of Salt and Drought Stresses on SOD and POD EnzymestivitiesofT.hinensisSeedlings. We an see from Figure 1, under mild drought stress, SOD ativity in leaves of T. hinensis inreased with the salt ontent derease, and the differene etween the salt stress treatment was signifiant (P < 0.05); ompared with CK, SOD ativity of leaves dereased signifiantly in the salt ontent of 0.4% (P < 0.05) and dereased oviously in the salt ontent of 1.2% and 2.5% (P < 0.01). Under low soil moisture onditions, the SOD ativity in leaves inreased first and then dereased with the salinity inreasing, and the ativity of SOD inreased aout 30% and 80%, respetively, ompared with CK in the salinity of 0.4% and 1.2%, then reahed the maximum value at salinity 1.2%, and was signifiantly lower in the salt ontent of 2.5% (P < 0.05). Under the same salt stress, the effets of different drought stress and salt stress effet on SOD ativity were signifiant (P < 0.01). y the doule fator variane analysis, SOD ativity in leaves of T. hinensis y ontaining salt and salt drought interross stress was signifiant (P < 0.01). Under mild drought stress ondition, the leaf POD ativity dereased first and then inreased and then dereased with the inrease of soil salt ontent; the differene among all treatments was extremely signifiant (P < 0.01). Under severe drought stress, POD ativity in leaves is inreased firstandthendereasedwiththeinreasingofsalinity,and the salt ontent of 0.4% and 1.2% was inreased 20% and 50%, respetively, more than those of CK and dereased approximately 15% ompared to those in the salt ontent 2.5% (P < 0.05). Under the same salt stress, the effets of different drought stress and salt effet on POD ativity also reahed extremely signifiant level. Doule fator variane analysis showed that salt stress, drought stress, and salt drought interross stress had signifiant effets on POD ativity of T. hinensis leaf Effets of Salt and Drought Stresses on MD Content. MD ontent in leaves of T. hinensis was firstly dereased and then inreased under mild drought stress and reahed the minimum value in the salt ontent of 1.2% and 0.4%. Under severe drought stress, the ontent of MD in leaves inreased first and then dereased and reahed the maximum (11.96 nmol mg 1 prot)atsalinity0.4%,3.75timesofck (P < 0.01). The ontent of MD in leaves dereased in the salinity 1.2% ut is still signifiantly higher than that of ontrol. t the salinity of 2.5%, MD ontent signifiantly dereased ompared to other treatments ut had no signifiant differene ompared to the ontrol. Doule fator variane analysis showed that the effet of salt stress on the ontent of MD was signifiant (P < 0.05), and drought stress or salt drought interross stress effet on the MD ontent reahed extremely signifiant level (P < 0.01). Under theseveredroughtandlightsaltstress,theontentofmd reahed a maximum value. 3.4.EffetofSaltStressandDroughtStressonProlineContent in Leaves. s seen from Figure 3, the proline ontent in the leaves of T. hinensis inreased at different extent with the inrease of salt and drought stress in this study. Under light drought stress ondition, the proline ontent inreased gradually with salt stress inreases, ut the had no signifiant differene ompared with CK (P > 0.05); under the severe drought, the proline ontent in leaves dereased first and then inreased with the enhanement of salt stress intensity, and the ontent at the salinity of 2.5% was signifiantly higher than that of CK (P < 0.05). When the salt onentration was elow 2.5%, the proline ontent under different drought stress had no signifiant differene (P > 0.05). Doule fator variane analysis showed that oth salt stress and drought stress had signifiant effets on the ontent of proline in leaves of Tamarix seedlings (P < 0.05), and the mild drought stress is ale to enhane aumulation

4 4 The Sientifi World Journal a 125 a SOD ativity (U mg 1 prot) C C POD ativity (U mg 1 prot) C 0 CK Salt ontent (%) 0 CK Salt ontent (%) Mild drought Severe drought Mild drought Severe drought (a) () Figure 1: The hanges of SOD and POD ativity under different salt and drought stresses. The different letters within the same treatment indiate the signifiant differene at 0.05 level. The stands for the signifiant differene at 0.01 level etween two treatments under the same salt stress. 15 MD ontent (nmol mg 1 prot) a 3 0 CK Salt ontent (%) Mild drought Severe drought Figure 2: The hanges of MD ontents under different salt and drought stresses. The different letters within the same treatment indiate the signifiant differene at 0.05 level. The stands for the signifiant differene at 0.01 level etween two treatment under the same salt stress.

