Mutant dn Influences Dry Matter Distribution, Assimilate Partitioning and Flowering in Lathyrus odoratus L.

The flowering mutant dn in sweet pea was used as a tool to study¹⁴C-assimilate and dry matter partitioning with respect to nutrientdiversion theories on the control of flower initiation. Wildtype plants (Dn^h) are photoperiodic and exhibit late floweringand profuse basal branching in short days while mutant plants(dn) are day neutral, early flowering and devoid of basal laterals.In short days, dn plants exported a significantly greater proportionof assimilate acropetally than (Dn^h) plants and the upper portionof dn plants had a greater dry weight. These differences werereduced dramatically when basal laterals were excised regularlyfrom the (Dn^h) plants although the difference in flowering remained.However, the effect of dn on resource allocation within theapical region may be more important in regard to flowering thanthe effect on acropetal versus basipetal movement. In shortdays, the dn plants partitioned significantly more resourcesinto their internodes and petioles, and less into their leaflets,than Dn^h plants as shown by dry weight and ¹⁴C-assimilate measurements.These differences were apparent from as early as node 7 up tothe node of flower initiation in dn plants (node 30) and theywere not eliminated by removal of basal laterals from Dn^h plants.Differences between dn and Dn^h plants in partitioning and floweringwere largely eliminated under long days. The fact that in thisspecies a single gene influences both resource allocation andflower initiation lends further support to nutrient diversionhypotheses on the control of flowering. Key words: Assimilate partitioning, branching, flowering, mutant, sweet pea     

Dependence of out-crossing indices on genotypic features in common wheat

The out-crossing indices (out-crossing rate, rate of plants on which out-crossing had occurred, and out-crossing intensity) in F₂ plants of soft winter wheat derived from the reciprocal crossing B-16 × Odesskaya Krasnokolosaya are analyzed using storage proteins as genetic markers. The out-crossing index is substantially dependent on the growing conditions. The out-crossing rate in a reciprocal population amounted to 0.35% (Odessa, 2000) and 5.11% (Kiev, 2004). The greatest out-crossing indices are observed in homozygotes for the presence of the rye 1BL/1RS translocation. The value of the out-crossing index in heterozygotes for the presence of this translocation is intermediate. Differences in the out-crossing index between plant populations derived from direct and reciprocal crossings are found. The multidirectionality of these differences with respect to out-crossing rate and the percentage of plants with out-crossing, on the one hand, and the out-crossing intensity, on the other hand, is noted.     

Dependence of cross-pollination indices on genotype characteristics of winter common wheat

Out-crossing indices (the out-rcrossing rate, the frequency of plants with cross-pollination and outcrossing intensity) in F2 plants of winter common wheat from the reciprocal cross B-16 x Odesskaya Krasnokolosaya were analysed using storage proteins as genetic markers. Outcrossing indices greatly differed depending on growth conditions. The out-crossing rate was 0,35 % (Odessa, 2000) and 5,11% (Kyiv, 2004). The highest out-crossing indices were detected in homozygotes for the presence of the rye 1BL/1RS translocation. The out-crossing indices in heterozygotes for the presence of the 1BL/1RS translocation were intermediate. Differences in the out-crossing indices were detected between populations of F2 plants derived from direct and reciprocal crossing. Different directions of these differences were noted for the out-rcrossing rate and the frequency of plants with cross-pollination, on the one hand, and out-crossing intensity, on the other hand.     

INFLUENCE OF THE QUINOLIZIDINE ALKALOID CONTENT OF LUPINUS ALBUS (FABACEAE) ON THE FEEDING CHOICE OF HELIX ASPERSA (GASTROPODA: PULMONATA)

Adult Helix aspersa snails were maintained individually forone week in plastic cages with 9 living Lupinus albus plantsas their only food. Among these 9 plants, 3 chemotypes bitter,intermediate and sweet which differed in their alkaloid contentwere equally represented. Each day, the leaf surface grazed and the number of leaves attackedby the snails were recorded for each chemotype and each snail.A consumption/ attack (C/A) ratio was calculated by dividing thesurface grazed (C) by the number of attacks (A). The numberof attacks and the grazed area were positively correlated foreach chemotype during the whole experiment, and the snails atesimilar quantities of lupin each day. After 4 and 6 days ofexperiment, we noticed a rejection of the bitter chemotype infavor of the intermediate and sweet ones respectively. Afterthe 6th day, the surface grazed per attack was significantlyhigher on the sweet chemotype than on the bitter plants. Wehypothesize that rejection of the bitter chemotype might berelated to (i) an alkaloids reaction threshold associated withan increase in the amount of alkaloids in the wounded plantsand/or (ii) aversive ingestive conditioning. (Received ; accepted 16 April 1999)     

