Soluble Amino Acid Content Research Articles

Effects of low‐pressure radio‐frequency cold plasma on the biochemical parameters and fatty acid profile of wheat flours

AbstractBackground and ObjectivesCold plasma (CP) treatment is a promising way to remove mycotoxins from cereal kernels, although its effects on nutrient contents remain unclear. This study evaluates the biochemical parameters, gelatinization properties, and fatty acid profile of Chinese hard‐white wheat flour treated with low‐pressure radio‐frequency (RF) CP (13.56 MHz, 140 Pa, helium or oxygen, 120 W, 0–180 s, 70 g sample).Findings120 W oxygen and helium plasma respectively required 90 and 120 s treatment to remove 50% deoxynivalenol (DON) from hard‐white wheat flour samples with 1.22 μg/g DON. A General Linear Model–Univariate analysis shows that oxygen and helium plasma both significantly increased water absorption rate, conductivity, and contents of reducing sugars, amylose, soluble protein, and saturated fatty acids in wheat flours but decreased the contents of soluble amino acids, total, unsaturated, mono‐unsaturated and poly‐unsaturated fatty acids, and enthalpy of gelatinization, and kept gelatinization peak temperature. At the same treatment time, helium plasma induced a higher water absorption rate, conductivity, and contents of pentosan and sulfhydryl groups in wheat flours than oxygen plasma. Oxygen plasma induced more reductions in mono‐ and poly‐unsaturated fatty acids in wheat flours than helium plasma. Compared with the untreated samples, helium plasma increased the values of water SRC, NaHCO3 SRC, and sucrose SRC, but decreased the lactic acid SRC, suggesting that the flour functional polymers were modified by helium plasma treatment, but oxygen plasma kept these four SRC values and did not significantly alter the functional polymers in wheat flour.ConclusionThe treatment with low‐pressure RF CP can increase hydrophilicity, and unsaturated fatty acid oxidation in wheat flours while kept starch gelatinization, and helium plasma can modify the flour's functional polymers.Significance and NoveltyThe suitable helium CP treatment (low‐pressure RF, 120 W, and 90–120 s) is a promising way to reduce the contaminants of wheat flours and improve their functional properties.

Rice freshness determination during paddy storage based on solvent retention capacity

AbstractBackground and objectivesRice is an important staple food that is often stored for long periods (e.g., 2 years) but is subject to aging effects that reduce quality. Therefore, a sensitive freshness detection method for long‐term paddy storage is required.FindingsThis study stored five varieties of Chinese paddy at 4°C, 15°C, 20°C, or 35°C for 10 months, and then analyzed their solvent retention capacity (SRC), freshness index, contents of fatty acids, amylose, protein and soluble amino acids, and their thermal and thermomechanical properties. The results show that the SRC values in water, 5% NaHCO3, 5% lactic acid, and 50% sucrose solution decreased with increases in storage temperature and duration, with no differences among the five varieties. The four SRC values were negatively correlated with an existing freshness index (D615–D690), which could not distinguish between the effects of storage temperature and duration. With the SRC values for newly harvested paddy stored at 4°C used as a reference, the mean and accumulated SRC reductions were found to increase with storage temperature and duration. A protocol for rice freshness detection was developed based on these four SRC values.ConclusionPaddy with a mean SRC reduction of ≤25% is eligible for preservation, that with a mean of 25%–30% is slightly ineligible for preservation, and that with a mean of >30% is unfit for preservation. If the sum of the four SRC reductions is ≤100%, the paddy is eligible for preservation, a sum of 100%–120% indicates that it is slightly ineligible for preservation, and a sum >120% indicates that it is unfit for preservation.Significance and noveltyThis novel method based on SRC values provides an improved way to assess the freshness of stored rice.

