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We studied stem bending in cut Gerbera flowers (Gerbera jamesonii cv. Tamara). Bending might be due to turgor loss. During vase life water uptake decreased more rapidly than transpiration, hence the flowers lost water. Net water loss did not occur in the floral head, but was found in the stem. It was largest in the segment (10–15 cm below the floral head) where bending was localised. When comparing flowers that showed stem bending with those that did not, on day 7 of vase life, the fresh weight loss of 5 cm stem segments was higher in the stems that had bent. Covering the stems with a flexible, thin sleeve of polypropylene plastic reduced transpiration and increased the time to stem bending from d 7 to d 14 of vase life. Additionally, stem bending might relate to stem elongation and to stem morphology and anatomy. Stems elongated by 1–1.5 cm, in the uppermost 10 cm, during the first two days of vase life. No relationship was found between stem elongation and bending. At harvest, the stems contained a large central cavity, starting at about 5 cm from the root–shoot junction, and ending about 10 cm below the floral head. The cavity extended upwards and laterally during vase life, but no relationship was found between cavity formation and stem bending. A cylinder of sclerenchyma in the stems was found to end about 20 cm below the floral head, in summer. Bending was correlated with the extent of sclerenchyma formation and stem lignin levels. It is concluded that stem bending is due to net water loss from the stem, particularly in the area of bending, and to low mechanical strength in the upper part of the stems, which lack a sclerenchyma cylinder.

Programmed cell death (PCD) is an integral part of plant development and of responses to abiotic stress or pathogens. Although the morphology of plant PCD is, in some cases, well characterised and molecular mechanisms controlling plant PCD are beginning to emerge, there is still confusion about the classification of PCD in plants. Here we suggest a classification based on morphological criteria. According to this classification, the use of the term 'apoptosis' is not justified in plants, but at least two classes of PCD can be distinguished: vacuolar cell death and necrosis. During vacuolar cell death, the cell contents are removed by a combination of autophagy-like process and release of hydrolases from collapsed lytic vacuoles. Necrosis is characterised by early rupture of the plasma membrane, shrinkage of the protoplast and absence of vacuolar cell death features. Vacuolar cell death is common during tissue and organ formation and elimination, whereas necrosis is typically found under abiotic stress. Some examples of plant PCD cannot be ascribed to either major class and are therefore classified as separate modalities. These are PCD associated with the hypersensitive response to biotrophic pathogens, which can express features of both necrosis and vacuolar cell death, PCD in starchy cereal endosperm and during self-incompatibility. The present classification is not static, but will be subject to further revision, especially when specific biochemical pathways are better defined.

The vase life of cut tulips (Tulipa spp.) is limited by a combination of leaf yellowing, tepal senescence, and tepal abscission. In many cultivars, moreover, high rates of stem elongation result in stem bending during vase life. In tests with the cvs. Apeldoorn and Frappant, stem bending could be prevented by treatment with ethylene or ethephon. However, these treatments resulted in poor flower opening. The ethephon treatment also resulted in precocious tepal abscission. The negative effect of ethephon on flower opening was overcome by a treatment with gibberellic acid (GA3). GA3 also somewhat delayed early leaf yellowing, but did not prevent the early tepal abscission induced by ethephon. The latter problem was overcome by a treatment with benzyladenine (BA). In addition, BA effectively delayed leaf yellowing and also delayed tepal senescence. However, BA produced browning of the lower stem end. This was prevented by the inclusion of calcium ions in the solution. The combination of chemicals (ethephon, GA3, BA, and calcium ions) was similarly successful in a large number of other tulip cultivars tested. After adaptation of the concentrations the four chemicals were also effective if given as a pulse treatment shortly after harvest.

Loosening of cell walls is an important developmental process in key stages of the plant life cycle, including seed germination, elongation growth, and fruit ripening. Here, we report direct in vivo evidence for hydroxyl radical ((OH)-O-center dot)-mediated cell wall loosening during plant seed germination and seedling growth. We used electron paramagnetic resonance spectroscopy to show that (OH)-O-center dot is generated in the cell wall during radicle elongation and weakening of the endosperm of cress (Lepidium sativum; Brassicaceae) seeds. Endosperm weakening precedes radicle emergence, as demonstrated by direct biomechanical measurements. By H-3 fingerprinting, we showed that wall polysaccharides are oxidized in vivo by the developmentally regulated action of apoplastic (OH)-O-center dot in radicles and endosperm caps: the production and action of (OH)-O-center dot increased during endosperm weakening and radicle elongation and were inhibited by the germination-inhibiting hormone abscisic acid. Both effects were reversed by gibberellin. Distinct and tissue-specific target sites of (OH)-O-center dot attack on polysaccharides were evident. In vivo (OH)-O-center dot attack on cell wall polysaccharides were evident not only in germinating seeds but also in elongating maize (Zea mays; Poaceae) seedling coleoptiles. We conclude that plant cell wall loosening by (OH)-O-center dot is a controlled action of this type of reactive oxygen species.

Here we present a summary of our study on cadmium-induced cell death signaling in a model system of suspension-cultured tomato cells. Exposure of the cells to CdSO4 induced typical for PCD (cytoplasm shrinkage and nuclear condensation) morphological changes of the dead cells. Ethylene and hydrogen peroxide were established to increase in response to Cd stress. By inhibitory studies we have demonstrated that CdSO4 induces cell death in tomato suspension cells that involve plant caspase-like proteases, indicating that Cd-triggered cell death is a form of programmed cell death. It is also shown that serine peptidases, oxidative stress, lipid signaling and ethylene are players in the Cd-induced cell death signaling. Cd-induced cell death in tomato suspension cells was categorised as non-lysosomal type.

Detached tobacco leaves were infiltrated with an AT toxin preparation from the foliar pathogen Alternaria alternata tobacco pathotype. The AT toxin preparation caused formation of necrotic lesions within 5 days post-infiltration in a concentration-dependent manner. Cell death was accompanied by increased levels of the stress metabolites hydrogen peroxide, malondialdehyde, free proline and by enhanced total protease activity. Lesion development and the production of stress metabolites were suppressed if the infiltration site was pre-infiltrated with caspase-specific peptide inhibitors (irreversible caspase-1 inhibitor acyl-Tyr-Val-Ala-Asp-chloromethylketone (Ac-YVAD-CMK) and the broad range caspase inhibitor benzyoxycarbonyl-Asp-2,6-dichlorobenzoyloxymethylketone (Z-Asp-CH2-DCB)), the serine protease inhibitor N alpha-p-tosyl-L-lysine chloromethylketone and the polyamine spermine. Extensive accumulation of reactive oxygen species (ROS), as determined by staining with 3-3'-diaminobenzidine and 2',7'-dichlorofluorescein diacetate, was found in the AT toxin-challenged lesions. The data show that AT toxin-induced cell death in tobacco is a type of programmed cell death in which caspase-like proteases and ROS signalling play a prominent role.

