Variation in base temperatures for germination in warm season grasses

Recently efforts have been made to develop heat unit based growth models fo r warm season grass production in cool season environments. These models re quire the accurate determination of base temperatures. Variations in base t emperatures for germination of four switchgrasses (Panicum virgatum L.), th ree big bluestem grasses (Andropogon gerardii Vitman), two indian grasses ( Sorghastrum nutans L. Nash) and two prairie sandreeds (Calamovilfa longifol ia (Hook) Scribn.) were determined. During the germination study seeds were allowed to germinate in Petri dishes at 4, 8, 12, 16 and 20 degreesC. The germination rates were used in estimating base temperatures using regressio n techniques. There were variations, among and within species in germinatio n. Estimates of base temperature for germination were 5.5 to 10.9, 7.3 to 8 .7, 7.5 to 9.6 and 4.5 to 7.9 for switchgrass, big bluestem, indian grass a nd prairie sandreed. Absolute values in each case depended on whether linea r or non-linear techniques were used. The results also indicated difference s between base temperature estimates for germination.