Integration of the metabolome and transcriptome reveals the mechanism of resistance to low nitrogen supply in wild bermudagrass (Cynodon dactylon (L.) Pers.) roots

BackgroundNitrogen (N) is an essential macronutrient that significantly affects turf quality. Commercial cultivars of bermudagrass (Cynodon dactylon (L.) Pers.) require large amounts of nitrogenous fertilizer. Wild bermudagrass germplasm from natural habitats with poor nutrition and diverse N distributions is an important source for low-N-tolerant cultivated bermudagrass breeding. However, the mechanisms underlying the differences in N utilization among wild germplasm resources of bermudagrass are not clear.ResultsTo clarify the low N tolerance mechanism in wild bermudagrass germplasm, the growth, physiology, metabolome and transcriptome of two wild accessions, C291 (low-N-tolerant) and C716 (low-N-sensitive), were investigated. The results showed that root growth was less inhibited in low-N-tolerant C291 than in low-N-sensitive C716 under low N conditions; the root dry weight, soluble protein content and free amino acid content of C291 did not differ from those of the control, while those of C716 were significantly decreased. Down-regulation of N acquisition, primary N assimilation and amino acid biosynthesis was less pronounced in C291 than in C716 under low N conditions; glycolysis and the tricarboxylic acid (TCA) cycle pathway were also down-regulated, accompanied by a decrease in the biosynthesis of amino acids; strikingly, processes such as translation, biosynthesis of the structural constituent of ribosome, and the expression of individual aminoacyl-tRNA synthetase genes, most of genes associated with ribosomes related to protein synthesis were all up-regulated in C291, but down-regulated in C716.ConclusionsOverall, low-N-tolerant wild bermudagrass tolerated low N nutrition by reducing N primary assimilation and amino acid biosynthesis, while promoting the root protein synthesis process and thereby maintaining root N status and normal growth.

Physiological Responses of the Tetrastigma hemsleyanum Plant under Different Color Films

Tetrastigma hemsleyanum is a traditional Chinese medicine herb, commonly used for its anti-inflammatory and antitumor properties. Flavonoids are the main functional constituents of T. hemsleyanum, and their production in the herb is affected by light quality. T. hemsleyanum is a shade-loving plant and is usually covered by black shade nets during cultivation. However, there are only a few studies on the effects of using color films on growth and flavonoid synthesis in T. hemsleyanum. In this study, we measured the influence of five different color films on growth indexes—sugar, soluble amino acid, soluble protein, and flavonoid content—and flavonoid-synthesizing enzyme activities in T. hemsleyanum. The films used were colorless plastic film as the control group (CK-W), red film (RF), yellow film (YF), green film (GF), and blue film (BF). BF promoted plant growth and increased yield, as evidenced by the highest growth indexes, soluble amino acid content, and chalcone isomerase (CHI) enzyme activity. RF increased the content of secondary metabolites, thereby enhancing herb quality, as evidenced by the highest phenylalanine ammonia lyase (PAL) activity and increased flavonoid content.

Maize plants have different strategies to protect their developing seeds against cadmium toxicity

This work aimed to quantify the concentration of soluble amino acids, nitrogen (N) and Cd in the developing seeds of maize plants that were grown in Cd-contaminated soil from seed sowing to the reproductive stages. The specific activities and feedback inhibition properties of lysine (Lys) metabolic enzymes were also determined in developing seeds. The potential maize yield was depressed by Cd exposure. Cadmium concentration in plant organs followed the decreasing order: roots > stems = leaves > developing seeds (37.04, 1.95, 1.46 and 0.22 mg kg−1 Cd, respectively). The relatively low Cd concentration in the remained developing seeds was a result from root- and ear-mediated reductions of the Cd translocation in plants. Plants under Cd exposure presented developing seeds with an increased N concentration (up to 7%) when compared to control plants. Furthermore, the level of soluble amino acids (particularly histidine, glycine, tyrosine, methionine, isoleucine and valine) was increased in the developing seeds of Cd-treated plants. In addition, changes in the feedback properties of dihydrodipicolinate synthase (DHDPS), an enzyme from lysine metabolism, were observed in developing seeds. In conclusion, the current study showed that maternal plant exposure to Cd can alter the concentration of soluble amino acids and the behavior of Lys metabolic enzymes in developing seeds. This study provided not only new information about the influence of the long-term Cd exposure on plants, but also data about protective plant strategies against Cd toxicity.

