Carbon Translocation in the Tomato: Pathways of Carbon Metabolism in the Fruit-

The rate of carbon import by tomato fruits has been relatedto their carbon metabolism by examining the effects of fruittemperature on the metabolism of imported assimilates. ¹⁴C–sucrose,–glucose, –fructose, –malic acid and –citricacid were injected individually into young growing tomato fruitswhich were subsequently maintained at 25 or 5 °C for 48h. Fruit temperature greatly affected the proportions of ¹⁴Clost from the fruits by export and respiration. Only 40 percent of the injected ¹⁴C from ¹⁴C–sugars and 20 per centfrom ¹⁴C–acids was recovered from fruits at 25 °C.Less than 10 per cent of the injected ¹⁴C was exported, thebalance being respired. In contrast, more than 50 per cent ofthe injected ¹⁴C was recovered from cooled fruits, in whichthe import rate of carbon was presumably reduced, and 20–36per cent of injected ¹⁴C was exported. Cooling enhanced thesynthesis of ¹⁴C–sucrose from injected ¹⁴C–hexosesand inhibited the incorporation of ¹⁴C into starch and insolubleresidue. When ¹⁴C–sugars were injected, radioactivityexported from the cooled fruits was detected as sucrose in thephloem of the peduncles; radioactivity was also detected instems and roots when fruits were cooled. In almost fully–grownfruits injected ¹⁴C–compounds were metabolized less readilythan in smaller fruits. Conversion of ¹⁴C–hexoses to ¹⁴C–sucrosewas again enhanced by cooling (5 °C, but was less in fruitsmaintained at 35 °C than in controls. Lycopersicon esculentum, tomato, fruit, translocation, carbon metabolism     

The Tomato Fruit: Import, Growth, Respiration and Carbon Metabolism at Different Fruit Sizes and Temperatures

Measurements of a complete carbon balance sheet over a 48 hperiod for growing tomato fruits at different fruit sizes andtemperature have been carried out. The rates of carbon import,respiration, and growth have been calculated and related toeach other and to the levels of certain carbon metabolites inthe fruit. It was found that there is an excellent linear relationshipbetween the import rate and the sucrose level in the fruit,consistent with the hypothesis that, for the tomato fruit, carbonflows down the sucrose concentration gradient at a rate proportionalto the gradient. This agrees with the findings of Mason andMaskell in cotton. Moreover, the resistance to transport wasrelatively independent of fruit size and temperature. The usualanalysis of respiration in terms of growth and maintenance componentsallowed the determination of conversion efficiencies and maintenancecoefficients for different fruit sizes and temperatures. Asobserved by other authors with other plants, the growth conversionefficiencies were temperature-independent, whereas the maintenancecoefficients were strongly temperature-dependent. The overallconversion efficiency was optimum at 25°C. The specificgrowth rate and the starch level in the tomato fruit were foundto be related.     

Carbon Translocation in the Tomato: Effects of Fruit Temperature on Carbon Metabolism and the Rate of Translocation

The effects of fruit temperature on the rate of carbon translocationand on the contents of the major carbon metabolites in the experimentalfruits were investigated. Carbon import, which was inverselyproportional to fruit size, was inhibited by fruit cooling (5°Cand enhanced by fruit warming (35°C) when compared withcontrols (25°C); furthermore, there was net export of carbonfrom the largest cooled fruits. The carbon translocation rateswere related both to the rates of accumulation or depletionof starch and insoluble residue and to the concentration ofsucrose in the fruit. The possible dependence of the rate oftranslocation on a gradient of sucrose concentration betweensource and sink is discussed.     

Effect of Heat Stress on Assimilate Metabolism in Tomato Flower Buds

Assimilate import by flower buds in two cultivars of tomato(Lycopersicon esculentum Mill.) was inhibited by heat stress.With increasing temperature, levels of sucrose in the sourceorgan increased while levels of starch decreased. The transportof radioactive carbon was correlated with the starch contentof the flower buds. In Saladette, a heat-tolerant cultivar,conversion of the imported carbon to starch occurred to a greaterextent than in Roma VF, a heat-sensitive cultivar. Uptake ofsucrose from agar medium by detached flower buds was negativelycorrelated with their internal ratio of sucrose to hexoses.Glucose uptake from agar medium by detached flower buds decreasedwith increasing temperatures. Sucrose hydrolysis was negativelyaffected by high temperatures, and this was more pronouncedin the heat-sensitive than in the heat-tolerant cultivar. Theeffect of heat stress on assimilate translocation from the leavesto the sink organ is discussed. Lycopersicon esculentum Mill., starch, sucrose, heat stress     

