Publisher Summary Moisture content plays a role in seed physiology in two ways. First, it may convey information about the expected metabolic activity of the seed—that is, development, resting, or germination. The proportion of structured or vicinal water in the tissue compared to the bulk water, and the change in absolute water content, may play a role here. A dehydration to air dryness would be necessary for the unequivocal switching of the water gradient polarity. This may explain why it is necessary to dry immature seeds below 60% moisture for good viability, even though germination occurs at 60% moisture. Therefore, the absolute moisture content does not dictate a specific physiological activity. Second, the expression of the perceived information is also controlled by moisture status. Severe dehydration irreversibly switches off production of reserve materials and switches on a controlled senescence program that continues at variable rates until the seed reserve structure is destroyed.