Accumulation Of Total Phenolic Compounds Research Articles

Dynamics of Bioactive Compounds under the Influence of Yellow, Blue, and Violet Light Filters on Hippophae rhamnoides L. (Sea Buckthorn) Fruits

The current study was carried out to monitor the dynamics of phenolic compounds and vitamin C variations in Hippophae rhamnoides L. (sea buckthorn) under the influence of different color filters, as follows: yellow (590 nm), blue (450 nm), and violet (400 nm). The fruits were harvested at maturity from different parts of the canopy (i.e., base, middle, and top), immediately stored at −18 °C, and afterward lyophilized to reduce the loss of compounds for preparing the chemical assays that were carried out. HPLC-DAD-ESI+ was used to determine the phenolic compounds and vitamin C content of the fruits. EPR (electron paramagnetic resonance) measurements were also carried out to confirm the antioxidant character of the berries. This is the first study to examine the effect of different color filters on the accumulation of phenolic compounds and vitamin C content in the fruits of sea buckthorn. Among the three color filters used, the violet filter proved to be the most beneficial for the accumulation of total phenolic compounds (3.326 mg/g) and vitamin C (1.550 mg/g) in the berries. To reach high contents of phenolic compounds and vitamin C, the best setup included using very-high-energy emission LEDs as close as possible to blue and violet (400–450 nm). Therefore, the different light color intensities and temperatures on each level of a canopy play key roles in enhancing the phenolic compound content, antioxidant activity, and vitamin C content of sea buckthorn fruits. This knowledge will help provide insights into the accumulation of secondary metabolites and improve future production strategies in sea buckthorn.

Quality and bioactive compound accumulation in two holy basil cultivars as affected by microwave-assisted hot air drying at an industrial scale

Holy basil (Ocimum Tenuiflorum L.) contains several bioactive compounds useful to the pharmaceutical and food industries. Microwave drying (MD) is a powerful technique for rapid drying of food or plant materials while preserving bioactive compounds during the process. However, little is known about the optimal combination of MD power with hot air drying (HAD) that can preserve the quality and yet only consume reasonable energy when drying holy basils. For that purpose, the effects of drying methods using MD combined with HAD at 45°C were examined to prevent losses in quality, antioxidant activities, and volatile flavor compounds in two holy basil cultivars (green and red cultivars). Holy basil leaves were dried at different MD powers of 200, 400, and 600 W combined with HAD and compared with a traditional tray drying (TD) at 45°C. Drying using MD at 600 W with HAD displayed significantly high levels of color retention, chlorophyll, and carotenoid content in both cultivars. The green cultivar showed a greater accumulation of total phenolic compounds (TPC), terpenoids, and DPPH free radical scavenging at 400 W with HAD. However, the red cultivar had the highest TPC, flavonoid, and terpenoid content at 600 W with HAD. The accumulation of major volatile organic compounds (VOCs) was also affected, and treatment at 600 W exhibited the highest methyl eugenol and β-caryophyllene content in both cultivars. The use of the highest power of MD (600 W) with HAD for leaf drying reduced the effective drying time and energy consumption among both cultivars. Taking into consideration the dried quality of antioxidant accumulation and energy consumed for drying, we recommend using MD at 400 or 600 W with HAD for the green cultivar and 600 W for the red.

Physiological responses and variation in secondary metabolite content among Thai holy basil cultivars (Ocimum tenuiflorum L.) grown under controlled environmental conditions in a plant factory.

