The Botanical Review

, Volume 63, Issue 1, pp 1–26

Azolla: A review of its biology and utilization

  • Gregory M. Wagner
Article

Abstract

TheAzolla-Anabaena symbiosis is outstanding due to its high productivity combined with its ability to fix nitrogen at high rates. Because of this, in recent decades, countless studies have been conducted on this association, but with insufficient synthesis and coordination. This paper, therefore, attempts to review and synthesize past and recent findings concerning the biology and utilization ofAzolla in hopes that this will facilitate increased future collaborative research on this “green gold mine.” It reviews the taxonomy, distribution, morphology, physiology, and reproduction ofAzolla as well as new developments in its manifold uses.

Because of the growing concern about conservation of the environment and the need for deploying renewable, sustainable resources; the application ofAzolla as a biofertilizer on agricultural crops, in order to provide a natural source of the crucial nutrient nitrogen, can be very beneficial to the future of our planet. Besides the environmental appropriateness of the use ofAzolla, for multitudes of farmers in many parts of the world who cannot afford chemical fertilizers,Azolla application can enhance their economic status, increasing yields while minimizing costs. Due to the fact that rice paddy fields form an ideal environment forAzolla, one of its most suitable applications is on rice.

Besides its utilization as a biofertilizer on a variety of crops,Azolla can be used as an animal feed, a human food, a medicine, and a water purifier. It may also be used for the production of hydrogen fuel, the production of biogas, the control of weeds, the control of mosquitoes, and the reduction of ammonia volatilization which accompanies the application of chemical nitrogen fertilizer.

Résumé

Une haute productivité associée avec une capacité à fixer l’azote atmosphérique démontre l’importance de la symbiose entreAzolla etAnabaena. Ce fait fut responsable des multiples études conduites et de l’intérêt porté à cette association durant les dernières décénnies. Mais il semblerait qu’une synthèse ainsi qu’une coordination entre ces différentes entreprises soient manquantes. L’article présenté ici tente de rassembler et synthétiser les résultats accumulés sur la biologie et l’utilsation possible d’Azolla, tout en espérant ainsi faciliter la collaboration future entre chercheurs investigant cette “mine d’or vert.” La taxonomie, la distribution, la morphologie, la physiologie et la reproduction d’Azolla seront couverts, ainsi que ses potentiels multiples usages.

De plus en plus, la conservation de l’environnement et le besoin d’employer des ressources renouvelables de manière à assurer leur usage continu, sont des priorités importantes. L’utilisation d’Azolla en tant qu’engrais vert pour l’agriculture, dans le but de fournir de l’azote, élément crucial du cycle nutritionel, pourrait offrir une alternative bénéfique pour le future de notre planète.Azolla peut être utilisée par des agriculteurs n’ayant pas les moyens d’employer des engrais chimiques, un peu partout dans le monds, de manière responsable pour le bien de l’environnement. Son application ameliorerait leurs revenus de part son impact sur l’accroissement des rendements tout en minimalisant le coût de production. Un des exemples les plus convaincant est son utilisation pour la culture du riz, etant donné que les champs de riz représentent un environnement idéal pourAzolla.

Outre son emploi en tant qu’engrais vert pour différentes productions agricoles,Azolla peut aussi très bien être utilisée en tant que nourriture pour les productions animalières, pour la consommation humaine, comme composant pharmaceutique, ou être utilisée dans un processus de purification de l’eau. Son emploi peut aussi inclure la production d’hydrogène en tant que combustible, la production de biogaz, le controle de plantes non désirées, le controle des moustiques, ou participer à la réduction d’émission d’azote lors de l’épandage d’engrais chimiques.

