Watermelon [Citrullus lanatus (Thunberg) Matsumura and Nakai] proliferating shoot meristems from established shoot cultures were inoculated on modified Murashige and Skoog salts medium supplemented with 10 txM 6-benzyladenine (BA) for shoot proliferation and on similar medium supplemented with 1 IxM BA and 10 txM gibberellic acid (GA3) for shoot elongation. Agar-solidified medium and microporous polypropylene membrane rafts in liquid medium were used to support the tissues. Growth over culture time of proliferating and elongating tissues in liquid and agar-solidified media were compared. Nutrient depletion in liquid medium was monitored and quantified using ion selective electrodes. Tissue fresh weights in both proliferation and shoot elongation media were greater in liquid than in agar-solidified medium. Relative dry matter content, however, was greater in agar-solidified than in liquid medium. More shoots elongated in agar-solidified than in liquid medium. The numbers of buds or unelongated shoot meristems, however, were comparable for both the liquid and agar-solidified medium. Proliferating and elongating tissues in liquid medium used Ca ++ and K ÷ minimally. NO 3 was utilized but not depleted by proliferating tissues. NH4, however, was depleted. Most of the NH 4 was utilized by the proliferating tissues within 21 days of culture when growth rate was greatest. At 35 days, residual Ca ++, K +, NO 3, and NH2 in proliferation medium were 81.0%, 67.8%, 55.7%, and 1.2% of initial levels, respectively. NO 3 and NH 4 in shoot elongation medium were depleted. The greatest NO 3 and NH 4 utilization was observed during the first 14 days of culture Ca , NO3 and NH4 in shoot elongation when the largest growth rate was obtained. The residual + ÷ K ÷ , , 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 proliferation and shoot elongation medium, respectively.

Investigations of materials and methods for growing plant tissue in a continual-flow, liquid nutrient medium as an alternative to semisolid agar medium have been made. Enhanced growth of plant tissue on microporous polypropylene membranes floating on a liquid nutrient has been demonstrated. Moreover, in vitro plantlets on the microporous membrane are free from entanglement with the support matrix and readily available to mechanized handling. Trained growth of plantlets through polypropylene netting shows potential for mechanization by mass handling (separation, singulation, and transfer) of plant tissue cultures. KEYWORDS. Plant tissue culture, Micropropagation, Mechanization. INTRODUCTION C onventional plant tissue culture technology involves growing micropropagules in small vessels on nutrient medium contained in semisolid agar or, less frequently, in liquid suspension which is constantly agitated to enhance aeration. Both methods are characterized by continual depletion of medium. Furthermore, frequent, highly labor-intensive transfers of plant tissue are required every 4-8 weeks. Harvested product cost ranges from $0.12 to $0.17/micropropagule. Labor can account for 40-90% of this total operating cost. Competitiveness of tissue culture products is currently limited to crops with high profit margins such as ornamentals or other plants with superior properties or restricted alternative procedures. Tissue culture propagation faces a substantial challenge to be competitive compared to conventional propagation of bedding plants (<$0.05 US/cutting) or of agronomic and forestry crops (<$0.01 US/cutting). Sluis and Walker (1985) projected that bridging this cost gap for growth in the industry will depend heavily upon advances in mechanization and automation.

High quality domesticVernonia anthelmintica (ironweed) seed was grown on many experimental test plots at a variety of locations during the 1963 season. Quality appeared to be related to seed density as judged by high oil content of 25 to 32%, the oils having oxirane oxygen values of 3.6 to 4.0% with low acidity, less than 2% calculated as epoxyoleic acid. Larger plantings in 1963 made without benefit of test plot data produced poor quality seed. For processing some of this seed was upgraded to fair quality by air‐elutriation. Processing in a small soybean continuous solvent extraction plant was successfully achieved with only minor changes in existing equipment. No enzymatic lipolysis occurred during these operations. The oil obtained was equal in quality to that prepared from the same seed in the laboratory by the best procedures available. Also, the oil was improved in quality by removal of the major portion of its free fatty acids and unsaponifiable material. The chief natural component of the seed oil, trivernolin, was prepared from a substantial quantity of the oil miscella to demonstrate the commercial feasibility of this operation.