Response of Phalaris Genotypes and Other Cool‐Season Grasses to Temperature1

Improved winter forage production is a major objective in breeding phalaris (Phalaris tuberosa L.) varieties for the southeastern United States. The purpose of our study was to determine morphological and physiological parameters accounting for winter forage productivity. Winter‐productive phalaris genotypes in field and growth chamber experiments responded rapidly to increasing temperatures with more rapid appearance of new leaves and greater leaf expansion rates than tall fescue (Festuca arundinacea Schreb.), reed canarygrass (Phalaris arundinacea L.), orchardgrass (Dactylis glomerata L.), or winter‐dormant phalaris types. Tiller numbers were not related to winter productivity. Fructosans comprised a higher percentage of total nonstructural carbohydrates in winter‐productive than in less winter‐productive phalaris genotypes. Phalaris genotypes did not differ in photosynthetic rates per unit area of leaf surface at several temperatures. Winter‐productivity of certain phalaris genotypes appears to result from rapid development of new leaves and rapid leaf expansion during short periods of favorable temperature, possibly aided by a supply of readily translocated carbohydrates.