Holy basil (Ocimum Tenuiflorum L.) is a widely used herb containing several bioactive compounds of interest for the food and pharmaceutical industries. Plant factories using artificial lighting (PFAL) is a modern agricultural system that offers opportunity to improve crop production and stabilizes productivity in many herbal plants. However, little is known about the variation among holy basil varieties that can be cultivated and provide reasonable biomass and bioactive compounds in PFAL. We therefore evaluated 10 Thai accessions and two commercial cultivars in a PFAL (with hydroponic cultivation) to categorize cultivar characteristics by investigating physiological responses and secondary metabolite variation at plant flowering stage. Among Thai varieties, net photosynthetic rate (Pn) was significantly highest in varieties OC059 and OC081. The greatest growth and biomass measures were observed in OC064. Antioxidant capacity also varied, with the greatest accumulation of total phenolic compounds (TPC), flavonoids, and antioxidant activity by DPPH assay in OC064, and highest terpenoid content in OC194. The accumulation of major compounds confirmed by showing the highest levels of eugenol in OC057, OC063, OC194, and OC195 and methyl eugenol in OC072 and OC081. The highest α-humulene content was found in OC059. PCA based on physiological responses and secondary metabolites indicate that OC064 was clearly distinguished from other cultivars/accessions. These findings demonstrate variation across holy basil accessions for physiologic responses, antioxidant capacity, and secondary compounds in PFAL. These insights lead to identification of suitable varieties which is the most important step of developing an efficient method for producing high quality raw materials of Thai holy basil for supplying the foods and pharmaceutical industries.

Different types of explants and natural ventilation systems influence the accumulation of dry weight and of total phenolic compounds in Aloysia gratissima (Verbenaceae)

The objective of this study was to evaluate the effect of the use of different natural ventilation systems on the growth and accumulation of total phenolic compounds in Aloysia gratissima. Nodal and apical segments with 1 pair of leaves were inoculated in flasks containing ½ MS culture medium without sucrose and supplemented with 0.1 mg L-1 indole-butyric acid. The cultivation systems included a conventional system (NMS) and alternative membrane systems with 1 (AMS1), 2 (AMS2) and 4 (AMS4) low-cost membranes. After 30 days, the in vitro growth, leaf area, dry weight and accumulation of phenolic compounds were evaluated. Plantlets from apical segments showed superior results in all variables analyzed. The use of the NMS compromised plantlet growth. However, improved results were obtained with the use of porous membranes, with the best growth observed in AMS4. The leaf area of plantlets originating from apical segments was 3.03 times greater than that of plantlets from nodal segments. Plantlets in the NMS had the lowest values of leaf area, root length, number of leaves and dry weight. However, the use of membranes allowed higher growth. The AMS4 treatment increased the leaf dry weight accumulation by 6.13-fold compared to that obtained with the NMS treatment. The accumulation of total phenolic compounds increased with the use of greater numbers of porous membranes. The use of apical segments and lids with 4 porous membranes is recommended for micropropagation of the species. The use of an alternative membrane system positively influences the accumulation of total phenolic compounds.

Effects of Supplemental UV-A LEDs on the Nutritional Quality of Lettuce: Accumulation of Protein and Other Essential Nutrients

Light plays an important role in influencing the nutritional quality of food crops, especially with regard to the health-promoting phytochemicals. However, its role in affecting the nutritional quality with regard to the essential nutrients is not well understood. In this study, the effects of preharvest UV-A treatment on the nutritional quality of lettuce (Lactuca sativa, cv. red-leaf ‘New Red Fire’ and green-leaf ‘Two Star’) in relation to the essential nutrients and health-promoting phytochemicals were explored. Lettuce plants were grown in a growth chamber and were subjected to supplemental UV-A LEDs (peak wavelength 375 nm) for a brief period (3–6 days) prior to harvest. UV-A LEDs were equipped with lenses to control the light dispersion. Many growth indices such as shoot fresh mass, leaf area, and leaf number were unaffected by supplemental UV-A in both varieties while shoot dry mass decreased in response to a 6-day UV-A treatment compared to the control. Leaf chlorophyll and carotenoid concentrations increased significantly in green-leaf lettuce after 3 or 6 days of UV-A treatment, but only after 3 days of UV-A treatment in red-leaf lettuce compared to the control. Leaf protein concentration increased significantly in both lettuce varieties along with a number of essential nutrients such as phosphorus, potassium, calcium, manganese, and sulfur in response to supplemental UV-A. Supplemental UV-A increased the accumulation of protein by approximately 48% in green-leaf lettuce and 31% in red-leaf lettuce compared to the control plants. Moreover, in addition to the above essential nutrients, green-leaf lettuce accumulated higher amounts of magnesium, copper, and zinc compared to the control plants, indicating that green-leaf lettuce was more responsive to preharvest supplemental UV-A treatment than red-leaf lettuce. However, the accumulation of total phenolic compounds and flavonoids in both varieties was lower under supplemental UV-A. Furthermore, the use of LED lenses did not have a consistent impact on most of the plant responses studied. Overall, the results indicate that a brief preharvest exposure of both red- and green-leaf lettuce varieties to UV-A increased their nutritional quality by enhancing the accumulation of protein and other major essential nutrients.