Increased organic acid production and decreased phytate phosphorus by high level of water content of Bacillus subtilis ATCC PTA-6737 fermentation of soybean meal

In order to enrich soybean meal (SBM) by microbial fermentation, SBM (3 mm particle size) with 78 or 85% moisture content were inoculated with 0.0 or 1x107 CFU/g (colony forming unit) Bacillus subtilis ATCC PTA-6737 and fermented at 37 oC for 0, 24, 48 and 72 h. There was a marked decrease in pH with 85% moisture content, associated at higher organic acid production, compared to increased pH at 24 h with 78% moisture content and a gradual decrease hereafter. Bacterial growth peaked at 48 h with both moisture contents. Fermenting SBM increased crude ash level by 65%, soluble amino acid nitrogen by 2.7 folds and degraded phytic acid by 65-75%. Moreover, there was a high level of organic acid production despite of decreased crude protein by 6-7%, but the effect of high moisture level was more pronounced in all case. In conclusion, fermentation SBM with water content of 85% at 35 oC by B. subtilis provided SBM an appreciable amount of bio-functionalities such reduced phytate content, increased soluble amino acid content and more importantly fortified with organic acids. The fermented SBM can therefore be used an antimicrobial agent due to its high organic acid level in animal nutrition.

Stress Effects of Chlorate on Longan (Dimocarpus longan Lour.) Trees: Changes in Nitrogen and Carbon Nutrition

Three-year-old potted longan (Dimocarpus longan Lour. cv. Shixia) trees were treated with potassium chlorate and effects on nitrogen and carbon nutrition were examined. The results showed that potassium chlorate at 10 and 20 g per pot failed to induce flower but suppressed shoot growth and caused leaf chlorosis and drop. The treatment significantly inhibited nitrate reductase but increased nitrogen concentration in the leaves and buds. Concentration of soluble amino acids in the leaves of treated trees increased within 14 days and then declined to the control level, while it increased constantly in buds. In both organs, the amino acid increase was an all-round one, with all the tested 21 amino acids increased. However, soluble proteins in the leaves were slightly increased by chlorate, indicating that de novo synthesis of amino acids was activated. Chlorate reduced photosynthetic rate and stomatal conductance but slightly increased CO2 concentration in the mesophyll, suggesting that chlorate treatment damaged photosynthetic apparatus. The damage was reflected by the destruction of thylakoids and grana in the chloroplasts. Chlorate also caused depletion of starch with significant accumulation of soluble sugars in the leaves. Accumulation of sugars and soluble amino acids indicates osmotic adjustment in response to the stress caused by chlorate treatment.

Physicochemical & Microbial Characterization of Overripe Tempeh

Abstract— Recent research showed potencies of overripe tempeh for development as condiment, and therefore, requirement of guiding parameters related to sensory properties. In this study, four samples of overripe tempeh from single source of soybean with different processing method were observed. All samples were characterized with comparable brown color (L* 52.96, a* 6.84, and b* 18.52), and total number of lactic acid bacteria (8.30 – 8.46 log CFU/g). All samples also have similar trends of protein and soluble amino acid content (50.32 – 61.77 mg BSA eq/g dry base, 357.39 – 418.78 mg tyrosine eq/g dry base) compared to fresh tempeh (62.43 mg BSA eq/g dry base, 71.70 mg tyrosine eq/g dry base). The findings indicated suitability of above parameters as guidance in target overripe tempeh for condiment ingredients. Observation of total microbial and total yeast and mould showed that these parameters were affected with production method of overripe tempeh.Keywords— Overripe tempeh, guiding parameters, microbial characterization, physicochemical characterization

Effects of intraspecific variation in rice resistance to aboveground herbivore, brown planthopper, and rice root nematodes on plant yield, labile pools of plant, and rhizosphere soil

