EVALUATION OF DIFFERENT TECHNIQUES FOR QUANTIFYING THE PHYSIOLOGICAL RESPONSE OF COTTON UNDER HIGH TEMPERATURES

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1 EVALUATION OF DIFFERENT TECHNIQUES FOR QUANTIFYING THE PHYSIOLOGICAL RESPONSE OF COTTON UNDER HIGH TEMPERATURES A.C. Bii, D.M. Oosterhuis, E.D. Gonis, nd F.M. Bourlnd 1 RESEARCH PROBLEM Extreme vriility in cotton (Gossypium hirsutum L.) yields from yer to yer, s well s lck of ny noticele increses in yield over the pst decde, hs cused mjor concern for producers. Although yield is minly controlled y genetics, environment, nd culturl inputs, it is now elieved tht temperture is one of the mjor fctors ffecting the development of cotton yield. Our erlier work hs indicted strong negtive correltion etween high tempertures nd low cotton yields in Arknss. However, there is limited informtion on the effects of high temperture on the physiology nd growth of cotton. In this study, it ws hypothesized tht numerous physiologicl nd iochemicl prmeters will e ffected y elevted tempertures, ut only few of these will e oth sensitive to high tempertures nd esy to mesure in lrge reeding trils. BACKGROUND INFORMATION Unpredictle yer-to-yer vriility in cotton yields nd stgntion of yields re mjor concerns of the cotton industry. Yield is controlled y genetic nd environmentl fctors s well s y culturl inputs. Of these, it is thought tht environmentl fctors exert the mjor influence on yield development during the seson. Reserchers hve suggested tht chnges in cotton germplsm over the pst thirty yers my hve resulted in reduced tolernce of modern cultivrs to environmentl stress (Lewis et l., 2; Brown nd Oosterhuis, 24). However, our erlier reserch hs indicted tht high temperture is the mjor fctor dversely ffecting cotton yields during the seson nd tht strong negtive correltion exists etween high tempertures nd low cotton yields in Arknss (Oosterhuis, 22). The idel temperture rnge for cotton is 68 to 86 o F (2 to 3 o C) (Reddy et l., 1991) with n optimum for photosynthesis eing 82 o F (28 o C) (Burke et l., 1988). However, verge mximum tempertures during oll development in the Mississippi Delt re lmost lwys well ove these optim. Improved tolernce 1 Grdute ssistnt, distinguished professor, grdute ssistnt, grdute ssistnt, Crop, Soil, nd Environmentl Sciences Deprtment, Fyetteville; nd director, Northest Reserch nd Extension Center, Keiser, respectively 94

2 Summries of Arknss Cotton Reserch 23 of cotton germplsm is oviously needed to stilize yields for consistent high of cotton germplsm is oviously needed to stilize yields for consistently higher yields. Gipson nd Johm, (1969) documented cotton yield response to high night temperture, ut reserch out the physiologicl response of the cotton plnt to high dy temperture is limited. The first step is to find relile nd prcticl technique to mesure temperture tolernce in cotton, so s to e le to use this in reeding efforts to improve temperture tolernce in cotton. RESEARCH DESCRIPTION Two studies were conducted in My 23 in growth chmers in the Altheimer Lortory, Fyetteville, Arknss. In the first growth-chmer study, four different fluorometer techniques were evluted. Cotton (Gossypium hirsutum L.) cv. Stoneville 213 nd 474 were plnted in 2L pots filled with Sunshine mix nd wtered with hlf-strength Peter s nutrient solution. The growth chmer ws mintined t 3 o F/2 o C (dy/night) tempertures, t 8% reltive humidity, nd with 12h photoperiods. Mesurements were strted t the pinhed squre stge using the fourth min-stem lef. Fluorescence ws mesured using the light-dpted test (using fluorometer with light-dpted clip); the drk-dpted test 1 (using the drk-dpted clip); the Lef-tissue technique (using lef punches 1.5 cm in dimeter plced in moistened environment nd fluorescence mesured with the drk-dpted test); nd the drk-dpted test 2 (using fluorometer with drkdpted clip on leves covered with lck gs). In the second growth-chmer study different techniques for quntifying temperture tolernce were evluted under elevted tempertures. Cotton (Gossypium hirsutum L.) cv. Suregrow 747 ws plnted in Sunshine mix nd wtered with hlf-strength Peter s nutrient solution. The plnts were mintined t 3 o F/2 o C until the pinhed squre stge, fter which they were divided into two sets nd hlf moved to 35/3 o C. After three dys t this temperture regime the temperture ws rised to 4/3 o C. Mesurements were tken four dys fter the plnts were plced in the elevted temperture, using the fourth min-stem lef from the terminl. Mesurements were mde of totl ctive proteins (Brdford, 1976); memrne lekge (using lef-discs plced in 2 ml ionized wter for 48 hours nd mesuring conductivity with n Automtic Seed Anlyzer); chlorophyll fluorescence (Modulted Chloropohyll Fluorometer OS1-FL); nd ntioxidnt enzymes (Anderson et l., 1992). RESULTS AND DISCUSSION Evlution of Different Fluorometer Techniques The sttisticl nlysis of the results (Fig. 1) showed tht the light-dpted test nd the drk-dpted test 2 hd consistent results with no significnt differences 95

