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Sulfated glycoproteins extracted for the first time from the Moroccan green seaweed Codium decorticatum were investigated for their ability to induce a natural defense metabolism in the roots and the upper leaves of tomato seedlings. The crude (AGB) and the purified fractions (AGP) were characterized chemically (Colorimetric assays) and structurally (SEC-MALS, GC-EI/MS, ATR-FTIR). The elicitor aqueous solutions (1 g/L) were applied by foliar spray and syringe infiltration into the internodal middle of 45-day-old tomato seedlings. Phenylalanine ammonia-lyase (PAL) activity, polyphenols, and lignin contents were measured in the roots and the leaves after 0 h, 12, 24, 48, and 72 h of treatment. The AGB and AGP extracts contained 37.67% and 48.38% of the total carbohydrates, respectively, and were mainly composed of galactose, glucose, arabinose, and a minor amount of xylose and rhamnose. They were characterized by an important molecular weight (Mw) > of 2000 × 103 g·mol−1 and a high degree of sulfation and protein (12–23% (w/w)), indicating that the extracted polysaccharides could be an arabinogalactan-rich protein present in the cell wall of the green seaweed C. decorticatum. Both crude and purified fractions exhibited an elicitor effect by inducing the PAL activity, the accumulation of phenolic compounds and lignin contents in the roots and the leaves of tomato seedlings. These responses were systemic in both the methods used (injection and foliar spray) and were mobilized throughout tissues that are not directly treated (roots and/or leaves). Regarding the elicitor activities, AGB and AGP presented globally similar patterns, which revealed the importance of crude extracts in the stimulation of plant immunity. These results suggest the new application of sulfated glycoprotein isolated from green seaweed in agriculture as inducers of natural defenses of plants.

Young barley plants are a good source of bioactive compounds. This paper presents the effects of gaseous O3 (trioxygen or ozone) on the biosynthesis of compounds, determining the antioxidant potential of young barley plants. The total content of polyphenols was determined along with their profile, as well as total antioxidant potential and vitamin C content. The highest contents of these compounds were identified in young barley plants exposed to gaseous O3. The main bioactive compound, representing polyphenols, determined in the examined raw materials was saponarin (isovitexin 7-O-glucoside). The induction of increased biosynthesis of these molecules was directly linked to the modification of the activity of selected enzymes. The increased polyphenol content resulted from the modified activities of polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL). On the other hand, the oxidative effect of ozone on barley plants was reduced, owing to the modified activities of catalases (CAT), glutathione peroxidases (SOD) and guaiacol peroxidase (GPOX). Analysis of the results showed that by applying gaseous O3 at a dose of 50 ppm for 10 min, the contents of bioactive compounds can be maximised in a residue-free way by activating oxidative stress defence mechanisms.

This study evaluated the chemical compositions of the leaves and fruits of eight black pepper cultivars cultivated in Par&aacute, State (Amazon, Brazil). Hydrodistillation and gas chromatography&ndash, mass spectrometry were employed to extract and analyze the volatile compounds, respectively. Sesquiterpene hydrocarbons were predominant (58.5&ndash, 90.9%) in the cultivars &ldquo, Cingapura&rdquo, &ldquo, Equador&rdquo, Guajarina&rdquo, Ia&ccedil, ar&aacute, &rdquo, and &ldquo, Kottanadan&rdquo, Bragantina&rdquo, Clonada&rdquo, Uthirankota&rdquo, displayed oxygenated sesquiterpenoids (50.6&ndash, 75.0%). The multivariate statistical analysis applied using volatile composition grouped the samples into four groups: &gamma, Elemene, curzerene, and &delta, elemene (&ldquo, /&ldquo, I), &delta, II), elemol (&ldquo, III) and &alpha, muurolol, bicyclogermacrene, and cubebol (&ldquo, IV). The major compounds in all fruit samples were monoterpene hydrocarbons such as &alpha, pinene, &beta, pinene, and limonene. Among the cultivar leaves, phenolics content (44.75&ndash, 140.53 mg GAE&middot, g&minus, 1 FW), the enzymatic activity of phenylalanine-ammonia lyase (20.19&ndash, 57.22 &micro, U&middot, mL&minus, 1), and carotenoids (0.21&ndash, 2.31 &micro, g&middot, 1) displayed significant variations. Due to black pepper&rsquo, s susceptibility to Fusarium infection, a molecular docking analysis was carried out on Fusarium protein targets using each cultivar&rsquo, s volatile components. F. oxysporum endoglucanase was identified as the preferential protein target of the compounds. These results can be used to identify chemical markers related to the susceptibility degree of black pepper cultivars to plant diseases prevalent in Par&aacute, State.

