JUICE VESICLE DISORDERS AND IN-FRUIT SEED GERMINAION IN GRAPEFRUIT

Transcription

1 (Table 4) are nt uncmmn. While sme grwers have reprted excellent results frm C 10 usage, many grwers have reprted medicre activity r cmplete failure. It is prbable that clder winter temperatures reduced the ef fectiveness f bth chemicals as has been reprted fr ther crps (1,6); and f the 5 experiments which shwed n TRIA activity, mst were applied during the Flrida winter perid (Table 6). In additin, TRIA has als been fund t be adversely affected by certain plastics (6). Flrida spray waters can als vary greatly, with mst being p 8 r abve. The manufacturers f C 10 recmmend that spray tank p be adjusted t 6-7 by apprpriate addi tives. Water surces are imprtant fr bth C 10 and TRIA but mre research will be necessary t further understand this prblem. Attempts t harvest 'Valencia' ranges fllwed by dip ping in a slutin f C 10 r TRIA prved ineffective as a substitute fr field applicatin. Althugh tests with C 10 and TRIA have nt effectively reduced white grapefruit acidity (Tables 4 and 6), researchers in Texas (4) reprt that in sme tests, C 10 significantly increased Brix and rati, and significantly reduced percent acid with 2 red grapefruit cultivars. Future research will be aimed at trying t achieve cn sistent results in cntrlling acidity in citrus fruit. T this end, the FMC handsprayer used by the Flrida Depart ment f Citrus has been mdified by remving all plastic materials where pssible, and with the additin f a 100% rubber spray hse and a 200 gal (757 1) stainless steel tank. Similar mdificatins have als been adapted by A. Duda and Sns, Inc. Relatively pure water surces will be utilized as much as pssible. The extreme high cst f registering new chemicals fr use n fd crps has greatly reduced chemical develp ment fr agricultural purpses, including PGR materials. The situatin will prbably nt imprve as envirnmental prtectin is an imprtant cnsideratin fr everyne and the necessary testing is very expensive, perhaps as much as $40 millin per chemical (E.. Beyer, persnal cm municatin). Therefre, research with envirnmentally safe bilgical materials shuld be pursued when available, even thugh at times incnsistent results may prve frus trating t the researcher. Literature Cited 1. Biernbaum, J. A., R. L. utz, and S. K. Ries Field studies with crps treated with cllidally dispersed triacntanl. J. Amer. Sc. rtsci. 113(5): Fwler, B. A. 1983a. Arsenical metablism and txicity t freshwater and marine species, p In: B. A. Fwler (ed.). Bilgical and envirnmental effects f arsenic. Elsevier, New Yrk, NY. 3. Fwler, B. A. 1983b. Bilgical and envirnmental effects f arsenic. Elsevier. New Yrk, NY. 4. Fucik, J. E. and D. Davila The effect f grwth stimulant sprays n Star Ruby grapefruit juice and fruit. Prceedings f the Plant Grwth Regulatr Sciety f America 15: Knapp, J. L., D. P.. Tucker, J. W. Nling, and V. V. Vandiver, Jr Flrida citrus spray guide. Flrida cperative Extensin Serv ice. (Revised annually). 6. Ries, S. K Regulatin f plant grwth with triacntanl. CRC critical reviews in plant science. Vl. 2: Squibb, K. S. and B. A. Fwler The txicity f arsenic and its cmpunds, p In: B. A. Fwler (ed.). Bilgical and en virnmental effects f arsenic. Elsevier, New Yrk, NY. 8. Tenzer, A. I NF-10 biactivatrs enhance phtsynthesis, plant grwth, yield and quality in cmmercial crps. Prceedings f the Plant Grwth Regulatr Sciety f America. 14: Wilsn, W. C Results f experiments using arsanilic acid t reduce acidity f grapefruit in Flrida. Prceedings f the Plant Grwth Regulatr Sciety f America. 