Potato (Solanum tuberosum L.) treatment with paclobutrazol resulted in short and compact plants having dark green and thicker leaves, and wider stem and root diameters. Investigating the underlying anatomical modifications in response to the treatment was the objective of the study. Plants of potato cultivar BP 1 were treated with 0, 45.0, 67.5, and 90.0 mg paclobutrazol per plant as a foliar spray. A month after treatment leaf, stem and root materials were taken from the control and plants treated with 67.5 mg paclobutrazol, and histological observations were made using light microscope. Leaves of treated plants showed an increased chlorophyll a and b contents, thicker epicuticular wax layer, elongated and thicker epidermal, palisade and spongy mesophyll cells. paclobutrazol increased stem diameter by about 58% due to induction of thicker cortex, larger vascular bundles, and wider pith diameter associated with larger pith cells. Widening the cortex and the induction of more secondary xylem vessels in response to paclobutrazol treatment increased the root diameter by about 52%. Paclobutrazol treatment remarkably increased the accumulation of starch granules in the stem pith cells and cortical cells of the stem and root. This study is similar to the other relevant studies in reporting an increased leaf thickness, and stem and root diameters; however, most of the underlying anatomical modifications described above have not been reported previously.
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