This study evaluated the chemical compositions of the leaves and fruits of eight black pepper cultivars cultivated in Pará State (Amazon, Brazil). Hydrodistillation and gas chromatography–mass spectrometry were employed to extract and analyze the volatile compounds, respectively. Sesquiterpene hydrocarbons were predominant (58.5–90.9%) in the cultivars “Cingapura”, “Equador”, “Guajarina”, “Iaçará”, and “Kottanadan”, and “Bragantina”, “Clonada”, and “Uthirankota” displayed oxygenated sesquiterpenoids (50.6–75.0%). The multivariate statistical analysis applied using volatile composition grouped the samples into four groups: γ-Elemene, curzerene, and δ-elemene (“Equador”/“Guajarina”, I); δ-elemene (“Iaçará”/“Kottanadan”/“Cingapura”, II); elemol (“Clonada”/“Uthirankota”, III) and α-muurolol, bicyclogermacrene, and cubebol (“Bragantina”, IV). The major compounds in all fruit samples were monoterpene hydrocarbons such as α-pinene, β-pinene, and limonene. Among the cultivar leaves, phenolics content (44.75–140.53 mg GAE·g−1 FW), the enzymatic activity of phenylalanine-ammonia lyase (20.19–57.22 µU·mL−1), and carotenoids (0.21–2.31 µg·mL−1) displayed significant variations. Due to black pepper’s susceptibility to Fusarium infection, a molecular docking analysis was carried out on Fusarium protein targets using each cultivar’s volatile components. F. oxysporum endoglucanase was identified as the preferential protein target of the compounds. These results can be used to identify chemical markers related to the susceptibility degree of black pepper cultivars to plant diseases prevalent in Pará State.

International audience; Polysaccharides extracted from marine algae have attracted much attention due to their biotechnological applications, including therapeutics, cosmetics, and mainly in agriculture and horticulture as biostimulants, biofertilizers, and stimulators of the natural defenses of plants. This study aimed to evaluate the ability of alginate isolated from Bifurcaria bifurcata from the Moroccan coast and oligoalginates derivatives to stimulate the natural defenses of tomato seedlings. Elicitation was carried out by the internodal injection of bioelicitor solutions. The elicitor capacities were evaluated by monitoring the activity of phenylalanine ammonia-lyase (PAL) as well as polyphenols content in the leaves located above the elicitation site for 5 days. Alginate and oligoalginates treatments triggered plant defense responses, which showed their capacity to significantly induce the PAL activity and phenolic compounds accumulation in the leaves of tomato seedlings. Elicitation by alginates and oligoalginates showed an intensive induction of PAL activity, increasing from 12 h of treatment and remaining at high levels throughout the period of treatment. The amount of polyphenols in the leaves was increased rapidly and strongly from 12 h of elicitation by both saccharide solutions, representing peaks value after 24 h of application. Oligoalginates exhibited an effective elicitor capacity in polyphenols accumulation compared to alginate polymers. The alginate and oligosaccharides derivatives revealed a similar elicitor capacity in PAL activity whereas the accumulation of phenolic compounds showed a differential effect. Polysaccharides extracted from the brown seaweed Bifurcaria bifurcate and oligosaccharides derivatives induced significantly the phenylpropanoid metabolism in tomato seedlings. These results contribute to the valorization of marine biomass as a potential bioresource for plant protection against phytopathogens in the context of eco-sustainable green technolog