Changes in Berry Tissues in Monastrell Grapevines Grafted on Different Rootstocks and Their Relationship with Berry and Wine Phenolic Content.

Monastrell grapevines grafted on the rootstocks 140Ru, 1103P, 41B, 110R, and 161-49C were subjected to regulated deficit irrigation (RDI) and partial root-zone irrigation (PRI). We analyzed the effects of the rootstock and irrigation method on the phenolic concentration in different berry tissues, its dilution/concentration due to the berry size, the anatomical and morphological traits of berries related to the phenolic compounds concentration, and the relationships of all these parameters with the final berry and wine phenolic content. The rootstock had an important effect on the accumulation of total phenolic compounds and anthocyanins in the skin (berries from 110R and 140Ru had the highest values). Moreover, the rootstock modified some anatomical and morphological characteristics that had a direct relationship with the final phenolic compounds concentration in the must. Large grapes and high must percentages (110R and 140Ru) produced a dilution effect, whereas small berries and a low must percentage increased the concentration (161-49C). For 110R, the small size of the cells of the epidermis and hypodermis in the grapes also could have contributed to the high phenolic compounds concentration in the skin. The percentage of cells in the skin with a uniform coloration was positively correlated with its total phenolic compounds and anthocyanins concentration and also with the phenolic quality of the wine. The PRI modified some specific morphological/anatomical skin/berry traits, and these may have contributed to important changes in the final concentration of phenolic compounds, depending on the rootstock. The better phenolic quality of the must and wines observed in some rootstocks under PRI could be due to smaller cells in the epidermis and hypodermis of the skin (161-49C), a higher percentage of cells with a uniform coloration in the hypodermis (110R), or a lower number of seeds per berry (161-49C). In contrast, the lower phenolic compounds concentration in the must of grapes observed in the most vigorous rootstocks under PRI could be due to a greater thickness of the epidermis (140Ru), greater cuticle thickness (41B), a higher number of seeds (140Ru), a lower skin/pulp ratio and percentage of skin (140Ru), a greater percentage of cells in the epidermis without coloration or with large inclusions, and a lower percentage of cells with a uniform coloration in the epidermis (140Ru). The final quality of the grape is related to some changes in histological and morphological aspects of the grape produced by the rootstock and irrigation strategy.

RELATION BETWEEN FUSARIUM WILT DISEASE AND ACCUMULATION OF PHENOLIC COMPOUNDS WITHIN RESISTANT AND SUSCEPTIBLE TOMATO CULTIVARS

Wilting disease of tomato caused by Fusarium oxysporum f. sp. lycopersici, (FOL) is one of the most destructive diseases. This disease causes significant yield losses in Egypt. Ten Fusarium isolates were isolated from wilted tomato plants growing in El-Menoufia Governorate during 2020 growing season. The most virulent isolate (isolate No. 6) was tested for its virulence on ten tomato cultivars under greenhouse conditions. The cultivars were significantly varied in their susceptibility toward the tested virulent isolate. The most susceptible cultivar was Carmen F1cv as it recorded the highest value of infection (100% and 96%) in seeds and seedlings experiments, respectively. On the other hand the results showed that Diamond Arwa cultivar was the most resistant tested cultivar where zero infection percentage was recorded on both seeds and seedling experiments. The chemical analysis using HPLC was conducted with the most susceptible tomato cultivar (Carmen) and the most resistant one (Diamond Arwa) one and three weeks post inoculation with pathogenic isolate of Fusarium. The results revealed that the accumulation of total phenolic compounds either in shoots or roots was higher three weeks after inoculation than one week post inoculation within the two tested cultivars. Remarkable that roots and shoots of most resistant cultivar tested recorded more total phenol concentrations rather than the susceptible one. Significant differences were detected among the resistant and the susceptible cultivars tested with the compounds detected at 21.2m; 26,2m and 29.1 minute in both shoots and roots three weeks after pathogen inoculation which suggesting potential role of these particular chemicals in resistance mechanism toward Fusarium wilt disease within resistant tomato cultivars.

