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At least 19 recordsLinked to original sources

Mycotoxins in fruits, fruit juices, and dried fruits.

This review gives an overview of the presence of mycotoxins in fruits. Although several mycotoxins occur in nature, very few (aflatoxins, ochratoxin A, patulin, Alternaria toxins) are regularly found in fruits. It has been shown that the presence of fungi on fruits is not necessarily associated with mycotoxin contamination. The formation of mycotoxins depends more on endogenous and environmental factors than fungal growth does. Mycotoxins may remain in fruits even when the fungal mycelium has been removed. Depending on the fruit and the mycotoxin, the diffusion of mycotoxins into the sound tissues of fruits may occur. The influence of the selection and storage of fruits and the influence of different processing steps involved in the production of fruit juices and dried fruits on possible mycotoxin contamination is described. It is shown that the careful selection, washing, and sorting of fruits is the most important factor in the reduction of mycotoxin contamination during the production of fruit juices. The processing of fruits does not result in the complete removal of mycotoxins.

Aflatoxins↗

Antisense inhibition of tomato fruit sucrose synthase decreases fruit setting and the sucrose unloading capacity of young fruit.

The role of sucrose synthase (SuSy) in tomato fruit was studied in transgenic tomato (Lycopersicon esculentum) plants expressing an antisense fragment of fruit-specific SuSy RNA (TOMSSF) under the control of the cauliflower mosaic virus 35S promoter. Constitutive expression of the antisense RNA markedly inhibited SuSy activity in flowers and fruit pericarp tissues. However, inhibition was only slight in the endosperm and was undetectable in the embryo, shoot, petiole, and leaf tissues. The activity of sucrose phosphate synthase decreased in parallel with that of SuSy, but acid invertase activity did not increase in response to the reduced SuSy activity. The only effect on the carbohydrate content of young fruit was a slight reduction in starch accumulation. The in vitro sucrose import capacity of fruits was not reduced by SuSy inhibition at 23 days after anthesis, and the rate of starch synthesized from the imported sucrose was not lessened even when SuSy activity was decreased by 98%. However, the sucrose unloading capacity of 7-day-old fruit was substantially decreased in lines with low SuSy activity. In addition, the SuSy antisense fruit from the first week of flowering had a slower growth rate. A reduced fruit set, leading to markedly less fruit per plant at maturity, was observed for the plants with the least SuSy activity. These results suggest that SuSy participates in the control of sucrose import capacity of young tomato fruit, which is a determinant for fruit set and development.

Caulimovirus↗

Radiation preservation of foods of plant origin. Part V. Temperate fruits: pome fruits, stone fruits, and berries.

The current status of research on the application of ionizing radiation for improving the storage of temperate fruits, i.e., apple, pear, peach, nectarine, apricot, cherry, plum, strawberry, bilberry, cranberry, raspberry, and black currant, is reviewed. Changes in fruit metabolism, chemical composition, texture, and organoleptic quality attributes are discussed with reference to the irradiation dose. The feasibility of using radiation either alone or in conjunction with heat treatment, refrigeration, and controlled atmospheres (CA) for the control of storage decay caused by fungal pathogens is considered. Areas of further research are suggested before irradiation could be considered for practical application in some of these temperate fruits. The recent trends in the possible use of irradiation for disinfestation of certain pome and stone fruits and the prospects for the commercial utilization of irradiation for improving the market life of strawberries are discussed.

Carbohydrate Metabolism↗

[Occurrence of nitrates and nitrites in certain frozen fruits, jams, stewed fruit and fruit-vegetable juices for children and in certain types of bee honey].

Nitrates and nitrites were evaluated spectrophotometrically by the method of Griess reaction, with previous reduction of nitrates to nitrites in a column filled with cadmium dust. The content of nitrates in frozen fruit (strawberries, black and red currant and plums) ranged from 2.50 to 57.38 mg KNO3/kg, with the highest content in garden strawberries. In cherry, strawberry, black and red currant jams the concentrations were from 6.30 to 97.38 mg KNO3/kg, the highest content was in cherry jam. In plum jam nitrates were found in low amounts from 11.65 to 12.09 mg/kg. In "Bobofrut" juices the nitrate content was higher than in the above products, ranging from 26.37 to 182.75 mg KNO3/kg. Nitrite content in all these groups of products was low, not exceeding 1 mg NaNO2/kg, with the exception of plum jam where the maximal value was found 1.65 mg NaNO2/kg. In stewed fruit and herb syrups and in honey nitrates ranged from 1.0 to 94.5 mg KNO3/kg. Nitrite content ranged from 0.17 to 1.92 mg/kg in herb syrups, from 0.0 to 1.20 mg/kg in stewed fruit, and from 0.0 to 0.40 mg NaNO2/kg in honey. The study showed that higher levels of nitrates were present as a rule in vegetable juices. However, the found concentrations were not harmful to the health of children, although this is possible in the case of carrot juice, especially when kept at room temperature for 24 hours.