14: Wilsn, W. C Methds fr cntrlling maturity (acidity) f citrus. In: W. F. Wardwski (ed.). Fresh fruit quality, shrt curse prceedings. Ft. Pierce, FL. Prc. Fla. State rt. Sc. 101: JUICE VESICLE DISORDERS AND IN-FRUIT SEED GERMINAION IN GRAPEFRUIT Yng-S wang1 and L. G. Albrig University f Flrida, IFAS Citrus Research and Educatin Center 700 Experiment Statin Rad Lake Alfred, FL AND D. J. UBER University f Flrida, IFAS Vegetable Crps Department Gainesville, FL Abstract. Juice vesicle disrders (vesicle cllapse [VC] r vesicle granulatin [G]) and in-fruit seed germinatin were studied in fruit f 2 grapefruit cultivars (Citrus pardist Macf. cv. Marsh Seedless and Ruby Red) harvested frm the same trees in each f 8 grves (4 per cultivar) during the late seasn Flrida Agricultural Experiment Statin Jurnal Series N 'This manuscript was prepared frm the dissertatin f the senir authr as partial fulfillment f the requirements fr a PhD degree in rticultural Science at the University f Flrida. Prc. Fla. State rt. Sc. 101: (March-May) in 3 successive years. Fruit were examined at harvest and after 40 days strage at 21 C. At harvest, sectin drying (SD) was fund primarily at the stem-end whereas during strage they als appeared in the stylar-end and cen tral fruit prtins. The ccurrence f VC was slightly higher than G at harvest. Bth disrders increased during strage but VC much mre than G. Mderate t severe VC ccurred in fruit frm the last harvest date (May). Grve t grve and year t year variability in VC and G was bserved. In-fruit seed germinatin appeared t be assciated with SD. SD and in-fruit seed germinatin were significantly psitively crre lated each year with 50% f the variatin in seed germina tin accunted fr by SD. Grapefruit prductin is a majr part f the citrus in dustry in Flrida. Grapefruit harvest usually extends thrugh May when physilgical disrders ften ccur. These disrders result in quality reductin f fruit at har vest r pstharvest. In previus studies, at least 2 distinct vesicle disrder types (granulatin [G] and dehydratin disrders [dry juice sac and cre dryness]) have been re- 161

2 prted in ranges (4, 5, 9). Granulatin begins with har dening f the affected vesicle fllwed by gradual cllapse f the inner cells. An empty crystalline-like cavity results. In cntrast, the dehydratin disrders begin with slight shrinkage fllwed by cmplete cllapse f the affected vesicles due t the lss f the tissue fluids. Affected vesicles are mre difficult t separate frm adjacent healthy vesi cles. Dry juice sac and cre dryness ccur primarily in stylar-end and central prtins f the fruit, respectively. Cl lapsed vesicles (VC) in grapefruit exhibit n hardening symptms and eventually shrink t paper thin wafers, but it is nt knwn whether VC in grapefruit ccurs by the same mechanism as dry juice sac and cre dryness in ranges. In this study, the term, "sectin drying (SD)," which was prpsed in a previus reprt (2), is used t describe vesicle disrders f grapefruit inclusively. In-fruit seed germinatin, ften fund in SD grape fruit, is als a serius prblem in late harvest fruit. Even the leading 'seedless' cultivars usually cntain viable seeds which will germinate late in the seasn. Grapefruit cntain ing spruted seeds are nt desirable fr fresh market r prcessing due t the presence f ff-flavrs (1). Seed ger minatin ften ccurs in late seasn fruit and becmes se vere during strage r transit (3, 15). Because citrus seed has n distinct drmancy requirement, seeds can germi nate in the fruit after the fruit is mature (12), but nly limited studies f this phenmenn have been cnducted E23 VC Marsh VC + G Seedless Ruby Red In this study, we examined the extent f SD (VC and G) and in-fruit seed germinatin in late seasn grapefruit under Indian River, FL cnditins. Materials and Methds Fur grves f each f 2 grapefruit cultivars ('Marsh Seedless' and 'Ruby Red', Citrus paradisi Macf.) were selected in the Indian River area. Sixty fruit were har vested mnthly frm each f the same 3 trees (March thrugh May) during 3 successive years ( ). alf f the fruit frm each tree were examined immediately. The remaining fruit were examined after 40 days strage at 21 C. Befre strage, fruit were washed, treated with a 600 ppm benmyl [methyl-(butyl-carbamyl)-2-benzimidazle-carbamate] nn-recvery spray, dried, and waxed with slvent wax. Fruit were examined fr SD n 3 cut surfaces perpen dicular t the cre axis: stem-end (apprximately 1/3 ttal