EFFECT OF TEMPERATURE ON THE GERMINATION OF SUNFLOWER (HELIANTHUS-ANNUUS L)

The germination characteristics of seeds of six varieties of sunflower (Helianthus annuus L.) were investigated at constant temperatures ran ging from 1.5 to 49.0 degrees C. There were variations among the varie ties in the way they responded to temperature. Relationships between g ermination rate (reciprocal of time to 50% germination) and temperatur e revealed that base temperature (T-b) ranged from 1.0 to 5.1 degrees C. The ranges for the optimum and maximum temperatures for germination were 34.0 to 36.7 degrees C and 45.5 to 50.9 degrees C, respectively. The practical significance of the cardinal temperatures and other ger mination characteristics of the seeds are discussed.