Climatic Variation in Forage Grasses. II. Germination, Flowering and Leaf Development in Mediterranean Populations of Phalaris tuberosa

Abstract

In forage grasses, the course of seasonal production is strongly influenced by the timing of flowering and seed production, and by the extent of any winter or summer dormancy. Earlier studies on local populations of Lolium and Dactylis, covering the climatic range from the Mediterranean region to northern and central Europe, revealed a regular cline in flowering responses to temperature and photoperiod (Cooper 1960; Calder 1964a, b) and also in leaf expansion and plant dormancy at low temperatures (Cooper 1964). It was suggested that these differences resulted from the selective action of limiting climatic factors, particularly summer drought in the Mediterranean environment, and winter cold in northern and central Europe. The next step was to discover how far similar local adaptation could occur within a single climatic region. The present paper, therefore, describes some of the environmental requirements for germination and flowering, and the pattern of leaf and tiller development in contrasting light and temperature regimes, in several collections of the perennial forage grass Phalaris tuberosa, all from the Mediterranean region, but from locations differing in their seasonal distributions of precipitation and temperature, and hence in potential growing season. MATERIAL