Carbon Translocation in the Tomato: Carbon Import and Fruit Growth

The rates of carbon import by fruits were measured over 48 has the sum of the change in the total organic carbon contentof the fruit and the respiratory loss of carbon. Over a rangeof fruit sizes from 20–90 per cent of the maximum volumethe smaller fruits imported carbon at an absolute rate (mgCfruit^–1 h^–1) nearly twice that of the larger fruits.The imported leaf assimilates, identified as the ¹⁴C-compoundsalong the pathway between a ¹⁴CO₂-fed leaf and a young fruit,comprised 90 per cent sucrose and 10 per cent glutamic acid,aspartic acid and malic acid. Within the fruit the imported¹⁴C-sucrose was hydrolysed into hexoses. The changes in thelevels of starch and insoluble residue in the fruit were positivelycorrelated with the carbon import rates. In the largest fruitswith the lowest import rates, there was breakdown of insolubleresidue and less accumulation of starch, but a significant increasein the level of sucrose. The sink strength of a tomato fruitis dependent more on sink activity than on sink size.     

Regulation of Assimilate Translocation Between Leaves and Fruits in the Tomato

Simultaneous measurement of export from leaves and import tofruits were made on tomato plants reduced to one fully expandedleaf and one fruit. Experimental leaves were exposed to sixlight flux densities (0.5–100 W m^–2) for 24 h whilerapidly growing fruits were kept in the dark at 22 °C. The rates of export of assimilate from these leaves varied from70 to 120 mg C leaf^–1 day^–1 corresponding with ratesof carbon fixation from 3 to 290 mg C leaf^–1 day^–1.Export from leaves with the lowest carbon fixation rates weremaintained by a loss of up to one-sixth of their initial carbon.In contrast, leaves with the highest carbon fixation rates exportedonly half the newly fixed carbon. The rates of import of assimilate to similar-sized fruits (c.16 cm³) were between 80 and 110 mg C fr^–1 day^–1but differed from the export rates of the source leaves. Thespecific growth rates and the specific respiration rates ofthe fruits were related to their initial carbon content at thebeginning of the experiment. Thus, over 24 h, the rate of importwas predetermined by the developmental stage of the fruit unalteredby the rate of current carbon fixation in the source leaf. Translocationof assimilate was regulated by sink demand under both source-and sink-limiting conditions in this short-term situation. The dynamic relationship between assimilate production in leavesand its utilization in fruits is discussed together with therole of sucrose concentration in these organs in regulatingtransport. Lycopersicon esculentumL, tomato assimilate translocation, source-sink relationships     

Possible Mechanism of the Detached Unripe Green Tomato Fruit Turning Red

In general, a mature green tomato will ripen and turn red on the vine or off the vine. Interestingly, an unripe green (UG) tomato also will turn red after being detached from the plant, but the mechanism behind this is unclear. Our study showed that detached UG fruits were able to become red-ripened at the room temperature (25?°C), although fruit quality was lower than that of the vine-ripened fruit. In addition, detached UG fruits exposed to light accumulated more lycopene and total soluble sugars than those incubated in darkness. When the detached UG fruits were stored at a low temperature (10?°C), the fruit-ripening process was nearly blocked, which displayed a non-ripening phenotype. At a high temperature (35?°C), the detached UG fruit showed a yellow-color on ripening, and fruit qualities such as lycopene and soluble sugars were obviously lower than those stored at 25?°C. Moreover, detaching the UG fruit from the plant evoked a rapid increase in total respiration as well as alternative pathway respiration, but ethylene production was not stimulated during the first 24 h of storage. Importantly, the application of nPG, an inhibitor of alternative pathway respiration, markedly suppressed the wound-induced rise in total respiration and delayed the ripening of detached UG fruit. These findings imply that wound-induced respiration might be a signature for launching the onset of the ripening of detached UG fruit, and the optimal conditions of light and temperature are beneficial for the color change and the ripening processes.     

