This research goals are to gathering the informations of optimum GA3 concentration and the perfect timing of the immersion time, along with the interaction between that concentration and how long the immersion of GA3 to a germination and the growth of mangosteen seed. The research was done on Desa Sangkanjoyo, Kajen, District of Pekalongan at an altitude of 55 meters above sea level, alluvial land. The experimental design which is used was a Group Random Design (Rancangan Acak Kelompok-RAK) with factorial treatment of 4 x 3.The first factor of GA3 concentration which consist of 4 standards, those are 0, 100, 200, and 300 ppm. The second factor is the length of immersion which consist of 3 standards, those are 12 hours, 24 hours, and 36 hours. Twelve kinds of treatment combination which in each combination is repeated for 3 times so there are 36 experimental units in whole. The observed variables include the following: the speed of germination, germination percentage, plant height, number of leaves per plant, leaves width per plant, stem diameter, wet plant weight, dry plant weight, primary root length, and number of secondary root. The GA3 concentration was really influential to all observed variables, except the germination percentage was not significantly different from quadratic influence pattern. The length of immersion was really influenced to all observed variables except the germination percentage was not significantly different from positive linear of influence pattern. There was an interaction between GA3 concentration and the length of immersion to plant height and number of leaves per plant. The best of germination and growth of mangosteen seed is gained at 200 ppm of GA3 concentration and 36 hours immersion long.

Keywords: Mangosteen, GA3 concentration, and length of immersion

• UPAYA PENINGKATAN PERKECAMBAHAN DAN PERTUMBUHAN BENIH MANGGIS (Garcinia mangostana L) DENGAN BERBAGAI KONSENTRASI DAN LAMA PERENDAMAN GA3