Crop Cycle Influences the Effectiveness of Pollination Techniques in Greenhouse Tomato

Transcription

1 Europ.J.Hort.Si., 74 (6). S , 29, ISSN Verlg Eugen Ulmer KG, Stuttgrt Crop Cyle Influenes the Effetiveness of Pollintion Tehniques in Greenhouse Tomto L. Mrtín-Closs, P. Puigdomèneh, J. Ll. Snfeliu nd A.M. Pelho (Deprtment of Hortiulture, Botny nd Grdening. University of Lleid. Lleid, Ctloni, Spin) Summry Fruit set limits the produtivity of the tomto rop in the greenhouse. In North Mediterrnen onditions two tomto rop yles n e rried out in the sme yer. Environmentl onstrints limiting pollintion in the yles my impose the use of different pollintion tehniques, oth from the produtive nd from the eonomil point of view. The im of this study is to nlyze whether flower virtion, umleee pollintion, or uxin sprying, improve fruit prodution of erly nd lte tomto greenhouse rops. Tretments were more effetive in the erly rop, rried out in spring, thn in the lte one in summer-utumn. For oth rop yles, the highest prodution ws for the umleee pollinted plnts. The mehnil flower virtion tehnique nd the uxin tretment signifintly inresed prodution in the erly rop, ut they were ineffetive in the lte yle rop. However, treting the erly rop with uxins my result in nipple-shpe fruits. Erliness ws not ffeted y the tretments. Fruit set ws improved y ll tretments tested nd in oth rop yles. In oth sesons, the use of umleees ws the most suessful tretment, nd the mximum effetiveness ws oserved during the periods of low night tempertures in the erly yle, when fruit set ws limited due to impired prodution of vile pollen nd/or poor pollen relese. Auxin nd virtion enhnement of fruit set ws higher for the erly thn for the lte rop yle. The environmentl onditions were determinnt for the effetiveness of the tretments. Moreover, the umleee effiieny ws demonstrted not only when the limti ftors were limiting for tomto fruit set, ut lso when fruit-set ws not limited y nturl limti onditions. Key words. uxins umleees Lyopersion esulentum mehnil virtor Introdution The tomto prodution nd qulity dereses when plnts re ultivted out of the min seson, either in the field or in unheted greenhouses. One of the mjor uses for this poor rop performne is the inomplete fruit set. The typil ommeril flower morphology determines tht self pollintion is the min pollen trnsfer system, while the level of ross pollintion in the field is very low (GROENEWEGEN et l. 1994). As tomto flowers do not produe netr, they re not frequently visited y insets. Flower or plnt shking helps relesing the pollen grins from the nthers nd trnsferring them to the stigm, therefore, ssuming tht vile pollen is produed, high self-pollintion nd fruit set rtes re otined (RYLSKI 1979; GEISENBERG nd STEWARD 1986). In the open field the wind is usully responsile for this tivity; in the greenhouse, without wind nd with few insets, the flower pollintion nd the orresponding fruit set is indequte (SHELBY et l. 1978). A plnt protetion tehnique, now in use in Mediterrnen greenhouses, is the overing of the greenhouse openings with inset proof sreens, therey reduing the nturl greenhouse ventiltion (MUÑOZ et l. 1999) nd the permeility of the greenhouse to the outside nturl pollintors. As result, pollintion is restrited to greter degree. Low tempertures in winter nd erly spring (PICKEN 1984; BAYTORUN et l. 1999), nd high tempertures in summer (PEET nd BARTHOLOMEW 1996), hve lso negtive effets on pollintion nd fruit set. These environmentl onstrints, mong others, lter the