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Literature Cited

  1. Ali, M. A. &S. Leeson. 1995. The nutritive value of some indigenous Asian poultry feed ingredients. Anim. Feed Sci. Technol.55: 227–237.CrossRefGoogle Scholar
  2. Anonymous. 1982. China and the West: Sharing solutions to agricultural problems. World Farm.24: 76–78.Google Scholar
  3. Ansari, M. A. &V. P. Sharma. 1991. Role ofAzolla in controlling mosquito breeding in Ghaziabad District villages (U.P.). Indian J. Malariol.28: 51–54.PubMedGoogle Scholar
  4. Ashton, P. J. &R. D. Walmsley. 1976. The aquatic fernAzolla and itsAnabaena symbiont. Endeavour19: 39–43.CrossRefGoogle Scholar
  5. Bar, E., S. A. Kulasooriya &E. Tel-or. 1991. Regulation of nitrogenase activity by light in theAzolla-Anabaena symbiosis. Bioresource Technol.38: 171–178.CrossRefGoogle Scholar
  6. Becking, J. H. 1976. Contributions of plant-algal associations. Pages 556–580in W. E. Newton & C. J. Nyman (eds.), Proceedings of the 1st International Symposium on Nitrogen Fixation. Vol. 2. Washington State University Press, Pullman.Google Scholar
  7. —. 1979. Environmental requirements ofAzolla for use in tropical rice production. Pages 345–373in International Rice Research Institute, Nitrogen and Rice. International Rice Research Institute, Los Banos, Philippines.Google Scholar
  8. Bottomley, W. B. 1920. The effect of organic matter on the growth of various water plants in culture solution. Ann. Bot.34: 353–365.Google Scholar
  9. Carrapico, F. 1991. Are bacteria the third partner of theAzolla-Anabaena symbiosis? Pl. & Soil137: 157–160.CrossRefGoogle Scholar
  10. Cary, P. R. &P. G. J. Weerts. 1992. Growth and nutrient composition ofAzolla pinnata R. Brown andAzolla filiculoides Lamarck as affected by water temperature, nitrogen and phosphorus supply, light intensity and pH. Aquatic Bot.43: 163–180.CrossRefGoogle Scholar
  11. Caudales, R., J. M. Wells, A. D. Antoine &J. E. Butterfield. 1995. Fatty acid composition of symbiotic cyanobacteria from different host plant (Azolla) species: Evidence for coevolution of host and symbiont. Intl. J. Syst. Bacteriol.45: 364–370.CrossRefGoogle Scholar
  12. Chung-Chu, L. 1984. Recent advances onAzolla research. Pages 45–54in W. S. Silver & E. C. Schroder (eds.), Practical application ofAzolla for rice production. Martinus Nijhoff/W. Junk, Dordrecht.Google Scholar
  13. Cunningham, W. P. &B. W. Saigo. 1990. Environmental science: A global concern. Wm. C. Brown, Dubuque, Iowa.Google Scholar
  14. Das, D., K. Sikdar &A. K. Chetterjee. 1994. Potential ofAzolla pinnata as biogas generator and as a fish-feed. Indian J. Environna. Health36: 186–191.Google Scholar
  15. De Waha Baillonville, T., H. F. Diara, I. Watanabe, P. Berthet &C. Van Hove. 1991. Assessment and attempt to explain the high performance ofAzolla in subdesertic tropics versus humid tropics. Pl. & Soil137: 145–150.CrossRefGoogle Scholar
  16. El-Sayed, A. F. M. 1992. Effects of substituting fish meal withAzolla pinnata in practical diets for fingerling and adult Nile tilapia,Oreochromis niloticus (L.). Aquac. & Fish. Managern.23: 167–173.Google Scholar
  17. Fogg, G. E., W. D. P. Stewart, P. Fay &A. E. Walsby. 1973. The blue-green algae. Academic Press, London.Google Scholar
  18. Forni, C., S. Gentili, C. Van Hove &M. Grilli-Caiola. 1990. Isolation and characterization of the bacteria living in the sporocarps ofAzolla filiculoides Lam. Ann. Microbiol. Enzimol.40: 235–244.Google Scholar
