In the testing grounds of the Tobacco and Tobacco Products Institute in Plovdiv, near the village of Markovo, in humus-carbonate soil, a field experiment was set up to determine the biological efficiency and selectivity of some soil herbicides used in growing oriental tobacco plants of the Plovdiv 7 variety. One of them was the Harnes herbicide with active ingredient acetochlor 90%.
Acetochlor was applied at a dose of 150 ml/dka and 250 ml/dka 72 hours prior to tobacco planting. During the vegetation period, some visible signs of phytotoxicity in the crop were observed - plant growth inhibition, leaf and vegetation tip deformation, weak chlorosis, etc.
For the purpose to determine the impact of the herbicide on tobacco leaf anatomy, samples from the midsection of the leaves were taken. The parameters taken into consideration were stomata number/mm2 and stomata size (μm) from the upper and lower epidermis, and size of the assimilation parenchyma (mesophyll) of the leaf. It was established that acetochlor caused considerable changes in the tobacco leaf anatomy, which found expression in reduction of stomata number/mm2, as well as reduction of the thickness of leaf lamina (blade), compared to those in the non-treated control plants.