5 The Sientifi World Journal 5 Proline ontent (mg/g FW) C CK Mild drought Severe drought C Salt ontent (%) a Figure 3: The hanges of proline ontents under different salt and drought stresses. The different letters within the same treatment indiate the signifiant differene at 0.05 level. The stands forthe signifiant differene at 0.01 level etween two treatments under the same salt stress. of proline in leaves of T. hinensis,toadapttothesaline environment. 4. Disussion 4.1. Salt-Drought Interross Stress ffeted Plant Growth and iomass lloation. s usually, salt-drought stress an delay plants growth and inhiit differentiation of plant tissue and redue fresh weight of leaf, stem, and root with the salt stress inrease [22]. Previous study showed that soils alongtheoastalareaouldformgradientsofsalinityand vegetation development during the desalinization proess [23]. With the salt ontent inreasing, Tamarix hispida stress symptoms eome more ovious, survival rate dereased, and high growth was inhiited [11]. Xanthoeras sorifolia seedlings adapt to drought stress y adjusting the iomass alloation and modified shape to ahieve effiient use of existing haitat resoures [24]. This study showed that T. hinensis had stronger tolerane of drought stress, ut its growth was affeted signifiantly y salt stress. Furthermore, the hanging of T. hinensis iomassisoviouswiththesalt stress intensified and to adapt to high sanity environment y reduing plant height, asal diameter, and dry matter weight. In a word, T. hinensis maintained the normal growth under salt and drought onditions y adjusting the iomass alloation and its form Salt-Drought Stress ffeted Enzyme System. SOD and POD are the main antioxidant enzymes in plants [7 9, 16] and play an important role in savenging superoxide ion, resisting lipid peroxidation, reduing memrane damage, andsoforth.thepreviousresearhresultsshowedthat,under stress onditions, the intensity and rise or fall of drought resistane related enzymes ativity were related losely to plant speies or varieties [25]. During experiment progress, enzyme ativity inreased with the stress inreasing or first inreased and then dereased. Like Gleditsia sinensis Lam, its SOD and POD ativity first inreased and then dereased under salt drought interross stress ondition, and in the same treatment ondition, oth SOD and POD ativities were dereased along with the extension of treatment time. This study showed that leaf SOD and POD ativity of T. hinensis had different hange patterns under different interross salt and drought stress. Under light drought stress, SOD ativity dereased; POD ativity dereased first and then inreased and then dereased; this dynami progress was related to that the low onentration of salt stress is ale to alleviate the effets related to drought stress. In ontrast, under severe salt stress, protetive enzyme system was reahed and enzyme ativity was inhiited strongly, leading to further redue in the moderate ativity. Under the severe drought ondition, the ativities of SOD and POD dereased so oviously that it was not enough to lear free radials in the ody; then it resulted in lipid peroxidation and the damage of memrane system [8, 16] Hydrauli-Salt Stress ffeted MD Contents. MD is often used as a major index to judge the memrane lipid peroxidation, and its ontent represents the degree of damage [7, 8, 26]. Researhers found that MD ontent of mmodendron ifolium and Gleditsia sinensis seedlings memrane permeaility inreased along with the salt and drought interross stress intensified. This study showed that appropriate salt drought interross stress an weaken the peroxidation of memrane lipid, and then MD ontent is relatively low, with less damage to the memrane system. However, under severe drought and mild to moderate salt stress, T. hinensis aumulated so muh free radial that initiated peroxidation of memrane lipid and then injured ell memrane. ut in severe salt and drought stress, MD ontent dereased signifiantly, whih may e a dominant fator and its salt drought interross stress adaptive regulation; its mehanism still needs further analysis and disussion Salt-Drought Stress ffeted Osmoti djusting Sustanes Contents. Osmoti adjusting sustanes play an important role for plants during the progress of growth, development, and reprodution in salt and drought stress [27]. Under

