Climatic variation in forage grasses. 1. Leaf development in climatic races of Lolium and Dactylis.
Leaf expansion was investigated in 10 ecotypes of Lolium perenne and 7 of Dactylis glomerata. Seasonal sowings revealed a regular cline in relative rate of leaf expansion in winter from the Mediterranean region, along the Atlantic coast to N. Europe and Scandinavia, associated with the winter temperatures of their places of origin. In controlled environment leaf surface expanded most rapidly at 25°/12°C, but at 10° and particularly 5°C leaf expansion was most rapid in the Mediterranean populations, least in the northern, and intermediate in the maritime material. Rate of leaf expansion and cold hardiness were negatively correlated. Varietal differences in rate of leaf expansion were mainly determined by temperature. [See also H.A. 34: 1167.] F. s.-R.B.