Shelf life of horticultural commodities is dependent on postharvest handling but also on a wide range of pre-harvest factors, which include genetic and environmental parameters. This study was conducted to explore the influence of cultivar, leaf position, and piece position on the leaf on visual quality of fresh-cut butterhead lettuce as well as the effect of a wide range of cultivation seasons on the postharvest quality and shelf life of baby leaves (spinach and &lsquo, wild&rsquo, rocket). Six butterhead lettuce cultivars were used (cultivated soilless in an unheated plastic greenhouse) while the effect of leaf position on the plant (outer and inner leaves) and the piece position on the leaf (piece one close to the leaf base and piece four close to the top) were also evaluated. Baby leaves were cultivated under an unheated plastic greenhouse for winter production and under a nethouse for the rest of the growing season, with a total of five and seven sampling dates for spinach and &lsquo, rocket respectively. The cultivar of butterhead lettuce had a significant effect on postharvest quality of fresh-cut product but more important was the piece position on the leaf. When this was closer to the base of the leaf, there was more browning on cut edges and limited shelf life for the fresh-cut lettuce. The result was associated in one tested cultivar with PAL activity, which was higher by 106% for piece one compared to piece four as an average for the whole storage period. The growing season of baby leaves had a great impact on their shelf life, with the season of mild environmental conditions achieving the highest marketability.

Banana blossoms are rich in fiber and nutrients and are a popular plant-based, vegan alternative to fish. However undesirable browning, usually visible at the peduncle cut-end, negatively impacts consumer acceptability of banana blossoms. The aim of this work was to develop safe alternatives to prevent browning in banana blossoms. First, the activities of primary enzymes associated with tissue browning, i.e., polyphenol oxidase (PPO), peroxidase (POD) and phenylalanine ammonia lyase (PAL), were assayed. Our data showed that PPO and POD were the key enzymes responsible for blossom browning as they increased in activity, reaching a maximum at pH 7, as browning developed. In contrast, PAL activity decreased, and total phenolic content did not change as browning progressed, indicating PAL was not induced by cutting and may not be involved in blossom browning. Second, to find antibrowning agents for banana blossoms that can substitute for the use of sodium metabisulfite (SMS), different organic acids of varying concentrations were tested. Among organic acids studied, treatment with 3% (w/v) oxalic acid was the most effective method and thus could be a safe substitution for SMS to prevent browning in banana blossoms.

The deterioration of surface color is a major factor limiting the marketability of fresh-cut stem lettuce. In this study, the impact of UV-C irradiation on fresh-cut stem lettuce was investigated. Slices were exposed to different doses (0, 1, 4, 8 or 12 kJ m−2) of UV-C light, then stored at 4 °C for 6 d. It was observed that all UV-C treatments could retard the occurrence of surface green fading and browning, and 8 kJ m−2 was determined as the optimal dose which used for further evaluation. Results showed that UV-C treatment decreased the degradation of chlorophyll, the loss of ascorbic acid (AsA) and the accumulation of phenolic compounds. Moreover, UV-C treatment did not show a distinct effect on activities of PPO and POD, but pronouncedly inhibited the activity of PAL. Based on this, the inhibited tissue browning upon application of UV-C should be mainly attributed to suppressed PAL activity. Additionally, the aroma data indicated that storage time was the main contributor to the changes of volatile components, whereas the impact of UV-C treatment was limited, especially in the first 4 d. These findings suggest that UV-C treatment has a potential practical application in preserving fresh-cut stem lettuce.