Food intake regulation comprises numerous components from peripheral and central pathways, including sensory and cognitive elements. This study investigated if congruency in different aroma–texture combinations within a dairy product influences satiation and food consumption in humans. Among seven different aromas, vanilla was rated as congruent and lemon as incongruent aroma in the context of creamy texture, while both aromas were highly liked and familiar. Creamy custard, either vanilla- or lemon-aromatised, was given to 32 subjects in a preload – ad libitum regimen. Satiation was measured on visual analogue scales and by salivary α-amylase concentration. Finally, the amount of ad libitum intake was determined. No effects of congruency were found on ad libitum consumption and perceived satiation. Subjects felt more satiated when preload and ad libitum intakes shared the identical aroma compared to varied aromas. This was not supported by increased salivary α-amylase levels, although those increased overall with intake. In conclusion, there was no relation between congruency in aroma and texture in dairy custard and food intake, but aroma perception possibly modulates perceived satiation.

Fresh hot pepper (Capsicum annuum L.) fruit were harvested on days 15, 20 or 25 after flowering (DAF) and were stored at 5 and 10 °C. Seed browning was severe in fruit stored at 5 °C, but only if harvested at 15 DAF. Severe browning was positively correlated with visible cell damage, the rate of electrolyte leakage, initial levels of free phenolics, and levels of thiobarbituric acid (TBA) reactive compounds. Browning was related to initial higher levels of saturated fatty acids and lower levels of unsaturated fatty acids. Browning was also positively correlated with higher initial activities of polyphenol oxidase (PPO), and continuously higher activities of phenylalanine ammonia lyase (PAL), superoxide dismutase (SOD), and lipoxygenase (LOX). In contrast, browning was negatively correlated with the activities of catalase (CAT) and peroxidase (POD). The results suggest that loss of membrane integrity in young seeds is a cause of browning at low temperature, and that the higher levels of unsaturated fatty acids of older seeds might protect against chilling-induced browning. The negative correlation of browning with CAT and POD might indicate that these enzymes protect against chilling injury.

Commercial ripening of banana fruit occurs at high relative humidity (RH), which prevents browning of damaged skin areas. In experiments with ripening at high RH (94 ± 1%) the individual fruit (fingers) of ‘Sucrier’ ( Musa acuminata , AA Group) banana exhibited a high rate of drop. The falling off of the fingers is due to rupture of the peel at the pedicel. In contrast, if the fruit was held at low RH (68 ± 3%) finger drop was absent. Water-soluble pectin in the peel at the rupture area was higher at high RH, indicating increased pectin degradation. However, the activities of polygalacturonase (PG) in the peel at the rupture zone were the same in both treatments. The activity of pectinmethylesterase (PME) was only slightly higher prior to rupture in the high RH treatment, whereas, that of pectate lyase (PL) was considerably higher. The lower rate of pectin degradation at low RH may explain, at least partially, why finger drop is inhibited. The decrease in pectin degradation was not accounted for by the measured PG activity, but could be partially accounted for by the measured PME and PL activities.

Sucrier¿ bananas (Musa acuminata, AA Group) show peel spotting when the peel is just about as yellow as green, which coincides with optimum eating quality. As consumers might relate the spotting to overripe fruit, early spotting is considered undesirable, especially for export markets. Fruit were left uncoated (controls) or coated with polyethylene parafilm wax at concentrations of 20%, 25%, and 30% (v/v) and then held at 29¿30°C for 5 days. Compared with controls, each of the concentrations delayed early peel spotting. Eating quality was not affected by the 20% coating, but was negatively affected by the higher concentrations. Further tests, using 20% coating, showed that the delay of peel spotting was not associated with a change in peel total free phenolics or with polyphenol oxidase (PPO) activity, but it was accompanied by reduced in vitro phenylalanine ammonia lyase (PAL) activity. Results suggest that the delay in peel spotting, after surface coating, is a result, at least in part, of reduced PAL activity. Low rate of oxygen diffusion through the coating might be the factor that limits the last step to blackening.

SUMMARY Susceptibility was evaluated of host and non-host plants to three pathogenic Botrytis species: the generalist B. cinerea and the specialists B. elliptica (lily) and B. tulipae (tulip). B. tulipae was, unexpectedly, able to infect plant species other than tulip, and to a similar extent as B. cinerea. To study host and non-host interactions in more detail, the three Botrytis species were inoculated on Arabidopsis wild-types and 23 mutant genotypes. Disease development was monitored macroscopically by quantifying the lesion area and microscopically by bright-field and fluorescence microscopy following histochemical staining. B. cinerea and B. tulipae were very similar in their ability to infect the tested Arabidopsis genotypes, whereas B. elliptica caused disease only on a few Arabidopsis mutant genotypes. Arabidopsis mutants with a delayed or reduced cell death response were generally more resistant to Botrytis infection, whereas mutants in which cell death was accelerated were more susceptible. Differences in susceptibility between genotypes were generally gradual. Only the camalexin-deficient mutant pad3 was fully susceptible to all three Botrytis species. Cellular changes were monitored during compatible and incompatible interactions. The formation of papillae, the presence of lysosome-like vesicles and the intracellular accumulation of H(2)O(2) and nitric oxide were visualized in the infection zones using fluorescent probes. Based on histology and responses of Arabidopsis mutants, a model is proposed in which resistance against Botrytis, besides the production of camalexin, depends on the balance between cell death and survival.

Programmed cell death (PCD) was studied in the petals of Antirrhinum majus, Argyranthemum frutescens, and Petunia hybrida, using DNA degradation and changes in nuclear morphology as parameters. The petals exhibit loss of turgor (wilting) as a visible symptom of PCD. DNA degradation, as shown on agarose gels, occurred in all species studied, prior to visible wilting. The number of DNA masses in all the petals of a flower, determined by flow cytometry, markedly increased in Argyranthemum and Petunia, but decreased in Antirrhinum. Many small DNA masses were observed in Argyranthemum and Petunia. The surface of each small DNA mass stained with the lipophilic fluorochrome 3,3'-dihexyloxacarbocyanine iodide (DiOC6), indicating that these masses were surrounded by a membrane. In Antirrhinum, in contrast, the chromatin fragmented into several small spherical clumps that remained inside a large membranous structure. Nuclear fragmentation, therefore, did not occur in Antirrhinum, whereas nuclear fragmentation possibly was a cause of the small DNA masses in Argyranthemum and Petunia. It is concluded that at least two contrasting nuclear morphologies exist during PCD. In the first, the chromatin fragments inside the nucleus, not accompanied--or followed--by nuclear fragmentation. In the second, a large number of DNA masses were observed each enveloped by a membrane. The second type was probably due, at least partially, to nuclear fragmentation.

