ISSN:
1365-3040
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Abstract Biomass increase, C and N content, C2H2 reduction, percentage dry weight and chlorophyll a/b ratios were determined for clones of Azolla caroliniana Willd., A. filiculoides Lam., A. mexicana Presl., and A. pinnata R. Br. as a function of nutrient solution, pH, temperature, photoperiod, and light intensity in controlled environment studies. These studies were supplemented by a glasshouse study. Under a 16 h, 26°C day at a light intensity of 200 μmol m−2 s−1 and an 8 h, 19° C dark period, there was no significant difference in the growth rates of the individual species on the five nutrient solutions employed. Growth was comparable from pH 5 to pH 8, but decreased at pH 9. Using the same photoperiod and light intensity but constant growth temperatures of 15–40°C, at 5°C intervals, the individual species exhibited maximum growth, nitro-genase (N2ase) activity and N content at either 25° or 30°C. There was no difference in the temperature optima at pH 6 and pH 8. The tolerance of the individual species to elevated temperature was indicated to be A. mexicana〉 A. pinnata〉 A. caroliniana〉 A.filiculoides. At the optimum temperature, growth rates increased with increasing photoperiod at both pH 6 and pH 8 but N2ase activity was usually highest at a 16 h light period. At photon flux densities of 100, 200, 400 and 600 μmol m−2 s−1, during a 16 h light period and optimum growth temperature of the individual species, N2ase activity was saturated at less than 200 μmol m−2 s−1 and growth at 400 μmol m−2 s−1.No interacting effects of light and pH were noted for any species, nor were light intensities up to 1700 μmol m−2 s−1 detrimental to the growth rate or N content of any species in a 5 week glasshouse study with a natural 14.5 h light period and a constant temperature of 27.5°C. Using the optimum growth temperature, a 16 h light period, and a photon flux density of at least 400 μmol m−2 s−1, the Azolla species all doubled their biomass in 2 days or less and contained 5–6% N on a dry weight basis.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/1365-3040.ep11581825
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