distance frm the stem), center (equatrial), and stylar-end (2/3 distance frm the stem-end). Severity f disrders was recrded frm the range 0 (n appearance) t 3 (mre than 2/3 f cut surface). Types f SD were recrded in 1987 and 1988, nly. Vesicles appearing hardened and having an empty cavity due t central juice cell cllapse were identified as G. VC vesicles were cllapsed and shriveled and did nt exhibit a hardening stage. After examinatin f SD, seeds were extracted and germinating seeds were cunted. Seeds with split seed cat were cnsid ered t be germinating. Seed extracted frm 'Marsh Seedless' fruit in Nvember were tested fr germinatin at 30 C with and withut seed cats. Sme seeds were treated with 4 x l(h5 M abscisic acid (ABA) and a furth treatment f scred seed cats was included. (0 Results and Discussin I I 5- at I 5^ I 30- fa The primary vesicle disrder in bth grapefruit cul tivars was VC (Fig. 1). In freshly harvested fruit, there was an increase in bth VC and G as the seasn prgressed. The variatin between harvest dates was significant, but the levels f each SD disrder were less than 10% f the fruit (Table 1). VC was slightly higher than G in 'Marsh Seedless' at the April harvest, and the disrders were slightly higher in 'Marsh Seedless' than 'Ruby Red' but usu ally nt significantly. After strage, the incidence f VC Table 1. Analysis f variance fr several factrs affecting sectin drying (SD) f grapefruit harvested frm Indian River grves, Flrida.2 Surce df F (bserved) (required) 0 Mar Apr May Mar Apr May Year (Y) Grve (G) Date () Strage (S) Time Fig. 1. Occurence f vesicle cllapse (VC), granulatin (G), r bth in 'Marsh Seedless' and 'Ruby Red' grapefruit. Results are frm the pled data f 1987 and Tp: at harvest, Bttm: after strage fr 40 days at 21 C. Different letters within a cultivar at harvest r stred indicate difference by Duncan's multiple test (p = 0.05). 162 Interactin GX GXS YX GXXS zanalysis was carried ut frm the pled data f 3 years ( ) and 2 grapefruit cultivars ('Marsh Seedless' and 'Ruby Red'). Prc. Fla. State rt. Sc. 101: 1988.

3 became much greater than G in bth cultivars. In ranges and mandarins, G can ccur in the early seasn r even in immature fruit (7). Grapefruit were rarely affected by VC in the early seasn (prir t these harvest dates), whereas G still ccurred in sme vesicles just beneath the peel tissue f the stem- r stylar-ends (data nt shwn). VC in grape fruit shwed similar symptms t stylar-end granulatin (dry juice sac) and cre dryness in ranges reprted by Barthlmew et al. (5) and Nrt (14). Vesicle cllapse began with disclratin fllwed by gradual shrinkage and cmplete cllapse at final stages. Whether r nt all these dehydratin disrders ccur under the same cndi tin^) has nt been studied. Dry juice sac in 'Valencia' ranges was prpsed t be assciated with excessive water lss. wever, in grapefruit, individual fruit wrapping with plylefin film, which greatly reduces water lss, did nt prevent r reduce SD (3). The fact that VC in grape fruit ccurs nly in the late seasn and increases during pstharvest strage suggests a relatinship between VC and fruit senescence. SD in grapefruit can ccur in any part f the fruit (Fig. 2). The amunt f SD between the fruit prtins differed smewhat in the 2 cultivars. In 'Marsh Seedless' at harvest, the stem-end was significantly mre affected except in March; in stred fruit, the stem- and stylar-ends were nearly equal and tended t have mre SD than the central prtin. In 'Ruby Red', the stem-end was slightly mre.8 15 affected by the May harvest, and after strage the stylar- 5- Marsh J Stem-end I Stylar-end I Center Seedless Ruby Red end tended t have the highest amunt f SD, significantly greater in May. The central prtin tended t be least af fected at harvest and after strage in bth cultivars, but was never significantly lwer than bth the stem- and sty lar-ends. Significant differences in SD develpment ccurred with harvest date, crp year, grve, and strage treatment (Table 1). SD differed significantly