pollen grin development, trnsfer, nd germintion, nd lso the fertiliztion of the ovry. If pollintion nd fertiliztion is not hieved, the flower will either ort (HO nd HEWITT 1986) or, under speifi environmentl onditions, produe prthenorpi fruits (RYLSKI 1979). These seedless fruits re usully slow growing nd will e smller thn the norml pollinted fruits (ABAD nd GUARDIOLA 1986). Different pprohes for improving tomto pollintion nd fruit set re pplied. In the Mediterrnen greenhouse systems, three tehniques in use re under disussion: ) estlishing umleee (Bomus terrestris) hives in the greenhouse, ) mehnil pollintion y virtion with n eletri ee, nd ) sprying flower lusters with plnt growth regultors, minly uxins. Other pollintion methods, suh s the use of honeyees, ir lowers, nd mnul or utomti shking of the overhed wires, re seldom used. Any of these systems represent n eonomi ost. VELTHUIS nd DOORN (26) review on the effiieny of umleee pollintion finds sustntil gins in yield nd fruit qulity when ompred with other fruit setting tehniques suh s mehnil virtion of Europ.J.Hort.Si. 6/29

2 242 Mrtín-Closs et l.: Crop Cyle Influenes the Pollintion of Greenhouse Tomto the infloresene (BANDA nd PAXTON 1991; RAVESTIJN nd SANDE 1991; KEVAN et l. 1991; ABAK et l. 1995; DOGTEROM et l. 1998; PRESSMAN et l. 1999) or sprying with plnt growth regultors (ORLOWSKI nd GRZESZCZUK 23; DAS- GAN et l. 24). Anlyses hve een rried out only for single rop yles, mostly in winter. Whenever the environmentl onditions hnge, the effiieny of these tretments is to e re-evluted. In North Mediterrnen onditions two 4 to 5 months long rop yles per yer re usully developed; one from lte winter to erly summer, nd the other from middle or lte summer to the eginning of the winter. This timing differs from the ones previously mentioned in other res (VELTHUIS nd DOORN 26) nd llows the rop esping from the low winter tempertures nd lso from the higher summer tempertures, thus voiding the ssoited expenses in heting nd ventiltion. In hortiulturl prodution, the possiility of removing one ost ftor hs lwys to e onsidered. Therefore, detiled informtion nd knowledge on the performne of the different pollintion methods in the tomto in the different rop yles of the Mediterrnen greenhouse systems re required. The im of this study is to nlyze the performne of three methods for the improvement of pollintion nd fruit set in tomto, in the two most ommon greenhouse rop yles under Mediterrnen onditions. Mterils nd Methods Tomto plnts (Lyopersion esulentum Mill. v. Bond ) were grown in soilless ulture system on rokwool slps, t plnt density of 2.8 plnts m 2. The plnts were trined to single stem, whih ws llowed to develop until the 5th truss, the usul prtie for eefstek tomtoes. The study ws rried out in ommeril thermi-polyethylene greenhouse t the Mediterrnen sin, in North-Est Spin. Bumleee (Bomus terrestris L.) hives (Bioest Biologil System) were estlished in n re inside the greenhouse previously isolted with n inset-proof net. In ddition, inside this re nother inset-proof net ws used to isolte prt of the plnts from the pollintors, nd three further tretments were rried out: ) self-pollintion (ontrol), ) uxin sprying ( mixture of NAA-mide nd 4-CPA, Prorpil, Byer), 3 ml L 1, twie per week, nd ) eletri ee virtion of the infloresenes, 2 seonds three times per week. Twenty five plnts were used per tretment, with fully rndomized distriution. Greenhouse temperture, reltive humidity, nd PAR rdition were monitored every 3 min with Hoo dtlogger H8 (Onset Computer Corportion, Bourne MA, USA). The greenhouse ws utomtilly heted when tempertures felt under 6 C. From lte My to erly Septemer, shding sreen ws used to void extreme temperture inreses ommonly ourring inside greenhouses in the Mediterrnen region. The ove four tretments were pplied t two onseutive rop yles. The plnts t the erly yle were trnsplnted in erly Mrh nd hrvested until erly July (121 d), while those of the lte yle, were trnsplnted in erly August nd hrvested until lte Deemer (136 d). The reprodutive ehviour of the rop ws nlyzed y weekly reording the opened flowers, fruit set, nd mrketle fruits, in eh plnt truss. Erliness ws expressed s numer of dys from trnsplnting to the first hrvest per truss. The prodution of mrketle nd non mrketle fruits ws quntified. Mrketle fruits were those over 5 mm in dimeter, with regulr shpe nd without externl disorders, whih ws ssessed visully. Too smll or visully norml tomtoes were lssified in five groups of non mrketle fruits: ) smll fruits, under 5 mm in dimeter; ) nipple-shpe fruits, visully distinguished y the elongtion t the lossom end; ) fruits with oth ) nd ) disorders; d) fruits with tfe nomlies, nd e) fruits with other visul nomlies (lossom-end rot, rking, misshpen fruits,...). All dt were nlyzed through ANOVA. Perentges were previously trnsformed to rsin vlues. Men vlues were seprted y Tukey t P.5. For eh pollintion tretment, dt differenes etween oth rop yles were nlyzed y the orresponding t-tests. Results nd Disussion Erly Cyle In the erly yle men monthly temperture rnged from 17 to 24 C, nd reltive humidity ws quite stle round 64 %. At fruit set period of time, from April to My, the monthly minimum men temperture ws 11.1 C, nd the mximum 31.7 C. During this period, tempertures only osionlly surpssed 36 C (Fig. 1) Men Mximum Minumum A 45 4 Men Mximum Minimum B Temperture (ºC) * * Mr April My June July Months Temperture (ºC) August Sept. Ot. Nov. De. Months Fig. 1. Men, mximum nd minimum dily tempertures of the erly (A) nd lte (B) rop yles. * The numers indite the flowering infloresene long the min stem t ny given time. Europ.J.Hort.Si. 6/29

3 Mrtín-Closs et l.: Crop Cyle Influenes the Pollintion of Greenhouse Tomto 243 Prodution (g.pl -1 ) Erly Cyle Lte Cyle A d C Aux. Vi. Bum.B. Tretment Fruits per Plnt Erly Cyle Lte Cyle B C Aux. Vi. Bum.B. Tretment Fig. 2. Effet of tretments on totl weight (A) nd numer of hrvested fruits (B) per plnt in the two rop yles. Tretments: C = ontrol, Aux. = uxin sprying, Vi.= eletri virtor, nd Bum.B. = Bumleees. Vlues re mens ± SD. For eh rop yle, different letters mong tretments indite signifint differenes (P.5). Men tempertures nd reltive humidity were ner the optimum, while the mximum tempertures were not limiting for pollintion nd fertiliztion (PICKEN 1984). Suoptiml night tempertures under 1 C previled during 16 d etween lte Mrh nd erly April. Pollintion requires night tempertures etween 13 nd 24 C nd dy tempertures etween 15.5 nd 32 C; t higher or lower tempertures fruit set dereses (ROBINSON et l. 1965; CHARLES nd HARRIS 1972; SHELBY et l. 1978; EL-AHMADI nd STEVENS 1979; RYLSKI 1979; MAISONNEUVE nd PHILOUZE 1982; DANE et l. 1991), thus detrimentl effets of tempertures n e foreseen. Likewise, the night tempertures my hve dversely ffeted pollen relese (CHARLES nd HARRIS 1972). No limittions in solr rdition should e expeted sine under Mediterrnen onditions t the time of fruit set, rdition is lredy high. In the erly yle, ll tretments differed signifintly in prodution. The