6 6 The Sientifi World Journal natural onditions, plants frequently suffer multiple environmental stresses, and the omined effets of environmental stresses on plants are omplex and are not equal to the sum y simply adding the effet of eah single fator [28]. Under the salt and drought stress onditions, large aumulation of intraellular solule sugar and proline improves the ell sap onentration, maintains normal ell turgor, prevents exessive water loss, and enhanes the resistane of plants [29]. large numer of studies showed that the solule sugar is one kind of important organi osmoti regulators under adversity ondition; it not only has a stailizing effet on ell memrane and protoplast and providing aron skeletons andenergyforthesynthesisofproteinutalsoindiretly transmuted into proline [30]. This study showed that, in the salt drought interross stress, solule sugar ontents in the leaves of T. hinensis seedlings gradually inreased with the stress degree enhanement, and in severe salt and drought stress, the solule sugar ontent egan to derease. That is to say that the solule sugar plays an important role in osmoti adjustment, ut the permeaility of solule sugar regulation has ertain limitations; for example, under serve drought stress, the osmoti adjustment aility of T. hinensis redued greatly or was lost. Proline is usually onsidered as one of main osmoti sustanes for plants used to regulate potential alane of ytoplasmi and vauolar infiltration under salt stress [31]. This study showed that proline of T. hinensis inreased gradually with inreasing of salt and drought stress, ut under mild drought stress it did not inrease signifiantly; the umulative amount of proline was low, only signifiantly inreased in severe salt stress and severe drought stress onditions. 5. Conlusion In summary, researh on the relationships etween plants and their environmental onditions has eome a hotspot in present eology studies. In this study, the growth and physioiohemial harateristis of T. hinensis is ale to adapt to the stress environment y adjusting the growth pattern and alternating solule sugar and proline ontent, protetive enzyme ativity, and other physioiohemial indexes to improve the aility to adapt to adversity. T. hinensis showed strong drought resistane and salt tolerane, and its growth onditions and physioiohemial harateristis were related losely to the outside environmental fators, suh as soil salinity and soil moisture status. On the other hand, the interross ompatiility of T. hinensis to salt and drought stresses an enhane the salt resistane under appropriate drought stress, and the dominant fator influening the physiologial iohemial harateristis of T. hinensis shows some differenes with the hanging of salt-drought interross stress gradients. s Tamarix hinensis ommunities degrades in the Yellow River Delta, due to environment hange and anthropogeni ativities, then, the resultsofthisstudyhasertaintheoretialandpratial signifiane for the evaluation of T. hinensis resistane and reprodutive tehnology, ut the internal adjustment mehanism and adaptation mehanism need to e further researhed in future. Conflit of Interests The authors delare that there is no onflit of interests regarding the puliation of this paper. uthors Contriution Junhua Liu and Jiangao Xia ontriuted equally to this work. knowledgments This study was supported y the National Natural Siene Foundation of China (nos , , and ), y Siene and Tehnology Plan of Universities in Shandong Provine (no. J13LC03), y the promotive researh fund for exellent young and middle-aged sientists of Shandong Provine (no. S2013NY010), and y the Priority ademi Program Development of Jiangsu High Eduation Institutions, PPD. Referenes [1].Cui,Q.Yang,K.Zhang,X.Zhao,andZ.You, Responses of saltedar (Tamarix hinensis) to water tale depth and soil salinity in the Yellow River Delta, China, Plant Eology,vol.209, no. 2, pp , [2] G. L. nderson, R. I. Carruthers, S. Ge, and P. 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