Azolla - IRRI books - International Rice Research Institute

and inoculate again into another medium. If it the main tank is maintained by the wall, whichfails to grow, try adjusting the sterilization time. serves as an overflow. The nutrient solution thatRegulated culture in liquid medium (UCL flows to the buffer tank through the outflow tubemethod). The UCL adapted an 8-m 2 room as a is filtered on a screen covered with cotton wool.growth chamber containing a culture tank that can The cotton is replaced when needed.accommodate the collection. The ceiling is cov- Algal development in the culture solution isered with a rack of 60 neon tubes (TL23, 40 watts) limited by the 10-mm thick tinted altuglass and byand 42 tungsten lamps (40 watts). For 10 h/d. the opaque tubings. The tank lids have regularlylights provide 16 klx. equivalent to 265 µE/m 2 per spaced holes to support individual strainers.s measured at the level of the Azolla culture Strainers are made of a nylon net 75 mm in(corresponding to 440 J/cm 2 per d). The tempera- diameter glued on a rigid ring. The strainers areture is maintained at 25/18°C and the humidity at commercially available nylon tea bags. The very55-70%. The temperature of the culture medium fine mesh of the nylon screens stops sporocarpsvaries between 22 and 16°C.from growing into the medium, but allows ionTo maintain the water level and nutrient exchanges in the solutions.concentration and to avoid desiccation of Azolla The culture solution is the Hoagland solutionfronds attaching on the inner wall of the contain- modified by substituting KC1 and CaCl 2 for KNO 3ers, a single culture tank is used for all strains and Ca(NO 3 ) 2 and diluting by adding 2 parts of(Fig. 2). The level of the medium is automatically the medium to 3 parts water.adjusted. Each collection is kept in a smallThe culture medium and filters are replacedstrainer, placed in a hole of the tank cover lid. every 4 wk and excess Azolla biomass is thinned.The design is composed of a tank with Azolla The culture medium in the main tank is drainedstrains enclosed in individual nets, and a buffer by releasing the stopper.tank for medium. A centrifuge pump ensures theflow and constant level of the medium with Collecting, transporting, and mailingminimum disturbance through an antifoam screen. Appendix I explains documentation required forLosses from evapotranspiration are compensated sending strains to or receiving them from IRRI.with demineralized water brought in through a Because Azolla is sensitive to desiccation,constant level device. The level of the medium in samples should be transported as fresh material.2. Design for the regulated culture of Azolla (UCL method). A = culture tank in 10-mm tinted aluminum (3600 x 600 x 120 mm, 200 liters); B = culturenet; C = buffer tank (600 x 400 x 200 mm, 40 liters); 1 = centrifuge pump (EHEIM model 1036; flow rate 1 Iiter/s), 2 = input of demineralized water;3 = constant level device; 4 = culture medium input; 5 = antifoam screen; 6 = medium outflow; 7 = outflow tube; 8 = filter (hydrophilic cotton);9 = nylon mesh (0.1 mm 2 ); 10 = PVC ring (88-72 mm diam); 11 = hole in the tinted altuglass Iid (72 mm diam); 12 = stopper.9