In agricultural ecosystems, most crop cultivars are bred for pest resistance with the aim of resisting aboveground herbivores, but it is unclear if this resistance also affects abundance, composition, and activity of underground pests and content of soil labile pools. A fully factorial greenhouse experiment was carried out, using four rice cultivars with distinct resistance to shoot herbivore brown planthopper, Nilaparvata lugens, with and without rice root nematodes, Hirschmanniella spp., to test two hypotheses: (1) rice cultivars resistant to brown planthopper are more susceptible to rice root nematodes and (2) rice root nematodes of resistant cultivars cause greater modification of labile pools of rhizosphere soil than those of susceptible cultivars by inducing more leakage of plant metabolites. Nematode abundance, soluble sugar and soluble amino acid contents of plant, and microbial biomass C and N, dissolved organic C and N, and soluble sugar and amino acid contents of rhizosphere soil were analyzed. The abundance of rice root nematodes substantially increased under all rice cultivars following root nematode inoculation. Rice cultivar resistance to brown planthopper did not affect the numbers of rice root nematodes but decreased negative effects of nematodes on root growth, shoot soluble sugar and amino acid contents, and labile pools of rhizosphere soil, probably implying that integrated complex mechanisms other than only resource allocation were involved in rice resistance to aboveground and belowground herbivores. Our study will contribute to a better understanding of aboveground–belowground interactions and to the development of integrated pest managements by considering belowground ecosystem responses in crop systems.

Effects of Ethylene-Chlormequat-Potassium on Leaf Nitrogen Assimilation after Anthesis and Early Senescence under Dif-ferent Planting Densities

To explore the effects of ethylene-chlormequat-potassium (ECK) on the physiological mechanisms of nitrogen assimilation and early senescence in summer maize, and provide a theoretical basis for high and stable yields of summer maize under high plant density by chemical regulation technology in North China Plain, we conducted a field experiment using two varieties of Zhongdan 909 and Xundan 20 with different planting densities in 2013 and 2014. The results showed that increasing plant density significantly decreased the activities of nitrate reductase (NR) and glutamine synthetase (GS) after anthesis, glutamate oxaloacetic transaminase (GOT) activity at anthesis, and glutamate pyruvate transaminase (GPT) activity at 30 days after anthesis. The soluble protein and free amino acid contents at 20 days after anthesis, and the SPAD value at 10 days after anthesis were significantly decreased with increasing plant density. For both varieties, grain yield reached the highest under 7.5×10 plants ha, while decreased under the density of ≥ 7.5×10 plants ha. The higher density resulted in early senescence. ECK treatment significantly increased the activities of NR, GS, and contents of free amino acid, soluble protein and SPAD value during middle and late grain filling stages. ECK treatment also significantly improved the GOT and GPT activities under 7.5×10−10.5×10 plants ha. Under the density ≥ 7.5×10 plant ha, the yields of Zhongdan 909 and Xundan 20 compared with their own control were respectively 第 12期 卢 霖等: 乙矮合剂对不同密度夏玉米花粒期叶片氮素同化与早衰的影响 1871 increased by 5.59%−6.63% and 6.73%−8.10%. ECK treatment significantly increased the nitrogen assimilation key enzyme activity of ear leaf and its product content under different planting densities, promoted normal nitrogen assimilation and prevented early senescence under higher planting densities, therefore increased yield. Thus, an appropriate planting density combined with ECK application could be an important technique for achieving high grain yield for summer maize production in North China Plain.

Calcium involved in the poly(γ-glutamic acid)-mediated promotion of Chinese cabbage nitrogen metabolism

