Patterns and main parameters of the dynamics of radioactive contamination of organs of Scots pine in the plantations of Chernobyl zone are presented. On the basis of this data and within the frameworks of the microdosimetric approach, the dosimetric model for the apical meristem of the pine trees was created. The dose rates were calculated for the trees of the experimental array growing at three sites in the exclusion zone and one outside, which differed by three orders of magnitude of the trees' radioactive contamination levels. Comparable high, up to several Gy/y, levels of the dose rate of chronic irradiation were shown for the plantation at the Red Forest site. Such an expressed radiation factor results in a high frequency of the morphological changes at this site. The dose rate-effect dependence was formulated for this type of the radiobiological effects.