GEOGRAPHIC VARIATION OF ROOT DEVELOPMENT OF PONDEROSA PINE (PINUS PONDEROSA LAWS.) SEEDLINGS AS RELATED TO SHOOT GROWTH AND SEED CHARACTERISTICS.

摘要

The root development, shoot growth, and seed characteristics of ponderosa pine (Pinus ponderosa Laws.) were studied. The materials included 16 half-sib families from Arizona, California, Colorado, Idaho, New Mexico, Oregon, South Dakota, and Wyoming.;Other differences among half-sib families included shoot length and dry weight, root-shoot ratios, length and number of cotyledon, length and diameter of aerial hypocotyl, needle fascicle length, seed characteristics, and 30-day germination percentage. With regard to shoot, families of the coastal regions had longer shoots and larger shoots as reflected in shoot dry weight than families of the inland regions. In root-shoot ratios, families of the coastal regions had lower root-shoot length ratios and higher root-shoot dry weight ratios than families of the inland regions. There were no distinct patterns of variations among families in length and number of cotyledons, length and diameter of aerial hypocotyls, and needle fascicle length. The differences among the families were randomly distributed. Seeds of the coastal families were longer and heavier, but had lower germination percentages than seeds of the inland families.;There were differences in primary root length and root dry weight among half-sib families from different geographic regions. Families from the coastal regions had longer primary roots and larger root systems as reflected in root dry weight than families from the inland regions. Primary root length was positively correlated with shoot length and shoot dry weight and aerial hypocotyl diameter. Primary root length was not correlated with seed length characteristics at any stages of growth and not correlated with seed weight characteristics, except at the 60-day stage measurement of primary root length. The nine-month root dry weight was positively correlated with shoot length and shoot dry weight, female gametophyte and embryo weight, and aerial hypocotyl diameter.