فنیل آلانین آمونیالیاز

Bell pepper (Capsicum annuum L.) belongs to the Solanaceae family, it contains high amounts of bioactive compounds such as phenolic, flavonoid, and antioxidant compounds. These nutrients have anti-cancer properties. However, bell pepper can usually be stored for several days during transport or at the time of sale in the store, or after purchase by consumers. In this period of time, the surface of the fruit loses its appearance and begins to lose its nutritional content. In order to postpone the senescence of bell pepper, various methods can be used, such as the atmosphere changing during the storage period, using chemical compounds, or natural compounds treatment. Researchers are looking for a compound that, while having the least harmful effect on human health, can give pepper the longest lifespan. Melatonin is an organic compound that has been studied in recent years on various biotic and abiotic stresses. The purpose of this study is to investigate the effect of melatonin treatment on the physiology of post-harvesting of bell pepper through its effect on the content of enzymatic and non-enzymatic antioxidant compounds during four weeks of storage time.

Materials and methods:

In this research, bell pepper fruit at the stage of physiological maturity was purchased from a local producer located in Tehran and immediately transferred to the research laboratory of Qom University. In the laboratory, the fruits that had damage or defects in appearance were discarded, and the rest were disinfected by immersing in a 1% (v/v) sodium hypochlorite solution for two minutes. In a preliminary experiment, bell peppers were treated with 25, 50, 100, 200, 250 and 300 µmol/L melatonin. Preliminary test results showed that 100 μmol/L melatonin had a significant effect on post-harvest appearance quality (primary test results not shown). Based on an initial experiment and selection of the best effective concentration in maintaining fruit quality, the treatment of 100 micromol/liter melatonin was used as a reference for the studies in this article. Bell peppers were divided into two groups, control and treatment, and after 2 hours immersion in 100 μmol/L as the treatment group and distilled water as the control group. Then it was kept for 4 weeks at a temperature of 4±1 degrees Celsius. In this research, the indicators of weight loss percentage, chilling injury percentage, antioxidant enzyme activity such as CAT and SOD, free radical content such as H2O2 and superoxide free radicals, and total phenol content, flavonoid content, and Phenylalanine amino lyase (PAL) and Tyrosine ammonia lyase (TAL) enzyme activity as enzymes controlling the phenylpropanoid pathway in weeks 0, 1, 2, 3 and 4 were evaluated after storage and with three repetitions.

The results of this study showed that the melatonin treatment of bell peppers was more effective in maintaining fresh weight during storage compared to the control group. In the first to the fourth week, the weight loss percentage of the melatonin treatment in the 2nd, 3rd and 4th weeks of storage was reduced by 39, 20 and 26.15%, respectively, compared to the control group. The results showed that there is a significant difference in the percentage of chilling injury in different weeks of storage between the control and the melatonin-treated group. The results showed that there is a significant difference in total phenol and flavonoid content between the control group and the melatonin-treated group during storage, and this increase was in line with the effect on the activity of PAL and Tal enzymes as key enzymes in the propanoid pathway. In both control and treated groups with melatonin, the content of hydrogen peroxide radical and superoxide radical showed a significant increase (p ≥ 0.05) during four weeks of storage at 4 ± 1 °C (Figure 3). However, in the second, third and fourth weeks of storage, the amount of hydrogen peroxide was significantly (p ≥ 0.05) lower in bell peppers treated with melatonin than in the control group. Compared to the control group, in bell peppers treated with melatonin during the second week of storage, the highest percentage decrease in hydrogen peroxide content was observed.The content of H2O2 and superoxide free radicals during the storage period showed a significant decrease compared to the control group, which showed that this result is consistent with the data obtained with the activity of antioxidant enzymes CAT and SOD.

