Thermal time requirements for germination of four subterranean clover cultivars

Abstract

ABSTRACT In vitro germination tests were performed at 11 constant temperatures (range 2.5–35°C) to quantify the maximum germination percentage and germination rate of four subterranean clover cultivars (‘Antas’, ‘Denmark’, ‘Monti’ and ‘Narrikup’). These were used to estimate their cardinal temperatures, base ( T b ), optimum ( T opt ) and maximum (T max ) and the thermal time requirements for seed germination. Germination percentages were ≥ 88% in the 5–25°C temperature range for all cultivars. The time to reach 50% of final germination ( T 50 ) decreased from 12 to 2 days as the temperature increased from 2.5 to 17.5°C. The determined T opt were 16°C for ‘Monti’ and ‘Narrikup’ and 22°C for ‘Antas’ and ‘Denmark’. At a common T b of 0°C the thermal time requirements for T 50 were 32 ± 1°Cd for ‘Antas’ and ‘Denmark’ and 39 ± 1°Cd for ‘Narrikup’ and ‘Monti’. ‘Antas’ and ‘Denmark’ (both from Italy) germinated at the widest range of temperatures.