Child↗

Influence of branch autonomy on fruit, scaffold, trunk and root growth during stage III of peach fruit development.

We studied the influence of branch autonomy on the growth of reproductive and vegetative organs by establishing different patterns of fruit distribution within and between large branch units (scaffolds) in mature peach trees (Prunus persica (L.) Batsch cv. 'Elegant Lady'). Different patterns of fruit distribution were established by defruiting either whole scaffolds (uneven fruit distribution between scaffolds; US) or several selected hangers (small fruiting branches) per tree (uneven fruit distribution between hangers; UH). The effects of these patterns were compared with the effects of an even fruit distribution treatment (EVEN) in which fruits were thinned to achieve maximum uniformity of fruit distribution within the canopy. The desired fruit loads were obtained by differentially thinning the remaining bearing parts. On a tree basis, the response of mean fruit mass to fruit load was strongly affected by fruit distribution. The steepest mean fruit mass to fruit load relationship was found in US trees, whereas the relationship in UH trees was intermediate between the US and EVEN trees. On a scaffold basis, differences in fruit size between EVEN and US trees with similar fruit loads, though statistically significant, were relatively small, indicating that scaffolds were almost totally autonomous with respect to dry matter partitioning to fruit during the final stage of peach fruit growth. Hangers also appeared to exhibit significant autonomy with respect to the distribution of dry matter during the final phase of fruit growth. Branch autonomy was evident in scaffold growth: defruited scaffolds in the US treatment grew more than fruited scaffolds, and fruit distribution treatments had little impact on scaffold cross-sectional area on a tree basis. On the other hand, as observed for fruit growth, branch autonomy did not appear to be complete because the fruited scaffolds grew more in US trees than in EVEN trees under heavy cropping conditions. However, the effect of fruit distribution occurred only over short distances, and was negligible on organs located farther away from the source of heterogeneity (fruits), such as the trunk and roots.

Fruit↗

The making of a bell pepper-shaped tomato fruit: identification of loci controlling fruit morphology in Yellow Stuffer tomato.

The heirloom tomato cultivar Yellow Stuffer produces fruit that are similar in shape and structure to fruit produced by the bell pepper varieties of garden pepper. To determine the genetic basis of this extreme fruit type in tomato, quantitative trait loci (QTL) analysis was performed on an F(2) population derived from a cross between Yellow Stuffer and the related species, Lycopersicon pimpinellifolium, which produces a small, round fruit typical of most wild species. F(2) plants were analyzed for both fruit size and the degree to which their fruit resembled the bell pepper. Three QTL were determined to influence bell pepper shape and seven QTL influenced fruit mass. The map positions of all three bell shape and six out of seven fruit size QTL appear to be allelic to components of fruit morphology analyzed in this population and to major fruit morphology QTL reported previously, adding support to the hypothesis that the majority of fruit size and shape variation in cultivated tomato is attributable to allelic variation at a limited number of loci. However, novel loci controlling components of fruit morphology, such as elongated fruit shape, bumpiness, number of seed per fruit and flowers per inflorescence were identified in this study as well. The three bell shape loci involved are: bell2.1, bell2.2 and bell8.1, and appear to correspond to locule number2.1 ( lcn2.1) and fruit weight 2.2 ( fw2.2) and fruit shape 8.1 ( fs8.1), respectively. The Yellow Stuffer alleles at lcn2.1 and fw2.2 increase locule number and fruit size, respectively, hence contributing to the overall bell pepper shape. The Yellow Stuffer allele at fs8.1 causes convex locule walls, giving the extended, bumpy shape characteristic of bell peppers. In addition, most fruit size QTL correspond to loci controlling number of flowers per inflorescence and/or stem-end blockiness. Comparisons among previously identified fruit morphology loci in tomato, eggplant and pepper suggest that loci affecting several aspects of fruit morphology may be due to pleiotrophic effects of the same, orthologous loci in these species. Moreover, it appears that the evolution of bell pepper-shaped tomato fruit may have proceeded through mutations of some of the same genes that led to bell pepper-type fruit in garden pepper.

