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This article in CS

  1. Vol. 26 No. 1, p. 107-111
    Received: Oct 9, 1984

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Predictive Models for the Growth Response of Eight Azolla Accessions to Climatic Variables1

  1. T. A. Lumpkin and
  2. D. P. Bartholomew2



Although the freefloating aquatic fern Azolla pinnata has been grown for centuries in northern Vietnam and southeastern China as a nitrogen-fixing green manure for rice and as a fodder for pigs, little is known of the environmental tolerance of the seven known Azolla species. In this study, the relative growth rates (RGR) of A. caroliniana, A. filiculoides, A. mexicana, A. microphylla, A. nilotica, A. pinnata var. pinnata, A. pinnata var. imbricata, and A. rubra were evaluated over a wide range of climatic conditions. The species were grown on nitrogen-free nutrient solution under a glass roof at a site where air temperatures ranged from −7°C in the winter to 38°C in the summer.The RGR was calculated from increases in dry weight over 26 growth cycles of one week to 1 month. The RGRs of individual species were most closely related to minimum water temperature during spring and fall (R2 = 0.67 to 0.99); minimum water temperature and daylength for spring plus fall (R2 = 0.59 to 0.92); and minimum water temperature, solar radiation, and relative humidity during summer (R2 = 0.66 to 0.85). This study suggests that temperature, daylength, solar radiation and relative humidity can be used for estimating the RGR of Azolla.

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