For a vast number of ornamental species, blocking the plant's response to ethylene is an efficient strategy to enhance the longevity of the flowers. The most effective ways to conduct such interference will be reviewed in this paper. A large number of chemical compounds have been evaluated for their effects on ethylene production and perception. Among these are a range of strained olefines. This has resulted in the discovery that cyclopropenes, among them 1-methylcyclopropene (1-MCP) and a number of other substituted cyclopropenes effectively block ethylene responses at the receptor level. A lot of testing remains to be done to uncover the full potential of these compounds, but they do offer promising new ways to extend the postharvest life of ornamentals. Also genetic modification appears to be a very effective way in controlling of ethylene synthesis and perception. Attempts to use both a reduced endogenous ethylene production and a reduced sensitivity to ethylene will be reviewed. Among these the use of the mutant ethylene receptor gene, etr1-1, from Arabidopsis seems most promising, especially when it is expressed under the control of a flower specific promoter.

Fruit drop of banana is due to breaking at the junction of the pedicel and pulp, and we found no true abscission zone. The breakage seems therefore due to weakening of the peel. We investigated pectin hydrolysis and some properties at the rupture zone, using ‘Hom Thong’ (Musa acuminata, AAA Group) and ‘Namwa’ (Musa x paradisiaca, ABB Group) fruit, which show massive drop and no drop, respectively. During the period of finger drop, the water content of the peel in ‘Namwa’ was similar to that of ‘Hom Thong’ and thus water content does not account for the high breakage in ‘Hom Thong’. The peel thickness at the rupture area in the two cultivars was not significantly different. During the period of finger drop, the level of water-soluble pectin in the peel at the rupture area of ‘Hom Thong’ was higher than that of ‘Namwa’, indicating pectin degradation. CDTA soluble pectin and insoluble pectin was lower in ‘Hom Thong’, also indicating more pectin breakdown in this cultivar. Polygalacturonase activity in the peel at the rupture area of ‘Hom Thong’ bananas rapidly increased, but not clearly more than in ‘Namwa’ bananas. Pectinesterase activity in the peel at the rupture area of ‘Hom Thong’ was much lower than that of ‘Namwa’ bananas, and thus does not account for the breakage. Pectate lyase in the peel of ‘Hom Thong’ was considerably higher than in that of ‘Namwa’. The present data indicate that the much higher pectate lyase activity in ‘Hom Thong’ might be responsible, at least partially, for the finger drop. © 2005 Elsevier B.V. All rights reserved.

Flower senescence is accompanied by the rapid death of large numbers of cells. In situ DNA degradation was studied in gypsophila (Gypsophila paniculata) petals during flower opening and senescence, using terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL). In flowers that had just opened, TUNEL staining was exclusively observed in nuclei in the vicinity of (developing) vessels, presumably reflecting xylem vessel differentiation. In fully open flowers, TUNEL positive nuclei appear in all the cells well before the increase in ethylene production and visible signs of senescence. Occurrence of TUNEL positive nuclei was stimulated by ethylene but not prevented by silver thiosulphate. The results show that gypsophila petal senescence is a form of PCD with features of animal apoptosis and suggest that nuclear DNA degradation is an early regulatory event rather than a result of massive cell death in the final stage of senescence.

Gravistimulation induced differential ethylene production in Antirrhinum majus L. cut flower stems with highest levels in the lower halves of the gravistimulated stems. Expression levels of three different 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS) genes, an ACC oxidase (ACO) and an ethylene receptor (ETR/ERS homolog) gene were studied in the bending zone after 9 h of gravistimulation. One of the ACS genes (Am-ACS3) was abundantly expressed in the lower halves but not in the upper halves of gravistimulated stems. This strongly suggests that Am-ACS3 is responsible for the observed differential ethylene production in gravistimulated stems. Am-ACO and Am-ETR/ERS gene expression was increased in both the lower and upper halves of gravistimulated stems, suggesting that they play no role in differential ethylene production. When gravistimulation was performed in an environment enriched with either 20 µL/L ethylene or 100 nL/L 1-methylcyclopropene (1-MCP), a slight stimulation of bending by 1-MCP and a slight inhibition of bending by ethylene were observed. The regulation and role of ethylene in gravitropism of cut snapdragon flowering stems is discussed.

The regulation of gravistimulation-induced ethylene production and its role in gravitropic bending was studied in Antirrhinum majus L. cut flower stems. Gravistimulation increased ethylene production in both lower and upper halves of the stems with much higher levels observed in the lower half. Expression patterns of three different 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS) genes, an ACC oxidase (ACO) and an ethylene receptor (ETR/ERS homolog) gene were studied in the bending zone of gravistimulated stems and in excised stem sections following treatment with different chemicals. One of the ACS genes (Am-ACS3) was abundantly expressed in the bending zone cortex at the lower side of the stems within 2 h of gravistimulation. Am-ACS3 was not expressed in vertical stems or in other parts of (gravistimulated) stems, leaves or flowers. Am-ACS3 was strongly induced by indole-3-acetic acid (IAA) but not responsive to ethylene. The Am-ACS3 expression pattern strongly suggests that Am-ACS3 is responsible for the observed differential ethylene production in gravistimulated stems; its responsiveness to IAA suggests that Am-ACS3 expression reflects changes in auxin signalling. Am-ACS1 also showed increased expression in gravistimulated and IAA-treated stems although to a much lesser extent than Am-ACS3. In contrast to Am-ACS3, Am-ACS1 was also expressed in non-bending regions of vertical and gravistimulated stems and in leaves, and Am-ACS1 expression was not confined to the lower side cortex but evenly distributed over the diameter of the stem. Am-ACO and Am-ETR/ERS expression was increased in both the lower and upper halves of gravistimulated stems. Expression of both Am-ACO and Am-ETR/ERS was responsive to ethylene, suggesting regulation by IAA-dependent differential ethylene production. Am-ACO expression and in vivo ACO activity, in addition, were induced by IAA, independent of the IAA-induced ethylene. IAA-induced growth of vertical stem sections and bending of gravistimulated flowering stems were little affected by ethylene or 1-methylcyclopropene treatments, indicating that the differential ethylene production plays no pivotal role in the kinetics of gravitropic bending.

Programmed cell death (PCD) applies to cell death that is part of the normal life of multicellular organisms. PCD is found throughout the animal and plant kingdoms; it is an active process in which a cell suicide pathway is activated resulting in controlled disassembly of the cell. Most cases of PCD described in animal systems take the form of apoptosis, a cell death process characterised by specific features such as cell shrinkage, blebbing of the plasma membrane, condensation and fragmentation of the nucleus and internucleosomal cleavage of DNA. The final stage of apoptosis is the fragmentation of the cell into cellular debris-containing vesicles called `apoptotic bodies` that are being phagocytosed by other cells. A specific class of cell death- associated cystein proteases (caspases) has been identified. Generally, apoptotic cell death involves a sequence of caspase activation events in which initiator caspases activate down-stream executioner caspases that process a variety of target proteins eventually leading to the apoptotic phenotype. The occurrence of hallmarks of animal apoptosis was studied in tomato cells treated with the anticancer drug and inducer of apoptosis, camptothecin (cpt). It was shown that cpt-induced cell death is accompanied by nuclear condensation, the appearance of TUNEL-positive nuclei, DNA laddering and formation of DNA-containing (apoptotic) bodies and was greatly inhibited by inhibitors of animal caspases. Together the results indicate that cpt induced a cell death pathway with similarities to caspase-mediated (apoptotic) cell death in animal systems. We used cpt-treated cells to study the possible involvement of ethylene in cell death. Treatment of the cells with relatively high concentrations of ethylene did not have any effect on viability of the cells. However, when ethylene was applied in combination with cpt, a significant increase in cell death was observed as compared to cpt treatment alone. Experiments with inhibitors of ethylene production or ethylene action showed that ethylene is an essential factor mediating cpt-induced cell death. Flower senescence is accompanied by rapid death of large numbers of cells. In situ DNA degradation was studied in gypsophila petals using TUNEL. We showed that TUNEL positive nuclei appear well before the onset of the increase in ethylene production and visible signs of senescence. The role of PCD in flower senescence is discussed.