Plant growth can reportedly be promoted by poly(γ-glutamic acid) (γ-PGA). However, the underlying mechanism is unknown. To reveal the mechanism of γ-PGA, we designed an experiment that investigated the effect of γ-PGA on the nitrogen metabolism of Chinese cabbage hydroponic cultured at different calcium (Ca) levels and varied exogenous Ca2+ inhibitors. The results showed that nitrate reductase (NR), glutamine synthetase (GS), glutamate synthase, and glutamate dehydrogenase activities in leaves and roots were obviously enhanced by γ-PGA at the normal Ca2+ level (4.0 mM). Meanwhile, γ-PGA increased the content of total nitrogen, soluble protein, and soluble amino acids in leaves. However, the promotional effect of γ-PGA on fresh weight weakened when Ca2+ was inadequate. Moreover, γ-PGA not only induced the influx of extracellular Ca2+ and Ca2+ in organelles into cytoplasm, but also increased the Ca2+-ATPase level to modify Ca2+ homeostasis in plant cells. In addition, exogenous Ca2+ inhibitors significantly suppressed the γ-PGA-mediated promotion of cytoplasmic free Ca2+ level, calmodulin (CaM) content, GS and glutamate dehydrogenase activities. In summary, γ-PGA accelerated the nitrogen metabolism of plants through the Ca2+/CaM signaling pathway, thereby improving the growth of the plant.

Effect of different growth regulators and phosphorus levels on nodulation, yield and quality components in green gram

An experiment was conducted to study the effect of foliar applications of 5 growth regulators, viz., indole acetic acid (25 ppm), naphthylene acetic acid (NAA: 50 ppm), ascorbic acid (25 ppm), ethrel (250 ppm) and gibberellic acid (30 ppm) and three levels of phosphorus viz., low (20 kg P2O5 ha−1), medium (40 kg P2O5 ha−1) and high dose (60 kg P2O5 ha−1) on nodulation, yield and quality of green gram during two consecutive years. The highest numbers of nodules, fresh and dry weights of nodules were obtained with high dose of phosphorus during different growth stages. NAA application resulted in highest number, fresh and dry weight of nodules, which increased steadily up to 55 DAS, thereafter these declined. Growth regulating chemicals and P increased the nitrogen, protein, sugar and free amino acid content of nodules significantly. NAA recorded the highest yield, i.e., 44 % increase over control, due to highest number of pods, number of seeds per pod and 1,000 seed weight. Among the P treatments, 60 kg ha−1 gave the highest seed yield as compared to lower P levels. Nitrogen, P and K content of seeds after harvest were significantly increased by growth regulators and P, and highest response was observed in NAA and high P level. Application of growth regulators and P significantly improved nutritional parameters of seed viz., total soluble sugar, starch, protein and free amino acid content.

Different stump heights with Toona sinensis bud vegetable yield and commodity characteristics with field coppice management

As a Chinese traditional food，Toona sinensis bud vegetable has rich nutrition and much benefit for human body health. Stump is a important method to improve Toona sinensis bud vegetable yield and actualize dwarf and close planting. Up to now，the problem of which is the best stump height for high vegetable yield and good commodity character is not resolved. This paper combined with Toona sinensis low production forest improvement project in Taixing City of Jiangsu Provence in China，objective to provide scientific evidence and reference for Toona sinensis high yeild cultivation. Using two-year-old Toona sinensis seedlings，the effects of different stump heights （0，20，40，60，and 80 cm） on bud vegetable yield and commodity characteristics with field coppice management were studied. Experimental design was one singel factor random repeated test（three times repeated，one repeat used fifty per plant）. Results with stumped seedlings showed （1） significant differences （P＜0.05） for both terminal bud and lateral bud vegetable yield when compared to content of soluble sugars，soluble proteins，vitamin C，and amino acids. Also，sensory quality of the lateral bud had significant differences （P = 0.004），but the terminal bud did not （P = 0.211）. （2） For high bud vegetable yield and sensory quality，the 60 cm stump height treatment was best with a 22.3% greater yield than the 0 cm stump height. （3） Considering terminal bud vegetable nutritional components，the 0 and 20 cm stump height treatments had mostly higher soluble sugar content and vitamin C conten；whereas the 60 and 80 cm stump height treatments had higher soluble protein content and amino acid content.［Ch，3 fig. 18 ref.］

Oxidative stress induced in sunflower seedling roots by aqueous dry olive-mill residues.

