جستجوی مقالات مرتبط با کلیدواژه « فعالیت آنزیمی » در نشریات گروه « اکولوژی »

In this study, larval midgut α-amylase activity of the Mediterranean flour moth reared on wheat flour under laboratory conditions was studied. Enzyme activity was evaluated by using a commercial kit and an autoanalayzer device. Specific enzyme activity was measured as international unit per mg protein (IU/mg Protein). In this study, some α-amylase enzyme properties such as optimum temperature and pH of enzyme activity, enzyme activity during different hours of the day and night, enzyme activity at different developmental stages of adult male and female, effect of starvation period, and the effect of storage conditions of enzyme at specified periods in two different temperatures were studied. The results revealed that incubation temperature significantly affected enzyme activity for both sexes and optimal enzyme activity was detected in 40˚C for both male and females. pH values also significantly affected enzyme activity and the optimal pHs for amylase activity in both sexes were 5. Effects of enzyme concentration on α-amylase activity were significant in both sexes. Increasing the concentration of enzyme in both sexes caused a sharp increase in enzyme activity. Storage period in -20˚C did not decreased enzyme activity significantly in both sexes, but storage period in 4˚C in males significantly decreased the activity in comparison with the control. The results of studying enzyme activity during 24 hr. periods showed significant differences during day and night and the most and the least enzyme activities in both sexes were recorded in 12 and 24 o’clock, respectively. Enzyme activity in different developmental stages showed significant differences and the most enzyme activities were detected in 5th female larvae, 5th male larvae, 4th male and females, female and male pre-pupa, and female and male adults, respectively. In male and female pupae, no detectable activity was observed.Enzyme activity in male and female fifth instar larvae showed Significant difference. Starvation periods significantly affected the digestive enzyme activity in both male and female larvae and the trends of enzyme activity during 4 days of starvation was the same in both sexes. The most and the least enzyme activity were detected 2 and 4 days after starvation, respectively.

A high level of cadmium (Cd) in the environment generally influences the population، activity and composition of soil microorganisms، especially N dynamics and enzyme activities، with a consequence for nutrient cycling and availability. The addition of organic materials to the Cd-polluted soils may reduce the detrimental effects of Cd on microbial activities and biochemical properties. The objective of the current study was to examine the effect of compost as a soil amendment on N mineralization، microbial biomass N and urease activity in soils spiked with fresh Cd. A 2×5 factorial experiment consisting of two levels of compost (0 and 2. 5 t ha-1) and five levels of Cd (0، 50، 100، 150 and 200 mg Cd kg-1) arranged in a completely randomized design with three replicates was carried out under laboratory conditions. Measured total and available cadmium at the end of incubation period indicated a stronger (and negative) correlation between the available fraction of Cd with soil N mineralization، microbial biomass N and urease activity than the total Cd level. Results showed that increasing Cd level had a significant، negative effect on all the measured soil properties. However، compost addition to soils contaminated with Cd resulted in a reduction of Cd toxicity on indicators of N dynamics، most likely through decreasing its bioavailability to soil biota. In brief، the application of organic materials in Cd-contaminated soils could alleviate the unfavorable and inhibitory effects of Cd on soil N dynamics and subsequently N availability to plant may increase.

Land use change of forest ecosystems in northern Iran changes the soil quality of Paresar (Gilan province) and Gorgan (Gorgan province) regions. In order to study changes in some biological soil quality indices due to land use change from forest to cultivated lands, composite soil samples from two depths (0-20 and 20-40 cm) were taken from Paresar and Gorgan regions and urease, alkaline and acid phosphatase, invertase and arylsulfatase enzymes activities besides some biological properties consisting of microbial biomass carbon and nitrogen, carbon and nitrogen mineralization and respiration due to substrate addition were measured. Results showed that land use change caused biomass carbon (44-82%), biomass nitrogen (30-200%) and their ratio (20-30%), carbon mineralization (11-67%), nitrogen mineralization (3-68%), respiration due to substrate (8-45%) and microbial enzymes activates to decrease in both regions (expect carbon and nitrogen mineralization in Paresar region). However, the metabolic coefficient (qCO2) in both regions increased due to land use change. Therefore, agricultural practices in forest lands cause oxygen availability to increase for soil microorganisms and this phenomenon stimulates the microbial activity and enhances organic matter decomposition and CO2-C emission from soil resulting in soil quality reduction. Also enhancement of carbon mineralization (microbial respiration), decreases soil organic matter concentration and reduces energy for microorganisms and this phenomenon caused soil microbial population to gradually decrease. According to the results it is recommended to reduce soil disturbance by using no-tillage or minimum tillage systems and planting perennial legumes can decrease greatly the harmful effects of cultivation.