Partitioning of [14C]sucrose and Acid Invertase Activity in Reproductive Organs of Pepper Plants in Relation to Their Abscission Under Heat Stress

The effect of heat stress on processes related to carbohydratepartitioning was investigated in young bell pepper (Capsicumannum L. cv. Maor) plants in relation to abscission of theirreproductive organs at different stages of development. None of the reproductive organs abscised after 5 d in a normalday/night temperature regime (25/18 °C). With a temperatureregime of 35 °C day, 25 °C night, abscission occurredin only a small portion of the flower buds and none of the flowersand fruitlets. However, when temperatures in the day and nightwere reversed (25/35 °C, day/night) all the buds and someof the flowers abscised during that time period. The young fruitat the first node did not abscise under any temperature regime.The abscission rate of the flower buds was reduced under heatstress if the developing fruit at the first node had been removed. High temperature during either the light or dark periods reducedthe export of [¹⁴C]sucrose from the source leaf (fed for 48h with [¹⁴C]sucrose). Both heat stress and fruit presence reduced the relative amountof [¹⁴C]sucrose which was exported to the flower buds, flowersand roots. Likewise, these treatments reduced the concentrationof reducing sugars in the reproductive organs. Concomitantly,the heat stress and fruit presence on the first node reducedthe activity of soluble acid invertase in the flower buds andthe roots, but not in young leaves. Overall, the results show that heat stress causes alternationin sucrose distribution in the plant, but may also have specificeffects on metabolic activities related to sucrose import andutilization in flower buds and flowers which in turn may enhancetheir abscission. Bell pepper, (Capsicum annuum L. cv. Maor), abscission, acid invertase, heat stress, reproductive organs, sink leaves     

Partitioning of [14C]sucrose and Acid Invertase Activity in Reproductive Organs of Pepper Plants in Relation to Their Abscission Under Heat Stress

The effect of heat stress on processes related to carbohydratepartitioning was investigated in young bell pepper (Capsicumannum L. cv. Maor) plants in relation to abscission of theirreproductive organs at different stages of development. None of the reproductive organs abscised after 5 d in a normalday/night temperature regime (25/18°C). With a temperatureregime of 35°C day, 25°C night, abscission occurredin only a small portion of the flower buds and none of the flowersand fruitlets. However, when temperatures in the day and nightwere reversed (25/35°C, day/night) all the buds and someof the flowers abscised during that time period. The young fruitat the first node did not abscise under any temperature regime.The abscission rate of the flower buds was reduced under heatstress if the developing fruit at the first node had been removed. High temperature during either the light or dark periods reducedthe export of [¹⁴C]sucrose from the source leaf (fed for 48h with [¹⁴C]sucrose). Both heat stress and fruit presence reduced the relative amountof [¹⁴C]sucrose which was exported to the flower buds, flowersand roots. Likewise, these treatments reduced the concentrationof reducing sugars in the reproductive organs. Concomitantly,the heat stress and fruit presence on the first node reducedthe activity of soluble acid invertase in the flower buds andthe roots, but not in young leaves. Overall, the results show that heat stress causes alternationin sucrose distribution in the plant, but may also have specificeffects on metabolic activities related to sucrose import andutilization in flower buds and flowers which in turn may enhancetheir abscission. Bell pepper, (Capsicum annuum L. cv. Maor), abscission, acidinvertase, heat stress, reproductive organs, sink leaves. Bell pepper, (Capsicum annuum L. cv. Maor), abscission, acid invertase, heat stress, reproductive organs, sink leaves.     

Effect of Temperature on the Growth and Development of Tomato Fruits

Tomato fruits ripened 95, 65, 46 and 42 d after flower openingwhen plants were grown under controlled environmental conditionsat 14, 18, 22 and 26 °C, respectively. A similar responseto temperature was observed when the temperature of individualtrusses was modified while the plants were grown at 20 °C.These data were used to develop a thermal time model for fruitmaturation. However, when buds/fruits were heated at differentstages in their development, the thermal time model proved tobe a poor predictor of the time of ripening. Fruits were moresensitive to elevated temperature in their later stages of maturation.Temperature also affected the rates of fruit growth in volume;these could be adequately described using a Gompertz function.Low temperatures reduced absolute volume growth rates and delayedthe time at which the absolute growth rate became maximal. However,the response of fruit growth to temperature differed when onlythe temperature of the fruits was modified. There was a tendencytowards small parthenocarpic fruits at both high (26 °C)and low (14 °C) temperature regimes which, combined withlow flower numbers and poor fruit set at 26 °C, resultedin low fruit yields. Temperature also affected the shoot drymatter content and partitioning. Copyright 2001 Annals of BotanyCompany Tomato, Lycopersicon esculentum, fruit, growth, ripening, temperature, temperature stress, parthenocarpy     

