The Damaging Effect of Water on Dry Pea Embryos During Imbibition

When pea seeds were imbibed in water without their seed coats, vital staining revealed that cells on the abaxial surface of the cotyledons were dead. No damage occurred on the surface of cotyledons when the seeds were imbibed intact, or beneath the testa when only half of the testa was removed. Cell death occurred as a result of rapid water uptake within the first 2 min of imbibition, since reducing the rate of imbibition in solutions of Carbowax 4000 lessened the damage. Cell death was restricted to the outer layers of the cotyledons; inner tissues remained alive. These observations supported the hypothesis that rapid early leakage during imbibition of dry embryos resulted from the death of cells caused by the physical disruption of membranes. Imbibition damage resulted in reduced respiration and germination, a decline in the rate of food reserve transfer from the cotyledons to the growing axis, and a lower growth rate in the seedlings produced. Greater sensitivity of embryos to imbibition damage at low temperature, and similarities between features of imbibition damage and chilling injury led to the suggestion that so-called chilling injury is the result of imbibition damage rather than the effects of low temperature.