Effects of Film Mulch and Soil Pesticides on Nematodes,Weeds, and Yields of Vegetable Crops

Field plots in Tifton loamy sand were treated with various soil pesticides in 1973 and 1974 and either left exposed or covered with biodegradable flint mulch. Test crops were cantaloup, slicing and pickling cucumber, squash, and sweet corn. Overhead sprinkler irrigation was used in 1973, and trickle irrigation under the film mulch was used on sweet corn in 1974. Soil was assayed for nematodes, and roots of plants were evaluated for damage by root-knot nematodes. Nematode populations were reduced by soil treatment with an organic phosphate or carbamate nematicide-herbicide-fungicide combination (NHF), DD-MENCS, methyl bromide-chloropicrin (MBR-CP), ethoprop, carbofuran, and sodium azide + ethoprop or carbofuran. Sodium azide, sodium azide + ethoprop or carbofuran, ethoprop, and carbofuran were less effective than DD-MENCS, MBR-CP, attd the NHF combination. The NHF combination controlled grasses and broadteaf weeds as effectively as the herbicide alone. Growth and yield were greatest when nematodes and weeds were controlled. Yields of marketable vegetables were highest from plants in plots treated with DD-MENCS with a film mulch.     

Parthenocarpic Fruit Growth Reduces Yield Fluctuation and Blossom-end Rot in Sweet Pepper

The aim of this work was to investigate whether parthenocarpicfruit growth could avoid flushing, i.e. an irregular yield pattern,in sweet pepper. Plants were grown in a greenhouse compartmentfrom April until August. Half of the plants were grown withouta fruit set treatment (control), whereas parthenocarpic fruitswere allowed to develop on the other plants by preventing self-pollinationand applying auxin to the stigma. For node positions 3 to 17,fruit set per node varied between 21 and 55% for control plants[coefficient of variation (CV) = 11%], whereas auxin-treatedplants showed much less variation in fruit set (41–57%;CV = 5%) and average fruit set was higher. In agreement withfruit set, fruit yield was also much more regular in the auxin-treatedplants. Fruit fresh yield varied between 0.2 and 1.0 kg m^-2forcontrol plants (CV = 20%), and between 0.4 and 0.8 kg m^-2forauxin-treated plants (CV = 9%). Results showed that developingseeds in sweet pepper fruits are the main cause of the abortionof new flowers, and irregular fruit set and yield. Parthenocarpicfruit growth resulted in flatter, 30% smaller fruits, becauseof a reduction in fruit growth rate; the duration of fruit growthwas 1 week longer than for fruits from control plants. Parthenocarpicfruits were hardly affected by blossom-end rot (BER) with only1% of fruits being affected compared to 31% in the control.Total dry mass production was the same for treated and controlplants; however, in auxin-treated plants, 50% of the total drymass was allocated to the fruits, compared to 58% in controlplants. Copyright 2001 Annals of Botany Company Abortion, auxin, BER, blossom-end rot, Capsicum annuum L., flushing, fruit set, irregular yield pattern, parthenocarpy, sweet pepper     

Identification of dynamin as an interactor of rice GIGANTEA by tandem affinity purification (TAP)

GIGANTEA (GI), CONSTANS (CO) and FLOWERING LOCUS T (FT) regulatephotoperiodic flowering in Arabidopsis. In rice, OsGI, Hd1 andHd3a were identified as orthologs of GI, CO and FT, respectively,and are also important regulators of flowering. Although GIhas roles in both flowering and the circadian clock, our understandingof its biochemical functions is still limited. In this study,we purified novel OsGI-interacting proteins by using the tandemaffinity purification (TAP) method. The TAP method has beenused effectively in a number of model species to isolate proteinsthat interact with proteins of interest. However, in plants,the TAP method has been used in only a few studies, and no novelproteins have previously been isolated by this method. We generatedtransgenic rice plants and cell cultures expressing a TAP-taggedversion of OsGI. After a two-step purification procedure, theinteracting proteins were analyzed by mass spectrometry. Sevenproteins, including dynamin, were identified as OsGI-interactingproteins. The interaction of OsGI with dynamin was verifiedby co-immunoprecipitation using a myc-tagged version of OsGI.Moreover, an analysis of Arabidopsis dynamin mutants indicatedthat although the flowering times of the mutants were not differentfrom those of wild-type plants, an aerial rosette phenotypewas observed in the mutants. We also found that OsGI is presentin both the nucleus and the cytosol by Western blot analysisand by transient assays. These results indicate that the TAPmethod is effective for the isolation of novel proteins thatinteract with target proteins in plants.     

