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121.
Bahiagrass (Paspalum notatum) is a warm-season grass used primarily in pastures and along highways and other low maintenance public areas in Florida.
It is also used in landscapes to some extent because of its drought tolerance. Bahiagrass can survive under a range of moisture
conditions from no irrigation to very wet conditions. Its well-watered consumptive use has not been reported previously. In
this study, bahiagrass crop coefficients (K
c) for an irrigated pasture were determined for July 2003 through December 2006 in central Florida. The eddy correlation method
was used to estimate crop evapotranspiration (ETc) rates. The standardized reference evapotranspiration (ETo) equation (ASCE-EWRI standardization of reference evapotranspiration task committee report, 2005) was applied to calculate
ETo values using on site weather data. Daily K
c values were estimated from the ratio of the measured ETc and the calculated ETo. The recommended K
c values for bahiagrass are 0.35 for January–February, 0.55 for March, 0.80 for April, 0.90 for May, 0.75 for June, 0.70 for
July–August, 0.75 for September, 0.70 for October, 0.60 for November, and 0.45 for December in central Florida. The highest
K
c value of 0.9 in May corresponded with maximum vapor pressure deficit conditions as well as cloud free conditions and the
highest incoming solar radiation as compared to the rest of the year. During the summer (June to August), frequent precipitation
events increased the cloud cover and reduced grass water use. The K
c annual trend was similar to estimated K
c values from another well-watered warm-season grass study in Florida. 相似文献
122.
Eddy covariance (EC) systems are being used to assess the accuracy of remote sensing methods in mapping surface sensible and
latent heat fluxes and evapotranspiration (ET) from local to regional scales, and in crop coefficient development. Therefore,
the objective was to evaluate the accuracy of EC systems in measuring sensible heat (H) and latent heat (LE) fluxes. For this
purpose, two EC systems were installed near large monolithic weighing lysimeters, on irrigated cotton fields in the Texas
High Plains, during the months of June and July 2008. Sensible and latent heat fluxes were underestimated with an average
error of about 30%. Most of the errors were from nocturnal measurements. Energy balance (EB) closure was 73.2–78.0% for daytime
fluxes. Thus, daylight fluxes were adjusted for lack of EB closure using the Bowen ratio/preservation of energy principle,
which improved the resulting EC heat flux agreement with lysimetric values. Further adjustments to EC-based ET included nighttime
ET (composite) incorporation, and the use of ‘heat flux source area’ (footprint) functions to compensate ET when the footprint
expanded beyond the crop field boundary. As a result, ET values remarkably matched lysimetric ET values, with a ‘mean bias
error ± root mean square error’ of −0.03 ± 0.5 mm day−1 (or −0.6 ± 10.2%). 相似文献
123.
Estimation of actual evapotranspiration for a drip-irrigated Merlot vineyard using a three-source model 总被引:3,自引:3,他引:0
A study was performed in order to evaluate the three-source model (Clumped model) for direct estimation of actual evapotranspiration
(ETa) and latent heat flux (LE) over a drip-irrigated Merlot vineyard trained on a vertical shoot positioned system (VSP) under
semi-arid conditions. The vineyard, with an average fractional cover of 30%, is located in the Talca Valley, Region del Maule,
Chile. The performance of the Clumped model was evaluated using an eddy covariance system during the 2006/2007 and 2007/2008
growing seasons. Results indicate that the Clumped model was able to predict ETa with a root mean square error (RMSE), mean bias error (MBE), and model efficiency (EF) of 0.33, −0.15 mm day−1 and 74%, respectively. Also, the Clumped model simulated the daytime variation of LE with a RMSE of 36 W m−2, MBE of −8 W m−2, and EF of 83%. Major disagreement (underestimated values) between observed and estimated values of ETa was found for clear days after rainfall or foggy days, but underestimated values were less than 10% of the data analysis.
The results obtained in this study indicate that the Clumped model could be used to directly estimate vine water requirements
for a drip-irrigated vineyard trained on a VSP. However, application of the Clumped model requires a good characterization
of the drip-irrigated vineyard architecture. 相似文献
124.