highest prodution ws mesured in the tretment with umleee pollintion (Fig. 2), nd ws 65, 43, nd 15 % higher thn in the ontrol, uxin, nd virtor tretments, respetively. These results re onsistent with those reported y PRESSMAN et l. (1999) nd y DASGAN et l. (24) in winter tomto rops, who otined higher prodution with umleees thn with uxin nd virtor tretments, ut they did not nlyze self-pollintion. Erliness ws not ffeted y the tretments, lthough in the uxin treted plnts the first fruits were hrvested few dys erlier. The numer of fruits per plnt ws highest in the umleee treted plnts, while the ontrol plnts rried 5 % less fruits (Fig. 2). The lower fruit numer results oviously in lower ompetition for ssimiltes nd ws presumly responsile for the lrger dimeter nd the higher weight of the ontrol fruits (Tle 1). Bigger fruits were expeted for the fewer fruits produed on the uxin thn on the umleee treted plnts (Fig. 2). However, their weight ws like nd their dimeter ws signifintly lower, suggesting the involvement of other developmentl ftors, mong them the inverse reltionship etween fruit size nd prthenorpy (MAPELLI et l. 1978). In ordne with other previous reports (RAMIN 23), Tle 1. The effet of pollintion tehniques on men fruit weight, fruit dimeter, proportion of non mrketle fruits, nd numer of opened flowers per plnt. Tretment Control Auxin Virtor Bumleees Erly yle Men fruit weight (g) 249. ± * ± ± ± 9.35 Fruit dimeter (mm) 79. ± 1.36 d 72.7 ± ± ±.69 Non mrketle fruits (%) 16.2 ± ± ± ±.55 Numer of opened flowers per plnt 37.7 ± ± ± ± 3.7 Lte yle Men fruit weight (g) ± ± ± ± Fruit dimeter (mm) 76.2 ± ± ± ± 1.81 Non mrketle fruits (%) 9.4 ± ± ± ±.37 Numer of opened flowers per plnt 28.7 ± ± ± ± 2.28 * Vlues re mens ± SD. For eh rop yle, numers followed y different letters indite signifint differenes mong tretments (P.5). Europ.J.Hort.Si. 6/29

4 244 Mrtín-Closs et l.: Crop Cyle Influenes the Pollintion of Greenhouse Tomto Tle 2. Non mrketle fruits (%): smll fruits (dimeter 5 mm), nipple-shpe fruits, fruits smll nd nipple-shpe (S+N), fruits with tfe nomlies, nd fruits with other nomlies (Other A.) (lossom-end rot, rking, misshpen fruits,...). Tretment Fruit disorder (%) Erly Cyle Lte Cyle Smll Nipple S+N Ctfe Other A. Smll Nipple S+N Ctfe Other A. Control Auxin Virtor Bumleees nd together with the well-known ft tht uxin tretments re relted to n inresed prodution of prthenorpi fruits with less seeds, it is suggested tht the lower fruit weight of the uxin treted plnts my e prtilly explined through lower numer of seeds (GORGUET et l. 25). However, sine the fruit seeds were not ounted, diret evidene on the fruits nture nnot e knowledged. Bumleee tretments produed the lowest perentge of non mrketle prodution, whih ws signifintly lower thn the ontrol (Tle 1). Most non mrketle fruits produed with the umleee or with the virtor tretments were ffeted y tfe disorders (Tle 2), whih is elieved to hve een triggered y norml development t flowering time (JONES 1999), prtly due to ool tempertures under 12.8 C (CHARLES nd HARRIS 1972). During the fruit set period, in April nd My, the greenhouse lower tempertures were frequently under this limit (Fig. 1). The inresing fruit setting in the ontrol tretment s the trusses develop (Fig. 3) is inditive of the less limiting temperture onditions in lte My. Nevertheless, the lower inidene of tfe disorders in the ontrol plnts revels tht low tempertures re not the only reson for the inidene of this disorder in the umleee nd virtor tretments. These tretments