Foraging Behaviour of Wild Bees at Hot Pepper Flowers (Capsicum annuum) and its Possible Influence on Cross Pollination

Native bees are effective pollinators of hot pepper plants,Capsicum annuum. In four gardens in south-central Brazil (Patosde Minas and Brasília) flowers of three cultivars receivedvisits from 16 species of bees in eight genera: Hylaeus(Colletidae),Dialictus, Halictus, Augochlora,Augochloropsis and Ceratalictus(Halictidae),Exomalopsis andBombus (Apidae). No other insects were observedto visit the flowers. Some species of bee occurred in more thanone garden. Individual bees gathered a full pollen load from18 to 47 flowers and visited one to eight plants on a singleforaging trip. In 76 shifts between plants, the bees made nineswitches between cultivars. It is suggested that small nativespecies of bees pollinate the flowers effectively and that theirsmall foraging areas are important in keeping the cultivarsof both hot and sweet peppers genetically distinct where severalcultivars are grown close together. Copyright 2000 Annals ofBotany Company Capsicum annuum, hot pepper, native bees, fruit set, Brazil     

Gall Flies, Inquilines, and Goldenrods: A Model for Host-race Formation and Sympatric Speciation

Host shifts and subsequent host-race formation likely play amore common role in the speciation of herbivorous insects thanhas generally been recognized. Our studies of the interactionsof goldenrod host plants (Solidago: Compositae), the gall flyEurosta solidaginis (Diptera: Tephritidae), and the stem- andgall-boring Mordellistena convicta (Coleoptera: Mordellidae)provide behavioral, ecological, and genetic evidence of insecthost races that may represent incipient species formed via sympatricspeciation. Eurosta solidaginis has developed genetically differentiatedand reproductively isolated host races that are associated withthe ancestral host Solidago altissima and the derived host S.gigantea. Conventional wisdom suggests that shifts even to closelyrelated host plants are limited by host preferences or the inabilityto utilize a chemically and developmentally distinct host. However,our preliminary work with Eurosta from S. gigantea implies thathost choice and gall induction do not deter a shift to S. canadensis.The galling of Solidago by Eurosta created a new resource thathas led to a subsequent host range expansion by the stem-boringbeetle. Mordellistena convicta from stems and galls are geneticallydistinct and likely shifted from stems to galls. Beetles fromS. altissima versus S. gigantea galls exhibit assortative matingand higher preference for and/or performance on their natalhost. The present-day distributions of the Eurosta host racesand their behavioral isolating mechanisms do not suggest thatgeographic isolation was required for their formation; ratherthese characteristics suggest a sympatric mode of differentiation.Our findings lend credence to recent assertions that sympatricspeciation may be an important source of biodiversity.     

Size of the Chrysanthemum Shoot Apex in Relation to Inflorescence Initiation and Development

The size of the apical dome of Chrysanthemum morifolium Ramat.at the transition to inflorescence initiation in continuouslight (long days) was not systematically influenced by eitherthe temperature or the irradiance under which the plants weregrown. It was generally 0.26 mm in diameter and c. 3.6 x 10^–3mm³ in volume when the first bract was initiated. The dimensionsof the apical dome of plants in short days were only slightlysmaller at this stage. Similarly, each step in the further developmentof the chrysanthemum inflorescence was associated with a narrowrange of apex sizes, indicating that inflorescence initiationand development are closely related to apex size. Chrysanthemum morifolium Ramat, shoot apex, inflorescence initiation     

Foliage Profile, Size Structure and Stem Diameter-Plant Height Relationship in Crowded Plant Populations

The relationships between vertical foliage profile of an individualplant, competition between individuals, size structure and allocationpattern between stem diameter (D) and plant height (H) wereinvestigated using canopy photosynthesis and two-dimensionalcontinuity equation models including D and H as two independentvariables. Broad-leaved type plants (more foliage mass in theupper layer than in the lower layer of the canopy of an individualwhen grown in isolation) showed curvilinear D-H relationshipand bimodal H distribution, and underwent more asymmetric competitionthan coniferous type plants (more foliage mass in the lowerlayer than in the upper layer of the canopy of an individualwhen grown in isolation) under crowded conditions. Coniferoustype plants showed almost linear D-H relationship (i.e. simpleallometry) and unimodal H distribution, and underwent more symmetriccompetition than broad-leaved type plants under crowded conditions.However, in both the cases D distributions were unimodal. Allocationpatterns between D and H affected these features only a little.These simulation results can explain many actual data alreadypublished. The value of     

