Effects of light intensity on growth of Azolla pinnata cultured in effluent collected from the Banka stream in West Bengal, India

Abstract

The effects of light intensity on growth of Azolla pinnata R.Br. cultured in effluent collected from three sites of the Banka stream in West Bengal, India during 1982–1984 were studied. The average values of the variables (chlorophyll: 12.7 mg g dry wt −1; organic carbon: 33.8%; nitrogen: 4.6%; phosphorus: 0.40% on dry wt basis; and dry wt (actual growth): 55 mg g wet wt −1) were higher at a light intensity of 1200±50 μmol m −2 s −1 than at that of 700±50 μmol m −2 s −1 (chlorophyll: 11.3 mg g dry wt −1; organic carbon: 30.7%; nitrogen: 3.8%; phosphorus: 0.33% on dry wt basis; and dry wt: 48 mg g wet wt −1). The highest values (the average values of chlorophyll: 14.9 mg g dry wt −1; organic carbon: 38.8%; nitrogen: 5.4%; phosphorus: 0.48% on dry wt basis; and dry wt: 62 mg g wet wt −1) were recorded in the months of August, September and October in a year of high light intensity. The variables were also highest with the highly-polluted water treatment (Site C, Sadhanpur water) and lowest with the non-polluted water treatment (Site A, Kanchannagar water); while the polluted water treatment (Site B, Alamganj water) was intermediate in the months of August, September and October in a year with light intensity of 1200±50 μmol m −2 s −1.