Interaction between light, nitrogen and mycorrhizal fungi on photosynthesis of ectomycorrhizal pine
Date
1983
Authors
Ekwebelam, Sebastian A., author
Reid, C. P. P., advisor
Doxtader, Kenneth G., committee member
Wallner, Stephen J., committee member
Hunt, H. William, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
The importance of mycorrhizae to the physiological functions of plants is relatively well documented. Despite the obvious benefits of mycorrhizae for the enhancement of seedling growth, study of the relationship between applied cultural practices, such as shading, fertilization and mycorrhizae formation, and growth and photosynthesis of containerized nursery stock has been limited. The long-term objective of the present study, therefore, was to gain a more complete understanding of how the aggregate factors of light, nitrogen fertilization and mycorrhizae formation influence growth and photosynthesis of containerized seedlings, aimed at optimizing seedling production in a nursery environment. Seedlings of lodgepole pine (Pinus contorta Dougl.) were grown for 16 weeks without ectomycorrhizae in the greenhouse at 3 level s of irradiance (high, medium and low) by use of shadecloth, and ammonium nitrate (3, 62 and 248 ppm N) . Measurements at 5, 10 and 16 weeks of age indicated that biomass increased significantly with increasing levels of irradiance and nitrogen over the ranges studied. Although root/shoot ratios increased from low to high irradiance at each harvest, nitrogen application resulted in increased ratios from 3 to 62 ppm N, but decreased ratios at 248 ppm N. Nitrogen and phosphorus concentration generally decreased with increase in irradiance, but total N content and photosynthesis per unit leaf area generally increased from low to high levels of both irradiance and nitrogen. In a mycorrhizal fungi inoculation study, lodgepole pine seedlings were grown for 10 weeks without ectomycorrhizae at the aforementioned 3 levels of irradiance and nitrogen. At 10 weeks, mycorrhizal treatments, inoculation with either Pisolithus tinctorius or Suillus granulatus, were superimposed on the light and nitrogen treatments, and the seedlings were grown for an additional 6 weeks. Mycorrhizae formation increased with increase in irradiance, while fertilization with 62 ppm N resulted in greater mycorrhizae formation than either 3 or 248 ppm N. Further, inoculated plants had significantly greater biomass and nutrient contents than nonmycorrhizal seedlings. Inoculation with P. tinctorius and granulatus resulted in photosynthetic rates, 1.87 and 1.85 mg CO2dm-2h-1, respectively, significantly greater than nonmycorrhizal plants (1.41 mg CO2dm-2h-1). Although the increase in growth of the mycorrhizal seedlings was associated with increased photosynthesis, the magnitude of this response depended on specific combinations of irradiance and nitrogen fertilization. These results emphasize the importance of the interactions among irradiance, nitro gen fertilization, and mycorrhizae development in the growth of containerized seedlings.
Description
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Subject
Lodgepole pine
Growth (Plants)
Photosynthesis
Mycorrhizas