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This study assessed the effects of different doses of ethephon and gibberellin A3 on germination and α- and β-amylase activity in Amaranthus caudatus seeds exposed to different levels of salt stress. NaCl at 25 and 50 mM only delayed germination; at 75, 100 and 125 mM it caused 50%, 90% and 99.5% inhibition of Amaranthus caudatus seed germination. Both ethephon and GA3 (0.01, 0.1, 0.3 mM) effectively counteracted inhibition of seed germination under salinity. The stimulatory effect of ethephon appeared earlier, and the seeds were more sensitive to ethephon than to GA3. Ethephon enabled seed germination in the presence of all NaCl concentrations (75, 100, 125 mM) even after 24 h. GA3 alleviated inhibition caused by 75 and 100 mM NaCl until 48 h and did not affect reduction of germination caused by NaCl at 125 mM. NaCl (100 mM) reduced α- and β-amylase activity and seed germination after 14 h, and enhanced α-amylase activity after 20 h, although germination was reduced. Ethephon and GA3 increased α- but not β-amylase activity under salt stress during the first 14 h of incubation
The isolation of rye ß-Amy1 and ß-Amy2 gene promoters from nuclear DNA using the inverse polymerase chain reaction (IPCR) technique and characterization of their sequences are presented. The conservation of ß-amylasc coding sequences allowed for simultaneous IPCR amplification of two different promoters with primers designed on the basis of the single known cDNA sequence. Two ß-amylasc gene promoters display a low sequence similarity (47%). Beside consensus TATA and CCAAT boxes, other sequence motives common to both promoters were found. In addition, the homology of amino acid sequences of plant ß-amylases available in the database is discussed.
Arsenic (As) is a potential contaminant of groundwater as well as soil in many parts of the world. The effects of increasing concentration of As (25 μM and 50 μM As2O3) in the medium on the content of starch and sugars and activity levels of enzymes involved in starch and sugar metabolism i.e. α-amylase, β-amylase, starch phosphorylase and acid invertase were studied in germinating seeds of two rice cvs. Malviya-36 and Pant-12 during 0-120 h period. As toxicity in situ led to a marked decline in the activities of α-amylase, β-amylase in endosperms as well as embryoaxes of germinating rice seeds. The activity of acid invertase increased in endosperms as well as embryoaxes whereas starch phosphorylase activity declined in endosperms but increased in embryoaxes under As treatment. In endosperms a decline in starch mobilization was observed under As toxicity, however under similar conditions the content of total soluble sugars increased in embryoaxes. The observed inhibition in activities of amylolytic enzymes might contribute to delayed mobilization of endospermic starch which could affect germination of seeds in As polluted environment, while the induced acid invertase activity and im creased sugar accumulation in embryoaxes could serve as a possible component for adaptation mechanism of rice seedlings grown under As containing medium.
The effect of chitosan coating in fresh-cut mushroom preservation, including microbiological, enzyme activities, colour characteristics and chemical quality attributes, was examined. However, application of chitosan coating to enzyme activity control and quality maintenance of fresh-cut mushroom was investigated. Fresh-cut mushroom were treated with aqueous solution containing 5, 10 and 20 g of chitosan/1 L, placed in polyethylene bags, and then stored at 4°C. Changes in total phenolic content, and cellulase (CEL), total amylase, α and β amylase, laccase (LAC), phenylalanine ammonia lyase (PAL), peroxidase (POD), catalase (CAT) and polyphenoloxidase (PPO) enzymes activities were measured. Applications of chitosan coating delayed discoloration associated with reduced enzyme activities of LAC, PAL, POD, CAT and PPO as well as lowered total phenolic content. Also, it slowed down texture changes associated with reduced enzyme activities of CEL, total amylase and α-amylase. Results showed that increasing the concentration of chitosan coating resulted in higher contents of total soluble solids (TSS), total acidity and TSS/T acid ratio of fresh-cut mushroom. In mushroom, during storage at 4°C for 15 days, 20 g/kg chitosan coating inhibited the growth of total bacteria, yeasts and moulds counts. Chitosan also had a good effect on the evolution of the colour characteristics and parameters (C* and BI) of fresh-cut mushroom during storage at 4°C. The results showed that increasing the concentration of chitosan coating enhanced the beneficial effects of chitosan on extended shelf-life and maintained quality of fresh-cut mushroom.
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