The Development of Alternative Storage Sink Sites in Sweet Potato Ipomoea batatas

Sweet potato plants were found to develop three alternativestorage sink sites: adventitious roots, replanted tubers andstems, indicating that the capacity for tuberization is notlimited to the root system. In each case, sink development occurredas a result of meristematic activity of the vascular cambiumand anomalous cambia associated with differentiating vascularbundles in the pith. The involvement of environmental, anatomicaland physiological parameters in the tuberization of sweet potatois discussed. Ipomoea batatas, sweet potato, tuberization, sink site     

Studies on factor(s) in sweet potato which specifically inhibits germ tube growth of incompatible isolates of Ceratocystis fimbriata

Sweet potato root contained a factor or factors which differentiallyinhibited the growth of various isolates of Ceratocystis fimbriata.The factor scarcely inhibited germ tube growth of sweet potatoisolate, compatible to sweet potato. On the other hand, thegrowth of prune, oak, taro and almond isolates, all incompatibleto sweet potato, was strongly inhibited. The germ tube growthof coffee and cacao isolates, incompatible to sweet potato,were less inhibited. Inhibitory factor was distributed throughvarious fractions when centrifuged on a sucrose density gradient.The germ tube growth of pre-germinated oak isolate became lesssensitive to the inhibitory factor after being treated withpronase, suggesting the interaction of the factor with someprotein-containing surface structure of the fungal cell. Treatmentof the factor by phospholipase c, lipase and pronase causedno changes in its inhibitory activity, whereas periodate treatmentpartially inactivated the factor. These results suggest thatthis inhibitory factor constitutes one of the factors determiningthe specificity in sweet potato-C. fimbriata interactions. (Received July 18, 1977; )     

The Effects of Competition with Agropyron repens and of Nitrogen-and Water Supply on the Nitrogen Content of Impatiens parviflora

The nitrogen contents of plants of Impatiens parviflora grownin pots with and without root competition from Agropyron repens,and with two levels of nitrogenand water-supply, were determined. The nitrogen percentage and the nitrogen content were depressedby competition and increased by nitrogen application. Wateringincreased nitrogen content and percentage in plants growingwith competition; the increased growth associated with suchwatering was approximately equivalent to the nitrogen increase.These effects were chieftly due to responses in the nitrogenabsorption rate per unit root dry-weight. Root dry-weight/totaldry-weight ratio changes were generally in the opposite direction,but were relatively small. When Net Assimilation Rate was calculated on a leaf nitrogenbasis, the effect of competition was relatively less than whenit was calculated on a leaf area basis, but the depression causedby high nitrogen status was much larger. When Net AssimilationRate calculated on a leaf area basis was compared with nitrogenper unit leaf area there was evidence of a single relationshipfor all treatments. It appeared that most of the variation inNet assimilation Rate between treatments was caused by differencesin nitrogen status.     

Topophysis affects the Potential of Axillary Bud Growth, Fresh Biomass Accumulation and Specific Fresh Weight in Single-stem Roses (Rosa hybrida L.)

Topophysis, the effect on growth and differentiation of positionof axillary buds along the shoot, was studied by propagatingfive-leaflet-leaf single-node cuttings which were excised fromseven stem positions and grown as single stemmed plants. InRosahybrida ‘Korokis’ Kiss®, ‘Tanettahn’Manhattan Blue®, and ‘Sweet Promise’ Sonia®,following release of the buds from apical dominance by excision,morphogenetic development was studied until anthesis. The timefrom excision/planting until onset of bud growth, visible flowerbud appearance, and anthesis was generally shorter in plantsoriginating from apical bud positions than from basipetal positions.Topophysis mainly affected the onset of axillary bud growth;the earliest growth and development was found in cuttings fromthe second uppermost node position. This node tended to havethe lowest plastochron value, which indicated the existenceof a transition between sylleptic and proleptic buds. Stem lengthat visible flower bud and at anthesis generally increased asthe cutting position changed basipetally until the second lowestposition, and the number of five-leaflet-leaves at anthesisand the total number of nodes generally increased basipetally.For internode length, growth rate, and fresh biomass efficiencythe cuttings taken from the uppermost and lowermost positionsgenerally had significantly lower values than cuttings fromall medial positions. At anthesis, plants originating from cuttingsexcised from lower medial positions generally had a higher freshweight, greater flower stem diameter, and a significantly higherspecific fresh weight than those plants originating from apicalor basal positions. Among the cultivars, Sonia was the mostefficient in increasing fresh biomass and had the highest growthrate, whereas Manhattan Blue possessed the highest specificfresh weight, indicating a higher plant quality. It is suggestedthat topophysis inRosa is an independent phenomenon intrinsicto the axillary bud. apical dominance; axillary bud growth; fresh biomass accumulation; cut rose; flowering; Rosaceae; Rosa hybrida L.; rose; shoot growth; single-stem roses; specific fresh weight; topophysis; quality     

