Interntionl Conferene on Energy nd Environmentl Protetion (ICEEP 16) Effets of Exogenous Meltonin on Photosyntheti Chrteristis of Lettue Seedlings under NCl Stress Zesheng Yn1,,Mi Li1, ndyi Tng,* 1 College of Hortiulture, Sihun Agriulturl University, Chengdu, Sihun, Chin Institute of Pomology nd Oleriulture, Sihun Agriulturl University, Chengdu, Sihun, Chin 37949591@qq.om, 16965575@qq.om,tngyisunguoho@sin.om *Corresponding uthor Keywords:Meltonin;NCl stress; Lettue; Photosyntheti hrteristis Astrt.A pot experiment ws onduted to study the effets of sprying meltonin(mt) on photosynthesis of lettue seedlings under NCl stress. The results showed tht net photosyntheti rte(pn), stomtl ondutne(gs), light use effiieny (LUE)nd trnspirtion rte (Tr) were improved, espeilly when the onentrtion of meltonin ws 1μmol L-1, inresed y 31.85% (P<.5), 55.8% (P<.5), 31.85% (P<.5) nd 48.64% (P<.5) ompred withontrol,respetively.therefore, exogenous MT ould effiiently inrese resistne oflettue seedlings toncl stress, nd themt onentrtion of 1 μmol L-1 ws the est. Introdution Amenities soil seondry sliniztion prolem hs eome one of the mjor onstrints to sustinle development of griulturl filities, prtiulrly in the solr greenhouse nd plsti greenhouses.[1]. N+, Mg+, C+ nd CO3-, HCO3-, Cl- nd SO4- ontentin soil solutions the min fetures of sline soil, espeilly N+ nd Cl- ontent []. With the djustment of industril struture in rurl res, the re of fility vegetle ultivtion ws 53 hm from 1978 to 11, the development of more thn 4 million hm[3]. Butproteted ultivtion presented ontinuous ropping,exessive fertiliztion, soil erosion lk of rin, wstewter irrigtion, whih widespred slt umultion nd seondry sliniztion, resulting in redued yield nd qulity of vegetles [4,5]. Meltonin (meltonin, MT) ws first disovered in the niml's pinel glnd, is strong ntioxidnt endogenous free rdil svenger [6]. Studies hve shown tht, MT n effetively llevite the high temperture [7], hilling [8], UV rdition [9] nd hevy metl ontmintion [1] nd other non-iologil ftors on plnt dmge. At the sme time, plnt inresed levels of endogenous MT [11], to prevent the degrdtion of hlorophyll, mintining ell memrne integrity. Zhng et l. hve shown tht meltonin helps improve ntioxidnt enzyme tivity, redue the dmge of slt stress on pennisetum. In reent yers, more nd more studies of plnt stress physiology of meltonin, ut the reserh on slt stress on photosynthesis of plnts is still rre. Thus, this experiment ws studied the influene of different onentrtions of meltonin on photosynthesis of lettue under sltstress,nd hope to provide referene for slted lettue ultivtion. 16. The uthors - Pulished y Atlntis Press 365
Mterils nd Methods Mterils. The experiments were onduted t Sihun Agriulturl University (3 4 N, 13 51 E), Wenjing,Chin.The seeds of lettuewere hrvested in 15nd purhsed from Chengdu, Chin. All hemils used in experiments were of nlytil grde. Meltonin ws purhsed from Sigm-Aldrih (St. Louis, MO, USA). Experimentl Design.Seeds were sterilized in 1% sodium phosphte solution for 3 minutes, flushed five times in distilled wter, nd then pled on 9-m-dimeter Petri dishes with three lyers of filter pper moistened with distilled wter nd germinted t 5 in drkness. Seeds were onsidered germinted when the seed ot ws roken nd rdile ws visile. After germintion, seeds were plnted in nutrition pot filled with vermiulite nd perlite, the pot wsten entimeters in dimeter nd height. Seedlings were irrigted withmlhoglnd nutrient solution ontining 5μmol L -1 onentrtions ofnclevery other dy, until the experiment finishing. When the third lef expnded, their leves were spryed with (CK), 5,1,,4 μmol L -1 onentrtions of meltonin solution until folige nd dorsl dripping. Seedlings were spryed with meltonin solution every other dy, nd three times in totl. Eh tretment onsisted of 1 pots with one plnt per pot. Positions of the pots were rndomly hnged dily to minimize positionl effets. 