The results of this research showed that the treatment of bell pepper with melatonin significantly reduced the effect on enzymatic and non-enzymatic antioxidant compounds compared to a control group, and these results confirm the results and the findings of previous studies about exogenous effect of melatonin. Harvested bell peppers during storage are susceptible to freezing stress, which increases the accumulation of reactive oxygen species such as superoxide radicals and hydrogen peroxide, and these compounds induce aging and reduce quality and marketability of agricultural products. The increase in the activity of PAL and TAL enzymes, especially in the first weeks of storage, may be due to the effect of exogenous melatonin on the expression and biosynthesis of genes involved in the phenylpropanoid pathway, and as a result, it leads to an increase in the activity of PAL and TAL enzymes. Increased production of enzymatic and non-enzymatic antioxidant system and activation of key enzymes of phenylpropanoid pathway (PAL and TAL) and increasing the content of total phenol and flavonoid compounds were observed. It seems that the enhanced antioxidant system has maintained the cell stability by reducing the concentration of reactive oxygen species and has increased the tolerance of the fruit to chilling stress. Phenolic and flavonoid compounds make plants resistant to abiotic and biotic stresses. In this study, the decrease in phenolic and flavonoid content due to storage at cold temperature in control group; was significantly increased in the pericarp of pepper treated with melatonin treatment. Based on the results obtained in this research, it can be said that melatonin treatment is beneficial on the post harvesting life of bell peppers and maintaining the appearance as well as the quality and levels of nutrients. Of course, for the final confirmation of this result, we need more studies on this or other fruits.

This study was performed to compare some physiological and molecular responses of lemon balm to osmotic stress imposed by drought and salinity stresses with equal osmotic potential in hydroponic culture. Growing lemon balm plants in hydroponic culture were treated with drought and salinity stress using polyethylene glycol 6000 and sodium chloride for 14 days. Then, seedlings were sampled to evaluate the amount of photosynthetic pigments, proline, phenolic compounds, malondialdehyde, ion leakage percentage, phenylalanine ammonialyase activity and the amount of rosmarinic acid. Also, the expression of phenylalanine ammonialyase and rosmarinic acid synthase genes was examined by real-time PCR. This experiment was performed as a completely randomized design with three replications. The results showed that photosynthetic pigments, phenolic compounds, free proline, malondialdehyde, ion leakage, enzyme activity and relative expression of phenylalanine ammonialyase gene, relative expression of rosmarinic acid synthase and rosmarinic acid content affected by drought and salinity stresses at one percent level of probability. Also, a significant reduction in photosynthetic pigments was observed in drought and salinity stresses. The phenolic compounds content in plants under salinity stress increased compared to the plants under drought stress and untreated. The increase in free proline in plants under drought and salinity stresses was 11% and 25%, respectively. The amount of malondialdehyde and the percentage of ion leakage in plants under drought and salinity stress increased compared to the control plants. Relative gene expression and phenylalanine ammonialyase activity increased in salinity stress. Increasing the relative gene expression of rosmarinic acid synthase in drought and salinity stresses increased rosmarinic acid content by 42 and 60% compared to untreated plants. According to the results, lemon balm responded differently to drought and salinity with iso-osmotic potential. In another words, the plant had a better response to osmotic stress induced by salinity than drought with more increase in proline, phenolic compounds, rosmarinic acid contents, relative gene expression and phenylalanine ammonialyase enzyme activity.

Salinity is one of the most important stresses that has affected food security. (Chenopodium quinoa) is a plant that is currently considered worldwide as a food substitute for wheat, rice, barley and corn. The aim of this study was to investigate the activity of antioxidants, some osmolites, ions and minerals to identify salinity resistant genotypes that can be grown by cultivating quinoa in hot and dry regions of the country that face temperature, drought and salinity stresses. This plant was used as food for humans and fodder for livestock.

In this study, physiological responses of 3 genotypes (Q18 ,Rosada ,Sajama) with relatively high yields were investigated at different levels of salinity stress (control (EC=1.5) and 8, 16, 32 dS/m) in greenhouse conditions and Plants were harvested in the twelfth week for morphophysiological and biochemical measurements and studies were performed on the plant.

