تعيين درجه حرارت هاي بحراني در شبدر ريززميني

Detrmination of cardinal temperature in trifolium subterraneum L

The germination characteristies of two varieties of subterranean clover (Trifolium subterraneum L) were investigated at 5 levels of constant temperatures ranging 5, 13, 20, 25 and 32 d. Germination percent ranged from 0 to 90% and the maximum were observed at 13ʹ c to 25 C. Germination percent declined rapidly at temperature greater than 20ʹc and reached zero at 32 c. Rate of germintion increased with increasing temperature to 25 c and then decreased with increase temperature. Linear relationships were demonstrated between germination rates (1/D50) and temperature for each varieties. The cardinal temperatures. base (Tb), optimum (T) and maximum (To) were obtained 2.5,25.2, 32 c and 32ʹc for york and 0.9, 24.7 and 32 c for goldborn respectively.