Polyploidy‐promoted phenolic metabolism confers the increased competitive ability of Solidago canadensis

Allelopathy plays an important role in the successful invasion of alien invasive plants. Phenolic compounds are one of the primary classes of secondary metabolites with strong allelopathic activities. Polyploidy can cause significant effects on the production and yield of plant secondary metabolites. However, the effect of allelopathic potential of phenolic compounds on the competitiveness of different geographical cytotypes of Solidago canadensis remains unknown. We conducted a common garden field experiment in the invasive habitat of China to compare the competitive ability of native and introduced diploid, tetraploid and hexaploid S. canadensis against intentionally planted local weeds. Results showed that introduced tetraploids and hexaploids outcompeted local plants and formed a monodominant community due to superior competitive ability. Phenolic metabolism analysis showed these populations had a high accumulation of total phenolic compounds in aerial parts and rhizosphere soil throughout three developmental stages, which contributed to significant allelopathic effects on tested weeds. However, diploids and native polyploids showed less allelopathic activities due to the low level of total phenolic content. Together, these results suggest polyploidization is one of the reasons that driving the differentiation of phenolic metabolism in different geo‐cytotypes of S. canadensis, and the allelopathic abilities of introduced polyploids are further enhanced through a post‐introduction adaptive evolution. Polyploidy‐promoted allelopathic potential makes introduced polyploids more competitive against local plants than diploids and native polyploids, which contribute to its successful invasion.

Exogenous application of GABA retards cap browning in Agaricus bisporus and its possible mechanism

In this study, the effect of exogenous γ-aminobutyric acid (GABA) at 0 (control), 0.01, 0.1, 1, and 10 mM on cap browning and quality of button mushrooms during 15 d of storage at 4 °C was investigated. GABA at 0.1 mM yielded the lowest cap browning. Weight loss, electrolyte leakage, and malondialdehyde (MDA) content were significantly lower in mushrooms treated with 0.1 mM GABA, while their firmness was higher. The increased accumulation of total phenolic compounds in the 0.1 mM GABA treated mushrooms was associated with a higher expression and activity of phenylalanine ammonia-lyase (PAL) accompanied by a lower expression and activity of polyphenol oxidase (PPO). GABA treatment was capable of reducing H2O2 content and increasing ascorbic acid (AsA) content. Exogenous GABA increased the endogenous GABA content by increasing the expression of the glutamate decarboxylase (GAD) gene and decreasing the expression of the GABA transaminase (GABA-T) gene. Overall, GABA treatment could be employed for retarding cap browning and maintaining the sensory and nutritional quality of button mushrooms during cold storage.

Supplemental UV-A and UV-B Affect the Nutritional Quality of Lettuce and Tomato: Health-Promoting Phytochemicals and Essential Nutrients