The contamination of soils with dry olive-mill residue can represent a serious problem as being an environmental stressor in plants. It has been demonstrated that inoculation of aqueous extract of olive oil-mill residue (ADOR) with saprobe fungi removes some phenolic compounds. In this paper we studied the effect of ADOR uninoculated or inoculated with saprobe fungi in sunflower seedling roots. The germination and root growth, O2·- generation, superoxide dismutase (SOD) and extracellular peroxidases (EC-POXs) activities, and the content of some metabolites involved in the tolerance of stress were tested. The roots germinated in ADOR uninoculated show a decrease in meristem size, resulting in a reduction of the root length and fresh weight, and in the number of layers forming the cortex, but did not alter the dry weight, protein and soluble amino acid content. ADOR caused the decreases in O2·- generation and EC-POX′s activities and protein oxidation, but enhanced SOD activity, lipid peroxidation and proline content. Fluorescence imaging showed that ADOR induced O2·- and H2O2 accumulation in the roots. The increase in SOD and the decrease in EC-POX′s activities might be involved in the enhancement of H2O2 content and lipid peroxidation. Control roots treated with ADOR for 10 min show an oxidative burst. Roots germinated in ADOR inoculated with saprobe fungi partially recovered normal levels of ROS, morphological characteristics and antioxidant activities. These results suggested that treatment with ADOR caused a phytotoxic effect during germination inducing an oxidative stress. The inoculation of ADOR with saprobe fungi limited the stress.

强潮区较高纬度移植红树植物秋茄的生理生态特性

Ximen island of Yueqing bay,the northern boundary of artificially planted mangroves,was chosen as the study site.Changes of 1-and 4-year-old Kandelia candel at the tidal level of 1.96,1.66 and 1.35 m above the zero tidal level of Yellow Sea(Waterlogging time at this tidal level are 3.18,3.65 and 4.07 h per-tide-cycle respectively) on growth,photosynthetic pigments,activities of protective enzymes in leaves,contents of total soluble sugars and free amino acid and ion contents in leaves and stems were investigated.The results showed that the tidal level of 1.66 m above the zero tidal level of Yellow Sea was suitable for planting Kandelia candel,because the waterlogging time at this tidal level was less than 3.65 h per-tide-cycle.When the tidal level was 1.35 m above the zero tidal level of Yellow Sea,the waterlogging time at the tidal level was 4.07 h per-tide-cycle,which caused a series of effects.A decrease in the contents of chlorophyll,carotenoid,total soluble sugars and free amino acid,the activities of peroxidase(POD) in leaves,and the ratio of K+/Na+ in stems and leaves of 4-years-old Kandelia candel were detected.Moreover,a rapid increase in the contents of malondialdehyde(MDA) in leaves and Na+ concentration both in leaves and stems of 4-years-old Kandelia candel were found.Based on results listed above,a growth retard was detected when the waterlogging time was 4.07 h per-tide-cycle for 4-year-old Kandelia candel.However,this growth retard was not found in 1-year-old Kandelia candel under the same waterlogging time.Therefore,it is concluded that the older Kandelia candel could grow at 1.66 m above the zero tidal level of Yellow Sea,which is due to the maintaining of normal carbon and nitrogen metabolism under waterlogging time(less than 3.65 hours per-tide-cycle) at this tidal level.

An engineered pathway for glyoxylate metabolism in tobacco plants aimed to avoid the release of ammonia in photorespiration