between harvest dates, but this was primarily due t SD differences after strage rather than at harvest (Fig. 1). The average f SD f bth cultivars (8 grves) in 1987 was 5.5% at harvest and 27.0% in stred fruit (the lwest SD year) whereas SD values in 1986 and 1988 were 8.4 and 6.6% at harvest, and 40.6 and 50.1% in stred fruit, respectively. Grve 2 and 8 shwed distinct differences in SD develpment during the experi ment (Fig. 3). In general, Grve 2 was least affected by SD whereas grve 8 was mst affected. SD values in fruit frm ther grves were intermediate and nt cnsistent frm year t year. Varius factrs ptentially cntributing t G have been reprted. These include crp lad, lcatin f grve, fruit size, rtstck, cultivar, cultural practices, and climate (4, 5,9). Little is knwn abut the ptential factrs respnsible fr VC and ther dehydrating disrders. Variability be tween grves and years suggests that SD f grapefruit may be influenced by varius factrs such as envirnment, cul tural practice, and fruit age. Nrt (14) reprted that ves icle disrders (granulatin, dry juice sac, and cre dryness) increased after relatively warm winters. e suggested that mderate temperatures during the winter perid might allw the tree t resume grwth earlier than is bserved fllwing cld winters, thus, fruit wuld be mre senescent at the same harvest date. wever, during this experi ment, there was n distinct difference between average minimum temperatures during the winter perids (8) be fre blm in the experimental area; n great differences in minimum average temperature during the winter perids f fruit maturatin were fund either. wever, the variatin in SD between years was great. Further studies are required t find ptential factrs, which lead t SD in grapefruit G2 I I V77X Stred G8 0) 60- i Mar Apr May Mar Apr May Q CO *WA Time Fig. 2. Severity f sectin drying (SD) in different fruit prtins f 'Marsh Seedless' and 'Ruby Red' grapefruit. Results are frm the pled data f Tp: at harvest, Bttm: after strage fr 40 days at 21 C. Different letters within a cultivar at harvest r after strage indicate difference by Duncan's multiple test (p = 0.05). Prc. Fla. State rt. Sc. 101: Year Fig. 3. Variatin in percentage f fruit with sectin drying (SD) ver 3 years fr grve number 2 (G2) with least SD and grve number 8 (G8) with mst SD ver 3 year perid, respectively. 163

4 Table 2. In-fruit seed germinatin2 in 'Marsh Seedless' and 'Ruby Red' grapefruit (percentage f fruit) harvested n 3 late seasn dates in 1986, 1987, and Table 3. Effect f seed cat and abscisic acid n grapefruit seed germina tin.2 date Year Germinatin (%)y Treatment 2 weeks 4 weeks March April s 0.1 ax 19.8c 5.1ab 38.7d 0.1a 10.0b 0.4a 13.4b b 0.6a 8.3b Intact seed cat Intact seed cat + ABAX Scred seed cat 27.2 ± ± ± ± ± 1.5 May s 8.9b 40.0d 2.8a 30.6c 1.4a 18.8c N seed cat 96.6 ± ± 0.0 Average S "Results are frm the pled data f 2 cultivars and 4 grves. Numbers are the average f fruit cntaining germinating seeds with 8 replicatins frm the pled data (1 rep./grve). y = at harvest, S = after strage fr 40 days at 21 C. xdifferent letters in a clumn indicate significant difference by Duncan's multiple test (p = 0.05). Average in-fruit seed germinatin data fr bth cul tivars cmbined in 1986, 1987, and 1988 are summarized in Table 2. Little germinatin was evident at harvest even in May but levels increased significantly during strage. Fruit with germinating seeds were 3 times higher in 1986 than in the lwest year, Washable inhibitrs in the seed cat r embry dr mancy were prpsed t be invlved with seed germinatin in citrus since watersaking, cld strage, and gibberellic acid treatment enhanced germinatin in range seed (6, 12). In grapefruit, it appeared that even as early as Nvember, neither inhibitrs nr embry drmancy were invlved in seed germinatin (Table 3, ref. 15). Seeds ger minated readily and did nearly as well with the seed cats present as lng as they were scred t allw rapid water uptake. Intact seed cats seem t be assciated with retard ing