High external sucrose concentration inhibits the expansion of detached tomato fruits grown in a novel semi-open device

The effect of sap sucrose concentration on fruit expansion is poorly understood. We investigated the effects of sucrose concentration on growth of tomato fruits, detached from the plant after the cell multiplication phase. A semi-open device was built to grow detached fruits, where the fruit pedicel was immersed in a nutrient solution which was automatically replaced each day. About 22 d after anthesis, tomato fruits were harvested, disinfected in alcohol, and placed in the device with a sterile nutrient solution containing 5% sucrose. After about 1 wk, the sucrose concentration was either increased to 15% or maintained at 5%. The fruit expansion rate decreased when the sucrose concentration was increased, and after about 1 wk, these fruits weighed less than those grown at 5% sucrose. Although all the fruits in the device grew much less than those maintained on the plant, a high sap sucrose concentration applied to the excised fruits after the cell multiplication phase inhibited the expansion of tomato fruits. The device and method developed here will be useful for future studies of fruit growth.     

The Effect of Low Temperature upon Starch, Sucrose and Fructan Synthesis in Leaves

Measurements on plants in a temperature gradient tunnel showthat diurnal accumulation of starch in illuminated leaves wasgreatly reduced at temperatures below 8 °C, whereas sucrosesynthesis was less affected under similar conditions. High chillingsensitivity for leaf starch accumulation was observed in a numberof chilling resistant temperate species. Enzymes of sucroseand fructan metabolism from mature leaves of Lolium temulentumwere less strongly inhibited at low temperatures than enzymesinvolved in starch synthesis. These results are discussed inrelation to carbon partitioning in species which grow and aremetabolically active at chilling temperatures. Lolium temulentum, starch, sucrose, fructan, temperature, enzyme activity, carbon partitioning     

Fruit Position and Fruit Set Sequence in a Truss as Factors Determining Final Size of Tomato Fruits

The position of fruits in a truss and the induction sequenceof fruit set has been examined for the effects on the finalsize of parthenocarpic fruits in tomato. Fruits at two developmentalstages were examined to measure the change of d. wt and theimport of ¹⁴C leaf assimilates. The sequence of induction largely determined the import rateinto fruits of the same truss and first-induced fruits are thereforelarger within the same truss. The position of fruits in thetruss modifies the extent of this ‘primigen dominance’effect. Possible mechanisms for this dominance phenomenon arediscussed. Position, set sequence, size, fruit, Lycopersicon esculentum Mill     

The Effect of Fruit Load, Defoliation and Night Temperature on the Morphology of Pepper Flowers and on Fruit Shape

The shape and regularity of bell pepper (Capsicum annuumL.)fruit are known to be determined at a very early stage of flowerdevelopment. Small, flattened fruit which are commonly parthenocarpicdevelop under low-temperatures (below 16 °C) from flowerswith enlarged ovaries. In such flowers self-pollination is notefficient because of the large distance between the stigma andstamens. Flower deformation of this kind is common during thewinter season. In the present study it was found that deformationsof flowers, similar to those found under low temperatures, wereinduced in 15 d by complete removal of fruit from plants growingunder night-time temperatures of 18 °C. Only flowers whichwere at the pre-anthesis stage at the time of fruit removalwere deformed by this treatment. Removal of leaves from thelower part of the plant (source leaves) partially reduced theeffect of fruit removal on the shape of the flowers and on subsequentfruit morphology. Fruit removal induced significant increasesin the concentrations of starch and reducing sugars, but notsucrose, in the flower buds. Likewise, flower buds of plantswhich grew under a night-time temperature of 12 °C containedmore carbohydrate than those which grew at 18 °C. Theseresults suggest that flower morphology in pepper is at leastpartly controlled by source-sink relationships. Assimilateswhich are normally transferred to developing fruit may be transported,upon fruit removal, to the flower buds which subsequently swell.A similar increase in assimilate translocation to flower budsmay occur under low temperatures, subsequently causing deformationof fruit.Copyright 1999 Annals of Botany Company Pepper, (Capsicum annuumL), flower shape, low temperatures, source-sink relationship, fruit shape, seeds, reducing sugars, sucrose, starch.     