3 mong the mesurements. The drk-dpted test 1 nd the lef tissue techniques showed significnt differences mong their mesurements. This cn e explined y the fct tht the tissue in oth techniques did not hve time to dpt to the drk conditions. Therefore, the tissue ws still under light conditions during the first mesurement ( min) nd the Fv/Fm vlues were lower. The light-dpted test ws significntly different compred with the other techniques. In conclusion ll four fluorometer techniques showed consistent mesurements of chlorophyll fluorescence with time. However, the light-dpted test ws more prcticl, relile, nd potentilly more esy to use in the field. Evlution of Different Techniques under Elevted Tempertures The preliminry study with contrsting tempertures determined tht 3-4 dys were needed t prticulr elevted temperture efore plnt metolic responses could e detected; i.e. y memrne lekge (ML), fluorescence (FL), proteins (PR), nd ctlse (CAT). Among these four mesurements (Fig. 2) the results showed tht ML nd CAT were the most sensitive nd ccurte methods for quntifying temperture tolernce (Tle 1). Memrne lekge ws the most sensitive technique tested in comprison study for quntifying temperture tolernce in the field. Fluorescence lso showed some sensitivity for quntifying temperture tolernce with the dvntge tht it is much esier technique for field use. Similrly ctlse ctivity ws sensitive ut time-consuming nd more pproprite for lortory nlysis. PRACTICAL APPLICATION Given the urgent need to identify cotton genotypes with temperture tolernce, this study evluted techniques to quntify plnt response to high tempertures. Memrne lekge ws the most sensitive technique tested while fluorescence lso showed some sensitivity for quntifying temperture tolernce. Furthermore, mesurement of the ctivity of the enzyme ctlse ws very sensitive ut very time consuming. The results will e used for screening cotton germplsm to identify lines to e used in plnt reeding for improving cotton response to high temperture for more efficient production nd stle yields. 96

4 Summries of Arknss Cotton Reserch 23 LITERATURE CITED Anderson, J.A., B.I. Chevone, nd J.L. Hess Sesonl vrition in the ntioxidnt system of Estern white pine needless s evidence for therml dependence. Plnt Physiology 98: Brdford, M.M A rpid nd sensitive for the quntittion of microgrm quntities of protein utilizing the principle of protein-dye inding. Anlyticl Biochemistry 72: Brown, R.S., D.M. Oosterhuis, D.L. Coker, nd L. Fowler, 24. Evlution of physiologicl responses of modern versus osolete cotton cultivrs under wter deficit stress for explining yield vriility. In: Proceedings, Beltwide Cotton Conferences. Ntionl Cotton Council, Memphis, Tenn. CD-ROM. Burke, J.J., J.R. Mhn, nd J.L. Htfield Crop-specific therml kinetic windows in reltion to whet nd cotton iomss production. Agronomy Journl. 8: Gipson, J.R. nd H.E. Johm Influence of night tempertures in growth nd development of cotton (Gossypium hirsutum L.) IV. Seed qulity. Agron. J. 61: Lewis, H., L. My, nd F. Bourlnd 2. Cotton yield components nd yield stility. Pp In: Proceedings, Beltwide Cotton Production Resource Conferences. Ntionl Cotton Council, Memphis, Tenn. CD-ROM. Reddy, V.R., D.N. Bker, nd H.F. Hodges Temperture effect on cotton cnopy growth, photosynthesis nd respirtion. Agronomy Journl 83: Oosterhuis, D.M Yield response to environmentl extremes in cotton. Pp In: D.M. Oosterhuis (ed.). Proceedings 1999 Cotton Reserch Meeting nd Summries of Reserch in Progress. Ark. Agri. Exp. St., Specil Report

5 Tle 1. Contrsting sensitivity of techniques on elevted tempertures. Mesurements Memrne Temperture Proteins Ctlse Fluorescence lekge tretment F g/ml mm/g FA/cm 2 3 C C % of control C C % of control Numers in column followed y the sme letter re not significntly different (P#.5). The higher temperture s percentge of the 3C..9 Fluorescence (Fms-Fs)/Fms Light Lef tissue Clip Plstic Minutes Fig. 1. Evlution of four fluorometer techniques under stle condition t 3 o C only. 98

6 Summries of Arknss Cotton Reserch 23 A Proteins (µg/ml) B Memrne lekge (µa/cm 2 ) o C 35 o C 3 o C 4 o C Temperture tretment 3 o C 35 o C 3 o C 4 o C Temperture tretment 99

7 18 Ctlse (mm/g fresh weight) ) Fluorescence [(Fms-Fs)/Fms o C 35 o C 3 o C 4 o C Temperture tretment 3 o C 35 o C 3 o C 4 o C Temperture tretment Fig. 2. Effect of elevted tempertures on proteins (A), memrne lekge (B), ctlse (C), nd fluorescence (D) of field- grown cotton. Fyetteville, Ark, 23. Different letters ove the pired columns show significnt differences (P=.5). 1