  19. Fremy, P. 1930. Les myxophycees de l’Afrique equatoriale francaise. Arch. Bot.3: 373–395.Google Scholar
  20. Hall, D. O., S. A. Markov, Y. Watanabe &K. K. Rao. 1995. The potential applications of cyanobacterial photosynthesis for clean technologies. Photosyn. Res.46: 159–167.CrossRefGoogle Scholar
  21. Hamdi, Y. A. 1982. Application of nitrogen-fixing systems in soil improvement and management. FAO Soils Bull. 49. Food and Agriculture Organization, Rome.Google Scholar
  22. Hardy, R. W. F., R. D. Holsten, E. K. Jackson &R. C. Burns. 1968. The acetylene-ethylene assay for N2 fixation: Laboratory and field evaluation. PI. Physiol.43: 1185–1207.Google Scholar
  23. Hechler, W. D. &J. O. Dawson. 1995. Factors affecting nitrogen fixation inAzolla caroliniana. Trans. Illinois State Acad. Sci.88: 97–107.Google Scholar
  24. Hill, D. J. 1975. The pattern of development ofAnabaena in theAzolla-Anabaena symbiosis. Planta122: 179–184.CrossRefGoogle Scholar
  25. —. 1977. The role ofAnabaena in theAzolla-Anabaena symbiosis. New Phytol.78: 611–616.CrossRefGoogle Scholar
  26. Hur, J. S. &A. R. Wellburn. 1993. Effects of atmospheric sulfur dioxide onAzolla andAnabaena symbiosis. Physiol. Pl. (Copenhagen)88: 65–72.CrossRefGoogle Scholar
  27. ——. 1994a. Effects of atmospheric O3 onAzolla-Anabaena symbiosis. Ann. Bot.73: 205–209.CrossRefGoogle Scholar
  28. ——. 1994b. Effects of atmospheric NO2 onAzolla-Anabaena symbiosis. Ann. Bot.73: 137–141.CrossRefGoogle Scholar
  29. Ismail, B. S., T. C. Sew &I. Mushrifah. 1995. Effect of molinate and carbofuran on nitrogen fixation byAzolla pinnata. Microbios82: 127–134.Google Scholar
  30. Ito, O. &I. Watanabe. 1985. Availability to rice plants of nitrogen fixed byAzolla. Soil Sci. Pl. Nutr.31: 91–104.Google Scholar
  31. Jain, S. K., P. Vasudevan &N. K. Jha. 1989. Removal of some heavy metals from polluted water by aquatic plants: Studies on duckweed and water velvet. Biol. Wastes28: 115–126.CrossRefGoogle Scholar
  32. Johnson, G. V., P. A. Mayeux &H. J. Evans. 1966. A cobalt requirement for symbiotic growth ofAzolla filiculoides in the absence of combined nitrogen. PL Physiol.41: 852–855.Google Scholar
  33. Joy, P. P. &G. V. Havanagi. 1990. Studies on the integrated use of fertilizer nitrogen, phosphorus and azolla biofertilizer for rice. Mysore J. Agric. Sci.22: 436–443.Google Scholar
  34. Kannaiyan, S. 1993. Nitrogen contribution byAzolla to rice crop. Proc. Indian Natl. Sci. Acad., B59: 309–314.Google Scholar
  35. Kolhe, S. S. &B. N. Mittra. 1990.Azolla as an organic source of nitrogen in a rice-wheat cropping system. Trop. Agric. (Trinidad)67: 267–269.Google Scholar
  36. Kondo, M., M. Kobayashi &E. Takahashi. 1989. Effect of phosphorus onAzolla and its utilization in rice culture in Niger. PL & Soil120: 165–170.CrossRefGoogle Scholar
  37. Krock, T., J. Alkamper &I. Watanabe. 1991. Azolla’s contribution to weed control in rice cultivation. PL Res. Developm.34: 117–125.Google Scholar
  38. Kushari, D. P. 1991. Multiplication of azolla associated with rice. Intl. Rice Res. Newslett.16: 18–19.Google Scholar
  39. — &I. Watanabe. 1992. Differential responses ofAzolla to phosphorus deficiency. II. Screening method under concentration controlled conditions. Soil Sci. Pl. Nutr.38: 65–73.Google Scholar