Capsicum↗

Comparison of the nutrient content of fresh fruit juices vs commercial fruit juices.

OBJECTIVE: To compare the types and quantities of carbohydrate, electrolytes, pH and osmolarity of fresh fruit juices and commercial fruit juices. MATERIAL AND METHOD: Forty kinds of fresh fruits available in Thai markets were analyzed for types and quantities of carbohydrate, electrolyte, pH and osmolarity and compared with previously obtained data for commercial fruit juices. RESULTS: Most fresh fruit juices did not contain sucrose, whereas, commercial fruit juices mostly have sucrose in the range of 3-112 g/L. Although both fruit juices were acidic (pH varied from 3.6-6.7 and 3.2-5.8 of fresh juice and commercial juice), fresh fruit juices had a more neutral pH than commercial fruit juices. Apple, guava, orange, pear, and pineapple juices from commercial fruit juices had a high osmolarity compared with fresh fruit juices. All types of fresh fruit juices contained less sodium than commercial ones, whereas, most fresh fruit juices contained more potassium, phosphorus, and magnesium than commercial fluids. CONCLUSION: The nutrient content of fresh fruit juices and commercial fruit juices from the same kinds of fruits are not the same, possibly due to the manufacturing process. Therefore, physicians should know the composition of fruit juices in order to advise patients properly.

Beverages↗

Early Application of Ethrel Extends Tomato Fruit Cell Division and Increases Fruit Size and Yield with Ripening Delay.

Flowers of tomato (Lycopersicon esculentum Mill.) plants cv. Castle Rock were sprayed with 100 ppm of ethrel, 0.5 mm aminooxyacetic acid (AOA), or water (control) 2 days after anthesis. The fruit period of cell division was extended up to 16-18 days after anthesis with the application of ethrel but reduced from 10-12 days (control) down to only 6-8 days with the application of AOA. In a trend opposite to AOA application, fruits that received ethrel treatment were of higher ethylene and 1-aminocyclopropane-1-carboxylic acid (ACC) levels than control. This was noticed not only during the first 2 weeks after anthesis but also during the fruit climacteric phase. Mesocarp cells of ethrel-treated fruits were greater in number/mm(2) but smaller in size than control; an opposite trend was obtained with the application of AOA. This was observed for a period of 18 days after anthesis, but by that time or at earlier ages, fruits of AOA treatment were larger in size and heavier in weight than control, and both were larger and heavier than ethrel-treated ones. At 5 weeks after anthesis and thereafter, the fruit response to all treatments was totally reversed because early ethrel-treated fruits became significantly larger in size and heavier in weight with a ripening delay of about 10 and 15 days compared with those of control and AOA-treated ones, respectively. When the same treatments were applied to the whole plant, similar results were obtained because the early application of ethrel increased the fruit yield by about 15% over control with a pronounced ripening delay; an opposite trend was obtained with the application of AOA. No significant differences were found among all treatments in terms of flower or fruit abscission or fruit number/plant. The data suggest that ethylene regulates tomato fruit transmission from cell division to cell enlargement. In addition, fruit cell division is terminated only when endogenous ethylene decreases to its basal level, allowing cell enlargement to dominate and proceed as in the case of the early application of AOA. The ripening delay of ethrel-treated fruits may be caused by the longer time required for the increased cell number to reach maturation. A low level of ethrel application at the tomato early fruiting stage may be used for increasing fruit yield by increasing fruit size and consequently its quality.Key Words. Tomato-Ethrel-AOA-Cell division-Cell enlargement-Ethylene-ACC-Ripeninghttp://link.springer-ny.com/link/service/journals/00344/bibs/18n1p15.html

Journal Article↗

Relationship between tomato fruit growth and fruit osmotic potential under salinity.