3 dys fter tretment, the photosynthesis of eh plnt ws determined y using LI-64 portle photosynthesis meter (LI-COR In., USA). The photosyntheti prmeters of the photosynthesis meter were mnul ontrol CO onentrtion 4 μmol CO mol -1, temperture 5, light intensity 1 μmol m - s -1. The determintion of photosyntheti prmeters were net photosyntheti rte (Pn), trnspirtion rte (Tr), stomtl ondutne (Gs) nd CO onentrtion of interellulr (Ci), nd eh tretment ws repeted three times. Wter use effiieny (WUE) = net photosyntheti rte (Pn) / trnspirtion rte (Tr), Light use effiieny (LUE) = net photosyntheti rte (Pn) / light intensity[11]. Sttisti nlyses. Sttistil nlyses were performed using SPSS 13. sttistil softwre (IBM, Chigo, IL, USA). Dt were nlyzed y one-wy ANOVA with lest signifint differene (LSD) t 5% onfidene level. Results nd Disussion Net PhotosynthetiRte (Pn).After sprying meltonin, Pnof lettue leves were signifintly higher thn ontrols. ThePn of lettue ws inresed with the inresing of MT onentrtion from μmol L -1 up to 1 μmol L -1. When the onentrtion of MT ws 1μmol L -1, the Pn of lettuews the highest, 31.85%(p<.5) higher thn CK.After sprying MT of nd 4μmol L -1, Pnderesed 18.3% (p<.5)nd 14.38% (p<.5)respetively,ompred with CK. Trnspirtion Rte (Tr).With meltonin onentrtion inresed, thetr of lettue leves were firstly inresed nd then deresed.when the meltonin onentrtion ws 1μmol L -1, Trrehed pek, enhned y 48.64% (P <.5) ompred with CK, nd hd signifint differene with other tretments. After spryed meltonin of 4μmol L -1,there were not signifint differene ontrompred with CK. Wter Use Effiieny (WUE).As shown in Fig. 3, the WUE of lettue ws deresed with the inresing of MT onentrtion from μmol L-1 up to 1μmol L-1. When the onentrtion of MT ws 1μmol L-1, the WUE of lettue rehed the lowest point.after spryde the onentrtion 366
of 5 nd μmol L-1, WUEthough deresedy 3.16% (P>.5),.83% (P>.5)ompred with CK, not signifint. Light UseEffiieny (LUE).MT promotedlue of lettue under NCl stress, The sme s Pn,sprying onentrtion of MT ws1μmol L -1,the tretmentenhned LUE y 31.85% (p<.5), ompred with CK. Pn (μmol CO m - s -1 ) 1 8 6 4 MT onentrtion(μmol L -1 ) Fig. 1 Pn of MT spryedlettue Tr (mol H O m - s -1 ) 1..8.6.4.. MT onentrtion(μmol L -1 ) Fig. Tr of MT spryedlettue WUE (μmol mol -1 ) 14 1 1 8 6 4 Fig. 3 WUE of MT spryedlettue MT onentrtion(μmol L -1 ) LUE(μmol CO μmol - 1 ).1.8.6.4.. MT onentrtion(μmol L -1 ) Fig. 4 LUE of MT spryedlettue 367
Gs (mol H O m - s -1 ).14.1.1.8.6.4.. MT onentrtion(μmol L -1 ) Fig. 5Gs of MT spryedlettue Ci (mmol CO mol -1 ) 35 3 5 15 1 5 MT onentrtion(μmol L -1 ) Fig. 6Ci of MT spryedlettue StomtlCondutne (Gs). It n e lerly seen from Fig.5, ompred with CK, fter sprying meltonin, Gsof lettue leves re signifintly inresed. When meltonin onentrtions of 5, 1 nd 4μmol L -1, these tretments enhned Gs oflettue y 4.33% (p<.5), 55.8% (p<.5), 4.6% (p<.5) nd 16.68% (p<.5), respetively. CO Conentrtion of Interellulr (Ci).Spryed 5 nd μmol L -1 meltonin, Ci of lettue under NCl stress hd no signifint differene with the ontrol, when the onentrtion of meltonin ws 1μmol L -1, Ci ws redued y 3.57%(p<.5). When the onentrtion of meltonin ws 4μmol L -1, Ci ws higher thn the ontrol, signifintly. Conlusions Slt stress led to photosynthesisimpired [1]. The studyfound tht the Pn,Tr, LUE nd Gsof lettuewere promotedy low onentrtion of MT nd inhiited y high onentrtion, whih my e high onentrtion of MT hs toxi effets on the photosyntheti pprtus. To sum up, sprying low onentrtions of MT n improve photosynthesis of lettue under NCl stress, in ddition,the est onentrtion of MT ws 1μmol L -1. Aknowledgements This work ws finnilly supported y the Sihun Agriulturl University Shung-Zhi Pln Foundtion, Sihun Provinil Deprtment of Edution Foundtion (15ZA11). Referenes [1] M. Y. Nong, N. M. Zhng nd J. Shi: Soil nd Fertilizer Sienes in Chin Vol.6(13), p. 6-1 (In Chinese). [] D. L. Liu nd Q. J. Wng:Chinese Journl of Soil SieneVol.33(), p. 449-455 (In Chinese). [3] S. R. Guo, J. Sun nd S. Suo: Chin Vegetles Vol.18 (1), p. 1-14 (In Chinese). [4] L. L. Tng, Z. J. Chen nd J. B. Zhou: Agriulturl Reserh in the Arid AresVol.4(6), p.7-74 (In Chinese). [5] C. Q. Zho: Shnxi Agriulturl Sienes Vol.(5), p.8-83 (In Chinese). [6] R. J. Reiter: Progress in NeuroiologyVol.56 (1998), p.359-384 (In Chinese). [7] T. Iskender,K. Huseyin: Journl of Pinel Reserh Vol.5 (1), p.33-339. [8] X. Y. Lei,R. Y. Zhu nd G. Y. Zhng :Journl of Pinel Reserh, Vol.36(4), p.16-131. 368
[9] L. J. Zhng, J. F. Ji nd K. Mei: Journl of Nuler Agriulturl Sienes, Vol.5 (15), p. 83-835 (In Chinese). [1] M. Posmyk Młgorzt, H. Kurn nd K. Mrinik: Journl of Pinel ReserhVol.45 (8), p.4-31. [11] M. B. Arno nd J.Hernández-Ruiz: Food Chemistry Vol.138 (13), p.11 114. [1] L. Sun, Y. F. Zhou nd F. X. Zhou: Sienti Agriultur Sini Vol. 45 (1), p. 365-37 (In Chinese). 369