Morphological and anatomical changes in Lilium cv. Arcachon in response to plant growth regulators

The effect of five concentrations of gibberellic acid (GA3), benzyladenine (BA) and paclobutrazol (PBZ) on the morphology and anatomy of Lilium cv. Arcachon was evaluated. To this end, bulbs were immersed for 24 h with five different concentrations (0, 25, 50, 100 or 200 mg L−1) of GA3, BA, or PBZ. Then the treated bulbs were immediately sown in 2.5 L pots containing tezontle. Pots containing bulbs were randomly distributed, kept under greenhouse conditions, and watered with Steiner solution. Morphological and anatomical traits were evaluated at the flowering phase. The results showed that height (85.3 cm), number of leaves (79.7), and leaf area (743.3 cm2) were not modified by GA3, but they diminished in response to BA. In contrast, stems were 80% smaller in response to PBZ but, did not affect the number of flower blooms. The biomass of bulbs (27.6 g) raised by 32 and 48% in response to BA and PBZ, respectively. The number of vascular bundles and shoot phloem area was similar in all treatments, whereas the number of vessel elements increased by 69% when compared with control plants (62 mm2 vessels). The length of epidermal cells in the leaves decreased between 30 and 48% in response to both GA3 and BA, whereas no effects were observed in response to PBZ. Mesophyll width was greater by applying PBZ. Finally, PBZ at 25 mg L−1 is enough to reduce the size of stems and improve their appearance as pot plants. Whereas PBZ affects significantly the size of the stems, the BA provoked bud abortion. This research shows in detail how the growth regulators modified the anatomy of the stems and leaves as well as the roots development in Lilium cv. Arcachon plants.