UV radiation plays an important role not only in plant growth and development but also in the accumulation of essential nutrients and health-promoting phytochemicals in plants. The main objective of this study was to examine the effects of supplemental UV-A, UV-B, and UV-AB on the nutritional quality of lettuce (Lactuca sativa, cv. red leaf “New Red Fire” and green leaf “Two Star”) and tomato (Solanum lycopersicum L., cv. BHN-589) grown in a greenhouse. Supplemental UV radiation was provided by UV lamps 5 - 6 days prior to harvest. Supplemental UV-A produced higher accumulation of total phenolic compounds and higher antioxidant capacity in red leaf lettuce compared to other treatments. Overall, supplemental UV-A produced a stronger response than other UV treatments and control in the accumulation of many phenolic compounds including luteolin-7-glucoside, quecetin-3-glucoside, and apigenin-3-glucoside in red leaf lettuce. However, UV-B and UV-AB had a negative response in the accumulation of many phenolic compounds including chlorogenic acid, luteolin-7-glucoside, quercetin-3-glucoside, and apigenin-3-glucoside in both red and green leaf lettuce varieties. In tomato fruits, supplemental UV-A had no effect on their total phenolic concentration. However, supplemental UV-B radiation for 3 h or UV-AB radiation for 9 h exposure produced higher total phenolic concentration in the fruits compared to other supplemental UV treatments. Supplemental UV-AB (3 hexposure) was generally more effective than other UV treatments in increasing the accumulation of a number of phenolic compounds including chlorogenic acid, caffeic acid, chicoric acid, luteolin-7-glucoside, and other flavonoids in ripe tomato fruits. Supplemental UV-A produced higher accumulation of carotenoids including lutein and β-carotene than other supplemental UV treatments, while supplemental UV-AB increased the accumulation of lycopene in fully ripe tomatoes. With regard to the essential nutrients, green leaf lettuce was more responsive to the supplemental UV treatments than red leaf lettuce. All the supplemental UV treatments produced an increase in protein concentration in the leaves of green leaf lettuce. However, supplemental UV-AB produced a stronger response compared to the control and other UV treatments in increasing the accumulation of many nutrients including protein, phosphorus, potassium, sulfur, and zinc in green leaf lettuce “Two Star”. Supplemental UV-treatments did not affect the accumulation of any essential nutrients in fully ripe tomato fruits. The results show that supplemental UV enhances the nutritional quality of lettuce in relation to both health-promoting phytochemicals and essential nutrients. Similarly, supplemental UV enhances nutritional quality in tomato fruits with higher accumulation of both phenolic compounds and carotenoids than does the control treatment.

Influence of Melatonin Treatment on Peel Browning of Cold-Stored “Nanguo” Pears

The effects of melatonin (MT) on chilling injury-induced peel browning of “Nanguo” pears were investigated during the fruit shelf-life at 20 °C, after storage at 0 °C for 120 days. Melatonin treatment alleviated the severity of peel browning, as evidenced by the lower incidence of peel browning and browning index of the MT-treated “Nanguo” pear, and delayed browning time compared to that observed in control fruit. In addition, MT treatment reduced lipoxygenase activity and malondialdehyde content and enhanced the activities of phenylalanine ammonia lyase, shikimate dehydrogenase, 4-coumarate:coenzyme A ligase, cinnamate-4-hydroxylase, and 6-phosphogluconate dehydrogenase but inhibited the activity of polyphenol oxidase, which catalyzes the oxidation of phenolic compounds to quinones. Furthermore, MT treatment enhanced the accumulation of total phenolic compounds, thereby improving antioxidant capacity and maintaining cell membrane integrity, and stimulated the accumulation of proline by promoting the activities of key enzymes involved in proline synthesis, namely Δ1-pyrroline-5-carboxylate synthase and ornithine δ-aminotransferase, which collectively contribute to improved chilling tolerance and delayed browning. These findings indicate that MT treatment effectively relieves peel browning of cold-stored “Nanguo” pears by regulating the metabolism of phenolic compounds and proline.

Role of active transport of potassium to leaves in the mechanisms of tolerance to salinity in common bean (Phaseolus vulgaris L.)

Biochemical markers are of great utility in screening for salt tolerance of crops. In common beans (Phaseolus vulgaris), lower levels of proline under stress have been associated with a better stress resistance of cultivars. In the present study, the responses to salinity have been analysed in six cultivars of common beans: four local landraces from Spain and two experimental lines from Cuba. Proline was used for ranking the relative tolerance of the cultivars, confirming a previous study which reported as more stress-tolerant two of the Spanish landraces. Total soluble sugars concentrations varied with treatments and between genotypes, but it was difficult to assess their role in stress tolerance of the analysed plants. Sodium concentration in leaves was the lowest in one of the two salt-resistant cultivars, and potassium did not vary or even increased under salt stress in all of them, except for the most susceptible one, where a drop of this cation was registered under 150 mM NaCl. Changes in malondialdehyde (MDA) contents did not indicate salt-induced membrane peroxidation resulting from secondary oxidative stress; consequently, accumulation of total phenolic compounds and flavonoids, as an antioxidant defence mechanism, was not detected. These results highlight the reliability of using proline as a biochemical marker of salt stress in common beans and the importance of the mechanism related to potassium transport to leaves in conferring stress tolerance to some common bean cultivars.