Programmed cell death (PCD) is an integral part of plant development and defence. It occurs at all stages of the life cycle, from fertilization of the ovule to death of the whole plant. Without it, tall trees would probably not be possible and plants would more easily succumb to invading microorganisms. Here, we have attempted to categorize plant PCD in relation to three established morphological types of metazoan cell death: apoptosis, autophagy and non-lysosomal PCD. We conclude that (i) no examples of plant PCD conform to the apoptotic type, (ii) many examples of PCD during plant development agree with the autophagic type, and (iii) that other examples are apparently neither apoptotic nor autophagic.

Explorative experiments were done to investigate the possibility that tomato plants infected by Botrytis cinerea have a different emission of volatile organic compounds (VOC) than healthy plants. This was done by headspace analysis of volatiles emitted by detached leaves of infected and healthy plants. Principal component analysis (PCA) of GC-FID chromatograms revealed clearly separated clusters between infected and control leaves and identification of an interesting compound. In further analysis by GC-MS, the significantly distinctive component (p≤0.05) was identified as the sesquiterpene α-copaene. In previous work on herbivore damage, α-copaene was not distinctive, which may suggest that α-copaene may be specifically associated to fungal infections in tomato.

Mango(Mangifera indica L.) fruit of six cultivars ('Kaew', 'Rad', 'Okrong', 'Tongdum', 'Nam Dok Mai' and 'Nungklangwun') were stored at 4, 8 and 12degreesC (85-90% RH) and randomly sampled every 5 days. Chilling injury was manifested initially as a gray to brown discoloration of the peel, followed by a color change in the pulp and the endocarp (seed coat). The seed tissue of most cultivars became brittle during storage at 4 and 8degreesC for as little as 5 days, and the seeds did not germinate. In all cultivars Studied, storage life was limited by skin discoloration. If acceptable skin color (no discoloration of more than 10% of the skin surface) after 5 days of shelf life at room temperature (about 30degreesC) was taken as a criterion, fruit of all cultivars, except 'Rad' and 'Okrong', could be not be stored for more than 5 days. According to this criterion, 'Rad' fruit Could be stored at 12degreesC for 15 days and 'Okrong' fruit for as long as 25 days. This variation in chilling injury (CI) sensitivity may be useful in breeding cultivars with improved storage life at low temperatures. (C) 2003 Elsevier B.V. All rights reserved.

The impact of programmed cell death (PCD) inhibitors on lesion formation and biochemical events in transgenic (ttr line) and non-transgenic (Nevrokop 1164) tobacco infected with Pseudomonas syringae pv. tabaci was tested. Programmed cell death in tomato cell culture was induced by Fumonisin B1 (FUM) and effectively abolished by the administration of protease inhibitors and lanthanum. Caspase inhibitors Ac-YVAD-CMK and Z-asp-CH2-DCB, serine protease inhibitor TLCK and LaCl3 were inoculated together with P. syringae pv tabaci in detached tobacco leaves or applied simultaneously with fungal toxin FUM in the tomato cell suspension. The results illustrate that cell death in normal Nevrokop 1164 and ttr transgenic tobacco at sites infected with P. syringae pv tabaci is apoptotic-like and caspase-like proteases and serine proteases are involved in lesion formation. The cell death in the lesions was accompanied with enhanced H2O2 accumulation and MDA production in, the wild type and with reduced levels of both metabolites in the transgenic line. Lanthanum, caspase inhibitors and TLCK reduced the amount of H2O2 and MDA in the affected lesions. FUM-induced cell death in tomato suspension cells was greatly suppressed by the application of protease inhibitors and lanthanum. The results indicated that apoptotic cell death occurs at bacteria inoculation of tobacco leaves, and in fumonisin treated tomato cells

Sucrier bananas (Musa AA Group; cultivar locally known as Kluai Khai) were stored at 10degreesC, which results in chilling injury (CI). Fruit was held in packages with and without a modified atmosphere (MA). Oxygen levels in the MA packages were about 12% while CO2 concentrations were about 4%. MA packaging resulted in less visible CI (i.e. greyish peel browning). Total free phenolics in the peel of control bananas decreased more rapidly than in fruit held in the MA package. Phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO) activities in the peel of control bananas were considerably higher than in MA-packed fruit. Pulp softness, sweetness and flavour of MA-packed fruit were better than in control fruit. MA thus reduced CI symptoms. PAL and PPO activities may be causally related to Cl-induced peel browning. (C) 2003 Elsevier B.V. All rights reserved.

Banana fruit (Musa cavendishii [Musa acuminata] AA Group cv. Sucrier) were placed in trays and held at 29-30 degreesC. Covering the trays with 'Sun wrap' polyvinyl chloride film prevented the early senescent peel spotting, typical for this cultivar. Carbon dioxide and ethylene concentrations within the packages increased, but inclusion of carbon dioxide scrubbers or ethylene absorbents, which considerably affected gas composition, had no effect on spotting. Experiments with continuous low oxygen concentrations confirmed that the effect of the package was mainly due to low oxygen. Relative humidity was higher in the packages but this had no effect on spotting. The positive effect of modified atmosphere packaging on peel spotting was accompanied by reduced in vitro phenylalanine ammonia lyase (PAL) activity in the peel, and by an increase of in vitro polyphenol oxidase (PPO; catechol oxidase) activity. We conclude that senescent spotting of banana peel requires rather high oxygen levels. It is not known which reaction becomes limiting for spotting, at low oxygen levels. Whatever the mechanism, the increase of in vitro PPO activity apparently shows an increase in potentially active protein. (C) 2003 Elsevier B.V. All rights reserved.