  40. Laurinavichene, T. V., A. F. Yakunin &I. N. Gogotov. 1990. Effect of temperature and photoperiod duration on growth and nitrogen fixation inAzolla. Fiziol. Rast. (Moscow)37: 457–461.Google Scholar
  41. Lay, W. L., S. N. Huang & C. T. Wang. 1989. Effects ofAzolla application on growth and yield of rice. Bull. Taichung Distr. Agric. Improvem. Sta., No.24: 3–12.Google Scholar
  42. Liu, C. C., W. D. Wei &D. Y. Zheng. 1984. Some advances inAzolla research. Page 57in C. Veeder & W. E. Newton (eds.), Advances in nitrogen fixation research. Martinus Nijhoff, The Hague.Google Scholar
  43. Lu, S. Y. 1987. Methods for usingAzolla filiculoides sporocarps to culture sporophytes in the field. Pages 27–32in International Rice Research Institute,Azolla utilization: Proceedings of the Workshop onAzolla Use. International Rice Research Institute, Los Banos, Philippines.Google Scholar
  44. Lumpkin, T. A. 1987a. Collection, maintenance, and cultivation ofAzolla. Pages 55–94in G. H. Elan (ed.), Symbiotic nitrogen fixation technology. Marcel Dekker, New York.Google Scholar
  45. —. 1987b. Environmental requirements for successfulAzolla growth. Pages 89–97in International Rice Research Institute,Azolla utilization: Proceedings of the Workshop onAzolla Use. International Rice Research Institute, Los Banos, Philippines.Google Scholar
  46. — &D. L. Plucknett. 1980.Azolla; Botany, physiology and use as a green manure. Econ. Bot.34: 111–153.Google Scholar
  47. ——. 1982.Azolla as a green manure: Use and management in crop production. Westview Press, Boulder, Colorado.Google Scholar
  48. Madhusoodanan, P. V. &P. J. Sevichan. 1992.Azolla microphylla Kaulfuss: An economically important biofertilizer for paddy fields of Kerala. J. Econ. Taxon. Bot.16: 73–76.Google Scholar
  49. Mahapatra, B. S. &G. L. Sharma. 1989. Integrated management ofSesbania, Azolla and urea nitrogen in lowland rice under a rice-wheat cropping system. J. Agric. Sci. (Cambridge)113: 203–206.Google Scholar
  50. Malavolta, E., W. R. Acorsi, A. P. Ruschel, F. J. Krug, L. I. Nakayama &I. Eimori. 1981. Mineral nutrition and N2-fixation inAzolla. Pages 205–211in P. B. Vose & A. P. Ruschel (eds.), Associative N2-fixation. Vol. 2. CRC Press, Boca Raton, Florida.Google Scholar
  51. Marwaha, T. S., B. V. Singh &S. K. Goyal. 1992. Effect of incorporation ofAzolla on wheat (Triticum aestivum var HD-2329). Acta Bot. Indica20: 218–220.Google Scholar
  52. Mian, M. H. &A. K. M. Azmal. 1989. The response ofAzolla pinnata R. Brown to the split application of phosphorus and the transfer of assimilated phosphorus to flooded rice plants. PI. & Soil119: 211–216.CrossRefGoogle Scholar
  53. Misra, S. &B. D. Kaushik. 1989a. Growth promoting substances of cyanobacteria: I. Vitamins and their influence on rice plants. Proc. Indian Natl. Sci. Acad.,B 55: 295–300.Google Scholar
  54. —. 1989b. Growth promoting substances of cyanobacteria: II. Detections of amino acids, sugars and auxins. Proc. Indian Natl. Sci. Acad.,B 55: 499–504.Google Scholar
  55. Mochida, O. 1991. Spread of freshwaterPomacea snails (Pilidae, Mollusca) from Argentina to Asia. Micronesica3: 51–62.Google Scholar
  56. Moore, A. W. 1969.Azolla: Biology and agronomic significance. Bot. Rev. (Lancaster)37: 17–34.Google Scholar
