Floral Induction and Development in Poa pratensis L. 1

SEPARATION of light and temperature effects on plant development received scant a t ten t ion by agricultural scientists until the development and general use of equipment for creation of artificial environments. Since then, much evidence has accumulated to indicate that flowering of some perennial grasses of temperate origin occurs as a result of a sequence of rather specific and precise environmental conditions. It is, of course, not surpr i s ing nor unnatural to find that the sequence of env i ronmen ta l requirements is in phase with the annual cycle of the climate. As the latitude increases, the seasonal variation in temperature and daily light period also increases, thus contrasting sharply with the relatively constant equatorial pattern. This fact may account for the general observation that plants indigenous to mid-temperate regions are quite exacting in their flowering requirements. It is of special interest and value to relate the effects of specific environmental factors, separately and in combinations or sequences to the physiological mechanisms involved in the plant. Such knowledge