1. In vitro multiplication of an industrial fiber plant: kenaf (Hibiscus cannabinus L.) Materials and Methods Plant materials consisted of 10 cm nodal microcutting excited from shoots of plants aged 50 days. Tests for the first culture phase (4 weeks) were conducted on basal Murashig and Skoog (1962) MS medium supplemented with 5 IBA (indolebutyric acid) concentrations (0; 0,25; 0, 5; 1; 2 mg.l -1 ) and 5 BAP (benzyl adenine) concentrations (0; 0, 25; 0, 5; 1; 2 mg.l -1 ). Rooting tests were conducted, during 4 weeks, on MS media supplemented with 3 IBA concentrations (0; 0,25; 0,5 mg.l-1). Growth parameters data were submitted to analysis of variance (ANOVA) using SAS program. The differences among means were analyzed by Student test at 5% significance level. - Means of the same column followed by different letters are significantly different at P< 0.05 according to Student Test. - Conditions of the test: Photoperiod 16 hours. Light Intensity 36 µmol.m -2.s -1. Temperature 23  1°C. Culture period: 4 weeks. Multiplicatio n Rooted vitroplants ARBAOUI Sarra a, CAMPANELLA Bruno b, ROGER Paul b and BETTAIEB Taoufik a Horticultural Science laboratory, National Agronomic Institute of Tunisia 43 Charles Nicolle Street, 1082 Tunis Mahragene, Tunisia b Environmental Toxicology laboratory, Gembloux Ago Bio Tech 2, Passage de Déportés, 5030 Gembloux, Belgium saraharb@hotmail.fr Introduction Kenaf (Hibiscus cannabinus L.) is an annual fiber plant of Malvacea family. The stem produces two types of fiber, a coarser fiber in the outer layer and a finer fiber in the core. It has been cultivated for the manufactures of ropes, textiles, paper, insulation and used in many industries including automobile industry. Problems encountered in the establishment of uniform, vigorously growing kenaf result from seed germination quality. The purpose of this study was to develop a suitable protocol for micropropagation of kenaf. Medium Plant growth regulator combinations (mg/l) Shoot induction (%) Number of shoots Number of nodes Shoot length (cm) Rooting (%) 0MS1001.38 ab2.22 ab1.67 ab66.66 1MS +0.25 BAP1001.22 b1.82 ab1.13 b44.44 2MS+ 0.25 IBA1001.30 ab1.15 c0.85 c40 3MS+ 0. 5 BAP+0.25 IBA1001.22 b1.82 ab1.23 b11.11 4 MS +0.25 BAP+0.5 IBA1001b3.17 a2.67 a100 5MS+ 1 BAP+ 0.25 IBA1001.44 a1.85ab 28.57 6MS+ 0.25 BAP+ 1 IBA1001.6 a2.56 ab2.66 a70 7MS+ 2 BAP1001.2 b1.2 c0.68 c0 8MS+ 2 BAP+0.25 IBA1001.2 b1.4 b0.52 c0 9MS+2 IBA1001.1 b1.6 b1.37 b100 Results Initiation of in vitro culture Initiation of in vitro culture is 100% in all culture media The highest number of nodes is obtained on the MS medium supplemented with 0.25 mg.l -1 BAP and 0.5 mg.l -1 IBA Table 1: Effect of plant growth on nodes formation, shoot induction (%) and growth Multiplication - The highest number of formed nodes 3.8 was obtained for MS control medium. - MS medium free growth regulators appeared to be the best medium for shoot induction. - Root induction was simultaneously observed along with shoot elongation. IBA (mg.l -1 )Rooting (%)Number of rootsRoot length (cm) 01008.67 a1.93 a 0.251008.66 a1.46 b 0.51005.50 b1.29 b Table 2: Effect of IBA Concentration on root induction (%) and length In vitro rooting - In vitro rooting tests led to a general rooting in shoots cultivated in different treatments. - The highest number of roots was obtained with growth regulators free medium and medium supplemented with 0.25 mg/l of IBA. - The longest roots were obtained with medium without growth regulators. - The exogenous supply of IBA does not improve rooting. Microcuttings Acclimatized vitroplants Conclusion An efficient micropropagation method has developed to initiate shoots and regenerate plants of Hibiscus cannabinus L. in a relative short time and high multiplication rate. The use of MS medium added with 0.25 mg.l -1 BAP and 0.5 mg.l -1 IBA stimulate shoot induction and nodes formation on the first in vitro culture step. During multiplication stage, MS free growth regulators was the best media for explant growth. In vitro micropropagation of kenaf does not require any additional rooting step regarding to its easy rooting aptitude. Rooted plant can growth to maturity and produce seed under open pollinated conditions. Acclimatization The kenaf plants show no ex vitro adaptation problem. The success rate of transplanted plants was 100%.