In this study, changes in the activities of Phenlylalanine ammonialyase (PAL) and polyphenol oxidase (PPO) during development and stages of wilt (Fusarium oxysporum Schlechtend.:Fr. f.sp. ciceri (Padwick) Matuo & K. Sato) disease infection in chickpea(Cicer arietinum L) were investigated. During the early stages of disease development, at pre-infectional stage (S1), cultivars did not show any significant change in PAL activity. The activity was significantly increased at infectional stage (S2) as compared with pre infectional stage (S1). Susceptible cultivars had the lower value of PAL at infectional stage (S2). However, at S2 stage cultivars GG-4 and JCP-27 were at par. At post infectional stage (S3), the activity was found to be increased in the all cultivars as compared to infectional or mid growth stage and the resistant and tolerant cultivars were at par. Susceptible cultivars (JG-62 and GG-4) had the lower activity as compared to the resistant and tolerant cultivars. The resistant cultivars WR-315 and JCP-27 revealed higher level of activity, the level of activity significantly increased marginally during infection. In the present experiment significantly higher activity in infected plants grown in sick plot also suggested that polyphenol oxidase might be involved in oxidation of phenolics in susceptible cultivar (JG-62). These observations suggest that the increase in PAL and PPO activities has an important role in disease resistance mechanism.

Excessive proliferation of filamentous green algae (FGA) has been considered an important factor resulting in the poor growth or even decline of submerged macrophytes. However, there is a lack of detailed information regarding the effect of decaying FGA on submerged macrophytes. This study aimed to investigate whether the decomposing liquid from Cladophora oligoclona negatively affects Hydrilla verticillata turion germination and seedling growth. The results showed that the highest concentrations of decomposing liquid treatments inhibited the turion germination rate, which was the lowest than other treatments, at only 84%. The chlorophyll a fluorescence (JIP test) and physiological indicators (chlorophyll a content, soluble sugars, Ca2+/Mg2+-ATPase and PAL activity) were also measured. The chlorophyll a content in the highest concentration (40% of original decomposing liquid) treatment group decreased by 43.53% than that of the control; however, soluble sugars, Ca2+/Mg2+-ATPase, and PAL activity increased by 172.46%, 271.19%, and 26.43% respectively. The overall results indicated that FGA decay has a considerable effect on submerged macrophyte turion germination and seedling growth, which could inhibit their expansion and reproduction. This study emphasized the need to focus on effects of FGA decomposition on the early growth stages of submerged macrophytes and offered technological guidance for submerged vegetation restoration in lakes and shallow waters.

Torbangun (Coleus amboinicus Lour) is a tropical plant from the Lamiaceae family. Torbangun leaves have a distinct aroma. Torbangun leaves have been traditionally used as a medicinal plant in North Sumatra, Indonesia. Bataknese lactating women in North Sumatra consumed torbangun leaves after giving birth with beliefs that it could increase their breast milk production (lactagogue), and that the leaves can function as anti-fungal and/or anti-bacterial, analgesic, to reduce blood cholesterol, and clean the human uterus. However, scientific evidence on this traditional herb is limited. This research was conducted to: (1) determine the leaf N, P, K, Ca and Fe in different position along the plant and the leaf age as to diagnose the secondary metabolites content of torbangun leaves, and (2) determine the relationship between N, P, K, Ca and Fe leaf concentrations with their metabolite production. The results of the study showed that: (1) the best leaf position and age to determine of the need of N, P, K, Ca and Fe nutrients are on the 3rd leaf position of 5 months-old plant (2) There was a positive correlation between leaf K concentrations with shoot dry weight, Ca with PAL activity, and Fe with total saponins on the 3rd leaf position of 5 months-old plant.Keywords: Coleus amboinicus Lour, torbangun, nutrient, correlation test, secondary metabolites.

Previously, we found that phenolic content and antioxidant capacity (AOX) in carrots increased with wounding intensity. It was also reported that UV radiation may trigger the phenylpropanoid metabolism in plant tissues. Here, we determined the combined effect of wounding intensity and UV radiation on phenolic compounds, AOX, and the phenylalanine ammonia-lyase (PAL) activity of carrots. Accordingly, phenolic content, AOX, and PAL activity increased in cut carrots with the duration of UVC radiation, whereas whole carrots showed no increase. Carrot pies showed a higher increase compared to slices and shreds. Phenolics, AOX, and PAL activity also increased in cut carrots exposed to UVA or UVB. The major phenolics were chlorogenic acid and its isomers, ferulic acid, and isocoumarin. The type of UV radiation affected phenolic profiles. Chlorogenic acid was induced by all UV radiations but mostly by UVB and UVC, ferulic acid was induced by all UV lights to comparable levels, while isocoumarin and 4,5-diCQA was induced mainly by UVB and UVC compared to UVA. In general, total phenolics correlated linearly with AOX for all treatments. A reactive oxygen species (ROS) mediated hypothetical mechanism explaining the synergistic effect of wounding and different UV radiation stresses on phenolics accumulation in plants is herein proposed.