To investigate the relationship between fruit growth and fruit osmotic potential (Psi(s)) in salty conditions, a sensitive tomato cultivar (Lycopersicon esculentum Mill.) and a tolerant accession of the wild species Lycopersicon pimpinellifolium Mill. were grown in a greenhouse with 0 and 70 mM NaCl, and the growth of the fruit studied from 15 to 70 days after anthesis (DAA). L. pimpinellifolium did not reduce significantly fruit weight in salty conditions throughout the growth period, whereas L. esculentum fruit weights decreased significantly with salinity from 45 DAA. L. esculentum fruit fresh weight reductions resulted from both less dry matter and water accumulation, although the fruit water content was affected by salinity before the fruit weight. In both species, fruit osmotic potential (Psi(s)) decreased significantly with salinity during the rapid fruit growth phase, although the changes were different. Thus, fruits from L. pimpinellifolium salt treated plants showed a Psi(s) reduction at the beginning (15 DAA) twice as high as that found in L. esculentum. As the advanced growth stage (from 15 to 55 DAA), the Psi(s) reduction percentages induced by salinity were quite similar in L. pimpinellifolium fruits, while increased in L. esculentum. Under saline conditions, the solutes contributing to reduce the fruit Psi(s) during the first 55 DAA were the inorganic solutes in both species, while in the ripe fruits they were hexoses. L. esculentum fruits accumulated K(+) as the main osmoticum in salty conditions, while L. pimpinellifolium fruits were able to use not only K(+) but also the Na(+) provided by the salt.

Journal Article↗

Studies on water transport through the sweet cherry fruit surface: III. Conductance of the cuticle in relation to fruit size.

Rain-cracking of sweet cherry fruit has been related to water absorption through the fruit surface and large fruit has been reported to be more susceptible to cracking than small fruit. Therefore, the effect of fruit size on water conductance of the cuticular membrane (CM) of exocarp segments excised from cheek, suture or stylar end region of mature sweet cherry fruit (Prunus avium L. cv. Sam) was investigated. Segments consisting of epidermis, hypodermis and several layers of mesocarp cells were mounted in diffusion cells filled with deionized water. Mass loss due to transpiration was monitored gravimetrically during an 8-h incubation period (25 +/- 2 degrees C) over dry silica in the dark. Conductance was calculated from the amount of water transpired per unit surface area and time divided by the difference in water vapour concentration across the segment. For an average size cv. Sam sweet cherry CM conductance was 1.06 x 10-4, 0.91 x 10-4 and 2.09 x 10-4 m s-1 in cheek, suture and stylar end region, respectively. Fruit size had no significant effect on conductance in cheek or suture regions, but for the stylar end region conductance was positively related to fruit size. Stomatal density in the cheek, but not the suture or stylar end region increased as fruit size increased. The area of the stylar scar was positively related to fruit size. Conductance of the stylar scar averaged 37.6 +/- 4.0 x 10-4 m s-1 and was 54-fold higher than that of the CM between stomata in the cheek region (mean 0.69 x 10-4 m s-1). Conductance calculated on a whole fruit basis is estimated to increase by 108% as fruit size increases from 6 to 12 g. Increased conductance on a whole fruit basis may be attributed to increased fruit surface area and increased conductance per unit fruit surface area, particularly in the stylar end region.

Journal Article↗

Variation in surface conductance to water vapor diffusion in peach fruit and its effects on fruit growth assessed by a simulation model.

Surface conductance to water vapor diffusion was measured in individual peach fruits (Prunus persica (L.) Batsch) and plotted as a function of fresh fruit mass for four cultivars. Surface conductance increased with fresh fruit mass, but the pattern differed with cultivar, and fruit-to-fruit variation occurred. Relationships between fruit mass and surface conductance were modeled by fitting mathematical equations to the data. The simulation model of Fishman and Génard (1998) was used to study dry mass and water components of fruit growth (1) when surface conductance varied with fruit size or was constant, and (2) when surface conductance values were high, moderate or low with respect to fruit mass. Increased surface conductance with fresh fruit mass resulted in fruit growth cessation. Fruits differing in surface conductance had similar dry mass. However, under well-watered conditions (stem water potential between -1 and -0.2 MPa), the water balance components of growth (osmotic and hydrostatic pressure, water potential and water balance) differed greatly and, as a result, the lower the surface conductance the greater the fresh fruit mass. These differences were buffered under drought conditions (stem water potential between -2.4 and -0.6 MPa).

Fruit↗

Ethylene biosynthesis in detached young persimmon fruit is initiated in calyx and modulated by water loss from the fruit.

