Volume 5, Issue 1, FebruaryPages: To cite this article: Journal of World Economic Research.
References Gaseous emissions from human activities are substantially increasing the concentrations of atmospheric greenhouse gases, particularly carbon dioxide, methane, chlorofluorocarbons and nitrous oxides. Global circulation models predict that these increased concentrations of greenhouse gases will increase average world temperature.
Although global circulation models do not all agree as to the magnitude, most predict greenhouse warming. There is also general agreement that global warming will be greater at higher latitudes than in the tropics.
Different global circulation models have predicted that global warming effects will vary diurnally, seasonally and with altitude. It is also possible that there will be an autocatalytic component to global warming.
Photosynthesis and respiration of plants and microbes increase with temperature, especially in temperate latitudes. As respiration increases more with increased temperature than does photosynthesis, global warming is likely to increase the flux of carbon dioxide to the atmosphere which would constitute a positive feedback to global warming.
This paper describes the effects of higher day and night temperatures on crop growth and yield. Temperature effects at different levels of organization - biochemical, physiological, morphological, agronomic and systems - are considered. This is followed by identification of options for germplasm improvement and crop management that may mitigate the adverse effects of higher day and night temperatures.
The main focus is on wheat Triticum aestivum L. Mechanisms for heat tolerance Crop plants are immobile. They must adapt to prevalent soil and weather conditions. Except for transpirational cooling, plants are unable to adjust their tissue temperatures to any significant extent. On the other hand, plants have evolved several mechanisms that enable them to tolerate higher temperatures.
These adaptive thermotolerant mechanisms reflect the environment in which a species has evolved and they largely dictate the environment where a crop may be grown.
Four major aspects of thermotolerance have been studied: The greatest concern is whether it is possible to increase the upper limit of enzyme stability to prevent denaturation. Failure of only one critical enzyme system can cause death of an organism.
The relationship between the thermal environment for an organism and the thermal dependence of enzymes has been well established Senioniti et al.
The shape of this function also describes temperature effects on most biological functions, including plant growth and development. The function can be categorized by the three cardinal temperatures - minimum, optimum and maximum.
Modellers frequently simplify the relationship into a stepwise linear function.
The stepwise linear function has a plateau rather than an optimum temperature Figure 6. The thermal dependence of the apparent reaction rate for selected enzymes may indicate the optimal thermal range for a plant.
The range over which the apparent Michaelis-Menten constant for CO2 Km is minimal and stable is termed the thermal kinetic window Mahan et al.
For crop plants, the thermal kinetic window TKW is generally established as a result of thermally induced lipid phase changes, rubisco activity and the starch synthesis pathway in leaves and reproductive organs Burke, In cotton and wheat, the time during which foliage temperature remained within the TKW was related to dry matter accumulation Burke et al.
The cumulative time that rainfed crop foliage is outside the TKW provides an index of the degree of extreme temperature stress of the environment Figure 6.
Irrigation is one management option to reduce crop exposure to heat stress. Temperatures that inhibit cellular metabolism and growth for a cool season C3 species such as wheat may not inhibit warm-season C3 species such as rice Oryza sativa L.
The identification of TKWs for different species can aid in the interpretation of the differential temperature stress responses for crop growth and development among species Burke, Seasonal foliage temperatures of wheat cv.
Kanking and cotton cv. Paymaster grown at Lubbock, Texas. The vertical lines represent the temperature range that comprises the species-specific thermal kinetic window as determined from the changes in the apparent Km of purified enzymes with temperature. Instruments were scanned at 1 min intervals with a 15 min average computed and stored.deceleration of growth rates in the mids and the subsequent revival since Similarly there are a number of studies on the issue of productivity, with some explorations of the link between trade policy and productivity growth.
Productivity improves by an extra % on average in the year an ESOP is adopted, and the higher productivity level is maintained in subsequent years. This one-time jump is more than twice the average annual productivity growth of the U.S. economy over the past 20 years. So what initially looks like a % growth in the economy really turns out to be only % growth after you factor in the effect of inflation (or the increase in prices between these two years).
II.2 Historical poverty in today's rich countries. We have already pointed out that in the thousands of years before the beginning of the industrial era, the vast majority of the world population lived in conditions that we would call extreme poverty today.
W. (). The Effects of Political Instability on Economic Growth: A Case for Sub-Saharan Africa.. The purpose of this study is to determine the effect of political instability on economic growth in Sub-Saharan Africa.
It is our belief In the period, growth of agricultural output fell even. OECD Journal: Economic Studies publishes articles in the area of economic policy analysis, applied economics, and statistical analysis, generally with an international or cross-country dimension.