Changes in quality attributes (discoloration, surface dehydration, translucency, color values, texture), respiration, phenolics and phenylalanine ammonia lyase (PAL) and polyphenol oxidase activities of sunchoke tuber slices were studied at 0, 5 and 10C. Cleanly cut smooth surfaces had less wound-induced discoloration and surface drying than rougher cut surfaces. The main quality defect was red discoloration, and a* and hue color values were highly correlated to this defect. The time course of discoloration was related to wound-induced respiration and PAL activity but not polyphenol oxidase activity or concentrations of soluble phenolics. Respiration rates of slices at 0, 5 and 10C averaged 5, 14 and 26 μL CO2/g-h, respectively, during 7 days. No decay was observed under any condition. Storage at 0 and 5C effectively retarded surface discoloration, but 0C was clearly better. A shelf life of 9–12 and 6–8 days was obtained with sunchoke slices at 0 and 5C, respectively, while shelf life was 3 days at 10C. Practical Applications Sunchoke tubers contain indigestible inulins and have potential as a fresh-cut product or a component in fresh-cut mixtures to be consumed raw or cooked. Sliced tubers retain quality when held at 0–5C, but discoloration, the main defect limiting shelf life, will occur more rapidly at 5C. The rate and severity of discoloration was related to storage temperature and to wound-induced increases in respiration and PAL activity. With this information, strategies to effectively control discoloration can be implemented.

Total phenol, total flavonoid, rutin and quercetin contents as well as antioxidant activity in ethanol extracts of common buckwheat (Fagopyrum esculentum Moench) and tartary buckwheat (Fagopyrum tararicum Gaertn) sprouts were determined, and the phenylalanine ammonia-lyase (PAL) activity in the sprouts were estimated. Total flavonoid content and rutin in the sprouts of both buckwheat species gradually increased and reached the maximum levels on days 7 and 9 of germination, respectively; total phenol and free phenylalanine content also had the same trend. However, quercetin in tartary buckwheat decreased from day 5 and became undetectable on day 7, similar to that observed in common buckwheat sprouts beyond the germinating period. An obvious positive linear relationship (r2 = 0.9792, P

Phenolic compounds are phytochemicals with high health-promoting properties. Carrot is a vegetable highly worldwide consumed although its phenolic content is low compared to other plant products. The aim of this work was to evaluate changes in phenolic compounds in carrots caused by abiotic stresses. The phenylalanine ammonia-lyase (PAL) activity, phenolic compounds and total antioxidant capacity (TAC) changes during storage up to 72 h at 15 °C after wounding (shredding), 9 kJ UV-C m−2 pretreatment and hyperoxia (80 kPa) conditions of carrots were studied. Shredding and hyperoxia storage induced the highest phenolic compounds and TAC enhancements. Accumulation of phenolic compounds in shredded carrots could be structured in the following phases: 1st phase (