We previously concluded that the xylem blockage that prevents water uptake into several cut flowers is mainly due to the presence of bacteria, whilst in chrysanthemum and Bouvardia we observed a xylem occlusion that was mainly due to a wound-reaction of the plant. We have further tested which of these two mechanisms was dominant in Astilbe,Viburnum and rose flowers. Astilbe x arendsii (cvs. Erica and Glut) flowers were stored dry in plastic bags (24 h at 5 degreesC, 100% RH) and placed in water at 20 degreesC without recutting the steins. The dry storage treatment considerably hastened a wounding-induced xylem occlusion in the stems. A 5 h pulse treatment with inhibitors of peroxidase (hydroquinone) and catechol oxidase (tropolone and 2,3-dihydroxynaphtalene), prior to dry storage, considerably delayed the xylem blockage. The 24 h dry storage treatment had no effect in rose (Rosa x hybrida cv. Red One), and Viburnum opulus (cv. Roseum). These flowers were therefore directly placed in water, with and without enzyme inhibitors. Except hydroquinone, all tested enzyme inhibitors reduced bacterial growth in the vase water. The latter chemicals could therefore not be used to distinguish between a plant-induced and a bacterial occlusion of the xylem. Hydroquinone had no effect on the time to wilting in roses, nor in Viburnum. It considerably delayed wilting in Astilbe flowers that were directly placed in water after harvest. It is concluded that the blockage in Astilbe is mainly due to the plant-induced xylem occlusion. The xylem occlusion in the tested rose and Viburnum cultivar was apparently not due to this mechanism. (C) 2004 Elsevier B.V. All rights reserved.

The effects of combined high-pressure thermal treatments on consistency, viscosity, colour, lycopene content, enzyme activity and micro-organisms were determined, and compared to conventional pasteurisation and sterilisation processes of tomato puree. High-pressure processing at ambient temperature (HPP) improved the colour and viscosity compared to heat pasteurisation, while the water binding capacity and lycopene content were unaffected by HPP. Products treated at 700 MPa, 20 °C resulted in inactivation of the natural flora to a level below the detection limit. After pressure treatment and during chilled storage a increase in viscosity was observed. HPP caused partial inactivation of polygalacturonase (70%), but activation of pectin methylesterase. After high-pressure sterilisation treatments combined with elevated starting temperatures (≥80 °C, HPS, one or two pulses) an ambient stable product was obtained. HPS (one pulse, 700 MPa, 30 s, 90 °C) reduced B. stearothermophilus spore contamination level in inoculated meatballs in tomato puree with at least 4.5 log units. HPS resulted in more than 99% inactivation of polygalacturonase and pectin methylesterase. HPS resulted in a lower viscosity compared to conventional sterilised samples, whereas the water binding capacity was improved. Colour appreciation was improved and lycopene content was retained compared to a 40% loss after conventional sterilisation.

Current day perishable supply chains require intermediate points for manual produce quality inspection. Over the last decade international seatransport of fruit and vegetables in reefer containers has grown tremendously. Reefer containers may completely close the cold chain only if produce quality inspection is automated. The observation of this growing need for automatic produce quality monitoring has triggered this research. The aim is twofold: to reveal a correlation between fruit gas exchange rates and actual produce quality aspects (1) and to automatically monitor fruit's gas exchange rates in containers from one-point gas concentration measurements only (2). Large experimental datasets have been collected to assess the correlation between respiration, ethylene production and ripeness-related firmness for Elstar apples. Both simulations and experiments have been done to test the feasibility of monitoring (variations in) respiratory activity over time. On the one hand the results prove that both objectives are feasible, at least for Elstar apples. On the other hand some uncertainties remain: 1. Uncertainty in the observed correlation between gas exchange rates and apple firmness, 2. On-line monitoring of gas exchange rates in reefer containers may be hampered by e.g. unknown leak rates, 3. To what extend may the observed correlation between quality aspects and gas exchange rates be generalised to other perishable commodities.

This paper presents an algorithm for estimation of respiration and fermentation rates in CA-stores under normal operation, which can be used for: • Monitoring the product state • Control of respiration and fermentation rates • Detection of anaerobic conditions All published estimation methods require either a steady state flow-through or a batch respiration chamber. For implementation in full-scale storage facilities the estimator must be able to handle both situations and especially the more difficult non-steady state flow-through condition. To our knowledge, the only attention for monitoring respiration rate in full-scale storage facilities is a proposal by Janssens et al. (1995). In this study a Kalman Filter is designed to estimate the respiration and fermentation rates recursively. The results are compared to calculated respiration and fermentation rates. The rates of respiration and fermentation estimated from the O2 and CO2-balances converge to their calculated values. Experiments are currently carried out and results will come available in the oncoming months.

Storage of pears under low oxygen levels (0.5-1.0 kPa) leads to decreased ascorbic acid and ATP levels, a lower ATP-production, and to internal browning, a storage disorder in pears. Addition of 5 kPa carbon dioxide to the storage atmosphere increased the severity of this disorder. Experiments showed that anoxia can result in off-flavours, but not in internal browning. Internal browning is caused by brown pigments (melanins), which are formed due to oxidation of vacuolar polyphenols under the influence of tyrosinase (EC 1.14.18.1). We hypothesise that internal browning is initiated by a combination of oxygen radical action and a lack of maintenance energy for, amongst others, the regeneration of antioxidants. The two factors together lead to decompartmentation, bringing tyrosinase from the plastids and substrates from the vacuole together.

In this paper we discuss the differences and similarities in the growth response of tomato plants to N and P limitation, and to their interaction. Two detailed growth experiments, with varied N or P supply, were conducted in order to unravel the effects of N and P limitation on growth of young tomato plants (Lycopersicon esculentum Mill.). Relative growth rate (RGR) initially increased sharply with increasing plant P concentration but leveled off at higher plant P concentrations. In contrast, RGR increased gradually with increasing plant N concentration before it leveled off at higher plant N concentrations. The relationship of RGR with organic leaf N and P showed the same shape as with total N and P concentrations, respectively. The difference in response is most likely due to the different roles of N and P in the machinery of the plant's energy metabolism (e.g., photosynthesis, respiration). Plant N concentration decreased with increasing P limitation. We show that this decrease cannot be explained by a shift in dry-mass partitioning. Our results suggest that the decrease in N concentration with increasing P limitation may be mediated by a decrease in leaf cytokinin levels and is less likely due to decreased energy availability at low P conditions. Dry-mass partitioning to the roots was closely linearly related to the leaf reduced-N concentration. However, treatments that were severely P limited deviated from this relationship.

Programmed cell death (PCD) is a process aimed at the removal of redundant, misplaced, or damaged cells and it is essential to the development and maintenance of multicellular organisms. In contrast to the relatively well-described cell death pathway in animals, often referred to as apoptosis, mechanisms and regulation of plant PCD are still ill-defined. Several morphological and biochemical similarities between apoptosis and plant PCD have been described, including DNA laddering, caspase-like proteolytic activity, and cytochrome c release from mitochondria. Reactive oxygen species (ROS) have emerged as important signals in the activation of plant PCD. In addition, several plant hormones may exert their respective effects on plant PCD through the regulation of ROS accumulation. The possible plant PCD regulators discussed in this review are integrated in a model that combines plant-specific regulators with mechanisms functionally conserved between animals and plants.