ould lso hve mehnil effet on the flower: the ontt etween the virtor nd the flowers or the smll fruits n sr the tissues; the umleees n lso dmge the flowers (JONES 1999; VELTHUIS nd DOORN 26) produing tfing-like effet to the fruits. Nipple-shpe fruits were produed only in the uxin treted plnts (Tle 2), whih is ttriuted to the stylr pex elongtion used y uxins (ABAD nd GUARDIOLA 1986). The inidene of this disorder dereses s temperture inreses, whih implies tht the prevlene of this disorder depends on the environmentl onditions t the time of uxin sprying. Exessive uxin sprying uses nd enlrges fruit deformtions previously indued y low tempertures (GEISENBERG nd STEWARD 1986). However, in the present experiment the produt reommendtions were refully onsidered, nd there were no negtive effets of uxin dose. The three pollintion tretments, umleee, virtion, nd uxins, where ll effetive in inresing fruit setting (Fig. 3), nd smll fruits, usully formed euse of inomplete pollintion (PICKEN 1984), were sre (Tle 2). Fruit setting ws higher with umleees, intermedite with the virtor nd uxin tretments, nd lowest in the ontrol plnts (Fig. 3). It is interesting to emphsize tht ll three tretments hd stle nd similr fruit set effetiveness in ll trusses, while there were ig differenes mong trusses in the fruit set of ontrol plnts. Indeed, in the lter the fruit set perentge mounted to 16 % in the first nd 6 % in the fifth truss. This ws sried to the ove mentioned fruit set enhnement s the minimum tempertures inrese. The pplition of the virtor nd the uxins to the lst truss did not sustntilly improve fruit setting, umleee pollintion eing the only effetive method for ll trusses (Fig. 3). Bumleees re etter pollintors thn mehn- Fruit set (%) C Aux. Vi. Bum.B. Truss A Fruit set (%) C Aux. Vi. Bum.B. Truss Men Men B Fig. 3. Effet of tretments on fruit set of the first to the fifth truss, nd verge fruit set per plnt (men), in the erly (A) nd in the lte (B) rop yle. Tretments: C = ontrol, Aux. = uxin sprying, Vi. = eletri virtor, nd Bum.B. = Bumleees. For the men vlue rs indite ± SD. For eh rop yle nd truss different letters mong tretments indite signifint differenes (P.5). Europ.J.Hort.Si. 6/29

5 Mrtín-Closs et l.: Crop Cyle Influenes the Pollintion of Greenhouse Tomto 245 il virtion euse they forge every flower more thn one per dy, ontrry to the mehnil virtion performed 2 3 times week (SHIPP et l. 1994; PRESSMAN et l. 1999). Additionlly, they n fvour ross pollintion, trnsferring vile pollen to mle sterile flowers rought out y temperture. Virtion ts on the infloresene nd it hrdly indues ross pollintion. There were signifintly more flowers opened in the ontrol plnts (Tle 1). The lower perentge of fruit setting in these plnts (Fig. 3) my hve fvoured the opening of the lte emerging flowers of the infloresenes. When fruit set is high, s in the umleee, virtor nd uxin tretments, the lst flowers do not open euse of the ompetition for ssimiltes with the lredy set fruits. Lte Cyle In the lte yle men monthly temperture vried from 11.8 to 27.2 C, nd reltive humidity ws round 7 %. At fruit set time, August to Septemer, the monthly minimum men tempertures were C, nd the mximum C. During this period, the temperture osionlly rose to 38 4 C in erly August nd never dropped elow 1 C (Fig. 1). Minimum tempertures nd reltive humidity were in the pproprite rnge for pollintion (PICKEN 1984); however, the mximum tempertures t fruit set time were over the sope, nd hrmful effets on pollintion my e expeted (SHELBY et l. 