  57. Mshigeni, K. E. 1982. Freshwater algal resources of Tanzania: A review and a discussion on their potential for agriculture, food production and other uses. Pages 175–201in H. A. Hoppe & T. Levring (eds.), Algae in pharmaceutical science. De Gruyter, Berlin.Google Scholar
  58. Murayama, N. 1979. The importance of nitrogen for rice production. Pages 5–23in International Rice Research Institute, Nitrogen and rice. International Rice Research Institute, Los Banos, Philippines.Google Scholar
  59. National Academy of Sciences. 1979. Microbial processes: Promising technologies for developing countries. Report of anad hoc panel of the Advisory Committee on Technology Innovation, Board on Science and Technology for International Development, Commission on International Relations. National Academy of Sciences, Washington, DC.Google Scholar
  60. Newton, J. W. 1976. Photoproduction of molecular hydrogen by a plant-algal symbiotic system. Science191: 559–561.PubMedCrossRefGoogle Scholar
  61. Nickell, L. G. 1958. Physiological studies withAzolla under aseptic conditions. I. Isolation and preliminary growth studies. Amer. Fern J.48: 103–108.CrossRefGoogle Scholar
  62. Nik-Khan, A. &M. Motaghi-Talab. 1992. The use ofAzolla in lactating cows. Iranian J. Agric. Sci.23: 47–56.Google Scholar
  63. Pablico, P. P. &K. Moody. 1991. Effect of fentin acetate on wet-seeded rice,Pistia stratiotes andAzolla pinnata. Crop Protect.10: 45–47.CrossRefGoogle Scholar
  64. Park, I. H., K. K. Rao &D. O. Hall. 1991. Photoproduction of hydrogen, hydrogen peroxide and ammonia using immobilized cyanobacteria. Intl. J. Hydrogen Energy16: 313–318.CrossRefGoogle Scholar
  65. Pasternak, P. S., V. G. Mazepa &G. K. Pristupa. 1988. The resistance of tree and shrub species to industrial emissions in the Poles’e region of the Ukraine. Lesnoe-Khozyaistvo7: 54–57.Google Scholar
  66. Peoples, M. B., D. F. Herridge &J. K. Ladha. 1995. Biological nitrogen fixation: An efficient source of nitrogen for sustainable agricultural production? Pl. & Soil174: 3–28.CrossRefGoogle Scholar
  67. Peters, G. A. 1975. TheAzolla-Anabaena azollae relationship III. Studies on metabolic capacities and a further characterization of the symbiont. Arch. Microbiol.103: 113–122.CrossRefGoogle Scholar
  68. —. 1976. Studies on theAzolla-Anabaena azollae symbiosis. Pages 592–610in W. E. Newton & C. J. Nyman (ed.), Proceedings of the First International Symposium on Nitrogen Fixation. Vol. 2. Washington State University Press, Pullman.Google Scholar
  69. —. 1977. TheAzolla-Anabaena azollae symbiosis. Pages 231–258in A. Hollaender (ed.), Genetic engineering for nitrogen fixation. Plenum Press, New York.Google Scholar
  70. —. 1978. Blue-green algae and algal associations. BioScience28: 580–585.CrossRefGoogle Scholar
  71. — &B. C. Mayne. 1974a. TheAzolla-Anabaena azollae relationship. I. Initial characterization of the association. PL Physiol.53: 813–819.Google Scholar
  72. ——. 1974b. TheAzolla-Anabaena azollae relationship. II. Localization of nitrogen fixing activity as assayed by acetylene reduction. PL Physiol.53: 820–824.Google Scholar
  73. — &S. K. Perkins. 1993. TheAtolla andAnabaena symbiosis: Endophyte continuity in theAzolla life cycle is facilitated by epidermal trichomes: II. Re-establishment of the symbiosis following gametogenesis and embryogenesis. New Phytol.123: 65–75.CrossRefGoogle Scholar