BackgroundThe photorespiratory nitrogen cycle in C3 plants involves an extensive diversion of carbon and nitrogen away from the direct pathways of assimilation. The liberated ammonia is re-assimilated, but up to 25% of the carbon may be released into the atmosphere as CO2. Because of the loss of CO2 and high energy costs, there has been considerable interest in attempts to decrease the flux through the cycle in C3 plants. Transgenic tobacco plants were generated that contained the genes gcl and hyi from E. coli encoding glyoxylate carboligase (EC 4.1.1.47) and hydroxypyruvate isomerase (EC 5.3.1.22) respectively, targeted to the peroxisomes. It was presumed that the two enzymes could work together and compete with the aminotransferases that convert glyoxylate to glycine, thus avoiding ammonia production in the photorespiratory nitrogen cycle.ResultsWhen grown in ambient air, but not in elevated CO2, the transgenic tobacco lines had a distinctive phenotype of necrotic lesions on the leaves. Three of the six lines chosen for a detailed study contained single copies of the gcl gene, two contained single copies of both the gcl and hyi genes and one line contained multiple copies of both gcl and hyi genes. The gcl protein was detected in the five transgenic lines containing single copies of the gcl gene but hyi protein was not detected in any of the transgenic lines. The content of soluble amino acids including glycine and serine, was generally increased in the transgenic lines growing in air, when compared to the wild type. The content of soluble sugars, glucose, fructose and sucrose in the shoot was decreased in transgenic lines growing in air, consistent with decreased carbon assimilation.ConclusionsTobacco plants have been generated that produce bacterial glyoxylate carboligase but not hydroxypyruvate isomerase. The transgenic plants exhibit a stress response when exposed to air, suggesting that some glyoxylate is diverted away from conversion to glycine in a deleterious short-circuit of the photorespiratory nitrogen cycle. This diversion in metabolism gave rise to increased concentrations of amino acids, in particular glutamine and asparagine in the leaves and a decrease of soluble sugars.

Effect in the quality of intact and minimally processed leaves of collard greens stored at different temperatures

The storage of minimally processed vegetables at low temperatures, in association with proper packaging, represents one of the available technological solutions to mitigate the variations that hinder the quality of final products during storage. We studied the physicochemical variations that occur straight after minimal processing, as well as those that occur during the storage of minimally processed and intact leaves of collard greens (Brassica oleracea var. acephala), stored in 50-µm thick polypropylene bags, with 810-μm diameter perforations. Leaves were stored for 15 and 9 days, at 5 and 10± 1ºC, respectively. There were losses of total chlorophyll, soluble sugars, starch, and soluble amino acids immediately after the minimal processing. The rates of degradation and/or use of chlorophyll, ascorbic acid, soluble sugars, and starch during storage were similar on minimally processed and intact leaves, independently of the storage temperature. On contrary, fresh mass loss was almost two fold larger in minimally processed leaves after nine days of storage, regardless of temperature. We also observed a transient increase in the content of soluble amino acids at the end of storage in minimally processed leaves. The increase in the storage temperature to 10°C enhanced the chemical variations both in minimally processed and intact leaves. As consequence, the rates of degradation and/or use of chlorophyll, ascorbic acid, sugars and starch mounted, and the accumulation of soluble amino acids was stimulated. We concluded that it is necessary to keep on searching for alternative packaging for minimally processed collard greens, and to associate it with storage at low temperatures, but mimicking distribution and commercialization conditions of the cold-chain. Thus, we can succeed in adequately reducing the physicochemical variations that induce quality losses in minimally processed vegetables.

Salicylic Acid–Induced Growth and Biochemical Changes in Salt‐Stressed Wheat

The interactive effect of salicylic acid and sodium chloride (NaCl) salinity on wheat (Triticum aestivum L.) cv. ‘Inqlab’ (salt‐sensitive) and cv. ‘S‐24’ (salt‐tolerant) was studied in a sand‐culture pot experiment in a net house. Wheat seeds soaked in water and 100 ppm salicylic acid solution for 6 h were sown in sand salinized with 0, 50, and 100 mM NaCl. Pots were irrigated with quarter‐strength Hoagland's nutrient solution. Fourteen‐day‐old seedlings were harvested, and growth parameters (leaf and root length, leaf and root dry weight) were recorded. Chlorophyll a and b content; soluble sugar (reducing, nonreducing, and total sugars) content; nitrate (NR) and nitrite reductase activity (NiR); soluble proteins, and total soluble amino acid content of fresh leaves were determined. Sodium chloride salinity significantly reduced growth parameters. Salicylic acid treatment alleviated the adverse salinity effect on growth. Salinity decreased the chlorophyll a and b content and chlorophyll a/b ratio in both varieties, but a decrease in the chlorophyll a/b ratio was less in salt‐tolerant wheat variety (‘S‐24’), which could be a useful marker for selecting a salt‐tolerant variety. Salinity (NaCl) stress considerably increased the accumulation of reducing sugars, nonreducing sugars, and total soluble sugars in leaves of 14‐day‐old wheat seedlings of both varieties. The salt‐tolerant variety (‘S‐24’) accumulated a higher sugar content, which also could be a useful marker for selecting a salt‐tolerant variety for slat‐affected areas. Salinity caused a reduction in nitrate reductase and nitrite reductase activity. The salt‐tolerant variety (‘S‐24’) showed resistance to a decrease of nitrate reductase activity under salinity. This could be a useful criterion for selecting salt‐tolerant varieties. In response to salinity, wheat seedlings accumulated soluble proteins and amino acids, which might reflect a salt‐protective mechanism.

