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Commercially produced membrane rafts containing Celgard D-304 microporous, polypropylene film are used to support the growth of micropropagated plants in liquid media. This method is used because growth experiments using membranes resulted in plant growth rates equal to or greater than those grown on agar. Inconsistent results of plant growth on these rafts led to an interest in measuring the water vapor transmission rates (WVTR) of the membranes. A modified WVTR test (ASTM E96-80) was used on 15 raft samples. Results showed that the supplier's value of 49.2 g/m2 ·hr falls within the range of measured values of 39.2 to 54.8 g/m2·hr. Inconsistencies in growth of micropropagated plants may not be due to variability in the WVTR of the Celgard film. It is possible that the WVTR of the film is not the most important factor in facilitating liquid nutrient transport across the membrane. Other properties of the film need to be measured to determine factors affecting growth rates observed.
Three Scutellaria species (Scutellaria lateriflora, S. costaricana, and S. baicalensis) were grown in different in vitro physical environments: agar, liquid culture, and liquid culture with fiber-supported paper (with initial media volumes of 20 mL and 30 mL). During an 8-week time course, tissue growth was assessed for each species by fresh weight (FW), dry weight (DW), percent DW, and multiplication ratio. Water use and hyperhydricity were also compared. Scutellaria lateriflora plantlets grown in liquid were hyperhydric despite the greatest accumulation of dry mass, but multiplication diminished with time as plants became hyperhydric. In contrast, S. costaricana and S. baicalensis plantlets had higher FW and DW on agar. With all Scutellaria species tested, plantlets grown on agar or fiber-supported paper were not hyperhydric, and fiber-supported paper with 20 mL initial volume yielded plants with the greatest percent DW. The lowered hyperhydricity was related to reduced water uptake. The flavonoids baicalin, baicalein, and wogonin were quantified in plants grown on fiber-supported paper culture. The baicalin concentrations in in vitro cultured S. lateriflora shoots was comparable to those of field-grown plants. The in vitro method presented a unique opportunity to enhance baicalein content and produce wogonin-rich roots. S. costaricana plantlets in vitro showed high levels of the three flavonoids compared with S. baicalensis and S. lateriflora. Growing non-hyperhydric tissues on fiber-supported paper, in vitro, allowed the clonal propagation of Scutellaria species with increased flavonoid content to proceed in a simple, controlled environment.
Weed competition is a main factor limiting sweetpotato [Ipomoea batatas (L.) Lam] production. Yellow nutsedge (Cyperus esculentus L.) is a problematic weed to control due to its ability to quickly infest a field and generate high numbers of tubes and shoots. Compounding this is the lack of a registered herbicide for selective postemergence control of yellow nutsedge. Research was conducted to evaluate the bentazon dose response of two sweetpotato cultivars and one advanced clone and to evaluate the plant hormone melatonin to determine its ability to safen bentazon post emergence. Bioassays using Murashige and Skoog (MS) media supplemented with melatonin (0.232 g a.i./L and 0.023 g a.i./L) and bentazon (0.24 g a.i./L) were conducted to evaluate the effect of bentazon on sweetpotato and to determine the interactive response of the Beauregard cultivar to bentazon and exogenous applications of melatonin. Beauregard swas the most tolerant cultivar and required dosages of bentazon that were two-times higher to cause the same injury compared with other cultivars. MS media containing melatonin and bentazon showed fewer injuries and higher plant mass than plants treated with bentazon alone. These results indicate that sweetpotato injury caused by bentazon may be reduced by melatonin.