The effects of l-phenylalanine (PHE) on cell growth and production of shikonin and its derivatives, acetylshikonin (ACS) and isobutyrylshikonin (IBS), in suspension cultures of Arnebia euchroma were examined. Supplementing media using PHE have been successfully utilized to enhance shikonin production in cell cultures of other species of Boraginaceae. l-Phenylalanine, the key compound in the phenylpropanoid pathway, is converted by phenylalanine ammonia lyase (PAL) to trans-cinnamic acid, which is the precursor of p-hydroxybenzoic acid (PHB). Coupling of PHB and geranyl pyrophosphate (derived from mevalonate pathway) by p-hydroxybenzoate-m-geranyltransferase leads later to biosynthesis of shikonins. The addition of 0.01 or 0.1 mM PHE to the culture medium stimulated cell proliferation, where the highest observed increase in fresh cell biomass (measured as a ratio of final weight to initial weight) was 12-fold, in contrast to an eightfold increase in control cultures. Whereas, growth media supplemented with 1 mM PHE markedly reduced the rate of cell growth (to only twofold). Precursor feeding had detrimental effects on both ACS and IBS production in all PHE-supplemented media. The highest total content (intracellular + extracellular) of the investigated red pigments (9.5 mg per flask) was detected in the control culture without PHE. ACS was the major component of the naphthoquinone fraction determined in cells and post-culture media. Shikonin itself was found only in the post-culture media from cultures supplemented with 0.01 or 0.1 mM PHE. Increases in PAL activity corresponded well with the accumulation of investigated naphthoquinones in control culture. However, peak PAL activity did not directly correlate with maximum production of shikonin derivatives. Cytotoxicity of extracts, prepared from the cells cultivated in the presence of PHE or in control cultures, was tested on three cancer cell lines: HL-60, HeLa, and MCF-7. The extracts prepared from the untreated control cultures proved to be the most potent against the examined cancer cell lines. The mean inhibitory concentration values were 0.3, 13, and 8 μg ml(-1) for the HL-60, HeLa, and MCF-7 cells, respectively.

A randomized complete block design experiment was designed to characterize the relationship between production of total flavonoids and phenolics, anthocyanin, photosynthesis, maximum efficiency of photosystem II (Fv/Fm), electron transfer rate (Fm/Fo), phenyl alanine lyase activity (PAL) and antioxidant (DPPH) in Labisia pumila var. alata, under four levels of irradiance (225, 500, 625 and 900 μmol/m(2)/s) for 16 weeks. As irradiance levels increased from 225 to 900 μmol/m(2)/s, the production of plant secondary metabolites (total flavonoids, phenolics and antocyanin) was found to decrease steadily. Production of total flavonoids and phenolics reached their peaks under 225 followed by 500, 625 and 900 μmol/m(2)/s irradiances. Significant positive correlation of production of total phenolics, flavonoids and antocyanin content with Fv/Fm, Fm/Fo and photosynthesis indicated up-regulation of carbon-based secondary metabolites (CBSM) under reduced photoinhibition on the under low light levels condition. At the lowest irradiance levels, Labisia pumila extracts also exhibited a significantly higher antioxidant activity (DPPH) than under high irradiance. The improved antioxidative activity under low light levels might be due to high availability of total flavonoids, phenolics and anthocyanin content in the plant extract. It was also found that an increase in the production of CBSM was due to high PAL activity under low light, probably signifying more availability of phenylalanine (Phe) under this condition.

In this study, the effect on differrent concentrations (20, 40, 80µM ve 100 µM CdCl2 ) of cadmium (CdCl2) on the activity of phenylalanine ammonia-lyase (PAL) and lipid peroxidation amount in leaf and stem of Kahramanmaras- Hot (Capsicum annum L.) pepper seedlings were researched. Activity of phenylalanine ammonia-lyase (PAL), the first enzyme in the phenylpropanoid biosynthetic pathway, was increased at 2 and 4 days in KM-Hot plants exposed to CdCl2 stress. The highest PAL activity was detected in 20 μM CdCl2 application, on the four day after the application in the leaves of KM-Hot pepper. Moreover, it was observed that treatment of pepper with Cd led to an increased the rate of lipid peroxidation (which is indicated by increasing MDA content) in the leaf and stem tissues. The highest MDA content was detected in 80 μM CdCl2 application, on the four day after the application in the leaf tissues. These results suggest that the activation of PAL may be associated with increased production of MDA