Сontent of phenolic compounds in the native and alien species of the <i>Bidens</i> genus growing in various regions of Belarus

The content of phenolic compounds and flavonoids in separate organs and aerial parts ofBidensspecies growing in different regions of Belarus was studied (alien species –Bidens frondosusL. andBidensconnatusWilld., native species –Bidens tripartitusL.). It was found that the leaves were characterized by the maximum accumulation of total phenolic compounds and total flavonoids. The accumulation of these metabolites decreased in the row of “leaves – inflorescences – stems and roots”. Approximately 14 % of phenolic compounds in leaves and inflorescences were flavonoids. The accumulation of phenolic compounds in the aerial parts ofB. frondosus,B. connatusandB. tripartitus, depending on the growing conditions, varied from 60, 55, 90 to 155, 130, 115 mg/g dry weight, flavonoids – from 7, 11, 8 to 20, 15, 19 mg/g dry weight, correspondingly.B. frondosusandB. connatusdemonstrated a wider range of variation in the sum of phenolic compounds thanB. tripartitus. A comparative analysis of the total phenolic accumulation in plants of different species collected in geographically close localities showed the absence of significant differences in the content of the studied secondary metabolites in alien and native species ofBidens.

Assessment of plant defence induction and biocontrol potential of Bacillus megaterium wr101 against Meloidogyne javanica

Summary The aim of this study was to evaluate biological control ability and induction of plant defence by Bacillus megaterium wr101, isolated from wheat rhizosphere, on disease severity induced by Meloidogyne javanica on cucumber. In addition, changes in some plant defence compounds (such as peroxidase, polyphenol oxidase, catalase, hydrogen peroxide (H2O2) and accumulation of total phenolic compounds) induced by B. megaterium wr101 and M. javanica were also evaluated. Results showed that application of B. megaterium wr101 reduced nematode disease indices compared to non-treated controls. Inoculation of cucumber roots with B. megaterium wr101 increased peroxidase and polyphenol oxidase activities in root tissue from the first day after inoculation (DAI), with maximum levels of these enzymes recorded 4 DAI and then reduced gradually. Catalase activity and H2O2 accumulation showed two peaks on 1 and 5 DAI, respectively, but the presence of nematodes in the plant significantly increased the activity level of catalase enzyme even in the presence of the bacterium. Bacillus megaterium wr101 also stimulated the accumulation of total phenolic compounds in cucumber roots.

Effects of Light-Emitting Diodes on the Accumulation of Glucosinolates and Phenolic Compounds in Sprouting Canola (Brassica napus L.).

In this study, we investigated optimal light conditions for enhancement of the growth and accumulation of glucosinolates and phenolics in the sprouts of canola (Brassica napus L.). We found that the shoot lengths and fresh weights of red light-irradiated sprouts were higher than those of sprouts exposed to white, blue, and blue + red light, whereas root length was not notably different among red, blue, white, and blue + red light treatments. The accumulations of total glucosinolates in plants irradiated with white, blue, and red lights were not significantly different (19.32 ± 0.13, 20.69 ± 0.05, and 20.65 ± 1.70 mg/g dry weight (wt.), respectively). However, sprouts exposed to blue + red light contained the lowest levels of total glucosinolates (17.08 ± 0.28 mg/g dry wt.). The accumulation of total phenolic compounds was the highest in plants irradiated with blue light (3.81 ± 0.08 mg/g dry wt.), 1.33 times higher than the lowest level in plants irradiated with red light (2.87 ± 0.05 mg/g dry wt.). These results demonstrate that red light-emitting diode (LED) light is suitable for sprout growth and that blue LED light is effective in increasing the accumulation of glucosinolates and phenolics in B. napus sprouts.