The present study investigated the effect of aroma exposure time and aroma concentration on ad libitum intake and subjective satiation. In a within-subject study, thirty-eight unrestrained, healthy female participants (age: 18–39 years; BMI: 18·5–26·0 kg/m2) were asked to consume tomato soup during lunchtime, until they felt comfortably full. Every 30 s, the participants consumed 10 g of a bland soup base while tomato soup aroma was delivered separately through the nose via a retronasal tube that was attached to an olfactometer. This gave the impression of consuming real tomato soup. For each sip, the aroma varied in exposure time (3 and 18 s) and concentration (5 × ), resulting in four different test conditions. Ad libitum food intake and appetite profile parameters were measured. A 9 % lower food intake was observed when the participants were exposed to the condition with 18 s exposure time and a high concentration than when exposed to the other three conditions. These results indicate that changing the retronasal aroma release by aroma concentration and aroma exposure time affects food intake.

During wintertime Viburnum opulus var. roseum (snowball) shrubs are forced in warm greenhouses to harvest early cut flowers. Early forcing is occasionally unsuccessful. This is probably due to a lack of hours with low temperatures that is needed to break bud dormancy. To gain more insight about the effect of temperature on breaking dormancy and early forcing results, shrubs were transferred into cold storage in week 41, 43 and 45 (2009) for 4, 6 or 8 weeks at a temperature of 2, 5 or 8°C. After storage, the shrubs were forced at a day-/night temperature of 28/23°C. Shrubs stored for at least 8 weeks from week 41, 6 weeks from week 43 and 4 weeks from week 45 gave good forcing results, regardless of storage temperature. Since growing conditions outside vary every year and differ between nurseries, it is difficult to determine when forcing can be started. To prevent poor forcing results, we aimed to develop a molecular diagnostic assay to determine the moment at which winter dormancy of snowball flower buds is sufficiently broken. In order to identify genes involved in bud breaking dormancy, an experiment was performed on a commercial nursery from October 2010 to January 2011. Flower buds of snowball shrubs outside were sampled weekly and in December and January batches of shrubs were placed every week in a greenhouse to observe forcing results. Genes involved in bud breaking dormancy were identified by performing next generation Illumina RNA sequencing on bud samples with poor and good forcing results. A set of candidate genes was validated during a second trial at two different commercial nurseries in 2011-2012.

Little is known about the influence of visual characteristics other than colour on flavor perception, and the complex interactions between more than two sensory modalities. This study focused on the effects of recognizability of visual (texture) information on flavor perception of odorized sweet beverages. Participants rated the perceived sweetness of odorized sucrose solutions in the presence or absence of either a congruent or incongruent visual context. Odors were qualitatively reminiscent of sweet foods (strawberry and caramel) or not (savoury). Visual context was either an image of the same sweet foods (figurative context) or a visual texture derived from this product (non-figurative context). Textures were created using a texture synthesis method that preserved perceived food qualities while removing object information. Odor-taste combinations were rated sweeter within a figurative than a non-figurative context. This behaviour was exhibited for all odor-taste combinations, even in trials without images, indicating sustained priming by figurative visual context. A non-figurative context showed a transient sweetening effect. Sweetness was generally enhanced most by the strawberry odor. We conclude that the degree of recognizability of visual information (figurative versus non-figurative), influences flavor perception differently. Our results suggest that this visual context priming is mediated by separate sustained and transient processes that are differently evoked by figurative and non-figurative visual contexts. These components operate independent of the congruency of the image-odor-taste combinations.

Bread and cereals contribute 30% to the daily intake of sodium (Na) in the western human diet. Since the average Na intake is double the recommended intake, pressure has built up for the food industry to lower Na in their products. Especially replacing functionality of Na as a tastant remains very difficult. In this study we describe a strategy to enhance saltiness intensity in bread using an inhomogeneous spatial distribution of Na. Our results demonstrate that sensory contrast provides a promising strategy to significantly reduce the Na content in bread without loss of saltiness intensity and without the use of sodium substitutes, taste or aroma additives. © 2010 Elsevier Ltd.

The Zinnia elegans mesophyll cell culture is a useful system for xylogenesis studies. The system is associated with highly synchronous tracheary element (TE) differentiation, making it more suitable for molecular studies requiring larger amounts of molecular isolates, such as mRNA and proteins and for studying cellulose synthesis. There is, however, the problem of non-uniformity and significant variations in the yields of TEs (%TE). One possible cause for this variability in the %TE could be the lack of a standardized experimental protocol in various research laboratories for establishing the Zinnia culture. Mesophyll cells isolated from the first true leaves of Z. elegans var Envy seedlings of approximately 14 days old were cultured in vitro and differentiated into TEs. The xylogenic culture medium was supplied with 1mg/l each of benzylaminopurine (BA) and alpha-naphthalene acetic acid (NAA). Application of this improved culture method resulted in stable and reproducible amounts of TE as high as 76% in the Zinnia culture. The increase was mainly due to conditioning of the mesophyll cell culture and adjustments of the phytohormonal balance in the cultures. Also, certain biochemical and cytological methods have been shown to reliably monitor progress of TE differentiation. We conclude that, with the adoption of current improvement in the xylogenic Z. elegans culture, higher amounts of tracheary elements can be produced. This successful outcome raises the potential of the Zinnia system as a suitable model for cellulose and xylogenesis research.

Objective: Parotid saliva flow is increased by mastication and its composition is also modified. The aim of this work was to clarify the relationships between flow rate, pH and protein concentration, during resting and short-duration simulated chewing, using continuous and fractional saliva collections. Design: Parotid saliva flow rate, pH and protein concentration, as it exits the Stensen's duct, were determined on seven subjects in response to one and 30 ipsilateral jaw clenches. To achieve this, we have developed a system able to collect parotid saliva and to measure continuously flow rate, pH and protein concentration and synchronised to the values at the exit of the duct. Results: With increase in flow rate, pH increased linearly and its protein concentration decreased linearly with the logarithm of the flow rate. With an increase in flow rate from 50 to 500 μl/min, the pH increased from 5.8 to 7.0 and the protein concentration decreased from 1.0 to 0.7 g/l. Measurements made on parotid saliva fractions confirmed the variations in pH and protein concentration with flow rate and showed that α-amylase concentration was significantly related to both salivary conductivity and protein concentration. Conclusions: Continuous measurements of salivary flow and composition offer a simple and convenient way to determine the precise relationships between different types of oral stimulation and parotid salivary flow and composition. © 2009 Elsevier Ltd. All rights reserved.

