Propagation and Irrigation Regime Affect the Development of Catnip

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1 Propgtion nd Irrigtion Regime Affect the Development of Ctnip R. St. Hilire, A.W. Hockmn nd S.M. Chvez Deprtment of Agronomy nd Horticulture New Mexico Stte University Ls Cruces, New Mexico, 883, USA Keywords: Indole-3-utyric cid (IA), Nepet ctri, nepetlctones, stomtl conductnce Astrct Historiclly, ctnip (Nepet ctri) hs een used s ct toy filler nd medicinl te, ut recent reserch hs shown ctnip ws 1 times more effective t repelling mosquitoes thn the compound used in most commercil ug repellents. We determined propgtion strtegies nd irrigtion regimes for the production of ctnip. Adventitious root formtion nd the susequent development of rooted cuttings were determined for terminl nd single-node cuttings of ctnip treted with indole-3-utyric cid (IA) nd rooted nd grown for different time intervls. After eight-week production period nd verged over ll IA tretments, terminl cuttings propgted for 2 or 3 weeks hd more dry weight (DW) llocted to shoots thn roots compred to cuttings propgted for 4 weeks. Single-node cuttings propgted for two or three weeks hd more nd longer roots thn those propgted for three weeks. Also, we determined whether irrigting plnts every 2,, nd 1 d for 12 weeks influenced physiologicl, ntomicl, nd growth trits of ctnip. Plnts irrigted every 1 d hd the lowest root nd shoot DW which verged 142 nd 19 g/plnt, respectively. Plnts irrigted every 1 d hd the lowest lef re (934 cm 2 ), while leves wtered every 2 nd d hd the thickest leves. In nother experiment, plnts were irrigted every 2,, nd 1 d for 6 weeks. Stomtl conductnce of plnts irrigted every 1 dys ws reduced to s little s 82 % of plnts wtered every 2 d. iomss production ws similr in plnts wtered every 2 or d. In conclusion, irrigting ctnip every 1 d reduces dry mss, ut irrigting every d might conserve wter without compromising iomss production. INTRODUCTION Currently, ctnip (Nepet ctri) is propgted minly from seed. This propgtion method is chllenge ecuse ctnip seeds re smll nd difficult to hndle, seed germintion rtes verge only %, nd it requires t lest three months for successful field estlishment of trnsplnts (Hockmn et l., 21). Thus, dditionl propgtion techniques, such s rooting of stem cuttings need to e evluted for ctnip. esides the lck of informtion on rooting stem cuttings, there lso is limited informtion out the impcts of irrigtion regime iomss yield, growth, nd physiology of ctnip. Previous horticulturl reserch on ctnip hs focused on wys to optimize iomss yields under nonstressed conditions (utterfield, 1997), ut not on its response to environmentl fctors. Trditionlly, ctnip hs een used s ct toy filler nd herl te (Ferguson et l., 1988). Recently, nepetlctones found in ctnip ws 1 times more effective t repelling mosquitoes thn DEET (N,N-diethyl-3-methylenzmide) the compound used in most mosquito repellents (Peterson et l., 22). Ctnip is ecoming incresingly populr s specilty field-grown crop (utterfield, 1997). The ojectives of this reserch were to 1) evlute rooting nd susequent development rooted cuttings, nd 2) compre development of ctnip plnts irrigted every two, five or 1 dys. Proc. XXVI IHC Future for Medicinl nd Aromtic Plnts Eds. L.E. Crker et l. Act Hort. 629, ISHS 24 Puliction supported y Cn. Int. Dev. Agency (CIDA) 321

