Germination of Dormant and Nondormant Rescuegrass Seed on the Thermogradient Plate 1

Dormant and nondormant rescuegrass (Bromus catharticus Vahl.) seed were tested on the two-way thermogradient plate to make a comprehensive comparison of their germination responses to alternating and constant temperatures within a range of 5 to 35 C. Nondormant seed germinated within 1 week at a constant temperature near 30 C and within 4 weeks over most of the temperatures above 15 C. Dormant seed did not germinate at constant temperatures. Moderate germination of dormant seeds was obtained at 4 weeks with alternating temperatures. Imbibition of dormant seed on 0.2% KNO₃-moistened blotters improved germination slightly. Clipping off the distal end of the caryopsis of dormant seed produced substantial germination at 3 weeks, but only at alternating temperatures. The combination of KNO₃ and clipping resulted in a germination response by dormant seed at almost the same temperature range favorable for germinating nondormant seed.