Saliva from parotid glands plays a role in taste perception. Parotid saliva is also stimulated by tastants. The aim of this work is to investigate the effects of different tastants on the parotid salivary response in six subjects. Five tastants were given in different concentrations in solution and held in the mouth for 10 s. The flow rate, protein concentration, and pH of secreted parotid saliva were monitored continuously for 5 min. Stimulation by tastants on flow rate response consists of an immediate rise in flow followed by a plateau and a rapid return to prestimulus flow. Response of pH results in a slower increase while protein concentration consists in a slower decrease, both followed by a return to prestimulus levels in about 4 min. From a resting flow rate of about 140∈μL/min, an increase in flow rate to 370∈μL/min was caused by stimulation for 10 s with 10 mL of solutions of 0.01 M citric acid, 0.13 M MgSO4, 0.25 M monosodium glutamate, 0.5 M NaCl, or 0.5 M sucrose. Comparisons of the different tastants showed that the pH of stimulated parotid saliva increased linearly (r∈=∈0.9), irrespective of the nature of the tastant. Protein concentration decreased (r∈=∈-0.45) and protein amount increases (r∈=∈0.58) with increase in flow rate for all tastants. Corrected for the effects of flow rate, protein amount depended on the nature of the tastant with the greatest secretion after stimulation by citric acid. Flow rate was largely responsible for pH but tastant appears to play an additional role with flow rate on protein secretion.

Senescence in flower petals can be regarded as a form of programmed cell death (PCD), being a process where cells or tissues are broken down in an orderly and predictable manner, whereby nutrients are re-used by other cells, tissues or plant parts. The process of petal senescence shows many similarities to autophagic PCD in animal cells including a massive breakdown of protein, DNA and RNA, the formation of autophagic vacuoles for the breakdown of cytoplasm and organelles therein and, the eventual rupture of these vacuoles that kills the cell. Chromatin condensation and DNA and nuclear fragmentation (traditionally considered being apoptotic-like features) are observed in both autophagic animal cells and in senescing petal cells. We present a conceptional model underlying petal senescence that integrates elements that have been associated with both apoptotic and autophagic types of PCD

The present study was focused on the elucidation of stress-induced cell death signaling events in the unicellular alga Chlamydomonas reinhardtii exposed to treatment with wasp venom mastoparan. By applying pharmacological approach with specific inhibitors, we have investigated the involvement of ethylene, nitric oxide and lipid signaling in MP-treated C. reinhardtii. Superior sensitive laser-based detectors were used for real-time measurement of trace amounts of ethylene and nitric oxide. The morphological features in the cells undergoing programmed cell death were detected by using laser-scanning confocal microscopy. Data showed that mastoparan induces programmed cell death in C. reinhardtii 137 C(+) that is associated with phospholipid signaling, including phospholipases C and D, ethylene and nitric oxide and, the dead cells express apoptotic-like cellular disintegration, involving cytoplasm shrinkage and condensation of the nucleus.

Programmed cell death is an integral part of the latest stage of differentiation of the tracheary elements of plant xylem vascular system. In this study, by applying a pharmacological approach with specific peptide inhibitors, we have elucidated the involvement of plant caspase-like proteases in cell death signaling during vessel elements formation in xylogenic zinnia (Zinnia elegans) cell culture. Cell culture was isolated from zinnia leaves and exposed to chemical treatments. Broad spectrum caspase inhibitor, caspase 1 and caspase-3 inhibitors were administrated to the cell culture where the cells were induced to differentiate with the addition of 1 mg/L benzylaminopurine and 0.1 mg/L ¿-naphthalene-acetic acid. The differentiation was substantially suppressed in presence of 100 nM concentration of the inhibitors. This indicates that the re-differentiation in cultured mesophyll zinnia cells is a PCD event that most probably occurs through signaling involving caspase-like proteases. The reported results are the first that provide evidence for participation of plant caspase-related enzymes in xylogenesis in zinnia. Laser scanning confocal microscopy revealed differentiation associated structural cellular changes, including formation of large vacuole, secondary wall thickenings, tonoplast rupture and cell autolysis to form hollow dead tracheary elements..

Plant-pathogen interactions are associated with plant defense mechanism known as hypersensitive response (HR), which is a form of programmed cell death (PCD). In the present work we have tested the potency of chemicals, proven as PCD inhibitors in other systems, to prevent the spread of cell death in detached tobacco leaves challenged with ß- xylanase from Aspergillus awamori K1. Xylanase induced cell death that was accompanied by electrolyte leakage and increased levels of the stress metabolites hydrogen peroxide and malondialdehyde. Lesion development, ion leakage and the production of stress metabolites were suppressed if the infiltration site was pre-infiltrated with broad range caspase inhibitor benzyoxycarbonyl-Asp-2,6-dichlorobenzoyloxymethylketone (Z-Asp-CH2-DCB), cysteine protease inhibitor iodoacetamide (IA), serine protease inhibitor 4-(2-aminoethyl) benzenesulfonyl fluoride hydrochloride (AEBSF), the antioxidant l-galactone-¿-lactone (L-gal) and the ethylene blocker (S)-trans-2-Amino-4-(2-aminoethoxy)-3-butenoic acid hydrochloride (AVG). Massive ROS accumulation, as determined by staining with 3-3¿-diaminobenzidine and 2¿,7¿-dichlorofluorescein diacetate, occurred in xylanase-infiltrated lesions and was substantially reduced by the inhibitors. To the best of our knowledge, this is the first report showing that ß- xylanase produced by Aspergillus awamori K1 induces cell death response in tobacco and proteolysis, ROS and ethylene are involved in the mediation of the signaling.

Digestion patterns of chromosomal DNAs of Bacillus cereus and Bacillus weihenstephanensis strains suggest that Sau3AI-type restriction modification systems are widely present among the isolates tested. In vitro methylation of plasmid DNA was used to enhance poor plasmid transfer upon electroporation to recalcitrant strains that carry Sau3AI restriction barriers.

Programmed cell death (PCD) is a genetically controlled cell death that is regulated during development and activated in response to environmental stresses or pathogen infection. The degree of conservation of PCD across kingdoms and phylum is not yet clear; however, whereas caspases are proteases that act as key components of animal apoptosis, plants have no orthologous caspase sequences in their genomes. The discovery of plant and fungi metacaspases as proteases most closely related to animal caspases led to the hypothesis that metacaspases are the functional homologues of animal caspases in these organisms. Arabidopsis thaliana has nine metacaspase genes, and so far it is unknown which members of the family if any are involved in the regulation of PCD. We show here that metacaspase-8 (AtMC8) is a member of the gene family strongly up-regulated by oxidative stresses caused by UVC, H(2)O(2), or methyl viologen. This up-regulation was dependent of RCD1, a mediator of the oxidative stress response. Recombinant metacaspase-8 cleaved after arginine, had a pH optimum of 8, and complemented the H(2)O(2) no-death phenotype of a yeast metacaspase knock-out. Overexpressing AtMC8 up-regulated PCD induced by UVC or H(2)O(2), and knocking out AtMC8 reduced cell death triggered by UVC and H(2)O(2) in protoplasts. Knock-out seeds and seedlings had an increased tolerance to the herbicide methyl viologen. We suggest that metacaspase-8 is part of an evolutionary conserved PCD pathway activated by oxidative stress.

