Mechanism of Seed Priming in Circumventing Thermodormancy in Lettuce

Abstract
Lettuce (Lactuca sativa L. cv Minetto) seeds were primed in aerated solutions of 1% K3PO4 or water at 15°C in the dark for various periods of time to determine the manner by which seed priming bypasses thermodormancy. Seeds which were not primed did not germinate at 35°C, whereas those which were primed for 20 h in 1% K3PO4 or distilled H2O had up to 86% germination. The rate of water uptake and respiration during priming were similar regardless of soak solution. Cell elongation occurred in both water and 1% K3PO4, 4 to 6 h prior to cell division. Both processes commenced sooner in water than K3PO4. Radicle protrusion (germination) occurred in the priming solution at 21 h in water and 27 h in 1% K3PO4.