Characterization of defense responses in the ‘green ring’ and ‘red ring’ on jujube fruit upon postharvest infection by Alternaria alternata and the activation by the elicitor treatment

Alternaria alternata is the major threat to postharvest storage of jujube (Ziziphus jujuba Mill.) fruit. A typical phenotype that a ‘red ring’ circling an enclosed ‘green ring’ area surrounding the spot of Alternaria rot on the jujube peel was first found and investigated in this study. Results indicated that the pathogenic infection is essential for the onset and development of the phenotype on jujubes, with high inoculum concentration and low incubation temperature leading to the enlarged ‘green ring’. The boundary line between the two rings seemed to be pre-fixed on the A. alternata-infected jujubes once the phenotype appeared. The ‘green ring’ was invaded gradually and ‘eaten-up’ eventually by the expansion of the surrounded rot spot. Biochemical measurements showed that such successful infection on jujubes might attribute to the great loss of individual phenolic compounds, including (+)-catechin, chlorogenic acid, (−)-epicatechin and p-coumaric acid, in the peel tissue of the ‘green ring’ and ‘red ring’, while some antifungal compounds increased in the flesh beneath the peel tissue in response to the infection. The elicitor salicylic acid (SA) triggered the early and rapid occurrence of the ‘green ring’ and ‘red ring’ on the A. alternata-infected jujubes. The SA treatment activated the phenylpropanoid pathway and elevated the accumulation of total phenolic compounds in the ‘green ring’ to combat the fungal attack and thereby restrict the expansion of disease lesion. Characterization of defense responses in the ‘green ring’ and ‘red ring’ on jujubes against Alternaria infection is helpful for unravelling the underlying mechanisms of the formation of defense resistance in fruit upon postharvest infection.

Salicylic acid modulates cutting-induced physiological and biochemical responses to delay senescence in two gerbera cultivars

The postharvest longevity of gerbera (Gerbera jamesonii) flowers has a critical importance in determining their commercial value; and therefore, there is a commercial demand for prolonging their vase life (VL). Here, we tested the efficacy of salicylic acid (SA, 150 µM) preservative in extending longevity of cut flower of two gerbera cultivars, namely the ‘Sunway’ and ‘Bayadere’, of which water-held ‘Bayadere’ has longer VL than water-held ‘Sunway’. The results indicated that exogenous SA could significantly prolong the VL of cut flowers of both ‘Sunway’ and ‘Bayadere’ cultivars, with better preservative effect being observed on ‘Sunway’. SA preservative was more effective in ameliorating relative water uptake and relative fresh weight in ‘Sunway’ than in ‘Bayadere’, which was accompanied by a greater decrease in proline accumulation. Application of SA prolonged the VL of two cut gerbera flower cultivars by inhibiting the activity of polyphenol oxidase involved in browning reaction, and decreasing oxidative stress through improving reactive oxygen species-scavenging antioxidant capacity, which included accumulation of total phenolic compounds and total flavonoids, and enhancement of enzymatic antioxidant activities. As a result, membrane lipid peroxidation levels were reduced in cut flowers of both cultivars, with higher reduction level being observed in ‘Sunway’ than in ‘Bayadere’. Additionally, SA preservative was more efficient in maintaining a greater content of total soluble proteins in ‘Sunway’ than in ‘Bayadere’. These findings clearly demonstrated that SA has higher preservative effects on extending VL of ‘Sunway’ than that of ‘Bayadere’. Taken together, SA can be recommended to farmers for postharvest treatments to maintain quality and delay senescence of gerbera flowers.