Biochemical and physiological changes in jack bean under mycorrhizal symbiosis growing in soil with increasing Cu concentrations

The influence of jack bean [ Canavalia ensiformis (L.) D.C.] mycorrhization, by the arbuscular mycorrhizal (AM) fungus Glomus etunicatum, in response to increasing Cu concentrations in soil (0, 50, 150 and 450 mg dm −3) was studied. In the highest Cu dose, mycorrhiza decreased Cu concentrations in plant organs and promoted biomass accumulation. In addition, mycorrhizal colonization was not affected by Cu suggesting certain tolerance of the inoculated AM fungus to this metal. Cu-induced proline accumulation and an increase in soluble amino acid contents in leaves, with higher proline contents in AM plants. Marked differences in foliar soluble amino acid composition were also observed in response to Cu in the soil. The activity of key antioxidant enzymes increased mainly in the leaves of non-AM plants, indicating increased production of reactive oxygen species. However, changes in malondialdehyde content were not observed suggesting an effective antioxidant system. Independent of mycorrhization, glutathione content in leaves decreased as Cu increased in the soil. Phytochelatins were detected in the leaves of both Cu treated and untreated plants, and quantitative and qualitative differences were observed due to mycorrhization. In summary, the AM fungus was able to maintain an efficient symbiosis with jack bean plants in soil containing high Cu concentrations. A combination of physiological and nutritional changes caused by the symbiotic association that might be of interest for phytoremediation strategies in Cu-contaminated soils.

Zn uptake, physiological response and stress attenuation in mycorrhizal jack bean growing in soil with increasing Zn concentrations

The influence of arbuscular mycorrhizal fungi (AMF) inoculation on Canavalia ensiformis growth, nutrient and Zn uptake, and on some physiological parameters in response to increasing soil Zn concentrations was studied. Treatments were applied in seven replicates in a 2 × 4 factorial design, consisting of the inoculation or not with the AMF Glomus etunicatum, and the addition of Zn to soil at the concentrations of 0, 100, 300 and 900 mg kg −1. AMF inoculation enhanced the accumulation of Zn in tissues and promoted biomass yields and root nodulation. Mycorrhizal plants exhibited relative tolerance to Zn up to 300 mg kg −1 without exhibiting visual symptoms of toxicity, in contrast to non-mycorrhizal plants which exhibited a significant growth reduction at the same soil Zn concentration. The highest concentration of Zn added to soil was highly toxic to the plants. Leaves of plants grown in high Zn concentration exhibited a Zn-induced proline accumulation and also an increase in soluble amino acid contents; however proline contents were lower in mycorrhizal jack beans. Plants in association or not with the AMF exhibited marked differences in the foliar soluble amino acid profile and composition in response to Zn addition to soil. In general, Zn induced oxidative stress which could be verified by increased lipid peroxidation rates and changes in catalase, ascorbate peroxidase, glutathione reductase and superoxide dismutase activities. In summary, G. etunicatum was able to maintain an efficient symbiosis with jack bean plants in moderately contaminated Zn-soils, improving plant performance under those conditions, which is likely to be due to a combination of physiological and nutritional changes caused by the intimate relation between fungus and plant. The enhanced Zn uptake by AMF inoculated jack bean plants might be of interest for phytoremediation purposes.