Effects of water table management on soil salinity and alfalfa yield in a semi-arid climate 总被引:2,自引:0,他引:2
Hamideh Noory Abdol-Majid Liaghat Mohamad Reza Chaichi Masoud Parsinejad 《Irrigation Science》2009,27(5):401-407
A lysimeter experiment was conducted to investigate the effect of water table management (WTM) on distribution of soil salinity
and annual alfalfa (Medicago scutellata) yield. Subirrigations with three levels of water table namely, 0.5 (WT0.5), 0.7 (WT0.7), and 1.0 m (WT1.0) and a free drainage
(FD) conventional irrigation treatment were selected for this study. All treatments were arranged in a complete randomized
block design with three replicates. The results of this study indicated that the average soil electrical conductivity of the
saturated extract (ECe) in the root zone gradually increased and exceeded the designated crop threshold value (4 dS/m) after
the first forage harvest in subirrigated lysimeters. A higher salt accumulation was observed at the WT0.5 treatment. The average
dry matter yield of annual alfalfa in WT0.5 and WT0.7 treatments was found to be 52 and 73% higher compared with the control
treatment, respectively. 相似文献
125.
Yoshimasa Sugiura Kohji Matsuda Takashi Okamoto Makoto Kakinuma Hideomi Amano 《Fisheries Science》2008,74(1):180-186
To investigate the anti-allergic effects of the brown alga Eisenia arborea. A strain of Brown Norway rats know to strongly respond to immunoglobulin E (IgE) were used as an allergy model animal. The
rats were immunized with ovalbumin by oral administration. The levels of serum IgE and histamine were suppressed in the rats
fed a diet supplemented with dried E. arborea powder. As for the cytokine pattern, the interferon-γ production in the spleens and mesenteric lymph nodes (MLN) was enhanced,
and the interleukin-4 (IL-4) production in the spleens and/or IL-10 production in the spleens and MLN were suppressed. These
results, together with the change in the Th1/Th2 balance, indicate that the rats fed with E. arborea became more anti-allergic, suggesting that E. arborea might possess anti-allergic effects. 相似文献
126.
ABSTRACT: The thermal stability of carp G-actin was investigated by monitoring loss of actin polymerization ability. To determine the amount of native actin remaining after heat treatment, actin was labeled with a fluorescence reagent, N-(1-pyrene)iodoacetamide. The loss of polymerization ability of carp actin during heat treatment, at between 45 and 55°C, occurred faster than that of chicken actin. The inactivation rate was influenced by concentrations of ATP and Ca2+ in solution. With the increase of Ca2+ concentration, the inactivation of carp actin was markedly suppressed. Furthermore, the activation energy of the inactivation of carp actin obtained from an Arrhenius plot was similar to that of chicken actin. These results indicated that the thermal instability of carp G-actin was due to the low affinites of ATP and Ca2+ for carp actin described in a previous report. 相似文献
127.
Teleost fish lack the enzyme for endogenous synthesis of ascorbic acid (AA), an essential micronutrient for fish. The aim
of this study was to examine the effect of higher levels of dietary vitamin C on growth, nutritional quality, and immunomodulation
in the Indian major carp, rohu (Labeo rohita). Four groups of L. rohita were fed experimental diets containing either no vitamin C (control) or supplemented with vitamin C at 500 mg kg−1 (Exp-1), 1000 mg kg−1 (Exp-2), or 1500 mg kg−1 (Exp-3) for 60 days. Growth parameters (NWG, ADG, and SGR), serological parameters (TSP, TSA, TSG, and A:G), haematological
parameters (TLC, TEC, Hct, MCV, and MCH), and different non-specific immunological parameters (PR, PI, respiratory burst activity,
and bactericidal activity) were evaluated during the experimental trial. Fish fed a vitamin C-supplemented diet showed higher
specific growth rate (SGR) up to 1000 mg kg−1 compared with control fish. Different haematological and serological parameters along with non-specific immune parameters
were influenced by vitamin C supplementation. Among the non-specific immune parameters phagocytic activity (PR and PI) and
respiratory burst activity (NBT cells) were significantly (P ≤ 0.05) enhanced by increasing doses of vitamin C supplementation. Higher levels of dietary vitamin C significantly (P ≤ 0.05) enhanced protection against Aeromonas hydrophila (AH1) infection compared with controls. Results from this study help to establish the beneficial effect of vitamin C on growth
and immunmodulation in rohu (L. rohita). 相似文献
128.
