Embryo Dormancy of Pinus jeffreyi Murr. Seed as Affected by Temperature, Water Uptake, Stratification, and Seed Coat.

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Abstract
At 25"C and 15[degree]C, removal of the seed coats and the papery membranes from unstratified Pinus Jeffreyi seeds permits rapid germination, while at 5[degree]C it does not. However, when the seed coats and papery membranes are removed from stratified seeds, germination is rapid at 5[degree]C as well as at 15[degree]C and 25[degree]C. This was interpreted as indicating a condition of "relative" embryo dormanyc which could be overcome by stratification. The seed coat and papery membrane surrounding the endosperm are permeable to water. Water uptake and germination are readily separable at 5[degree]C but not at 25[degree]C. Furthermore, "stratification" can be accomplished with only that amount of water absorbed by the seed during its first 48 hours in contact with water. Thus, water uptake per se does not appear to limit germination. The data suggest a convenient working hypothesis for the continued study of the seed dormancy mechanism in pine. In effect a two-step process is indicated such as S[long dash][forward arrow]I[long dash]# G where "S"is the substrate, "I" is one or more intermediate compounds, and "G" is growth. The effect of the seed coat on germination at 15[degree]C and 25[degree]C suggests reactions of the same general type as those associated with the Pasteur effect.

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