Effects of Temperature, Light, Nutrients and Carbon Dioxide on the Strength of the Self-Incompatibility Response in Detached Flowers of Lycopersicon peruvianum

The effects of temperature, light, nutrients and CO₂on the gametophyticself-incompatibility response in a clone of Lycopersicon peruvianumhave been quantified using fluorescence microscopy of stylesquashes prepared from detached flowers held under experimentalconditions for 48 h after self pollination. Self-incompatibilitywas significantly weakened by raising the temperature from 15°C to 22 or 25°C, and by incubating flowers withoutan energy source - i.e. in the dark and/or without externallysupplied sucrose. The sucrose effect was not duplicated by equimolarmannitol or a full mineral nutrient solution plus vitamins.CO₂ applied at 5% in air for 8 h after pollination had no detectableeffect on pollen tube arrest. Observed weakening effects werenot sufficient for use in production of selfed seed. They indicate,however, that self-incompatibility in this clone of L. peruvianumis a temperature-sensitive, energy-dependent process, and supportthe oppositional model of self-incompatibility in which incompatiblepollen tubes are actively inhibited. Lycopersicon, Solanaceae, carbon dioxide, light, nutrients, self-incompatibility, temperature     

Sporulation in Rhizopus sexualis and Some Other Fungi Following a Period of Intense Respiration

Rhizopus sexualis grown at 20° C. on liquid I per cent.malt or glucose-asparagine medium showed a peak of respiratoryactivity between 40 and 55 hours-after inoculation. Rate ofrespiration then fell until it reached a steady low level whichcoincided with maximum mycelial growth. Zygospore initiationoccurred at or just after the peak of respiration. At a low temperature (9° C.) or with high concentrationsof glucose the respiration peak was less marked and no zygosporesdeveloped. Single ‘plus’ or ‘minus’strains of the heterothallic species Mucor hiemalis and Phycomycesblakesleeanus showed a pattern of respiration and mycelial growthsimilar to that of R. sexualis but no zygospores were formed.Zygospores did not develop without a preliminary period of intenserespiration, but such a peak period could occur without beingfollowed by zygospore formation. A strain of Sordaria fimicola was grown at 25° C. on a syntheticmedium with 5.0 per cent. sucrose or glucose as source of carbon.Respiration reached a peak at approximately 4 and 5 days respectively,the actual peak value being twice as large on sucrose as onglucose. Dry weight of mycelium was greater on glucose thanon sucrose. Perithecia were formed only on the sucrose medium.Visible peri-thecial initials were first seen shortly afterthe occurrence of the respiratory peak. Mature perithecia werepresent 3 days later. The possible significance of these results is discussed.     

Sucrose Synthase in Wild Tomato, Lycopersicon chmielewskii, and Tomato Fruit Sink Strength

Here it is reported that sucrose synthase can be readily measured in growing wild tomato fruits (Lycopersicon chmielewskii) when suitable methods are adopted during fruit extraction. The enzyme also was present in fruit pericarp tissues, in seeds, and in flowers. To check for novel characteristics, the wild tomato fruit sucrose synthase was purified, by (NH₄)₂SO₄ fraction and chromatography with DE-32, Sephadex G-200, and PBA-60, to one major band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The following characteristics were obtained: native protein relative molecular weight 380,000; subunit relative molecular weight 89,000; K_m values with: sucrose 53 millimolar, UDP 18.9 micromolar, UDP-glucose 88 micromolar, fructose 8.4 millimolar; pH optima between 6.2 to 7.3 for sucrose breakdown and 7 to 9 for synthesis; and temperature optima near 50°C. The enzyme exhibited a high affinity and a preference for uridylates. The enzyme showed more sensitivity to divalent cations in the synthesis of sucrose than in its breakdown. Sink strength in tomato fruits also was investigated in regard to sucrose breakdown enzyme activities versus fruit weight gain. Sucrose synthase activity was consistently related to increases in fruit weight (sink strength) in both wild and commercial tomatoes. Acid and neutral invertases were not, because the published invertase activity values were too variable for quantitative analyses regarding the roles of invertases in tomato fruit development. In rapidly growing fruits of both wild and commercially developed tomato plants, the activity of sucrose synthase per growing fruit, i.e. sucrose synthase peak activity X fruit size, was linearly related to final fruit size; and the activity exceeded fruit growth and carbon import rates by at least 10-fold. In mature, nongrowing fruits, sucrose synthase activities approached nil values. Therefore, sucrose synthase can serve as an indicator of sink strength in growing tomato fruits.     

