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EVALUATION OF AN ALTERNATIVE NUTRIENT DELIVERY SYSTEM FOR GROWING PLANTS IN MICROGRAVITY. J.F. Romagnano and P.J. Weathers. Dept. Biology/Biotechnology, Worcester Polytechnic Institute, Worcester, MA 01609.

   To grow plants in microgravity, porous tubes have been used to deliver liquid media to the root zone.  Growth has, however, been less than desirable. The lack of a gravity vector likely leads to the formation of stagnant air pockets, and inadequate gas availability to the roots.  We have compared an alternative nutrient delivery system using a mist with the porous tube system to feed germinating peas. The mist and porous tube systems were also compared against hypoxic and normoxic controls.   After one week roots were harvested, weighed, and assayed for alcohol dehydrogenase (ADH) activity as an indicator of root hypoxia.  Of the two experimental and two control systems, the mist system yielded the greatest fresh root mass per germinated seed.   The hypoxic control supported the least amount of root mass.  ADH activity of roots grown in the mist, porous tube, and normoxic controls were all about 10% of the activity measured in the hypoxic controls. When compared with the ADH activity of the hypoxic control, however, ADH activity of the mist system was significantly less than that of the porous tube. These results suggest that at least during germination, a mist system might be more successful than the porous tube for growing plants in microgravity.  Work comparing fully developed plants grown using porous tubes to those grown in mist systems is underway.