1978; EL-AHMADI nd STEVENS 1979; DANE et l. 1991; SATO et l. 2). The highest prodution ws otined in the umleee pollinted plnts (Fig. 2), whih showed n inrese of up to 14.3 % in omprison with the other three tretments. Signifint differenes in this yle were deteted only etween umleee nd ontrol tretments. The virtor nd the uxin tretments were not signifintly different from the ontrol, neither from the umleee tretments, nd erliness ws not ffeted y ny of the tretments. Consequently, t the ssyed onditions, the use of uxin or virtion is questionle. Although the lte yle lsted longer thn the erly one, its prodution ws onsiderly lower (Fig. 2). This is likely relted to the lower photosyntheti rdition ville, 889 versus 236 mol m 2, respetively. In ddition, the periods of high tempertures in summer nd the low tempertures in lte utumn (Fig. 1) stressed the rop t fruit growth time. For ll tretments, the perentge of non mrketle fruits ws lower thn 1 %, nd s for the erly rop yle, umleees signifintly redued it y. 5 % (Tle 1). Neither the umleee tretment produed tfing fruits, nor the uxin tretment produed nipple-shpe fruits (Tle 2). Tempertures t fruit setting were higher in the lte yle thn in the erly one (Fig. 1). The high perentge of non-mrketle nipple-shpe fruits in the uxin treted plnts of the erly rop, long with the sene of suh fruits t the lte yle rop, is in ordne with the relevne of the environmentl onditions t the uxin tretment time (ABAD nd GUARDIOLA 1986), nd suggests tht only during the erly yle rop prthenorpi fruits were produed. Fewer flowers opened in the lte thn in the erly yle rop, regrdless of the tretment (Tle 1). The min reson ws likely the high tempertures (CHARLES nd HARRIS 1972; EL-AHMADI nd STEVENS 1979). RYLSKI (1979) found tht in the seond to fifth infloresene flower ortion inresed s dy temperture rose from 17 to 27 C, thus fvouring the vegettive versus the reprodutive growth, nd inresing respirtion. In these irumstnes, in the erly stge of the infloresene growth, the vilility of ssimiltes for flower development diminishes. Also, s in the erly yle, more flowers opened in the ontrol plnts (Tle 1). Fruit set ws lowest in the ontrol plnts; the first truss hd the minimum fruit set, ut it ws onsiderly higher thn in the erly yle rop (Fig. 3), therey suggesting tht the high summer tempertures were less limiting thn the low tempertures in the erly yle. Fruit set ws similr for the virtion nd the uxin treted plnts, higher thn in the ontrols, ut signifintly lower thn in the plnts grown with umleees. Agin, it is remrkle tht umleee treted plnts hd the highest fruit setting. The differene with the ontrol plnts ws greter for the first trusses thn for the lst ones (Fig. 3), ut s in the erly yle, the effetiveness of umleees on fruit setting remined high mong trusses. The tomtoes were somewht smller in the lte thn in the erly yle, whih is ttriuted to the redution in solr rdition ville (HO nd HEWITT 1986). On the other hnd, nd s it ws lredy found in the erly yle rop, ontrol plnts produed the heviest nd iggest fruits (Tle1), nd s previously reported y RYLSKI (1979) under high dy tempertures, uxin treted plnts produed the smllest fruits. Pollen germintion is generlly higher under mild tempertures thn during the old seson (KARAPANOS et l. 26); ordingly, differenes etween treted nd ontrol plnts should e higher under old onditions. In our study the min limiting fruit set ftor of the erly yle ws the low temperture; it might hve restrited pollen formtion nd relese, redued germintion, nd slowed