Growth and nutrition of pansy as influenced by N‐form ratio and temperature

Abstract

Pansy (Viola xwittrockiana Gams.) producers often observe nutrient disorders among plants grown during warm periods (>18°C) of the growing season. These disorders typically are not seen when production temperatures are optimal (≥18°C) even though fertility regimes may remain the same. Our objectives were to assess the effects of temperature and nitrogen (N) fertility on growth and nutrition of pansy. Pansies cultivar ‘Crown White’ were grown until lateral branches had open flowers. Treatments consisted of two temperatures (12 and 22°C) and three NO₃ ^?:NH₄ ⁺ molar % ratios (100:0, 62:38, and 25:75) with a total concentration of 100 mg N L^?1. A modified Hoagland's solution was used with NO₃ ^?‐N supplied as Ca(NO₃)₂ and KNO₃ and with NH₄ ⁺‐N as (NH₄)₂SO₄. Cumulative nutrient absorption and foliar nutrient content were determined when plant lateral branches flowered. Root and shoot growth were limited when NH₄ ⁺ was present in solutions at high ambient air temperature (22°C), but not at low temperature (12°C). Individual absorption and accumulation of plant nutrients varied with N regimes and temperatures. Overall, pansies absorbed more total N, NH₄ ⁺, NO₃ ^?, calcium (Ca), potassium (K), magnesium (Mg), phosphorus (P), zinc (Zn), and less iron (Fe) and manganese (Mn) at 12°C than at 22°C. In addition, absorption of NO₃ ^? by pansy was negligible if any NH₄ ⁺ was present in solutions at 22°C. Results suggest that pansy growers should adjust fertility programs according to production temperatures to avoid possible nutritional disorders and maximize plant growth. If maximum growth is to be obtained in warm temperatures, the use of NH₄ ⁺‐containing fertilizers should be reduced or eliminated. However, the choice of NO₃ ^?:NH₄ ⁺ ratio for nutrition may be less important under cool growing conditions.     

Hemodynamic and electrocardiographic effects of graded doses of amiodarone in healthy dogs anesthetized with morphine/alpha chloralose

This research was designed to study acute hemodynamic and electrocardiographic effects of amiodarone and to determine an IV dose of amiodarone that minimally affects left ventricular function and does not increase the tendency for ventricular arrhythmia.     

Comparing denitrification rates and carbon sources in commercial scale upflow denitrification biological filters in aquaculture

Aerobic biological filtration systems employing nitrifying bacteria to remediate excess ammonia and nitrite concentrations are common components of recirculating aquaculture systems (RAS). However, significant water exchange may still be necessary to reduce nitrate concentrations to acceptable levels unless denitrification systems are included in the RAS design. This study evaluated the design of a full scale denitrification reactor in a commercial culture RAS application. Four carbon sources were evaluated including methanol, acetic acid, molasses and Cerelose™, a hydrolyzed starch, to determine their applicability under commercial culture conditions and to determine if any of these carbon sources encouraged the production of two common “off-flavor” compounds, 2-methyisoborneol (MIB) or geosmin. The denitrification design consisted of a 1.89 m³ covered conical bottom polyethylene tank containing 1.0 m³ media through which water up-flowed at a rate of 10 lpm. A commercial aquaculture system housing 6 metric tonnes of Siberian sturgeon was used to generate nitrate through nitrification in a moving bed biological filter. All four carbon sources were able to effectively reduce nitrate to near zero concentrations from influent concentrations ranging from 11 to 57 mg/l NO₃–N, and the maximum daily denitrification rate was 670–680 g nitrogen removed/m³ media/day, regardless of the carbon source. Although nitrite production was not a problem once the reactors achieved a constant effluent nitrate, ammonia production was a significant problem for units fed molasses and to a less extent Cerelose™. Maximum measured ammonia concentrations in the reactor effluents for methanol, vinegar, Cerelose™ and molasses were 1.62 ± 0.10, 2.83 ± 0.17, 4.55 ± 0.45 and 5.25 ± 1.26 mg/l NH₃–N, respectively. Turbidity production was significantly increased in reactors fed molasses and to a less extent Cerelose™. Concentrations of geosmin and MIB were not significantly increased in any of the denitrification reactors, regardless of carbon source. Because of its very low cost compared to the other sources tested, molasses may be an attractive carbon source for denitrification if issues of ammonia production, turbidity and foaming can be resolved.     

