Thermal time requirements for germination of four annual clover species

Abstract

Germination of ‘Cefalu’ arrowleaf, ‘Bolta’ balansa, ‘Prima’ gland and ‘Mihi’ Persian clovers was determined from constant temperature (5–40 °C) from incubator experiments. A ‘broken stick’ regression of germination rates against temperature was used to quantify thermal time (Tt) requirements and cardinal (base, optimum and maximum) temperatures. Tt requirements for 75% germination were higher for ‘Cefalu’ arrowleaf (34 °Cd) than ‘Bolta’ balansa (32 °Cd), ‘Prima’ gland (28 °Cd) and ‘Mihi’ Persian (25 °Cd) clovers. All species had a base temperature of 0 °C. ‘Mihi’ Persian clover had an optimum temperature (T opt ) of 33 °C and a maximum temperature (T max ) of 45 °C, while all the other species had T opt between 16–20 °C and T max of c. 34 °C. The maximum final germination percentage was above 60% for ‘Cefalu’ arrowleaf clover and 80% for the other three species.