Anatomical aspect of 2,4,5-T and dalapon toxic action on Norway spruce (Picea abies) seedlings

The results are presented of investigations on the effect of 2,4,5-T (butyl ester of 2,4,5-trichlorophenoxy acetic acid) and dalapon (sodium salt of 2,2-dichloropropionic acid) on tracheid differentiation and mitotic divisions of vascular cambium and phellogen in 1- and 2-year-old shoots of spruce seedlings treated with herbicides in concentrations of 10, 100, 1000, 5000, and 50000 mg l−1 before and after bud differentiation.The investigations showed that 2,4,5-T at 100 and 1000 mg l−1 can periodically stimulate mitotic activity of the cambium, resulting in an increase of tracheid number. Increased mitotic activity of phellogen, which resulted in an increase in number and expansion of cortical and peridermal cells, caused by 2,4,5-T, was also observed. Dosages of 5000 mg l−1 and higher of 2,4,5-T supressed mitotic divisions.No stimulatory effects of dalapon, applied on seedlings either before or after bud differentiation, were observed either in the cambium or in the cortex and the periderm. High dalapon concentrations (over 5000 mg l−1) retarded mitotic divisions in the cambial zone.