Effects of chronic oral amiodarone on left ventricular function,ECGs, serum chemistries,and exercise tolerance in healthy dogs

Amiodarone, a class III antiarrhythmic with beta-adrenergic blocking and antimuscarinic properties, has a wide spectrum of clinical use in humans. This study was conducted to establish the effects of a 25 mg/kg q12h loading dose and a 30 mg/kg q24h maintenance dose of amiodarone, each given PO for 3.5 weeks, on systemic arterial pressure, echocardiographic (ECHO) indices of left ventricular function, ECGs, exercise tolerance, and serum biochemistries in adult, clinically normal dogs. Means were calculated and were compared by analysis of variance with repeated measures. When a significant F statistic was identified, specific means were compared by Bonferroni's post hoc test. Body weight and heart rate (HR) decreased, and PQ, QT, and corrected QT (QTc) increased significantly (P < .05) for the weeks that the dogs received the loading dose, but all parameters returned to values the same as those in the pretest for the weeks when dogs received the maintenance dose. Serum activity of hepatic enzyme activities and cholesterol concentrations increased, and serum concentrations of thyroid hormones (triiodothyronine [T3] and thyroxine [T4]), phosphorous, and total carbon dioxide decreased. The changes in PQ, QT, and QTc are similar to those obtained previously, but the detailed ECG and ECHO observations have not been reported. A dose of 25 mg/kg q12h, but not 30 mg/kg q24h, is an appetite suppressant, and the lower dose produces neither ECG nor ECHO changes of clinical or toxicological significance in normal dogs.     

Blood Viscosity in Horses With Colic

Whole blood viscosity (WBV) was measured on six healthy horses and ten horses presented for colic surgery. A Wells-Brookfield cone-and-plate microviscometer at 6 rpm was used to determine WBV and WBV was adjusted for packed cell volume (PCV). The ten colic horses were divided into two groups: five horses that died or were euthanatized (group 1) and five horses that were discharged after surgery and medical therapy (group 2). The mean WBV for each group was compared using analysis of variance followed by Duncan multiple-range tests. Mean WBV of group 2 (5.81 +/- 1.48 centipoise [cp]) and normal horses (7.1 +/- 2.3 cp) was significantly (P less than 0.01) lower than group 1 (17.15 +/- 5.71 cp). This preliminary trial shows that horses that died or were euthanatized had a significantly higher WBV than horses surviving. Since viscosity was adjusted for PCV, the differences may represent changes in other factors such as fibrinogen, rouleaux formation, red blood cell deformability, PaO2, or intracellular calcium ion concentration. Thus, increases in WBV in horses with colic may indicate severely compromised regional perfusion that may lead to significant tissue damage. In this preliminary study, it appears that WBV may be a prognostic aid in horses with colic.     

Antiarrhythmic effects of diazepam during coronary artery occlusion in dogs.

The ventral interventricular branch of the left coronary artery was ligated in a 2-step operation in 10 dogs whose electrocardiograms and systemic arterial blood pressures were then monitored during the next 7 days. Monitoring was done in awake dogs given 1 mg of diazepam per kilogram of body weight (intravenously administered in 3 dogs and orally in 7). Because ventricualr ectopic activity was greatest during the interval of 10 to 48 hours after ligation, the antiarrhythmic activity of diazepam was recorded during this 38-hour interval. After administration of diazepam by either route, frequency of ventricular ectopic beats decreased from 98 to 80%. THIS REDUCTION BETAN IMMEDIATELY AFTER THE INTRAVENOUS ADMINISTRATION AND PERSISTED FOR ONLY 5 MINUTES; REDUCTION BEGAN APPROXIMATELY 1 HOUR AFTER THE ORAL ADMINISTRATION AND PERSISTED 4 TO 6 HOURS. Systemic arterial blood pressure decreased only after the intravenous administration. It is concluded that diazepam is effective in reducing the frequency of ventricular ectopic activity after occlusion of major branches of coronary arteries, that diazepam works independent of alterations in systemic arterial blood pressure, and that orally administered diazepam prolongs antiarrhythmic activity. Possibly, the adjuvants present in the parenteral form of diazepam reduce antiarrhythmic activity by being, themselves, arrhythmogenic.