By studying the results of Na+ content in salinity stress, it seems that Sajama and Rosada have more ability to prevent Na+ transfer from root to shoot and prevent K+ reduction, also the total amount of elements (Cu+2, Mn+2, Ca+2, Zn+2, Fe+2) decreased at salinity 32 dS/m. The results showed that comparing the growth parameters and increasing proline and decreasing the protein content at salinity 32 dS/m can be associated with reduction of chlorophyll, carotenoids, reduced sugars, total carbohydrates, increased oxidative stress and H2O2 content. However, total ascorbate and glutathione content remained constant at salinity 32 dS/m in Q18, but Sajama and Rosada decreased and phenylalanine ammonialyase activity increased in all genotypes and all salinity levels. Phenolic compounds, flavonoids and anthocyanins in genotyp Rosada showed a greater increase in salinity stress than the other two genotypes.

The total results showed according to the rate of reduction of growth parameters, genotype Sajama seems to be more tolerant of salt than the other two genotypes and the salinity tolerance of Rosada genotype is lower than the other two genotypes but there is no relationship between increased phenolic compounds, flavonoids and anthocyanins and salinity resistance in this genotype

The use of salt tolerant plants in arid and semi-arid regions of the world, including Iran, is one of the ways to achieve high yields. The aim of this study was to investigate the effect of different salinity treatments in hydroponic culture on physiological characteristics, phenylalanine-ammonialyase (PAL) activity and also the small amount of flavonoid compounds kaepmferol and quercetin in field saffron (Crocus sativus L.). For this purpose, saffron corms were planted in pots containing perlite and irrigated in controlled laboratory conditions with ½ Hoagland nutrient solutions containing concentrations of 0, 30, 60, 90, 120 and 150 mM sodium chloride. Based on the obtained results, the effect of salinity stress was not significant on chlorophyll a and b levels at 5% level. Carotenoids and glucose levels in the 60 mM treatment had a significant increase of 27% and 56%, respectively, compared to the control treatment. The effect of salinity on leaf amino acid proline was not significant..The relative water content (RWC) in 150 mM with a decrease of 20%, had the highest decrease compared to the control treatment. The activity of PAL enzyme in only 150 mM had a significant increase of 50%. The amount of kaempferol in all concentrations except 150 mM and the amount of quercetin in only 150 mM showed a significant increase (100%) compared to the control treatment. It seems that according to the test results, the tolerance threshold of saffron plant to salt is in the range of 60 to 90 mM and the defense mechanisms mentioned in this range and above help the plant to tolerate salt.

Salinity resistance is one of the main concerns in arid and semi-arid regions. In this study, the effect of acetic acid pretreatment in salinity stress was investigated on parameters such as relative water content, electrolyte leakage, proline, malondialdehyde, phenolic compounds, protein and photosynthetic pigments content, phenylalanine ammonialyase enzyme activity and expression of important enzymes in rosmarinic acid biosynthesis (phenylalanine ammonialyase and rosmarinic acid synthase) in hydroponic culture of Melissa officinalis L. The seedlings were grown in Hoagland’s solution were pre-treated with acetic acid (10 µM) and then salinity stress was done with NaCl (35 mM) for 11 days. The results indicated that electrolyte leakage percent and malondialdehyde content were decreased, whereas, proline and phenol content were increased in acetic acid pretreated plants in salinity stress. Also, photosynthetic pigments content showed less reduction in acid acetic pretreated plants compared to the control plants. Phenylalanine ammonia lyase activity and gene expression increased in salinity stress. Increasing in rosmarinic acid synthase gene expression resulted in increasing rosmarinic acid content. Also, the amount of rosmarinic acid had a positive and significant relationship with the activity and expression of key genes in its biosynthesis. The results suggest that the use of acetic acid pretreatment, by initiating support mechanisms such as decreasing in peroxidation of membrane lipids, increasing in proline, phenolic compound, activity and expression of genes involved in phenolic compound and photosynthetic pigments played an important role in salinity stress modulation.

