The Role of the Oxygen Permeability of the Seed Coat in the Dormancy of Seed ofXanthium pennsylvanicumWallr

Abstract

A method for direct identification and quantitative measurements of mixed or pure gases diffusing through seed coats was devised to test the hypothesis that the dormancy of Xanthium pennsylvanicum seeds is caused by oxygen-impermeable seed coats. The diffusion of oxygen through seed coats of X. pennsylvanicum was shown to obey Fick's first law. Oxygen diffused through the lower and upper seed coats at the same rate. Imbibed lower and upper seeds showed essentially equal oxygen uptake rates before radicle emergence. This uptake was lower than the rate at which oxygen can diffuse into the seed. Therefore upper seeds are not dormant because of seed coat restriction of oxygen diffusion. The relationships of oxygen with other factors involved in seed dormancy are discussed.