  74. Rains, D. W. &S. N. Talley. 1979. Use ofAtolla in North America. Pages 419–431in International Rice Research Institute: Nitrogen and rice. International Rice Research Institute, Los Banos, Philippines.Google Scholar
  75. Rajendran, R. &R. Reuben. 1988. Laboratory evaluation of the water fern,Azolla pinnata for mosquito control. J. Biol. Control2: 114–116.Google Scholar
  76. ——. 1991. Evaluation of the water fernAzolla microphylla for mosquito population management in the rice-land agro-ecosystem of south India. Med. Vet. Entomol.5: 299–310.PubMedGoogle Scholar
  77. Ram, H., P. Krishna Raja &M. V. S. Naidu. 1994. Effect ofAzolla on soil properties and yield of mungbean (Vigna radiata L.). J. Indian Soc. Soil Sci.42: 385–387.Google Scholar
  78. Robins, R. J., D. O. Hall, D. J. Shi, R. J. Turner &M. J. C. Rhodes. 1986. Mucilage acts to adhere cyanobacteria and cultured plant cells to biological and inert surfaces. FEMS Microbiol. Lett.34: 155–160.CrossRefGoogle Scholar
  79. Rosenani, A. B. &H. A. Chilian. 1992. Availability of nitrogen from nitrogen-15 labeledAzolla pinnata and urea to flooded rice. Pl. & Soil143: 153–161.CrossRefGoogle Scholar
  80. Satapathy, K. B. 1993. Effect of different plant spacing pattern on the growth ofAzolla and rice. Indian J. PL Physiol.36: 98–102.Google Scholar
  81. Saunders, R. M. K. &K. Fowler. 1992. A morphological taxonomic revision ofAzolla Lam. sectionRhizosperma (Mey.) Mett. (Azollaceae). Bot. J. Linn. Soc.109: 329–357.Google Scholar
  82. ——. 1993. The supraspecific taxonomy and evolution of the fern genusAzolla (Azollaceae). PL Syst. Evol.184: 175–193.CrossRefGoogle Scholar
  83. Saxena, D. K. 1995. Purification efficiency ofLemna andAzolla for WIMCO effluent. Proc. Natl. Acad. Sci. India,B 65: 61–65.Google Scholar
  84. Sculthorpe, C. D. 1967. The biology of aquatic vascular plants. Edward Arnold, London.Google Scholar
  85. Shi, D. J. &D. O. Hall. 1988. TheAzolla-Anabaena association: Historical perspective, symbiosis and energy metabolism. Bot. Rev. (Lancaster)54: 353–386.Google Scholar
  86. Silvester, W. B. 1977. Dinitrogen fixation by plant associations excluding legumes. Page 141in R.W. F. Hardy & A. H. Gibson (eds.), A treatise on dinitrogen fixation: Section IV, agronomy and ecology. Wiley-Inter Science, New York.Google Scholar
  87. Singh, A. L. &P. K. Singh. 1990a. Intercropping ofAzolla biofertilizer with rice at different crop geometry. Trop. Agric. (Trinidad)67: 350–354.Google Scholar
  88. ——. 1990b. Phosphorus fertilization and the growth and nitrogen fixation ofAzolla and blue-green algae in rice field. Indian J. Pl. Physiol.33: 21–26.Google Scholar
  89. Singh, D. P. &P. K. Singh. 1995. Response ofAzolla caroliniana and rice to phosphorus enrichment of theAzolla inoculum and phosphorus fertilization during intercropping. Exp. Agric.31: 21–26.Google Scholar
  90. Singh, P. K., D. P. Singh &R. P. Singh. 1992. Growth, acetylene reduction activity, nitrate uptake and nitrate reductase activity ofAzolla caroliniana andAzolla pinnata at varying nitrate levels. Biochem. Physiol. Pflanzen.188: 121–127.Google Scholar
  91. Singh, R. P. &P. K. Singh. 1988. Symbiotic algal nitrogenase activity and heterocyst frequency in sevenAzolla species after phosphorus fertilization. Hydrobiologia169: 131–318.CrossRefGoogle Scholar
  92. ——. 1989. Effect of nitrogen fertilizers on nitrogen fixation and heterocyst frequency of cyanobacteriumAnabaena azollae in 7 species ofAzolla. Biochem. Physiol. Pflanzen.185: 429–433.Google Scholar
