Effect of inbreeding in Korean white pine, Pinus koraiensis S. & Z. Ⅰ. The Most Suitable Time for Pollen Collection

This investigation of pollen formation and germination, and strobilus characteristics in Pinus koraiensis was carried out to determine the most adequate time for pollen collection. The pollen before the first mitotic cell division, not having a prothalial and a central cell, did not germinate; only the pollen containing 2 to4nuclei (after the first, second, or third mitotic division) germinated. The pollen procured from the male strobili (which ware dried in the shade for 3 days immediately after collection) showed 59% germination rate. At this stage, the pollen grains completed the third mitotic cell division. The staminate flowers were a light yellow-green or a bright yellow-green color. The tip part of staminate strobilus was tinted with dull red or deep red-purple spots. The bracts were bent back and individual sporangia separated each other. The pollen at the stage of dispersion showed germination rate of 99%.