Agriculture and Agri-Food Canada

About: Agriculture and Agri-Food Canada is a facility organization based out in Ottawa, Ontario, Canada. It is known for research contribution in the topics: Population & Soil water. The organization has 10921 authors who have published 21332 publications receiving 748193 citations. The organization is also known as: Department of Agriculture and Agri-Food.

Ammonia Volatilization Loss from Surface-Broadcast Urea: Comparison of Vented- and Closed-Chamber Methods and Loss in Winter Wheat–Summer Maize Rotation in North China Plain

Abstract: Ammonia (NH3) volatilization is an important pathway for fertilizer nitrogen (N) loss from soil and is also a major source of air and environmental pollution. On calcareous soils in North China Plain, application of N fertilizer in the form of urea under intensive cropping with winter wheat (Triticum aestvum L.) and summer maize (Zea mays L.) rotation can lead to serious NH3 loss. The objective of this study was to compare a modified vented-chamber method with the traditional closed-chamber method to measure NH3 volatilization loss under laboratory and field conditions and to determine in situ NH3 volatilization in the field from surface broadcast urea at 0, 120, 240, and 360 kg N ha−1 rates to each crop (for winter wheat, one-half at sowing and the other half at the elongation growth stage; for summer maize, one-half at the 3-leaf and the other half at the 10-leaf growth stage) in a winter wheat and summer maize rotation at the northern edge of North China Plain from October 1998 to September 19...

The effects of ethylene, depressed oxygen and elevated carbon dioxide on antioxidant profiles of senescing spinach leaves

Abstract: It has been suggested that antioxidants play a role in regulating or modulating senescence dynamics of plant tissues. Ethylene has been shown to promote early plant senescence while controlled atmospheres (CA; reduced O2 levels and elevated CO2 levels) can delay its onset and/or severity. In order to examine the possible importance of various antioxidants in the regulation of senescence, detached spinach (Spinacia oleracea L.) leaves were stored for 35 d at 10 degrees C in one of three different atmospheres: (1) ambient air (0.3% CO2, 21.5% O2, 78.5% N2), (2) ambient air + 10 ppm ethylene to promote senescence, or (3) CA (10% CO2, 0.8% O2 and 89.2% N2) to delay senescence. At weekly intervals, material was assessed for activities of the antioxidant enzymes ascorbate peroxidase (ASPX; EC 1.11.1.11), catalase (CAT; EC 1.11.1.6), dehydroascorbate reductase (DHAR; EC 1.8.5.4), glutathione reductase (GR; EC 1.6.4.2), monodehydroascorbate reductase (MDHAR; EC 1.6.5.4), and superoxide dismutase (SOD; EC 1.15.1.1), and concentrations of the water-soluble antioxidant compounds ascorbate and glutathione. Indicators of the rate and severity of senescence (lipid peroxidation, chlorophyll, and soluble protein levels) were also determined. Results indicated that the rate and severity of senescence was similar between the leaves stored in ambient air or CA until day 35, at which point the ambient air-stored leaves exhibited a sharp increase in lipid peroxidation. Tissues under both storage regimes demonstrated significant declines only in levels of ASPX, CAT, and ascorbate. Glutathione content in the CA-stored tissue also significantly dropped, but only on day 35. In contrast, spinach leaves stored in ambient air + ethylene experienced a rapid decrease in levels of all the antioxidants assessed except SOD. Declines in levels of ASPX, CAT, and ascorbate over the 35 d storage period regardless of the composition of the storage atmosphere suggests that regulation of H2O2 levels plays an important role in both the dynamics and severity of post-harvest senescence of spinach.

Polyamines on the Reproductive Landscape

Abstract: The polyamines are ubiquitous polycationic compounds. Over the past 40 yr, investigation has shown that some of these, namely spermine, spermidine, and putrescine, are essential to male and female reproductive processes and to embryo/fetal development. Indeed, their absence is characterized by infertility and arrest in embryogenesis. Mammals synthesize polyamines de novo from amino acids or import these compounds from the diet. Information collected recently has shown that polyamines are essential regulators of cell growth and gene expression, and they have been implicated in both mitosis and meiosis. In male reproduction, polyamine expression correlates with stages of spermatogenesis, and polyamines appear to function in promoting sperm motility. There is evidence for polyamine involvement in ovarian follicle development and ovulation in female mammals, and polyamine synthesis is required for steroidogenesis in the ovary. Studies of the embryo indicate a polyamine requirement that can be met from maternal sources before implantation, whereas elimination of polyamine synthesis abrogates embryo development at gastrulation. Polyamines play roles in embryo implantation, in decidualization, and in placental formation and function, and polyamine privation during gestation results in intrauterine growth retardation. Emerging information implicates dietary arginine and dietary polyamines as nutritional regulators of fertility. The mechanisms by which polyamines regulate these multiple and diverse processes are not yet well explored; thus, there is fertile ground for further productive investigation.

Eating well with Canada's Food Guide (2007): development of the food intake pattern.

Abstract: A food intake pattern specifying amounts and types of food was created for Canada's revised food guide, Eating Well with Canada's Food Guide (2007), using a two-step modeling process. In step one, food composites were manipulated to develop a food intake pattern. The second step used the step one food intake pattern to create 500 simulated diets for each of 16 age and gender groups. The resulting nutrient content distributions were evaluated relative to Dietary Reference Intake reference values. The modeling cycled between these two steps until a satisfactory pattern was achieved. The final pattern reflects modeling, a review of associations between foods and chronic disease, and input received during consultation.