Commercially produced membrane rafts containing Celgard D-304 microporous, polypropylene film are used to support the growth of micropropagated plants in liquid media. This method is used because growth experiments using membranes resulted in plant growth rates equal to or greater than those grown on agar. Inconsistent results of plant growth on these rafts led to an interest in measuring the water vapor transmission rates (WVTR) of the membranes. A modified WVTR test (ASTM E96-80) was used on 15 raft samples. Results showed that the supplier's value of 49.2 g/m2 ·hr falls within the range of measured values of 39.2 to 54.8 g/m2·hr. Inconsistencies in growth of micropropagated plants may not be due to variability in the WVTR of the Celgard film. It is possible that the WVTR of the film is not the most important factor in facilitating liquid nutrient transport across the membrane. Other properties of the film need to be measured to determine factors affecting growth rates observed.
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