Euphorbia pulcherrima is one of the most beautiful and popular potted flowers in the world (especially at Christmas) that has recently been able to occupy a special place in global markets. Preservation of anthocyanin pigments is one of the main factors in determining the quality of Euphorbia pulcherrima. Also growth and maintenance along with maintaining high quality and durability is of great importance in the flower growing industry. For this porpose, experiment was performed to investigate the effect of four levels of benzyl adenine (0, 30, 60 and 90 mg/l) on the quantitative and qualitative characteristics of Euphorbia pulcherrima potted flowers of Christmas Eve cultivar. Experiment in a completely randomized design with 3 replications and each repetition contains 3 experimental units it was done in a commercial greenhouse located in Golzar Pakdasht in 2013. Results showed that spraying with different levels of benzyladenine significantly increased fresh and dry weight of shoots and roots, plant height, total number of leaves and colored brackets, total leaf chlorophyll, anthocyanin bracket and phenylalanine ammonialyase activity, and the number of color brackets, decreased, but the effect was greater at a concentration of 30 mg/l benzyl adenine. The results of this study suggest that benzyl adenine, in particular at benzyl adenine 30 mg/l, the best effect on the quantitative and qualitative characteristics of Christmas Eve cultivar compared to the control and other treatments.

The aim of this study was the investigation of the effect of chitosan on phenolic compounds, rosmarinic acid content, and  key genes expression involved in the biosynthesis of these compounds in Melissa officinalis L. cell suspension culture.

A combination of NAA (1mg L-1), 2, 4-D (1mg L-1), and kinetin (0.5 mg L-1) and stem explants were used for callus induction. After initiation of cell suspension culture, chitosan treatment (0, 50, and100 mg L-1) was performed for one, three, and five days in a factorial experiment based on a completely randomized design with three replications. Phenylalanine ammonia-lyase (PAL) activity, soluble protein, phenolic compound, and rosmarinic acid content were measured. Also, the expressionof phenylalanine ammonia-lyase and rosmarinic acid synthase (RAS) genes was evaluated by real-time PCR.

PAL activity at 50 mg L-1 chitosan showed the highest increase after three days of treatment, which was accompanied by an increase in phenolic compounds. The relative expression of the PAL gene at 50 mg L-1 chitosan increased 2.5 fold at three days after treatment compared to control. This increase in the expression of the PAL gene resulted in an increase in enzyme activity. However, the highest increase in expression of the RAS gene was observed at 100 mg L-1 chitosan in five days after treatment, which led to an increase in rosmarinic acid content.

According to the results, chitosan treatment is recommended to increase of rosmarinic acid content in lemon balm cell culture for five days.

UV ray is able to change several physiologic and anatomic properties of the plants. UV ray can also prevent the plants growth and their desirable performance. Effective role of Silica Nanoparticles in different plants has been proved to enhance plant resistance against biological and non-biological stresses. The present study was performed in the laboratory of the Faculty of Science of Urmia University, in a factorial and random framework to investigate the influence of silica nanoparticles on the growth and physiological characteristics of Lepidium sativum L. during UV-B stress. This study was performed with three treatments (UV-B, Si Np, and simultaneous treatment) in which the concentration of Nanoparticles were determined as 50 mg/L. It should be mentioned that each treatment was repeated three times in equivalent experimental circumstances. The obtained results demonstrated that the length of shoot, the number and surface of the leaves were increased significantly when treatment with Nanoparticles was done. The aforementioned characteristics weren’t increased in simultaneous treatment. Conversely, the thickness of the leaves exhibited a reversed behavior during simultaneous treatment and treatment with silica Nanoparticles, compared with two former properties. The thickness of xylems and phloem were only increased in the case of treatment with UV-B. In all treatments, the concentration of Malone di-aldehyde was increased and a depletion was observed in dissolved sugar content. Moreover, the activity of ascorbate peroxidase and phenyl alanine ammonia lyase were improved in three treatments with Silica Nanoparticles, UV-B stress, and simultaneous treatment. Based on the results of this study, it was observed that the existence of Silica Nanoparticles have positive role to minimize destructive effects of UV-B stresses.