Background: Accurate measurement of physical activity patterns can be used to identify sedentary behaviour and may facilitate interventions aimed at reducing inactivity. Objective: To evaluate the activ PAL physical activity monitor as a measure of posture and motion in everyday activities using observational analysis as the criterion standard. Methods: Wearing three activ PAL monitors, 10 healthy participants performed a range of randomly assigned everyday tasks incorporating walking, standing and sitting. Each trial was captured on a digital camera and the recordings were synchronised with the activ PAL. The time spent in different postures was visually classified and this was compared with the activ PAL output. Results: Intraclass correlation coefficients (ICC 2,1) for interdevice reliability ranged from 0.79 to 0.99. Using the Bland and Altman method, the mean percentage difference between the activ PAL monitor and observation for total time spent sitting was 0.19% (limits of agreement −0.68% to 1.06%) and for total time spent upright was −0.27% (limits of agreement −1.38% to 0.84%). The mean difference for total time spent standing was 1.4% (limits of agreement −6.2% to 9.1%) and for total time spent walking was −2.0% (limits of agreement −16.1% to 12.1%). A second-by-second analysis between observer and monitor found an overall agreement of 95.9%. Conclusion: The activ PAL activity monitor is a valid and reliable measure of posture and motion during everyday physical activities.

This experiment was carried to investigate the optimum time and times of abscisic acid (ABA) treatment for the coloration in `Kyoho` grapes. The L-phenylalanine ammonia-lyase (PAL) enzyme activities were showed highly in both ABA treatments at veraison and 10 days after veraison. However, PAL enzyme was slightly higher in ABA treatment at 10 days after veraison than in that at veraison. Anthocyanin content showed a tendency that were increased during fruit development after veraison in all treatments, and was the highest in ABA treatment at 10 days after veraison. Fructose and glucose as soluble sugars were detected by HPLC and showed little differences in all treatments. In times of ABA treatment, PAL activity showed a tendency that decreased after increased in all treatments. PAL activity in 2 times treatment of ABA was higher than other treatments. Also, anthocyanin content was highest in 2 times treatment of ABA, as 5 folds of control and folds of 1 time treatment of ABA. Both fructose and glucose contents in all ABA treatments was slightly higher than control.

The effect of the intensity of damage on the phenylalanine ammonia lyase (PAL) activity, on browning of midrib tissue and on the overall visual quality (OVQ) of minimally processed Romaine lettuce was studied. In highly wounded leaves two peaks of PAL activity were observed. In whole and in less-damaged leaves only one peak was detected. The rate of change in PAL activity during the first day of storage was found to be related to the intensity of damage. Browning in midrib tissue developed in the most highly damaged leaves after 4 days of storage. Dehydration and wilting reduced the OVQ of lettuce before the onset of browning and the occurrence of peaks in PAL activity.

Wounding lettuce leaves induces the de novo synthesis of phenylalanine ammonia-lyase (PAL, EC 4.3.1.5), the accumulation of phenolic compounds, and subsequent tissue browning. A brief heat-shock at 45degreesC reduces the rise in wound-induced PAL, the accumulation of phenolic compounds, and tissue browning. The activity of PAL measured 24 h after wounding and the content of phenolic compounds (absorbance of methanol extract at 320 nm) measured 48 h after wounding was highly correlated (R-2 > 0.90) in tissue developing the normal wound response and in tissue subjected to 0-180 s of heat-shock after wounding. The synthesis of a unique set of proteins called heat-shock proteins (hsps) is induced by these heat-shock treatments. Western-blot analyses of proteins isolated from wounded and heat-shocked Iceberg and Romaine lettuce mid-rib leaf tissue was done using antibodies against hsp 23. Only those heat-shock treatments that were effective at inducing the synthesis of hsp 23 were effective in reducing the activity of PAL induced by wounding and the subsequent accumulation of phenolic compounds. Hsps induced in non-wounded, whole leaves by exposure to 45degreesC for 150 s did not significantly interact with PAL previously synthesized in non-heat-shocked wounded leaves to limit its activity. The preferential synthesis of hsps over that of wound-induced PAL, rather than the presence of hsps, may be responsible for the ability of a heat-shock treatment to reduce the wound-induced increase in PAL activity. Our results support this novel concept, and the possibility that heat-shock treatments can have significant physiological effects on the response of the tissue to other stresses, not because of the specific genes they induce or repress, or the products they cause to be synthesized, but by their secondary action of influencing the synthesis of other proteins (e.g. PAL) by the suppression of non-hsps protein synthesis.

