NUTRIENT UTILIZATION IN LIQUID MEMBRANE SYSTEM FOR WATERMELON MICROPROPAGATION

Watermelon [Citrullus lanatus (Thunberg) Matsumura and Nakai] prolifer ating shoot meristems from established shoot cultures were inoculated on modified Murashige and Skoog salts medium supplemented with 10 muM 6-benzyladenine (BA) for shoot proliferation and on similar medium sup plemented with 1 muM BA and 10 muM gibberellic acid (GA3) for shoot el ongation. Agar-solidified medium and microporous polypropylene membran e rafts in liquid medium were used to support the tissues. Growth over culture time of proliferating and elongating tissues in liquid and ag ar-solidified media were compared. Nutrient depletion in liquid medium was monitored and quantified using ion selective electrodes. Tissue f resh weights in both proliferation and shoot elongation media were gre ater in liquid than in agar-solidified medium. Relative dry matter con tent, however, was greater in agar-solidified than in liquid medium. M ore shoots elongated in agar-solidified than in liquid medium. The num bers of buds or unelongated shoot meristems, however, were comparable for both the liquid and agar-solidified medium. Proliferating and elon gating tissues in liquid medium used Ca++ and K+ minimally. NO3- was u tilized but not depleted by proliferating tissues. NH4+ however, was d epleted. Most of the NH4+ was utilized by the proliferating tissues wi thin 21 days of culture when growth rate was greatest. At 35 days, res idual Ca++, K+, NO3-, and NH4+ in proliferation medium were 81.0%, 67. 8%, 55.7%, and 1.2% of initial levels, respectively. NO3- and NH4+ in shoot elongation medium were depleted. The greatest NO3- and NH4+ util ization was observed during the first 14 days of culture when the larg est growth rate was obtained .The residual Ca++, K+, NO3- and NH4+ in shoot elongation medium at 38 days were 63.5%, 37.9%, 21.2%, and 24.3% of initial concentrations, respectively. At the end of experiment, 72 .3% and 42.8% of initial sugars were still remaining in the shoot prol iferation and shoot elongation medium, respectively.