WATER-VAPOR DIFFUSIVITY IN VITREOUS AND MEALY WHEAT ENDOSPERM

The water vapor diffusivities of vitreous and mealy wheat endosperms were measured using diffusion cells containing wax-sealed cylinders of endosperm. The diffusion cells were incubated in a chamber that was maintained at a constant temperature and relative humidity. A water vapor gradient was created by filling each diffusion cell with desiccant. A steady-state condition was achieved within 24h. The mean diffusivities for the vitreous endosperm samples of cvs Arizona and Len were 2.0 x 10(-8) cm(2)/s. The diffusivities for mealy samples of cvs Logan and Titan were 3.5 and 9.1 x 10(-8) cm(2)/2, respectively. The liquid water diffusivities of whole caryopses were similar for five vitreous and five mealy wheat samples tested. No change was detected in the diffusion mechanism for any of the samples in the temperature range tested. The energy of activation (E) was significantly (P<0.05) higher for endosperm for cv. Len, a vitreous sample, than for cv. Titan, a mealy sample.