CONTRIBUTIONS TO THE HISTO-ANATOMICAL STUDY OF THE CALENDULA OFFICINALIS L. LEAVES TREATED WITH THIOPHANATE METHYL (TOPSIN M)

The study analyzes the histo-anatomical modifications of the Calendula officinalis leaf, caused by the treatment with thiophanate methyl, applied 3 times, in two different concentrations, of 0.1% and, respectively, 0.4%. The cross-sections made at the three levels of the leaf, as well as the surface ones, evidenced some quantitative differences between the two variants of treatment and the reference, while the differences of qualitative type are minimum, referring to the different distribution of the pallisadic tissue on the two sides of the foliar limb; consequently, the leaf structure is different: bifacial unequally equifacial in the reference and bifacial heterofacial, respectively, in the treated samples. The quantitative type modifications are related to the prominence extent of the median nervure, thickness of the meristematic area, size and number of the conducting fascicles and the xylem vessels (which are intensely stimulating parameters in the two treatments), the presence of secretory hairs, width and thickness of the foliar limb which, at a concentration of 0.4%, are slightly inhibited, in spite of the fact that the median nervure is much more prominent, even comparatively with the 0.1% concentration treatment.