Dorafshan S Kalbassi MR Pourkazemi M Amiri BM Karimi SS 《Fish physiology and biochemistry》2008,34(3):195-200
The aim of this study was a comparison of key haematological features of diploid (2n) and triploid (3n) Caspian salmon (Salmo trutta caspius). Morphometric indices of erythrocytes were determined on blood smears by light microscopy. Triploidy significantly (P < 0.001) increased all morphometric indices measured in the erythrocytes including cell size, cell surface area, and cell
volume. The increase in cell size was larger for the major (27%) axis than for the minor (22%) axis, thus making erythrocytes
of 3n Caspian salmon more ellipsoidal. The estimated increase in erythrocyte nuclear volume (87%) was bigger than the theoretical
expected 50% increase. Haematological indices were measured manually by hemocytometry. Triploids had lower numbers of red
blood cells (RBC: 1,120,000 cells/mL in 2n vs. 700,000 cells/mL in 3n; P < 0.001) but they were larger in size (mean erythrocytic volume [MEV]: 363.1 nm3 in 2n vs. 483.3 nm3 in 3n; P < 0.001). The decrease in RBC number was not compensated by the increase in MEV and, thus, triploidy affected the haematocrit
(Hct: 38.8% in 2n vs. 33.06% in 3n; P < 0.05). Total blood hemoglobin concentration was lower in triploid fish (Hb: 9.9 g/dL in 2n vs. 8.9 g/dL in 3n; P < 0.05). In contrast, mean erythrocytic hemoglobin (MEH: 95 μg in 2n vs. 133.2 μg in 3n; P < 0.001) was higher for 3n Caspian salmon as a result of their larger erythrocytes, although MEH concentration (MEHC: 0.26 g/dL
in 2n vs. 0.27 g/dL in 3n) did not significantly differ (P > 0.05). White blood cell (WBC) counts (lymphocytes and neutrophiles) were measured and WBC/RBC ratios were calculated. There
were no significant differences in WBC (15,710 cells/mL in 2n vs. 12,683 cells/mL in 3n; P > 0.05), lymphocytes, and neutrophils as %WBC as well as WBC/RBC ratios between two ploidy levels (P > 0.05). Triploid Caspian salmon showed higher erythrocyte abnormalities such as ‘twisted’, ‘tailed’, and ‘anucleated’ cells
as well as high portions of immature RBC in blood smears in comparison with diploids (P < 0.001). 相似文献
129.
130.
In this study, the energy budget of the Manila clam, Ruditapes philippinarum, was evaluated after one-week acclimation periods at 5, 10, 15, 20, and 25°C. Small clams (151 ± 12 mg DW) and large clams
(353 ± 16 mg DW) were fed with the microalgae, Isochrysis galbana. Filtration rate, ingestion rate, assimilation efficiency, oxygen-consumption rate, and ammonia excretion rate were measured.
Both filtration rate and ingestion rate of small and large clams were found to be related to temperature. The highest Q
10 values were measured in the range 15–20°C for both small and large clams. Assimilation efficiency of both small and large
clams was not significantly influenced by temperature, although the maximum mean values were detected at 20°C. Oxygen consumption
rate and ammonia excretion rate of small and large clams were found to be related directly to temperature over the entire
range, with a maximum being detected at 25°C. The highest Q
10 value was estimated in the range 10–15°C with regard to oxygen consumption rate, and in the range of 15–20°C with regard
to ammonia excretion rate. Scope for growth (SFG) was positive at all temperatures, achieving a maximum value at 20°C in both
small and large clams, primarily as a consequence of the enhanced ingestion rate which offset the concomitant elevation in
the metabolic rate. In this study we have estimated the thermal optimum for this species at 20°C. 相似文献