Synthesis of 125I-ubiquitin conjugates in extracts of Lemna minor

Low levels of ubiquitin conjugating activity are typically detectedin the green tissues of plants, an observation that may at leastpartially explain why no method to purify multi-ubiquitinatedproteins from photosynthetic cells has been reported in theliterature. The present paper provides a contribution to improvethe available methodology for the isolation of an efficientubiquitin conjugating system from photosynthetic cells. We haveselected Lemna minor L. as a plant system and have developeda simple and rapid methodology to synthesize and purify highmolecular mass ubiquitin-protein conjugates, formed with endogenoussubstrates and exogenous ¹²⁵I-ubiquitin, using small amounts(<2g) of green tissue. It is demonstrated that L. minor possessesan ATP-dependent activity capable of forming ubiquitin conjugateswith endogen ous proteins in vitro. Anion exchange chromatographyon diethylaminoethyl-cellulose provides a simple and rapid techniqueto remove endogenous ubiquitin and to concentrate and partiallypurify the enzyme system responsible for ubiquitin conjugatingactivity. This enriched fraction has therefore been utilizedto syn thesize high molecular mass ¹²⁵I-ubiquitin conjugatesformed with L. minor proteins. These conjugates were subsequentlypurified by directly loading the reaction mixture on a SephacrylS-300 gel filtration column, with no requirement for additionalconcentration or purification steps. This methodology is highlyreproducible. Key words: Ubiquitin, ubiquitin-protein conjugates, synthesis, purification, Lemna minor     

A Further Analysis of Hybrid Vigour in Zea mays during the Vegetative Phase

Employing the procedures of growth analysis further pot experimentson hybrid vigour in Zea mysa have been conducted in a glasshouse.By serial sampling the changes in plant weight and leaf areahave been followed for six hybrids and their immediate parentsof either dent or flint type. Within 2–3 weeks from sowingthe relative growth-rate (RGR) of the hybrid was significantlygreater in four out of the six triplets and in the remainingtwo the rate for the hybrid exceeded that of one parent. Thesedifferences diminished with time but when observations ceasedat the end of 7 weeks the weight and area of the hybrid wasfrom 1.5 to 1.9 times greater than that of the larger parent.By this time too all but one of the hybrids but none of theparents were in flower. The two components of growth, the leaf-area ratio (LAR) andthe net assimilation rate (NAR) did not differentiate in a consistentmanner between the hybrid and the parents, because of the considerablevariation between emergence and flowering. All the hybrids atsome time up to 28 days had a significantly higher LAR thanthose of one or both parents. Similarly for NAR on no occasionup to 4 weeks did any parent exceed the level of the hybridbut for some hybrids and for some occasions the NAR was significantlyhigher than that of at least one of the parents. Later for bothparameters none of the differences within triplets were significant. A flint and a dent triplet were grown at constant air temperaturesof 10, 15, and 20 °C and illuminated for 14 h at 22 600lx and sampled during the vegetative phase. The results showedthat there were marked differences in the temperature responseswithin and between triplets. The flint hybrid grew faster thanits parents at 15 and 20 °C but not at 10 °C. In contrast,the superiority of the RGR of the dent hybrid was greatest at10 °C. These differences are largely reflected by changesin NAR rather than LAR. The higher NAR of the flint hybrid isfound at 15 and 20 °C, but the superiority of the dent hybridis most evident at 10 °C. The comparative performance within one triplet was examinedfor small and large grains. The patterns of change in the growthcomponents were not influenced by grain size. The interacting effects of genotype, stage of development, andtemperature level are discussed. It is concluded that in thefield the over-riding factor determining hybrid vigour is thehigher RGR in the postemergence phase and that the genetic variationover the six triplets is greater for NAR than LAR.     

