Aquatic Plant Control Program. Technical Report 11. Effects of CO2 Laser on Water Hyacinth Growth.
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MISS
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As a result of earlier experiments indicating the possibility of controlling water hyacinths with laser irradiation, a prototype CO2 laser system 10.6-micrometer wavelength was designed, fabricated, and adapted for use in an outdoor environment. In the fall of 1972, the laser system was tested and evaluated near Bayou Gauche, Louisiana. Deficiencies were discovered in the test of the prototype. A scanning, flat-mirror system was substituted for the spherical-mirror system. A chiller system was installed to dissipate the excessive heat. Finally, the effects of the salt-air environment were eliminated when the system was moved to Lake Concordia, Louisiana, a freshwater inland lake, where in 1973 and 1974 controlled irradiation ranging from 0.2 to 100 Jsq cm was applied to plots of water hyacinth plants collected in the lake. Plant biomass, height, number, coverage, and number of flowers were measured periodically. Results of the analyses show that laser irradiation causes a significant decrease in growth rates with an increase in irradiation level, but this effect decreases as time passes until there is no significant difference between treated and control plots. Rates of photosynthesis were not significantly affected by laser irradiation.
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