germinatin thrugh mechanical resistance by the uter seed cat (testa) r impermeability f the inner seed cat. Germinatin was delayed by the intact seed cat but essentially all f the seeds germinated (Table 3). Treatment with ABA delayed germinatin and nly 60% f the seed germinated in Nvember harvested seed. These data seem t supprt Purvis and Albrig's (15) suggestin that infruit seed germinatin during the nrmal harvest seasn f Flrida grapefruit nly requires warm temperature and misture, prbably frm juice leaked frm the vesicles. Juice is nrmally cmpletely separated frm the seed be cause it is stred in the inner cells f juice vesicles which are enclsed by a waxy cuticle (10, 16). This lead us t examine the crrelatin between SD (primarily VC) and in-fruit seed germinatin. A very significant crrelatin was fund between SD and in-fruit seed germinatin dur ing the experimental perid althugh variatin in the amunt f seed germinatin existed between years (Fig. 4). The regressin slpes were nearly identical in 1986 and 1987; therefre, fr these years, nly 1986 is represented (Fig. 4A). The slpe f the relatinship in 1988 was nly ne-furth f the 1986, 1987 values, but apprximately 50% f the ttal variatin in in-fruit seed germinatin was still crrelated t SD (Fig. 4B). The intercepts in all 3 years were nt significantly different frm a zer intercept. 164 zseeds were islated frm 'Marsh Seedless' grapefruit harvested in Nv ynumbers are the average f 4 replicatins ± SE (50 seeds/ replica tin). XABA (4 x 5 M) was added t the germinating medium f sterile water. 80 Injectin f sterile water int late-seasn fruit stimu lated seed germinatin (data nt shwn) indicating that free water is sufficient t stimulate seed germinatin in these late-seasn fruit. In-fruit seed germinatin was lw est in 1988 (Table 2) while SD was high (50%) and cmpar able t 1987 (44%). This indicates that in-fruit seed germi natin is prbably influenced by ther factrs besides avail- 60- E O LL C rr.56 y-0.97x f 4.09 r= 0.49 yi 0.27x Ttal Severity (X I 00 ) Fig. 4. Relatinship between severity f sectin drying (SD) and infruit seed germinatin in grapefruit. Results are frm the pled data f 2 cultivars in 1986 and Ttal severity is the sum f severity frm 3 cut surfaces (XI00). Prc. Fla. State rt. Sc. 101: 1988.

5 able free water frm SD. These might include the water ptential gradient between juice and seed and the acidity f the juice. Even thugh previus wrk demnstrated n effect n germinatin f juice versus distilled water when applied as the germinating medium (15), the ttal sluble slids (TSS) and acids may be assciated with in-fruit seed germinatin. Fruit prduced in cntained lw TSS and acid (11) and in-fruit seed germinatin was high est. Lw seed germinatin ccurred in 1988 while brix and acid levels in the juice were high (11). Mbayen and Milthrpe (13) reprted that citrus seed germinatin was de layed in high salt medium. If in-fruit seed germinatin in grapefruit depends n leaked juice frm SD, it is prbable that water mvement frm juice t seeds is mre favrable when juice cntains lw TSS and acid because a greater water ptential gradient ccurs. Acids and TSS f juice frm SD vesicles were lwer than frm nrmal vesicles (data nt shwn), hwever, n infrmatin is available abut critical levels f water ptential t allw water mve ment frm juice t seed and subsequently seed germina tin. It is suggested that further studies shuld evaluate seasnal and grve changes in water ptential gradient be tween juice cmpnents f healthy and disrdered vesicles and the seeds and any influence this has n seed germina tin. Literature Cited 1. Albrig, L. G. and R. D. Carter Structure f citrus fruits in relatin t prcessing. Citrus Science and Technlgy. Vl. 1. S. Nagy, P. E. Shaw, and M. K. Veldhuis (eds.). p The AVI Publishing C. Inc., Westprt, CT. 2. Albrig, L. G., K. Kawada, P. W. ale, J. J. Smt, and T. T. attn, Jr Effect f harvest date and preharvest and pstharvest treat ments n Flrida grapefruit cnditin in exprt t Japan. Prc. Fla. State rt. Sc. 