Initial Root Development of Ponderosa Pine Seedlings as Related to Germination Date and Size of Seed

Abstract Seeds of Pinus ponderosa Laws. of different sizes were planted weekly during the summer in tilted metal boxes with a glass front. The metal boxes slipped into a wooden frame buried in the soil. Taproots growing along the glass front were measured weekly. In November, seedlings werewashed from the boxes and the number of lateral roots and dry weights were determined. Seedlings that germinated early produced larger, deeper, and heavier root systems than those that germinated later. There were significant differences in growth between seedlings that germinated only oneweek apart. Weekly root penetration was closely related to the average air temperature. Size of seed had little or no influence on rate of germination, germination percent, or seedling growth.