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Arnold J. Bloom

Professor, Department of Plant Sciences

Research Interests:

Nitrogen availability, low temperatures, and elevated carbon dioxide are interrelated environmental factors that strongly influence crop production.

Nitrogen is the inorganic nutrient that plants require in greatest quantity and that most frequently limits productivity in agricultural systems. To insure high yields, farmers in the U.S. apply over 11 million metric tons of nitrogen fertilizer annually; manufacture and distribution of this fertilizer account for over one-third of the total energy expended in agriculture.

Low soil temperatures not only inhibit all root metabolic functions, but can cause permanent damage. Many crops are chilling sensitive so that brief exposures to temperatures lower than 10°C result in significant losses. In California, low temperatures define the growing season for most vegetables.

Although elevated CO2 dramatically stimulates short-term carbon fixation in C3 plants, its effect on longer-term productivity is highly variable. Some vegetables such as tomato and cucumber suffer declining yields under elevated CO2, while others show only slight gains. With atmospheric concentrations of CO2 increasing by over 0.5% year and CO2 fertilization of greenhouse vegetables becoming more commonplace, elevated CO2 is no longer just a laboratory phenomenon.

Our research focuses on the interrelations among these factors and addresses the following issues: (a) chilling tolerance in tomato, and (b) effects of elevated CO2 on plant carbon-nitrogen relations.

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