In this experiment, we made a comparison between various Light Emitting Diode (LED) lights including red LED (R), blue LED (B), red (70%) + blue (30%) LED (RB), and white LED (W) as well as fluorescent (F) light, in addition to two lightening time (time1 and time2), on Arabidopsis plant’s response to wounding. In response to wounding, LED-exposed plants, especially RB-irradiated plants, maintained significantly higher shoot dry weight and antioxidant enzyme activities compared to those irradiated with fluorescent lights. The concentration of H2O2 was significantly higher under the condition of RB and B lights in time 1, and in B and florescent lights in time 2, compared to the other light environments. The highest amount of MDA was observed in F and B exposed plants in both times 1 and 2 of the experiment. The highest level of phenolic compounds was found in wounded leaves exposed to RB and R lights. Among the LED-irradiated plants, the highest expression level of the PAL gene in response to wounding was detected in RB-exposed plants in time 1, and in B exposed plants in time 2 of the experiment, one week after wounding. Late-induction of JA biosynthesis-associated genes (AOC and AOS) in response to wounding was observed in all LED conditions, with the highest intensity in W light-exposed plants. The results of COI1 relative expression also suggest more JA signaling in W exposed plants in comparison with other light conditions. Collectively, we concluded that LED light conditions provide a better capability for Arabidopsis thaliana to recover from wound stress mainly by increasing the antioxidant capacity and secondary metabolites production. Among LED light conditions, we candidate RB condition as the best environment for Arabidopsis growth and tolerance to wound stress, and we think, through improving antioxidant capacity, pre-treatment with LED light can provide a better condition for plants to tolerate wound stress. Different amounts of hydrogen peroxide production in response to wounding between different light-exposed plants suggests the possible signaling role of ROS in light-induced wound responses.

In this study, the effects of drought on some physiological characteristics of winter and spring leaves of jasmin (Jasminum fruticans L.) were examined in plants grown in pots and treated with or without water stress for 25 days. Our results showed significant difference in pigment content and phenolic metabolism between winter and spring leaves of jasmine during spring season. In this study, winter leaves showed the higher Chlb, carotanoids, total phenol, flavonoids as well as phenylalanine ammonia lyase (PAL) activity, and relative water content (RWC) as compared to spring leaves, indicating winter leaves are sufficient in their capacity for non-photochemical energy dissipation via these mechanisms. However, water stress did not significantly affect these parameters. Drought significantly increased the amount of malondoialdehyde (MDA) and hydrogen peroxide (H2O2) following significant enhancement of peroxidase (POD) activity. However, in winter and spring leaves treated with water stress, decrease in the maximal quantum efficiency of PSII (Fv/Fm) was not statistically significant. In contrary, spring leaves exhibited a significant decrease in the performance index (PIabs) parameter under drought conditions. Notably, the kinetics of the OJIP chlorophyll fluorescence curve exhibited a quicker difference between winter and spring leaves of jasmine under well watered conditions. Thus, photosynthetic apparatus of winter leaves maintained a higher PIabs during spring season, and showed more tolerance to water stress by dissipating excess light energy by carotenoids; and by screening of photoradiation by phenolic compounds.

Salicylic acid (SA) and Methyl jasmonate (MeJA) as Phyto hormone regulate synthesis of secondary metabolites in a wide range of plant species. The present research designed to evaluate the effect of SA and MeJA elicitation on accumulation of phenolic compounds, flavonoids, Anti-oxidant activity, wet weight and PAL enzyme activity on Stevia plant callus. Results showed that, when elicitors applied to cell culture, phenyl propanoid compounds, antioxidant activity and PAL enzyme activity was increased. Application of MeJA and SA at 100 and 200µM had the highest effect on the production of measured phenyl Propanoides. in both elicitors treated samples, the maximum content of secondary metabolites and PAL enzyme was observed in samples were treated with 100 µM SA+ 100 µM MeJA. A positive correlation between antioxidant activities, total phenol and total flavonoids showed that phenolic compounds may play a key role in antioxidant activity of stevia. Although it’s remarkable that accumulation of Phenolic compounds, antioxidant activity and PAL enzyme activity is in positive correlation, that may be sign of key role of PAL on phenolic compounds production. Observed negative correlation of elicitors’ application with callus fresh weight indicates that under real or pseudo stress condition the plant cell try to balance primary and secondary metabolites. Based on the obtained results, it can be concluded that poly phenolic compounds production, can be strongly changed by application exogenous elicitor compounds.