Persimmon (Diospyros kaki Thunb.) fruit are usually classified as climacteric fruit; however, unlike typical climacteric fruits, persimmon fruit exhibit a unique characteristic in that the younger the stage of fruit detached, the greater the level of ethylene produced. To investigate ethylene induction mechanisms in detached young persimmon fruit, we cloned three cDNAs encoding 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (DK-ACS1, 2, and -3) and two encoding ACC oxidase (DK-ACO1 and -2) genes involved in ethylene biosynthesis, and we analyzed their expression in various fruit tissues. Ethylene production was induced within a few days of detachment in all fruit tissues tested, accompanied by temporally and spatially coordinated expression of all the DK-ACS and DK-ACO genes. In all tissues except the calyx, treatment with 1-methylcyclopropene, an inhibitor of ethylene action, suppressed ethylene production and ethylene biosynthesis-related gene expression. In the calyx, one ACC synthase gene (DK-ACS2) exhibited increased mRNA accumulation accompanied by a large quantity of ethylene production, and treatment of the fruit with 1-methylcyclopropene did not prevent either the accumulation of DK-ACS2 transcripts or ethylene induction. Furthermore, the alleviation of water loss from the fruit significantly delayed the onset of ethylene production and the expression of DK-ACS2 in the calyx. These results indicate that ethylene biosynthesis in detached young persimmon fruit is initially induced in calyx and is modulated by water loss through transcriptional activation of DK-ACS2. The ethylene produced in the calyx subsequently diffuses to other fruit tissues and acts as a secondary signal that stimulates autocatalytic ethylene biosynthesis in these tissues, leading to a burst of ethylene production.

Amino Acid Oxidoreductases↗

fw2.2 directly affects the size of developing tomato fruit, with secondary effects on fruit number and photosynthate distribution.

fw2.2 is a quantitative trait locus responsible for approximately 30% of the difference in fruit size between large, domesticated tomatoes (Lycopersicon esculentum Mill.) and their small-fruited wild relatives. The gene underlying this quantitative trait locus was cloned recently and shown to be associated with altered cell division in ovaries (Frary et al., 2000). However, it was not known whether the change in fruit size is associated with other changes in plant morphology or overall fruit yield-changes that could potentially cause the fruit weight phenotype. To shed light on this issue, a detailed comparison was made between nearly isogenic lines differing for alleles at this locus to search for pleiotropic effects associated with fw2.2. Field observations show that although the small-fruited nearly isogenic line produced smaller ovaries and fruit as expected, this was compensated by a larger number of fruit-due mainly to a significantly greater number of inflorescences-but with no net change in total fruit mass yield. This strongly suggests that fw2.2 may have a pleiotropic effect on how the plant distributes photosynthate among fruit. In a flower removal experiment to control for differences in inflorescence size and number, fruit size remained significantly different between the nearly isogenic lines. These observations indicate that the primary effect of fw2.2 is in controlling ovary and fruit size, and that other associated phenotypic effects are secondary.

Alleles↗

Beta-carotene content of postharvest orange-fleshed muskmelon fruit: effect of cultivar, growing location and fruit size.

The influence of two growing locations (soil types), six fruit sizes, and two years on the postharvest Beta-carotene content of muskmelon (Cucumis melo L. var. reticulatus Naud.) fruit was studied with two different cultivars. Fully abscised commercial size fruit: 9, 12, 15, 18, 23, and 30 (fruit/0.04 M3 shipping box) had highly variable Beta-carotene contents (5.3 to 33.8 micrograms/g fresh weight) that varied by size class, soil type and cultivar. Beta-carotene content increased with fruit size up to a maximum, though fruit size continued to increase. Find sandy loam soil produced fruit with less Beta-carotene content than silty clay loam soil. The cultivar Primo contained higher Beta-carotene content levels than cultivar Cruiser. Mesocarp percent moisture content for both 'Cruiser' and 'Primo' at both locations by fruit size was not significantly correlated (r = 0.40) with Beta-carotene content. Indicating fruit cell dilution may not contribute to the differences in Beta-carotene content in different fruit size classes. Beta-carotene content of size class '18' fruit from six cultivars grown on the silty clay loam soil for two consecutive years, showed a year, and year by cultivar effect for some cultivars. Whereas, some cultivars did not differ in Beta-carotene content between the two years. This indicates a potential for controlling Beta-carotene content of muskmelon fruit at a constant, high level by careful selection of production cultivar.

Crops, Agricultural↗

A fruit-specific phospho enolpyruvate carboxylase is related to rapid growth of tomato fruit.