2 MATERIALS AND METHODS Propgtion Experiments In the first experiment, terminl cuttings (9 cm long nd.3 cm thick) were selected from greenhouse-grown ctnip plnts. Proximl ends were treted with, 1, 3 or 8 mg kg -1 IA (, 1, 3, or 8 ppm) (distilled wter, Hormodin #1, #2, or #3; E.C. Geiger, Hrleysville, PA) in the tlc form. Using completely rndomized design, 28 cuttings in ech of four IA tretments were inserted in plstic flts (Dyn-flt, A. H. Hummert, Erth City, Missouri) filled with Metromix 36, (Scotts-Sierr, Mrysville, Ohio) nd misted for 1 sec every 7 min in mist chmer. Rooting nd the development of seven cuttings in ech IA tretment were ssessed nondestructively fter two, three, nd four weeks in the mist chmer. Immeditely fter mesurement, ech rooted cutting ws repotted singly into #1 plstic pots filled with Metromix 36 (Scotts-Sierr) nd llowed to continue growth in greenhouse. Plnts were irrigted s needed nd fertilized weekly with 1 ppm N. At four weeks, oth nondestructive nd destructive methods were used to ssess rooting nd plnt development of the remining seven cuttings in ech of the four IA tretments. Eight weeks fter cuttings were first plced in the mist chmer, four plnts (out of seven) from ech IA/week comintion were hrvested rndomly. This hrvest resulted in plnts tht were in the greenhouse for six, five, nd four weeks fter hving een propgted for two, three, nd four weeks, respectively. Dry weights of roots, stems, nd leves nd lef res were determined. A second experiment ws strted using similr experimentl procedures s the first study. However, suterminl, single-node cuttings were used. Secondly, cuttings nd rooting nd plnt development were determined one, two, nd three weeks fter cuttings were plced in the mist ench. Irrigtion Experiments In one experiment, nine 3L, greenhouse-grown plnts of ctnip were wtered y using three irrigtion schedules: irrigted every two, five, or 1 dys. After 12 weeks of irrigtion tretment, ll plnts were destructively hrvested. Totl lmin re of five plnts in ech tretment ws determined. Lef discs were tken from five plnts nd processed for light microscopy. Oven dry weights of stems, leves, nd roots were determined. In the second irrigtion experiment, plnts were irrigted every two, five, or 1 dys for six weeks. For the first four weeks of the experiment, plnt stomtl conductnce ws mesured every dys with LI-COR stedy stte porometer (LI-16, LI-COR, Lincoln, Nersk) two hours (middy) efore plnts were irrigted. All plnts were destructively hrvested t the end of six weeks. For oth experiments, the experimentl design ws completely rndomized design with nine replictions in ech of three moisture regimes. RESULTS AND DISCUSSION Propgtion Experiments Regrdless of the concentrtion of IA, terminl cuttings rooted for four weeks hd longer shoots (Fig. 1A) nd roots (Fig. 1), nd less shoot dry weight (Fig. 1C) thn cuttings propgted for two or three weeks. Extended periods in the low rdition levels of mist will reduce crohydrte synthesis nd this might hve contriuted to reduced iomss production in cuttings rooted for four weeks. Cuttings rooted for four weeks nd llowed to grow in the greenhouse for four weeks hd less iomss prtitioned into shoots thn those propgted for two or three weeks nd llowed to grow for six nd five weeks, respectively (Fig. 1D). Cuttings rooted for four weeks nd treted with 3 mg kg -1 IA hd the most root dry weight (Fig. 2). While root iomss my not e prt of the economiclly importnt yield, reltively lrge root mss would help to mintin long-term growth (Smlley nd Dirr, 1987). Single-node cuttings propgted for two or three weeks hd more nd longer roots 322

3 thn those propgted for one week (Tle 1). The length of the longest primry root ws longer in cuttings tht received IA (Tle 1). Root to shoot dry weight rtio ws lowest in cuttings propgted for one or two weeks nd grown in the greenhouse for seven or six weeks, respectively (Tle 1). The lower lloction of iomss to roots in single-node cuttings propgted for one or two weeks suggests tht nursery producers could consider propgting plnts for one or two weeks if shoot dry mss production is the ojective. Cuttings treted with 8 mg kg -1 IA hd the most dry mss prtitioned into roots (Tle 1). Irrigtion Experiments In the first irrigtion experiment, root dry weight (Fig. 3A), shoot dry weight (Fig. 3), nd totl lef re (Fig. 3C) were lowest in plnts irrigted every 1 dys. This suggests tht plnts irrigted every 1 dys ccumulted the lest dry mss. Ctnip essentil oils re extrcted from leves, stems, nd flowers (Chlcht nd Lmy, 1997). Irrigtion tretments tht do not curtil ove-ground dry mss production could e dvntgeous for essentil oil production. Plnts irrigted every 1 dys hd the thinnest leves (Fig. 3D), nd irrigtion tretment did not ffect specific lef weight (dt not shown). Tken together, these dt suggest tht irrigting plnts every 1 dys might hve cused decrese in cell size while mintining the density of the cellulr contents. In the second experiment, stomtl conductnce of plnts irrigted every 1 dys ws reduced to s little s 82 % of plnts wtered every two dys (Fig. 4). Stomtl closure under short-term drought might llow the plnt to mintin turgor nd conserve moisture. However, prolonged stomtl closure curtils CO 2 uptke nd thus reduces dry mtter production (Jones, 1998). This cn e surmised y our dt which indicted tht lthough plnts irrigted every 2 or dys hd similr iomss (264 nd 298 g, respectively; Lest Significnt Difference= 7), this dry mtter production ws less thn tht of plnts wtered every 1 dys (194 g). CONCLUSION Within the eight-week production period, terminl cuttings of ctnip propgted for two or three weeks nd grown for six or five weeks, respectively, ccumulted more shoot dry weight thn cuttings rooted for four weeks nd grown for four weeks. Ctnip growers might vlue this result when using terminl cuttings to propgte the plnts ecuse the economic yield of the plnts is otined from shoots nd flowers. If single-node cuttingsre the propgule of choice, then nursery producers could mximize shoot iomss ccumultion y rooting cuttings for one or two weeks insted of three weeks. While irrigting ctnip plnts every 1 dys clerly reduced dry mtter ccumultion, plnts receiving wter every 2 or dys hd similr dry mtter production. This result might e significnt to ctnip producers growing the plnt on restricted wter udget. Irrigting plnts every dys might conserve wter resources without reducing the economic yield of the plnt. ACKNOWLEDGEMENTS Contriution of the New Mexico Agriculturl Experiment Sttion, New Mexico Stte University, Ls Cruces. Thnks to Erick Aguilr for ssistnce with microscopy procedures. Literture Cited utterfield, L.J.W Medicinl her tril Conn. Agric. Expt. St. ul. 943, pp. 21. Chlcht, J.C. nd Lmy, J Chemicl composition of the essentil oils isolted from wild ctnip (Nepet ctri L. cv. Citriodor) from the Drome region of Frnce. J. Essentil Oil res. 9: Ferguson, J.M., Weeks, W.W. nd Fike, W.T Production of ctnip in North Crolin.. In: J. Jnick nd J.E. Simon (eds.). Advnces in New Crops: Proceedings of the First Ntionl Symposium on New Crops, Indinpolis, IN. Hockmn, A.W., Chvez, S., Aguilr, E. nd St. Hilire, R. 21. Wter deficit stress 323

