EFFICACY OF PACLOBUTRAZOL ON THE GROWTH AND FLOWERING OF Jacobinia carnea (LINDL.) NICHOLSON

Jacobinia carnea (Lindl.)Nicholson is a plant species belongs to ornamental flowering shrubs (Fam.Acanthaceae).The effect of different methods and rates of paclobutrazol application on Jacobinia carnea have not been previously studied under the Egyptian conditions.Therefore, this study was conducted at Sakha, Agricultural Research Station, Kafr El-Sheikh Governorate, Egypt, during two successive seasons of 2005/2006 and 2006/2007 to study the effect of two methods of application of paclobutrazol (Bonzi) and rates on some vegetative and roots growth traits, flowering and some chemical composition of Jacobinia carnea plants, aiming to use it as a new flowering indoor pot plant.The first application method of paclobutrazol was foliar spray at the rates of 15, 20, and 25 ppm while the second application method was soil drench at the rates of 1.0, 2.0, and 3.0 mg/pot.Twice foliar spray and soil drench of paclobutrazol at 2 weeks interval were applied to potted plants of Jacobinia cornea.Results indicated that plant height, fresh and dry weights of leaves, leaf area, fresh and dry weights of branches, root length as well as fresh and dry weights of roots were significantly decreased with raising paclobutrazol concentration in both methods of application in both seasons.However, number of branches exhibited a slight and insignificant increment between all treatments.Moreover, number of flower heads/plant was increased.Meanwhile, the application of all concentrations in both methods decreased the number of florets/flower heads and delayed flowering time as compared to the control especially with the high rates in the first and second seasons.The contents of chlorophyll (a), chlorophyll (b), and total chlorophyll, total carbohydrates and indoles in the leaves were linearly decreased with raising paclobutrazol concentration in both methods of application.However, phenols content in leaves was increased as affected by these treatments.A linear slope regression showed that application of paclobutrazol as soil drench on Jacobinia cornea plants was more efficient on reduction of most parameters under study compared with application of foliar spray.Therefore, it could be recommended to use paclobutrazol as a foliar spray at 20 ppm or as soil drench at 2.0 mg /pot, twice time at fortnight interval, according to user preference, and to obtain good potted flowering indoor plants of Jacobinia carnea plantlets should be treated 4-4.5 month old under similar conditions of this investigation.