Malic and citric acids accumulate in cherry tomato (Lycopersicon esculentum Mill.) fruit during the period of rapid growth, from the end of cell division to the onset of ripening. The involvement of phospho enolpyruvate carboxylase (PEPCase, EC 4.1.1.31) in organic acid accumulation and tomato fruit development was investigated. Two PEPCases, named LYCes;Ppc1 and LYCes;Ppc2 and mapped to chromosomes 12 and 7, respectively, were shown to be differentially expressed during tomato fruit development. LYCes;Ppc1 mRNA was present in all fruit tissues and in all other plant organs examined. In contrast, LYCes;Ppc2 was strongly and specifically expressed in fruit from the end of cell division to ripening. No LYCes;Ppc2 expression was detected by northern blot in other plant tissues. In fruit, the increase in LYCes;Ppc2 mRNA was closely followed by an increase in fruit PEPCase protein and activity, and was coincident with the increased accumulation of malate and citrate during the initial period of rapid growth rate, from 8 to 20 days post anthesis. Localization of LYCes;Ppc2 mRNA in young tomato fruit by in situ hybridization revealed that LYCes;Ppc2 is preferentially expressed in large cells of the pericarp and in enlarging cells of the gel surrounding the seeds. Examination of the kinetic and regulatory properties of the PEPCases of growing and ripening fruit further showed that PEPCase in growing fruit is less sensitive to low pH and malate inhibition, indicating a high phosphorylation state and/or the presence of a PEPCase isoform with these characteristics. Taken together, these results indicate that in developing tomato fruit PEPCase is probably important in permitting the synthesis of organic acids to provide the turgor pressure necessary for cell expansion.

Chromosome Mapping↗

Socioeconomic differences in the consumption of vegetables, fruit and fruit juices. The influence of psychosocial factors.

BACKGROUND: The aim was to investigate whether social network and social support factors can explain socioeconomic differences in the risk of consuming low amounts of vegetables, fruit and fruit juices. METHODS: The Malmö Diet and Cancer Study was a prospective cohort study. The present cross-sectional study examined data from a subpopulation of 11,837 individuals that completed baseline examinations in 1992-1994. Dietary habits were assessed using a modified diet history method, and socioeconomic and social network factors were measured with a structured questionnaire. Low consumption was defined as the lowest consumption quartile for vegetables and fruit, while fruit juice consumption was dichotomized to separate users from non-users. RESULTS: Socioeconomic differences were most pronounced regarding the consumption of vegetables and fruit juices. For both sexes, unskilled manual workers had a twice as high risk of low vegetable and fruit juice consumption as higher non-manual employees. No socioeconomic differences in fruit consumption were observed for men, and only moderate differences for women with a higher consumption in higher socioeconomic groups. When the psychosocial variables were introduced in the multivariate model, social participation moderately reduced the socioeconomic differences in vegetable consumption, and the female socioeconomic differences in fruit consumption, but had no effect on the socioeconomic differences in fruit juice consumption. The other psychosocial variables had no effect on the socioeconomic differences. CONCLUSION: Considerable socioeconomic differences in vegetable, fruit and fruit juice consumption were observed. Social participation seemed to be a strong determinant for these food choices. However, this effect was largely independent of the socioeconomic differences.

Beverages↗

Partial purification of tomato fruit peroxidase and its effect on the mechanical properties of tomato fruit skin.

Peroxidase (EC 1.11.1.7)-mediated stiffening of cell walls within the fruit skin of tomato is hypothesized to regulate fruit growth. However, to date, there is no experimental evidence demonstrating that peroxidase affects the mechanical properties of skin tissue. Here, the mechanical properties of skin strips excised from a range of fruits at different ages were determined using an 'Instron' universal material testing instrument. The stiffness of tomato fruit skin strips increases 3-fold with increasing fruit age. Application of partially-purified peroxidase from the cell walls of mature tomato fruit skin significantly increased the stiffness of fruit skin irrespective of the age of fruit. Furthermore, the application of hydrogen peroxide significantly increased the stiffness of skin strips excised from fruit of an age when endogenous peroxidase isozymes associated with the termination of growth are first detected. The results support the hypothesis that the tomato fruit skin plays an integral role in the regulation of tomato fruit growth, and that changes in its mechanical properties may be mediated by peroxidase. As far as is known, this is the first demonstration that peroxidases alter the mechanical properties of the plant cell wall.

Electrophoresis, Polyacrylamide Gel↗