4 ffects physiologicl, ntomicl, nd growth trits of Nepet ctri L. (1 Aug. 21) (Astr.). Jones, H.G Stomtl control of photosynthesis nd trnspirtion. J. Expt. ot. 49: Peterson, C.J., Nemetz, L.T., Jones, L.M. nd Cotes, J.R ehviorl ctivity of ctnip (Lmicee) essentil oil components to the Germn cockroch (lttode: lttellide). J. Econ. Entomol. 9: Smlley, T.J. nd Dirr, M.A Effect of cutting size on rooting nd susequent growth of Acer rurum Red Sunset cuttings. J. Environ. Hort. : Tles Tle 1. Rooting nd developmentl trits of single-node cuttings treted with IA, rooted nd llow to grow for different intervls ut hrvested t 8 weeks. Weeks of Propgtion 1 IA (mg kg -1 ) Rooting nd growth trits Numer of primry roots c Length of longest primry root (cm) Root to shoot dry weight rtio Cuttings propgted for 1, 2, or 3 weeks grew in the greenhouse for 7, 6, nd weeks, respectively. 2 Within ech row for weeks of propgtion or IA level, numers with letter in common re not significntly different t p=. %. 324

5 Shoot Dry Weight (g) Root to Shoot Dry Weight Rtio Shoot Length (cm) Root Length (cm) Figurese A c C c D 1.1 Fig. 1. Influence of propgtion time on (A) length of the longest shoot (shoot length), () root length (length of the longest root), (C) shoot dry weight, nd (D) root to shoot dry weight rtio on ctnip terminl cuttings. There ws no interction etween propgtion time nd IA for these prmeters. Columns with the sme letter re not significntly different t p=. %. 32

6 Root Dry Weight (g) Lef Thickness (µm) Root Dry Weight (g) Shoot Dry Weight (g) A Totl Lef Are (cm 2) Irrigtion Intervl (dys) C Irrigtion Intervl (dys) D Irrigtion Intervl (Dys) Irrigtion Intervl (dys) Fig. 2. Root dry weight of terminl cuttings of ctnip in response to propgtion period nd concentrtion of IA. Columns with the sme letter re not significntly different t p=. % c IA (mg/kg) Weeks of Propgtion Fig. 3. Root dry weight (A), shoot dry weight (), verge totl lef re per plnt (C), nd verge lef thickness of ctnip plnts irrigted every 2,, or 1 dys. Columns with the sme letter re not significntly different t p=. % 326

7 Stomtl Conductnce (mmolm -2 s -1 ) J LSD = 11 2 J J H H J H J J Dys of Irrigtion Tretment Irrigtion Tretment Every 2 dys J Every dys H Every 1 dys Fig. 4. Stomtl conductnce of ctnip plnts irrigted every 2,, or 1 dys. Ech point represents the men of vlues. 327