Dendrobium flowers, pollinated with pollinia from individuals of the same cultivar or other cultivars, usually show rapid post-pollination effects such as floral epinasty, a change in flower colour and early perianth senescence. However, pollination with the pollinia of cv. Karen or cv. Kenny flowers did not produce these effects. We compared these two cultivars with cvv. Pompadour, Willie and Sakura, and tested the hypotheses that the differences were related to levels of 1-aminocyclopropane-1-carboxylic acid (ACC) in the pollinia, ethylene production by the pollinated flower, pollen germination, or pollen tube growth. The pollinia of cvv. Karen and Kenny contained as much ACC as the pollinia of cv. Pompadour, but less than the pollinia of cvv. Willie and Sakura. Ethylene production after pollination with cvv. Karen and Kenny pollinia was much lower than after pollination with pollinia from the other cultivars tested. The pollen grains showed normal germination, but cvv. Karen and Kenny pollen grains exhibited much less tube growth than those of the other cultivars. Pollen tube growth in cv. Pompadour was positively affected by ethylene. Ethylene was required and sufficient for the induction of epinasty, rapid perianth colour changes and early perianth senescence, very similar to the changes after pollination. The absence of these effects after pollination with cvv. Kenny and Karen seems to be due to the low ethylene production induced by the pollinia of these cultivars. This low ethylene production could not be accounted for by the ACC content in the pollinia of cvv. Kenny and Karen.

Our aim was to investigate the ability of cadmium to induce programmed cell death in tomato suspension cells and to determine the involvement of proteolysis, oxidative stress and ethylene. Tomato suspension cells were exposed to treatments with CdSO(4) and cell death was calculated after fluorescein diacetate staining of the living cells. Ethylene was measured in a flow-through system using a laser-driven photo acoustic detector; hydrogen peroxide was determined by chemiluminescence in a ferricyanide-catalysed oxidation of luminol. We have demonstrated that cadmium induces cell death in tomato suspension cells involving caspase-like proteases, indicating that programmed cell death took place. Using range of inhibitors, we found that cysteine and serine peptidases, oxidative stress, calcium and ethylene are players in the cadmium-induced cell death signaling. Cadmium-induced cell death in tomato suspension cells exhibits morphological and biochemical similarities to plant hypersensitive response and to cadmium effects in animal systems.

Various triterpenoid glycosides were extracted from whole unripe tomato fruits ( Lycopersicon esculentum cv. Cedrico), using aqueous 70% (v/v) ethanol to study their surfactant properties. Cation-exchange chromatography using a Source 15S column and subsequent semipreparative HPLC using an XTerra RP18 were employed to purify individual triterpenoid glycosides from the extract. The structure of the purified compounds was established by mass spectrometry and nuclear magnetic resonance spectroscopy. The furostanol glycoside tomatoside A (749 mg/kg of DW) and the glycoalkaloids alpha-tomatine (196 mg/kg of DW) and esculeoside A (427 mg/kg of DW) were the major triterpenoid glycosides present. Furthermore, minor amounts of a new dehydrofurostanol glycoside, dehydrotomatoside, were found. The critical micelle concentrations of the major triterpenoid glycosides, alpha-tomatine, tomatoside A, and esculeoside A, were determined as 0.099, 0.144, and 0.412 g/L, respectively. The results show that tomatoside A, and not the more well-known alpha-tomatine, is the predominant triterpenoidal surfactant in unripe tomato fruits.

Banana fruit of cv. Gros Michel (Musa acuminata, AAA Group, locally called cv. Hom Thong) and cv. Namwa (Musa x paradisiaca, ABB Group) were immersed for 5, 10 and 15 min in water at 42 degrees C, or in water at 25 degrees C (control), and were then stored at 4 degrees C. Hot water treatment for 15 min delayed peel blackening during cold storage by about 4 days in cv. Gros Michel and by 2 days in cv. Namwa. In both cultivars the delay of blackening was correlated with an increase in the ratio of unsaturated to saturated fatty acids. Hot water treatment in cv. Gros Michel but not cv. Namwa was correlated with lower lipoxygenase (LOX) activity and lower levels of thiobarbitutic acid-reactive compounds. The results suggest that the rapid peel blackening of cv. Gros Michel is related to detectable membrane degradation, whereas the membrane-associated changes might be below the detection limit in the slower blackening cv. Namwa. The delay of peel blackening in cv. Gros Michel was associated with reduced expression of a catechol oxidase gene, which might partially explain the lower catechol oxidase activity after hot water treatment. The hot water treatment also increased the abundance of a Hsp70 transcript. The changes in gene expression found in cv. Gros Michel were not observed in cv. Namwa. Taken together the delay of blackening by hot water treatment in cv. Namwa was only correlated with a change in the ratio of unsaturated to saturated fatty acids, whereas that in cv. Gros Michel was additionally correlated with lower LOX activity, lower mRNA abundance of a gene encoding a catechol oxidase and lower catechol oxidase activity.

An important aspect of the ripening process of tomato fruit is softening. Softening is accompanied by hydrolysis of the pectin in the cell wall by pectinases, causing loss of cell adhesion in the middle lamella. One of the most significant pectin-degrading enzymes is polygalacturonase (PG). Previous reports have shown that PG in tomato may exist in different forms (PG1, PG2a, PG2b, and PGx) commonly referred to as PG isoenzymes. The gene product PG2 is differentially glycosylated and is thought to associate with other proteins to form PG1 and PGx. This association is thought to modulate its pectin-degrading activity in planta. An 8 kDa protein that is part of the tomato PG1 multiprotein complex has been isolated, purified, and functionally characterized. This protein, designated `activator¿ (ACT), belongs to the class of non-specific lipid transfer proteins (nsLTPs). ACT is capable of `converting¿ the gene product PG2 into a more active and heat-stable form, which increases PG-mediated pectin degradation in vitro and stimulates PG-mediated tissue breakdown in planta. This finding suggests a new, not previously identified, function for nsLTPs in the modification of hydrolytic enzyme activity. It is proposed that ACT plays a role in the modulation of PG activity during tomato fruit softening.

Dendrobium orchid inflorescences were treated for 4 h at 25 °C with or without 100–500 nl/l 1-MCP and were then placed in water at 25 °C to follow abscission. In controls, depending on the experiment, 20–80% of the floral buds and 0–20% of the open flowers abscised within 1 week. The 1-MCP pretreatment largely prevented this abscission. If flowers were exposed to 1.0 μl/l ethylene for 3 days, all floral buds and all open flowers abscised within the 3 days of treatment. 1-MCP treatment just prior to ethylene treatment largely prevented the ethylene effect. Treatment with STS was as effective as treatment with 1-MCP. Dendrobium inflorescences are usually shipped by air in cardboard boxes lined with plastic film. The stem ends are placed in plastic tubes filled with water. After shipment and placement in water, a considerable percentage of the buds, and some flowers, abscise. This is probably due to elevated ethylene concentrations inside the boxes. Treatment of the inflorescences with 100–500 nl/l 1-MCP prior to simulated air transport largely prevented abscission during vase life. 1-MCP treatment inhibited ethylene production of the inflorescences by lowering both ACC synthase in open flowers and ACC oxidase activity in floral buds.