Diurnal Patterns of Transport and Accumulation of Minerals in Fruiting Plants of Lupinus angustifolius L.

Fluctuations in mineral elements id xylem (tracheal) sap, fruitphloem sap, leaflets and dmloping fruits were studied in a fieldpopulation of Lupinus angustifolius L. by three-hourly samplingover a 39 h period. Elements usually reached maximum contentsor concentrations at or near noon, minimum levels during thenight. Amplitudes of diurnal fluctuations in minerals lay withinthe range ±4–33 per cent of the mean content ofleaflets, and ±17–157 per cent of the mean concentrationsin xylem and phloem sap. Most minerals elements fluctuatcd inphase with daily changes in sugar level of phloem sap and drymatter and carbohydrate fluctuations of leaflets, suggestinga coupling of translocation of photosynthate and minerals fromthe leaflets. Rates of import of minerals by shoots wereestimatedfrom shoot transpiration and mineral concentrations in trachealsap. Average day time rates of import of most elements were12–25 times those at night. Translocation of minerals,nitrogen and carbon to fruits also exhibited diurnal periodicity,average rates of import king three to seven times higher inthe day than at night. A model of transport based on the carbonand water economy of the fruit suggested that P, K, Fe, Zn,Mn and Cu were imported predominantly by phloem. Estimates ofvascular import accounted for 87–104 per cent of the fruit'sactual increment of these elements. Na and Ca were gauged tobe imported mainly by xylem, Mg almost equally by xylem andphloem. However, large discrepancies existed for these threeelements between estimated vascular import and actual intakeby the fruit. Lupinus angustifolius L., mineral transport, accumulation, fruits, xylem sap, phloem sap, transpiration     

RNA Metabolism During Breakage of Seed Dormancy by Low Temperature Treatment of Fruits of Acer plataanoides(Norway Maple)

Stratification of Acer platanoides fruits at 4 °C led toan accumulation of RNA in the embryo axis and to breakage ofseed dormancy. The accumulated RNA was mainly rRNA. Storageof fruits at 17 °C led neither to an accumulation of RNAnor to breakage of dormancy. The proportion of embryo axis mRNA,as measured by poly(A) content, decreased during both fruitstorage and stratification, although levels of poly(A) wereconsistently lower in embryo axes from stored seeds. Isolatedembryos from both stored and stratified fruits were capableof incorporating [³H]uridine into embryo axis RNA. When assayedat 17–20 °C, however, this incorporation was significantlylower in embryos of stored fruits. The distribution of radioactivitybetween the different RNA species was similar in both storedand statified seeds. Acer platanoides, Norway Maple, dormancy, fruit, seed, ribonucleic acid, stratification, nucleic acid metabolism     

Factors Affecting Calcium Transport and Basipetal IAA Movement in Tomato Fruit in Relation to Blossom-end Rot

Factors affecting the uptake and distribution of calcium (Ca)by detached tomato (Lycopersicon esculentum Mill.) fruit wereinvestigated in seven cultivars with different susceptibilitiesto blossom-end rot (BER), a physiological disorder caused byCa deficiency. Plants were grown with different levels of salinityin the root zone or under shade to induce BER. In addition,fruit grown at different salinities were treated with CME, aninhibitor of auxin transport to alter IAA movement. The basipetalmovement of indole-3-acetic acid (IAA) out of detached fruit(i.e. IAA efflux) was determined concurrently with ⁴⁵Ca uptaketo assess the possible involvement of IAA in Ca import or theincidence of BER. High salinity in the root zone during fruitdevelopment decreased both the uptake and distribution of ⁴³Cato the blossom-end of the detached fruit. Shading and the applicationof CME reduced ⁴⁵Ca uptake to a lesser extent. IAA efflux, however,was not consistently reduced by these treatments. Neither theuptake and transport of ⁴⁵Ca within, nor the efflux of IAA from,detached fruit was related to the cultivar susceptibility toBER. The proposed role of IAA on the uptake and distributionof Ca by tomato fruit is assessed. Key words: Tomato, calcium, IAA, blossom-end rot, salinity