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291.
Comparison of two versions of the acetylene inhibition/soil core method for measuring denitrification loss from an irrigated wheat field 总被引:5,自引:0,他引:5
Two versions of the acetylene inhibition (AI)/soil core method were compared for the measurement of denitrification loss
from an irrigated wheat field receiving urea-N at a rate of 100 kg ha–1. With AI/soil core method A, the denitrification rate was measured by analysing the headspace N2O, followed by estimation of N2O dissolved in the solution phase using Bunsen absorption coefficients. With AI/soil core method B, N2O entrapped in the soil was measured in addition to that released from soil cores into the headspace of incubation vessels.
In addition, the two methods were also compared for measurement of the soil respiration rate. Of the total N2O produced, 6–77% (average 40%) remained entrapped in the soil, whereas for CO2, the corresponding figures ranged from 12–65% (average 44%). The amount of the entrapped N2O was significantly correlated with the water-filled pore space (WFPS) and with the N2O concentration in the headspace, whereas CO2 entrapment was dependent on the headspace CO2 concentration but not on the WFPS. Due to the entrapment of N2O and CO2 in soil, the denitrification rate on several (18 of the 41) sampling dates, and soil respiration rate on almost all (27 of
the 30) sampling dates were significantly higher with method B compared to method A. Averaged across sampling dates, the denitrification
rate measured with method B (0.30 kg N ha–1 day–1) was twice the rate measured with method A, whereas the soil respiration rate measured with method B (34.9 kg C ha–1 day–1) was 1.6 times the rate measured with method A. Results of this study suggest that the N2O and CO2 entrapped in soil should also be measured to ensure the recovery of the gaseous products of denitrification by the soil core
method.
Received: 12 May 1998 相似文献
292.
Mahmood Sinaie Kazem Darvish Bastami Masoud Ghorbanpour Hossein Najafzadeh Majid Shekari Sara Haghparast 《Fish physiology and biochemistry》2010,36(4):1235-1242
It is of crucial importance to study on the biomarkers types to assess the specification of the pollutants and health status
of marine ecosystems in environmental evaluation projects. In this respect, total metallothionein biosynthesis and mercury
bioaccumulation in the liver and gills under acute mercury exposure were investigated in fish, Scat (Scatophagus argus). Spotted scat was exposed to different mercury concentrations (0, 10, 20, 30) for 24, 48, 72 h. Total MT levels were determined
by enzyme-linked immunosorbent assay (ELISA) method. Mercury contents were determined through cold vapor atomic absorption
spectrometry (CVAAS). Induction of MT during exposure was tissue specific, displaying different response pattern in gills
and liver. Mercury accumulated in liver much higher than in gills and the latter also showed lower MT level (P < 0.05). MT biosynthesis in liver showed a significant (P < 0.05) increase after exposure to different mercury concentration with increase in exposure time, whereas total MT content
did not significantly (P > 0.05) change in gills except for 72 h exposure at 30 μg l−1. Nonetheless, the relationship between MT biosynthesis and Mercury bioaccumulation in both tissues was significant (P < 0.05). The results suggest that this form of MT in S. argus was Hg inducible and could be extended as a biomarker of mercury pollution in marine ecosystems. 相似文献
293.
Plant regeneration from tuber discs of potato (Solanum tuberosum L.) using 6-benzylaminopurine (BAP)
Summary Shoots, roots and callus were formed from tuber discs of potato, cultivar Désirée, when grown in vitro on the basal medium
of Murashige & Skoog (1962) (MS) supplemented with 2,4-D and/or BAP. Callus was formed in MS medium with 1 mg l−1 BAP plus 0.5 mg l−1 2,4-D, callus and roots were formed in MS with 1 mg l−1 BAP plus more than 0.5 mg l−1 2,4-D and shoots were formed directly on tuber discs cultured on MS medium with 1 mg l−1 BAP without the addition of 2,4-D.
Nodules produced at the explant surface after the 4th week increased in size following subculture onto the same medium (MS+BAP
alone), and 2 to 6 shoots developed from each nodule. After 9 weeks total time in culture, these shoots were excised and transferred
as cuttings to MS medium without growth regulators, after which roots developed and plantlets were formed.
A histological study of the explants at the sites of nodule formation indicated that the shoots developed from meristematic
zones initiated within small outgrowths of tissue similar to those occuring in adventive organogenesis but the presence of
shoot and root meristems associated with the same axis suggests the formation of somatic embryos. 相似文献
294.
The hydraulic performance of canals and related delivery structures is highly dependent on the management of cross-regulators.
The HEC-RAS model was applied to Ordibehesht Canal at the Doroodzan irrigation network, northwest of Fars province in Iran
for evaluation of water delivery performance due to operation of cross-regulators. Discharge deviations of offtakes due to
cross-regulator gate position changes and deviations of water delivery equity were evaluated. Results showed that small changes
in gate positions of check structures (cross-regulators) cause considerable changes in the offtake discharges and equity (spatial
uniformity) of water delivery to the offtakes along the main canal. Results of the study led to the development of two sensitivity
indicators. “Offtake sensitivity to check setting” that represents the changes in offtake discharges due to changes in cross-regulator
setting, and “Sensitivity of the equity indicator to the gate position change” are the two developed indicators which can
be used for better management of water delivery systems. 相似文献