  93. Singh, S., R. Prasad, S. K. Goyal, B. V. Singh, T. S. Marwaha &S. N. Shanna. 1992. Effect ofAzolla, blue-green algae and fertilizer nitrogen on wetland rice (Oryza sativa). Indian J. Agron.37: 569–571.Google Scholar
  94. Sisworo, E. L., D. L. Eskew, W. H. Sisworo, H. Rasjid, H. Kadarusman, S. Solahuddin &G. Soepardi. 1990. Studies on the availability ofAzolla nitrogen and urea nitrogen for rice growth using nitrogen-15. Pl. & Soil128: 209–220.CrossRefGoogle Scholar
  95. Stumpe, J. M. &P. L. G. Vlek. 1991. Acidification induced by different nitrogen sources in columns of selected tropical soils. Soil Sci. Soc. Amer. J.55: 145–151.CrossRefGoogle Scholar
  96. Sutton, S. D., G. W. Barrett &D. H. Taylor. 1991. Microbial metabolic activities in soils of old-field communities following eleven years of nutrient enrichment. Environna. Pollut.73: 1–10.CrossRefGoogle Scholar
  97. Tan, B. C., P. Payawal, I. Watanabe, N. Lacdan &C. Ramirez. 1986. Modern taxonomy ofAzolla: A review. Philipp. Agric.69: 491–512.Google Scholar
  98. Teckle-Haimanot, E. V. D. 1995. Comparison ofAzolla mexicana and N and P fertilization on paddy taro (Colocasia esculenta) yield. Trop. Agric. (Trinidad)72: 70–72.Google Scholar
  99. Thangaraju, M. &S. Kannaiyan. 1993. Effect of nitrogen fixing water fernAzolla and different forms of urea application on the growth, nitrogen uptake and grain yield of rice crop. Acta Agron. Hung.42: 69–76.Google Scholar
  100. Tuan, D. T. &R. Q. Thuyet. 1979. Use ofAzolla in rice production in Vietnam. Pages 395–405in International Rice Research Institute, Nitrogen and rice. International Rice Research Institute, Los Banos, Philippines.Google Scholar
  101. Tung, H. F. &R. C. Shen. 1985. Studies of theAzolla pinnata-Anabaena azollae symbiosis: Concurrent growth ofAzolla with rice. Aquatic Bot.22: 145–152.CrossRefGoogle Scholar
  102. Vaishampayan, A., Y. R. Reddy, B. D. Singh &R. M. Singh. 1992. Reduced phosphorus requirement of a mutantAzolla-Anabaena symbiotic N2-fixing complex. J. Exp. Bot.43: 851–856.CrossRefGoogle Scholar
  103. Van Cat, D., I. Watanabe, W. J. Zimmerman, T. A. Lumpkin &T. De Waha Baillonville. 1989. Sexual hybridization amongAzolla species. Canad. J. Bot.67: 3482–3485.CrossRefGoogle Scholar
  104. Van Hove, C. 1989.Azolla and its multiple uses with emphasis on Africa. Food and Agriculture Organization, Rome.Google Scholar
  105. Venkataraman, G. S. &B. D. Kaushik. 1980. Save on N fertilizers by the use of algae on rice fields. Indian Farm.30: 27–30.Google Scholar
  106. Ventura, W. &I. Watanabe. 1993. Green manure production ofAzolla microphylla andSesbania rostrata and their long-term effects on rice yields and soil fertility. Biol. Fertil. Soils15: 241–248.CrossRefGoogle Scholar
  107. —— &G. B. Mascarina. 1992. Mineralization ofAzolla nitrogen and its availability to wetland rice: II. Fertilizer effect and nitrogen-15 uptake by rice from different species ofAzolla with varying nitrogen contents. Soil Sci. Pl. Nutr.38: 505–516.Google Scholar
  108. Wagner, G. M. 1983. The ecology and nitrogen-fixing capacity of freshwater blue-green algae in selected localities in Tanzania. M. Sc. thesis, University of Dar es Salaam.Google Scholar