pollen tue growth (ROBINSON et l. 1965; CHARLES nd HARRIS 1972; RYLSKI 1979; MAISONNEUVE nd PHILOUZE 1982), thus resulting in poor fertiliztion. In the lte yle, limittions in fruit set due to tempertures ppered only t the eginning of the ulture: high tempertures my ffet nther development, espeilly in tissues with importnt roles in pollen development nd relese (SATO et l. 2; SATO nd PEET 25), nd re deleterious to fruit development (PEET et l. 1998). Virtion nd Bumleee inresed fruit set y enhning pollen relese, espeilly in erly spring, when it is stiky nd ggregted (MAISONNEUVE nd PHILOUZE 1982; PICKEN 1984). Bumleees were more effiient when dy tempertures were mild thn in the lte yle when the tempertures t fruit set were frequently ove 32 C nd limited forging. Auxins t in different wy; they sustitute pollintion nd trigger fruit development (GORGUET et l. 25). Under suoptiml tempertures prthenorpi fruits n e spontneously produed, ut they do not reh ommeril weight unless treted with uxins (RYLSKI 1979; SATO et l. 21). Also, uxins my inrese fruit set y improving fruit growth in poorly fertilized flowers (RYLSKI 1979). The otined results show tht ll tretments were effetive in inresing fruit set, lthough umleees produed the est results in oth rop yles. In the erly yle, only umleees were ple of inresing fruit set fter the fourth truss. The enhnement in fruit setting Europ.J.Hort.Si. 6/29

6 246 Mrtín-Closs et l.: Crop Cyle Influenes the Pollintion of Greenhouse Tomto inresed the prodution, ut not the fruit size, nd erliness ws not ffeted y ny tretment in ny of the two rop yles. Nevertheless, the effetiveness of the three tretments in inresing finl prodution ws losely dependent on the yle of the rop, nd ll three tretments were onsiderle less effetive in the lte thn in the erly rop yle. Referenes ABAD, M. nd J.L. GUARDIOLA 1986: Influeni de ls uxins en l lidd del fruto de tomte ultivdo en inverndero j tempertur. Investig. Agrri: Prod. y Proteión Vegetl 1, 9 23 (In Spnish). ABAK, K., N. SARI, M. PAKSOY, O. KAFTANOGLU nd H. YENINAR 1995: Effiieny of umle ees on the yield nd qulity of eggplnt nd tomto grown in unheted glsshouse. At Hort. 412, BANDA, H.J. nd R.J. PAXTON 1991: Pollintion of greenhouse tomtoes y ees. At Hort. 288, BAYTORUN, A.N., S. TOPÇU, K. ABAK nd Y. DASGAN 1999: Growth nd prodution of tomtoes in greenhouses t different temperture levels. Grtenuwissenshft 64, CHARLES, W.B. nd R.E. HARRIS 1972: Tomto fruit-set t high nd low tempertures. Cn. J. Plnt Si. 52, DANE, F., A.G. HUNTER nd O.L. CHAMBLISS 1991: Fruit set, pollen fertility nd omining ility of seleted tomto genotypes under high-temperture field onditions. J. Am. So. Hort. Si. 116, DASGAN, H.Y., A.O. OZDOGAN, O. KAFTANOGLU nd K. ABAK 24: Effetiveness of umleee pollintion in nti-frost heted tomto greenhouses in the Mediterrnen sin. Turk. J. Agri. For. 28, DOGTEROM, M.H., J.A. MANTTEON nd R.C. PLOWRIGHT 1998: Pollintion of greenhouse tomtoes y North Amerin Bomus vosnesenskii (Hymenopter: Apide). J. Eon. Entomol. 91, EL-AHMADI, A.B. nd M.A. STEVENS 1979: Reprodutive responses of het-tolernt tomtoes to high tempertures. J. Am. So. Hort. Si. 14, GEISENBERG, C. nd K. STEWARD 1986: Field Crop mngement. In: ATHERTON, J.G. nd J. RUDICH (eds.): The tomto rop. Chpmn nd Hll, London, GORGUET, B., A.W. VAN HEUSTEN nd P. LINDTHOUT 25: Prthenorpi fruit development in tomto. Plnt Biol. 7, GROENEWEGEN, C., G. KING nd B.F. GEORGE 1994: Nturl ross pollintion in Cliforni ommeril tomto fields. Hortsiene 29, 188. HO, L.C. nd J.D. HEWITT 1986: Fruit development. In: ATHER- TON, J.G. nd J. RUDICH (eds.): The tomto rop. Chpmn nd Hll, London, JONES, J.B. 1999: Tomto plnt ulture. CRC Press, Bo Rton, USA, KARAPANOS, I.C., C. FASSEAS, C.M. OLYMPIOS nd H.C. PASSAM 26: Ftors ffeting the effiy of gr-sed sustrtes for the study of tomto pollen germintion. J. Hort. Si. Biotehnol. 