This study was carried out during the two successive seasons of 2011/2012 and 2012/2013 to evaluate the effect of paclobutrazol (PP333) at 0.0, 50, 100 and 150ppm and cycocel (CCC) at 0.0, 1000, 1500 and 2000ppm on growth, flowering, chemical composition and histological features of potted Tabernaemontana coronaria plants. The obtained data showed that: All PP333 and CCC concentrations decreased plant height and leaf area, especially PP333 at 150ppm in both seasons. On contrary, all applied treatments of PP333 and CCC significantly increased the number of branches and leaves / plant to reach its maximum with the highest concentration for each. The heaviest fresh and dry weights of leaves/plant were gained by 100ppm pp333-sprayed plants in the two seasons. Also, PP333 and CCC treatments delayed the flowering of Tabernaemontana plant when compared with control plants which induced the earliest flowering in both seasons. In addition, number of flowers/plant as well as their fresh and dry weights were significantly increased with PP333 and CCC treatments in the two seasons. However, the highest number of flowers/ plant was scored by 150ppm PP333-sprayed plants, whereas the heaviest flowers fresh and dry weights/plant were gained by CCC at 2000 ppm sprayed plants. Moreover, the highest show value (plant width/ height ratio) was existed with PP333 at 150 and 100 ppm in the two seasons. The highest number of roots/plant as well as their fresh and dry weights were registered by 2000ppm CCC- sprayed plants in both seasons. Furthermore, PP333 and CCC treatments significantly increased leaf N, P, K, total carbohydrates and total chlorophylls contents as compared with un- sprayed plants in the two seasons. As for the endogenous phytohormones, all PP333 and CCC treatments increased cytokinins and abscisic acid (^g/g F.W), but they decreased gibberellins and auxins (^g/g F.W) of Tabernaemontana leaves. With regard to the anatomical features of leaf anatomy, most traits were increased with different applied treatments, particularly PP333 at 150 and 100 ppm and CCC at 2000 ppm. Among these anatomical features were the most important ones, i.e., thickness of leaf midrib, length & width of vascular bundle, phloem & xylem tissues and number of xylem vessels in vascular bundle as well as the leaf blade thickness. |
