Carleton University

About: Carleton University is a education organization based out in Ottawa, Ontario, Canada. It is known for research contribution in the topics: Population & Context (language use). The organization has 15852 authors who have published 39650 publications receiving 1106610 citations.

Agricultural adaptation to climatic variation

Abstract: Assumptions underlying impact assessments of climatic change for agriculture are explored conceptually and empirically. Variability in climatic conditions, the relevance of human decision-making, and the role of non-climatic forces are reviewed and captured in a model of agricultural adaptation to climate. An empirical analysis of farmers' decisions in light of variations in climate and other forces is based on a survey of 120 farm operators in southwestern Ontario. Many farmers were affected by variable climatic conditions over a six-year-period, and some undertook strategic adaptations in their farm operations. Frequency of dry years was the key climatic stimulus to farming adaptations. However, only 20 percent of farmers were sufficiently influenced by climatic conditions to respond with conscious changes in their farm operations.

A rapid method for isolation of purified, physiologically active chloroplasts, used to study the intracellular distribution of amino acids in pea leaves.

Abstract: A procedure is described for the rapid ( 240 nmol/mg chl), even thought it is proportionately lower in the chloroplast relative to the rest of the cell. The chloroplasts contain about 20% of many of the amino acids of the cell, but for individual amino acids the percentage in the chloroplast ranges from 8 to 40% of the cell total. Glutamic acid, glutamine and aspartic acid are enriched in the chloroplasts, while asparagine, homoserine and β-(isoxazolin-5-one-2-yl)-alanine are relatively lower. Leakage of amino acids from the chloroplast during preparation or repeated washing was ca. 20%. Some differences exist between the amino-acid composition of chloroplasts isolated from intact leaves and from protoplasts. In particular, γ-aminobutyric acid accumulates to high levels, while homoserine and glutamic acid decrease, during protoplast formation and breakage.

Hydraulic conductivity in frozen soils

Abstract: An apparatus has been developed for investigation of hydraulic conductivity of frozen soils. The test procedure is isothermal and involves the passage of water from one reservoir into the frozen sample and out of the frozen sample into a second reservoir. The water in the reservoirs remains unfrozen because it contains dissolved lactose. The concentration of lactose is such that, initially, the water in the reservoirs is in thermodynamic equilibrium with the water in the soil. On application of pressure to one reservoir a known hydraulic gradient is established and flow takes place. Flow is shown to vary linearly with hydraulic gradient. The hydraulic conductivity coefficient depends on soil type and temperature and is related to the unfrozen water content. At temperatures within a few tenths of 0°C the coefficient apparently ranges from 10−5 to 10−9 cm sec−1, and decreases only slowly below about −0·5°C. Soils known to be susceptible to frost heave are shown to have significant hydraulic conductivities well below 0°C.