81, KEVAN, P.G., W.A. STARVER, M. OFFER nd T.M. LAVERTY 1991: Pollintion of greenhouse tomtoes y umle ees in Ontrio. Pro. Entomologil Soiety of Ontrio 122, MAPELLI, S., C. FROVA, G. FORTI nd G.P. SORESSI 1978: Reltionship etween set, development nd tivities of growth regultors in tomto fruit. Plnt Cell Physiol. 19, MAISONNEUVE, B. nd J. PHILOUZE 1982: Ation des sses tempértures noturnes sur une olletion vriétle de tomte (Lyopersion esulentum Mill.). I. Etude de l prodution de fruits et l vleur féondnte du pollen. Agronomie 2, (In Frenh). MUÑOZ, P., J.I. MONTERO nd A. ANTON 1999: Effet of inset-proof sreens nd roof openings on greenhouse ventiltion. J. Agri. Eng. Res. 73, ORLOWSKI, M. nd M. GRZESZCZUK 23: Use of umle ees for pollintion of herry tomto in unheted polyethylene tunnel. Vegetle Crop Reserh Bull. 59, PEET, M.M. nd M. BARTHOLOMEW 1996: Effet of night temperture on pollen hrteristis, growth, nd fruit set in tomto. J. Am. So. Hort. Si. 121, PEET, M.M., S. SATO nd R.G. GARDNER 1998: Compring het stress effets on mle-fertile nd mle-sterile tomtoes. Plnt, Cell Environ. 21, PICKEN, A.J.F. 1984: A review of pollintion nd fruit set in tomto. J. Hortiult. Si. 59, PRESSMAN, E., R. SHAKED, K. ROSENFELD nd A. HEFETZ 1999: A omprtive study of the effiieny of umle ees nd eletri ee in pollinting unheted greenhouse tomtoes. J. Hort. Si. 74, RAMIN, A.A. 23: Effets of uxin pplition on fruit formtion in tomto growing under stress temperture in the field. J. Hort. Si. Biotehnol. 78, RAVESTIJN, W. Vn nd J. VAN DER SANDE 1991: Use of umleees for the pollintion of glsshouse tomtoes. At Hort. 288, ROBINSON, R.W., S. SHANNON nd W. MISHANEC 1965: Low temperture influenes pollen prodution nd fruit set of tomtoes. Frm Res. 31, RYLSKI, I. 1979: Fruit set nd development of seeded nd seedless tomto fruit under diverse regimes of temperture nd pollintion. J. Am. So. Hort. Si. 14, SATO, S., M.M. PEET nd J.F. THOMAS 2: Physiologil ftors limit fruit set of tomto (Lyopersion esulentum Mill.) under hroni mild het stress. Plnt Cell Environ. 23, SATO, S., M.M. PEET nd R.G. GARDNER 21: Formtion of prthenorpi fruit, undeveloped flowers nd orted flowers in tomto under modertely elevted tempertures. Si. Hort. 9, SATO, S. nd M.M. PEET 25: Effets of modertely elevted temperture stress on the timing of pollen relese nd its germintion in tomto (Lyopersion esulentum Mill.). J. Hort. Si. Biotehnol. 8, SHELBY, R.A., W.H. GREENLEAF nd C.M. PETERSON 1978: Comprtive fertility in het tolernt nd het sensitive tomtoes. J. Am. So. Hort. Si. 13, SHIPP, J.L., G.H. WHITFIELD nd A.P. PAPADOPOULOS 1994: Effetiveness of the umle ee, Bomus imptiens Cr. (Hymenopter, Apide), s pollintor of greenhouse sweet pepper. Si. Hort. 57, VELTHUIS, H.W. nd A. VAN DOORN 26: A entury of dvnes in umleee domestition nd the eonomi nd environmentl spets of its ommeriliztion for pollintion. Apidologie 37, Reeived Otoer 26, 26 / Aepted July 27, 29 Addresses of uthors: Luís Mrtín-Closs (orresponding uthor), Pere Puigdomèneh, Jordi Ll. Snfeliu nd An M. Pelho. Deprtment of Hortiulture, Botny nd Grdening, University of Lleid, Avd. Allde Rovir Roure 191, Lleid, Spin, e-mil: mrtin@hj.udl.t Europ.J.Hort.Si. 6/29