The Inhibitory mechanism of onion juice on the browning of shredded lettuce during storage was investigated. Browning and phenylalanine ammonia-lyase (PAL) activity of the control sample dipped in distilled water stored at 5°C increased immediately after cutting. When shredded lettuce dipped in onion juice for 5 minutes, browning and PAL activity of shredded lettuce was suppressed for 48 hours. Polyphenol oxidase (PPO) activity of the shredded lettuce was slightly lower than the control sample, but the rise time of PPO activity was familiar to the control sample. Direct inhibition of onion juice on the PAL activity was not observed at the level of concentration that could inhibit browning almost completely, if treated immediately after cutting. On the other hand, the PPO activity was suppressed about 60% of the control upon the addition of ten percent onion juice in the reaction mixture. However, browning was suppressed negligibly, if the shredded lettuce was treated with onion juice of the concentration immediately after cutting. When the sample turned to brown already after cutting was dipped in onion juice, the Hue angle rised rapidly. After the treatment, browning of shredded lettuce was almost suppressed. The results indicate that onion juice act on the delay in the increase of PAL activity of shredded lettuce, the partial direct inhibition of PPO activity and elimination of color formed by browning reaction. Especially, the inhibition of browning in shredded lettuce during storage mainly depended on the suppression of the increase in PAL activity, if the shredded was treated with onion juice immediately after cutting.

Wounds and injuries incurred during preparation of fresh-cut lettuce (Lactuca sativa L.) stimulate phenolic metabolism, which leads to tissue browning. Phenylalanine ammonia-lyase (PAL, EC 4.3.1.5.) is the first committed enzyme in the phenylpropanoid pathway and regulates its overall activity. Maximum activity of wound-induced PAL occurred sooner as the storage temperature increased from 0 to 25 °C, but the maximums were lower. A heat shock at 50 °C for 90 seconds protected fresh-cut lettuce tissue against browning, helped retain greenness, and decreased subsequent production of phenolics when applied either after or before wounding. Browning was reduced when the heat shock was applied up to 36 hours after wounding, while the maximum effect occurs around 6 hours before cutting. Like the heat-shock treatment, the protein synthesis inhibitor cycloheximide reduced wound-induced PAL activity, but it did not prevent tissue browning. When cycloheximide was applied in combination with heat-shock treatments, browning did not occur. Heat shocks may control tissue browning by more than just interfering with protein synthesis.

Transformed hairy root cultures of chilli pepper (Capsicum frutescens cv. cayenne) containing the CaMV 35S promoter linked to the parsley PAL-2 cDNA were generated. These transformants showed increased PAL activity at early and late stages of culture. The morphology, colour and growth rate of these transformants were quite different from the control hairy roots. Measurements of cell dry weight, content of fibre and lignin-like material, suggested that the altered characteristics of the PAL transformants might be linked to lignification. HPLC analyses of phenolic compounds in transgenic roots revealed the accumulation of several substances that were not found in the controls. In response to the addition of salicylic acid or phenylalanine, lignification of the control hairy roots increased. However, the content of lignin-like substances in the PAL transformants was not increased by these treatments. These results indicate that lignification of the PAL transformants had reached a level that could not be further increased.

This study was undertaken to determine if endogenous IAA content and axillary bud development correlate with phenylalanine ammonia-lyase (PAL) induction and russet spotting (RS) susceptibility among RS susceptible and resistant cultivars of Iceberg lettuce (Lactuca sativa L.). Final levels of ethylene-induced PAL activity and RS development were highly correlated among cultivars, field conditions, and harvest dates. Harvested Iceberg lettuce midribs contained relatively low amounts of free IAA (maximum of 5.2 ng·g-1 fresh weight). There was poor correlation between free IAA content in lettuce leaf midribs and final RS development among all cultivars, growing conditions, and harvest dates. Axillary bud development, as measured by the number of visible buds per head, bud weight, or bud length, were not significantly correlated with final RS development or midrib IAA content. Cultivars with higher initial free IAA content lost much of their IAA after 8 days storage at 5C in air ± ethylene.