Pulsed LED light increases the phytochemical level of basil microgreens

The effects of pulsed light-emitting diode (LED) lighting on antioxidant and antiradical activities of basil microgreens were investigated. Basil (Ocimum basilicum L. 'Sweet Genovese') was grown in a controlled-environment growth chamber (21/17±2°C day/night temperature; 55±5% relative air humidity) for 14 days after sowing in peat substrate. The main lighting system of high-pressure sodium (HPS) lamps (SON-T Agro, Philips) was supplemented with 20±2 µmol m‑2 s‑1 flux of monochromatic LEDs with peak emission of royal blue 455 nm, blue 470 nm, cyan 505 nm, yellow 590 nm, or red 627 nm (Luxeon® III Star, Philips Lumileds Lighting Company, USA), and the total photosynthetic photon flux density (PPFD) was 200±10 µmol m(‑2) s(‑1) (16 h day(‑1)). Frequencies at 2, 32, 256, and 1024 Hz with a duty cycle of 50% of monochromatic LEDs were applied. Reference plants were grown under HPS lamps supplemented with continuous light of monochromatic LEDs. The results showed that the effects of supplemental pulsed light on total phenolic compounds, total anthocyanins, 2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical scavenging activity and ascorbic acid depended on the wavelength of monochromatic LEDs and frequency. Supplemental lighting of blue 470 nm or red 627 nm at 1024 Hz was the most effective for accumulation of total phenolic compounds as well as total anthocyanins. The highest antiradical activity in basil microgreens treated under all supplemental LEDs, was determined, except red 627 nm at 256 Hz. Accumulation of ascorbic acid was promoted by pulsed light at all frequencies, but higher contents of ascorbic acid were determined under the treatments of 32 and 256 Hz in comparison with other frequencies.

Effect of gamma irradiation on some active constituents and metabolites of Cichorium pumilum Jacq.

A biotic stress mostly controls medicinal compounds productivity in the plant. This study was carried out to investigate the effect of gamma irradiation on some active constituents in shoot and root of Cichorium pumilum (Chicory). Irradiated seeds with 20, 40, and 80 gray (Gy) by cobalt 60 gamma irradiation were cultivated under normal field conditions. Results showed that the plant dry weight was stimulated at the first growth stage and inhibited at the following stages. Photosynthetic pigments (chl. a & b) were inhibited but carotenoids increased as a defensive effect to the increase in gamma doses. Alkaloids content was twice the phenolic and several times the saponins content under the control plant. Saponin content in the plant root increased with all gamma doses and the highest increase (69.5%) was at 40 Gy compared to the control. Likewise, the total alkaloids content was increased by 49.7% at the 40 Gy in the plant shoot. Accumulation of alkaloids was more sensitive to gamma radiation in shoot than in root. The 40 Gy dose enhanced accumulation of total phenolic compounds in root. Increasing gamma dose to 80 Gy inhibited the accumulation of three secondary metabolites in plant shoots and roots especially the alkaloids content that was reduced per plant to the half. The study suggested 40 Gy dose as an efficient dose to induce the metabolism and accumulation of active compounds of Chicory plants. In addition, it certified the vegetative stage which used as a human food to produce such compounds from the total plant (shoots and roots).

Mild salt stress improves strawberry fruit quality

Strawberry is one of the most popular fruits because of its shape, color and taste, and the presence of antioxidant compounds. Because severe abiotic stresses result in detrimental consequences to plant growth, the effect of cultivating under mild stress conditions has rarely been investigated. Therefore, we evaluated the effect of mild salt stress on yield and quality of strawberry fruit. Mild salt stress did not affect yield. The lower level of mild salt stress evaluated showed increased vegetative growth (24%), higher photosynthetic effectiveness, and increased activity of phenoloxidase (22%) and polyphenoloxidase (33%), as well as the accumulation of sucrose (5%) and anthocyanins (60%) in the fruit, compared to non-stressed plants. The higher level of mild salt stress increased root growth (30%), the activity of phenylalanine ammonia lyase (68%), and the accumulation of total phenolic compounds (14%), and total antioxidant activity (13%) in the fruit, compared to non-stressed plants. The only phenolic compound improved in these treatments was (+)- catechins. Both levels of salt stress affected the expression of genes involved in the phenylpropanoid and flavonoid pathways, cell wall disassembly and abscisic acid-related genes. Therefore, mild salt stress improves strawberry fruit quality.