93: Albrig, L. G., M. A. Ismail, P. W. ale, and T. T. attn, Jr Shipment and strage f Flrida grapefruit using unipack film bar riers. Prc. Int. Sc Citriculture p Awasthi, R. D. and J. P. Nauriyal Studies n granulatin in sweet range (Citrus sinensis Osbeck). II. Effect f age, tree cnditin, tree aspect, fruit size, rtstck and tree variatin n granulatin. J. Res. 10(10: Barthlmew, E. T., W. B. Sinclair, and F. M. Turrell Granu latin f 'Valencia' ranges. Calif. Univ. Agr. Expt. Sta. Bull Burger, D. W. and W. P. ackett Influence f lw tempera ture and gibberellic acid treatment n the germinatin f 'Valencia' range seed. rtscience 17(5):8O1-8O3. 7. Chakrawar, V. R. and R. Singh Studies n citrus granulatin. I. Physical and quality aspects f granulatin. aryana J. rt. Sci. 6: Climatlgical Data, Annual Summary, Flrida, 1985, 86, 87, 88. U.S. Dept. f Cmmerce, Envirnmental Data Service. 9. El-Zeftawi, B. M Factrs affecting granulatin and quality f late-picked 'Valencia, ranges. J. rt. Sci. 53: Fahn, A., I. Shmer, and I. Ben-Gera Occurrence and struc ture f epicuticular wax n the juice vesicles f citrus fruit. Ann. Bt. 38: Flrida Department f Agriculture & Cnsumer Services, Divisin f Fruit and Vegetable Inspectin. 1986, 87, and , , and seasn Annual Reprt, Winter aven, Flrida. 12. Mbayen, R. G Germinatin f trifliate range in relatin t fruit develpment, strage and drying. J. rt. Sci. 55: Mbayen, R. G. and F. L. Milthrpe Citrus seed germinatin as influenced by water ptential and salinity. Prc. Int. Sc. Citricul ture 2: Nrt, G. V Dryness in navel fruit. Prc. 1st Int. Citrus Symp. 3: Purvis, A. C. and L. G. Albrig Seasnal and temperature effects n seed germinatin in stred grapefruit. Prc. Fla. State rt. Sc. 97: Schneider, The anatmy f citrus, pp In The Citrus Industry. Vl. II. W. Reuther, L. D. Batchelr, and. J. Webber (eds.). Univ. Calif. Div. Agr. Sci. Prc. Fla. State rt. Sc. 101: AN APPROAC TO BETTER DESIGN OF PRESSURE-COOLED PRODUCE CONTAINERS Michael T. Talbt University f Flrida, IF AS Agricultural Engineering Department Gainesville, Flrida Additinal index wrds, air cling, airflw, heat transfer, mdeling. Abstract. T determine a better methd fr design f the vent lcatins f pressure-cled prduce cntainers, a cmmercial finite element mdel was used t determine the pressure and velcity fields fr air flw thrugh a three-dimensinal range cartn using prus media flw analysis. An existing heat transfer mdel incrprating the calculated pressure and vel city data was mdified and used t calculate the cling respnse fr ranges packed in an experimental shipping cn tainer with six different vent arrangements. The calculated cling respnse was cmpared t the experimental cling respnse t evaluate the feasibility f prus media flw thery fr the finite bundary cnditin f air flw thrugh fresh prduce packed in cntainers. Althugh several areas Flrida Agricultural Experiment Statins Jurnal Series Number Prc. Fla. State rt. Sc. 101: fr imprvement were nted, the prus media flw analysis was fund t prvide valuable infrmatin if variable prs ity within the range cartn was cnsidered. Temperature is the mst imprtant envirnmental fac tr that influences the deteriratin rate f harvested cm mdities. Thus imprved cling f fruits and vegetables befre r during shipment, alng with prper temperature maintenance thrughut the marketing channels, has the ptential f greatly reducing these lsses. Pressure- (frced-air) cling is a ppular precling methd develped by Guillu (7) extensively used n cm mdities which are highly perishable r susceptible t water-brne decay rganisms. When applied fr cling f prducts in fiberbard cntainers, air is frced int and thrugh the vented cntainers stacked and placed in the air circulatin system. The air flws thrugh the vents n the side f the cntainers expsed t the fan utlet, thrugh the spaces between the prducts, ut the side f the cntainers expsed t the fan utlet, and then back t the fan. Althugh pressure cling is a fairly rapid, efficient, and ecnmical methd f cling f prduce in cntain- 165