  109. —. 1988. The role of freshwater blue-green algae in biological nitrogen fixation in selected localities in Tanzania. Pages 29–33in J. R. Mainoya (ed.), Proceedings of the Symposium on Two Decades of Science Development in Tanzania, 1965–1985, Dar es Salaam, Tanzania, 2–6 September 1985. University of Dar es Salaam and Tanzania National Scientific Research Council, Dar es Salaam.Google Scholar
  110. -. 1992. Algae in agriculture with special emphasis on their application in rice production. Pages 359–373in K. E. Mshigeni, J. Bolton, A. Critchley & G. Kiangi (eds.), Proceedings of the First International Workshop on Sustainable Seaweed Resource Development in Sub-Saharan Africa, Windhoek, Namibia, 22–29 March 1992.Google Scholar
  111. -. 1996. TheUtricularia-Cyanophyta andAzolla-Anabaena associations: Their ecology, nitrogen fixation rates, and effects as biofertilizers on rice. Ph.D. thesis, University of Dar es Salaam.Google Scholar
  112. Wang, S. M., Q. L. Wang, S. H. Li &J. R. Zhang. 1991. A study of treatment of spring wheat with growth promoting substances from nitrogen-fixing blue-green algae. Acta Hydrobiol. Sinica15: 45–52.Google Scholar
  113. Watanabe, I. 1982.Azolla-Anabaena symbiosis—Its physiology and use in tropical agriculture. Pages 169–185in Y. R. Dommergues & H. G. Diem (eds.), Microbiology of tropical soils and plant productivity. Martinus Nijhoff/W. Junk, The Hague.Google Scholar
  114. —. 1984. Use of symbiotic and free-living blue-green algae in rice culture. Outlook Agric.13: 166–172.Google Scholar
  115. —. 1985. Limiting factors in increasing N2-fixation in rice fields. Pages 436–453in H. Ssali & S. O. Keya (eds.), Biological nitrogen fixation in Africa: Proceedings of the First Conference of the African Association for Nitrogen Fixation. The Nairobi Rhizobium Microbiological Resources Centre, Nairobi.Google Scholar
  116. — &C. C. Liu. 1992. Improving nitrogen-fixing systems and integrating them into sustainable rice farming. PL & Soil141: 57–67.CrossRefGoogle Scholar
  117. — &C. M. Ramirez. 1984. Relationship between soil phosphorus availability andAzolla growth. Soil Sc. Pl. Nutr.30: 595–598.Google Scholar
  118. — &W. Ventura. 1992. Long-term effects of azolla and sesbania on rice yield and fertility of tropical wetland rice soil. Pages 331–342in Proceedings of the International Symposium on Paddy Soils, Nanjing, China, 15–19 September 1992. Academia Sinica, Beijing, China.Google Scholar
  119. —,N. S. Berja &D. C. Del Rosario. 1980. Growth ofAzolla in paddy field as affected by phosphorus fertilizer. Soil Sci. Pl. Nutr.26: 301–307.Google Scholar
  120. —,C. R. Espinas, N. S. Berja &B. V. Alimagno. 1977. Utilization of theAzolla-Anabaena complex as a nitrogen fertilizer for rice. Intl. Rice Res. Inst. Res. Pap. Ser.11: 1–15.Google Scholar
  121. —,T. Lapis, R. Oliveros &W. Ventura. 1988. Improvement of phosphate fertilizer application toAzolla. Soil Sci. Pl. Nutr.34: 557–569.Google Scholar
  122. Yatazawa, M., N. Tomomatsu, N. Hosoda &K. Nunome. 1980. Nitrogen fixation inAzolla-Anabaena symbiosis as affected by mineral nutrient status. Soil Sci. Pl. Nutr.26: 415–426.Google Scholar

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© The New York Botanical Garden 1997

Authors and Affiliations

  • Gregory M. Wagner
    • 1
  1. 1.Department of Zoology and Marine BiologyUniversity of Dar es SalaamDar es SalaamTanzania

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