Roy E. Young

Nutrient utilization in liquid/membrane system for watermelon micropropagation

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 μM 6-benzyladenine (BA) for shoot proliferation and on similar medium supplemented with 1 μM BA and 10 μM 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. NO3− was utilized but not depleted by proliferating tissues. NH4+, however, was depleted. Most of the NH4+ was utilized by the proliferating tissues within 21 days of culture when growth rate was greatest. At 35 days, residual 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+ utilization was observed during the first 14 days of culture when the largest 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 proliferation and shoot elongation medium, respectively.

Approaching Mechanization of Plant Micropropagation

ABSTRACT, 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.

Mass Handling of Watermelon Microcuttings

Modifications were made in the configurations of the unitizing, nonselective wire cutters used by Alper et al. (1992) for mass cuttings of Stage II Citrullus lanatus cv. Charlee (watermelon) plant tissue cultures to further enhance productivity. Mounting the cutter in an inverted position over the receiving vessel eliminated time required for filling. This cut-and-dump technique became 4.8 times more productive for the total transfer process than the conventional scalpel and forceps technique when both time and yield of cut segments with visible buds were considered. A concept for growing fewer, larger tissue clusters per vessel in mini-trays with orienting cells and cutting with correspondingly sized oriented cell wire cutters yielded as much tissue fresh weight as conventional agar vessels and afforded the potential to reduce time required for the removal job function with the cut-and-dump technique.

Unitized, nonselective cutting of in vitro watermelon

Unitized, nonselective mass cutting of Stage II Citrullus lanatus cv. Charlee (watermelon) plant tissue cultures has been achieved with various configurations and sizes of wire cutter devices. Time studies revealed that the wire cutters increased the productivity of the cutting function over conventional scalpel and forceps by a factor of 14. Total transfer productivity, including the manual functions of removing tissue from an initial culture vessel and filling (sorting and placing cut tissue segments) new vessels, was increased by a factor of 1.8. The square grid-type cutting devices yielded from 48 to 59% as many viable bud clusters per culture vessel as hand cutting and from 65 to 95% as much tissue fresh weight. An oriented-cell configuration of wire cutter actually increased tissue fresh weight about 20% over hand cutting. The simplicity of construction and quality of material of the wire cutter render it readily autoclavable and highly flexible to function both as an aid to small operations and as an element in more sophisticated mechanical devices for larger operations.

Use of Low Temperature to Improve Storage of in vitro Broccoli Seedlings Under Various Light Qualities

ABSTRACT Broccoli (Brassica oleracea L. Botrytis Group ‘Green Duke’) seeds were germinated in vitro photoautotrophically (without sugar in medium) or photomixotrophically (with sugar in medium) for 3 weeks at 23 ° C and 150 μmol · m−2 · s−1 photosynthetic photon flux (PPF). Vessels were then stored at 1 ± 0.35°C under 1.6 ± 0.20,4.1 ± 0.35, or 8.6 ± 0.50 μmol · m−2 · s−1 constant PPF each of white (400–800 nm), red (600–700 nm), or blue (400–500 nm) light. Concentrations of CO2 inside the vessels were monitored until equilibrium was reached. Light compensation point was reached at

Micropropagation medium composition on-line sensing system development

2.0 μmol · m−2 · s−1 for photoautotrophic seedlings and at

Plant Height Control by Photoselective Filters: Current Status and Future Prospects

4.0 μmol · m−2 · s−1 for photomixotrophic seedlings. Therefore, in the long-term storage experiment, seedlings were stored for 4, 8, or 12 weeks at 1 ± 0.35°C in darkness or under 3 μmol · m−2 · s−1 constant PPF (average light compensation point) of white, red, or blue light. Variable to maximal chlorophyll fluorescence (Fv/Fm) of leaves decreased as storage time increased, regardless of media composition. Illumination during storage was necessary to maintain dry weight and regrowth potentials of in vitro seedlings. All photo-autotrophic seedlings stored in darkness were of poor quality and died when transferred to the greenhouse. Seventy-five percent of dark-stored photomixotrophic seedlings survived storage for 12 weeks but declined in appearance, dry weight, total soluble sugars (TSS), and chlorophyll fluorescence. Red light during storage increased seedling dry weight, TSS, and regrowth potential. Supplying 2% sucrose in the culture medium increased dry weight and maintained overall seedling quality during irradiated storage.

Growth responses of chrysanthemum and bell pepper transplants to photoselective plastic films.

A plant micropropagation system has been developed with the capacity of allowing periodic, automatic, aseptic monitoring of culture medium composition. The system was able to sample automatically culture medium from a liquid/membrane bioreactor without compromising asepsis or disturbing plant tissue. Media samples were analyzed to determine sucrose and dextrose concentrations. Bioreactor media was automatically replenished to compensate for volumes lost due to sampling. For a 28-day culture period using Stage 1 Nicotiana tabacum (tobacco) explants as a model culture system, media sucrose concentration decreased with a corresponding increase in dextrose concentration and tissue fresh weight.