Influence of Parasitism by Pilostyles ingae (Rafflesiaceae) on its Host Plant, Mimosa naguirei (Leguminosae)

Mimosa naguirei (Leguminosae) is parasitized by Pilostyles ingae(Rafflesiaceae) in the Serra do Cipó, in southeasternBrazil. The study examined the influence of this parasite onvarious parameters of M. naguirei in an attempt to establishgeneral patterns for future research. It was found that thepercentage of parasitized plants varied along an altitudinalgradient of 500 m. The parasitic plant influenced the architectureof the host plant. The number of branches on parasitized plantswas significantly greater than the number of branches on non-parasitizedplants. Branches of parasitized plants were significantly shorterthan branches on non-parasitized plants. The density of P. ingaeflowers decreased from the stem base to apex. The number offruits produced by parasitized plants was not greater than thenumber of fruits produced by non-parasitized plants, althoughparasitized plants produced smaller fruits and lighter seeds.Seed germination did not differ significantly between parasitizedand healthy plants.Copyright 1994, 1999 Academic Press Holoparasite, Leguminosae, Mimosa naguirei, plant parasitism, Pilostyles ingae, Rafflesiaceae     

Monitoring of Ultrasonic and Audible Emissions from Plants With or Without Vessels

Our studies on the occurrence, origin, and intensity of audioand ultrasonic acoustic emissions (AAE and UAE) have been extendedby examining a range of plants with contrasting anatomical characteristics.Stem samples, excised shoots, and whole plants have been monitoredfor AAE and UAE simultaneously. AAE was attenuated less, i.e. transmitted further, than UAEin plant materials generally; Distances travelled by AAE considerablyexceeded 40 mm in all species tested. UAE were transmitted upto 40 mm in Thuja, a vessel-less species, but only 10 mm ina range of other species, with, and without, vessels. The extentof attenuation seems to depend upon the properties of the woodyxylem. UAE were studied in Thuja by Dixon, Grace, and Tyree in 1984.We have extended their findings by studying both UAE and AAEfor the first time in Thuja and also Tasmannia, another vessel-lessspecies. These plants produced fewer AAE than UAE; also theirrate of AAE production was lower. Seemingly, tracheids can produceAAE: vessels are not essential for audio emissions. AAE and UAE were monitored in Ricinus, a woody plant with vessels.AAE production tended to predominate. We have shown previouslythat Ricinus petioles produce only AAE whereas stems produceboth AAE and UAE. This difference apparently hinges on the attenuationproperties of the tissues surrounding the stem-mounted probes.Such probes could detect AAE from petioles distributed overthe whole plant whereas UAE were only detectable locally. Whenexcised stem tissue was dehydrated, UAE were produced in abundance.Apparently the dual-probe technique is thus useful for locatingsites of cavitation in whole plants. By comparing AAE and UAE totals with anatomical estimates ofcavitatable units we have estimated our counting efficiency;selecting highest totals to represent optimal numbers detectedper unit volume of stem vascular tissue (calculated from diameterand length measurements). In general, AAE detection ranged from0.13% to 5.1% whereas UAE were considerably greater, rangingfrom 27% to 76% (cf. 16% for Chamaecyparis found by Sandfordand Grace, 1985). Key words: UAE, AAE, xylem vessels, cavitation     

Effects of the bitter additives naringin and sucrose octa-acetate on sweet persistence and sweet quality of neohesperidin dihydrochalcone

The maximal perceived sweet intensity (Ip_max) and the sweetpersistence constant (T) of neohesperidin dihydrochalcone (NHD),were significantly reduced in a mixture containing naringin(NAR), a bitter flavone analog of NHD Sucrose octa-acetate (SOA),another bitter stimulus, reduced the Ip_max of NHD in mixtures,but no appreciable decrease in T values was found. Linear regressionanalyses performed on the IP_max data of either NHD + NAR orNHD + SOA (logIp_max versus log concentration) produced slopevalues lower than those of NHD alone. Moreover, taste similarityexperiments revealed that the mixture of NHD + NAR was locatedfurther than NHD from the sugar area in the multi-dimensionalscaling (MDS) map. It is concluded that the reduction in Tvaluesof NHD by NAR was apparently related to the reduced Ip_max levelsand that such a mixture produces a sweet quality inferior tothat of NHD.