Development and Histochemistry of Resin Ducts of Secondary Xylem in the Stem of Pinus tabulaeformis Carr.

The dynamic changes of resin droplets and starch grains in resin duct cells at different developmental stages of resin duct of secondary xylem were studied by histochemistry.At the initial stages, few resin droplets and starch grains observed in the cytoplasm.At formative stages,the number of starch grains gradually increases while their volume enlarges.Resin droplets charge with a same trend.At the mature stage,the volume of starch grains obviously decreases,no great charge take places in the number of starch grains.The volume of resin droplets enlarges while the number decreases.