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Tae-Cheol Seo, Changhoo Chun, Hyung-Kweon Yun and Han-Cheol Rhee

Edible chrysanthemum, pak-choi, endive, chicory, and lettuce were hydroponically cultured under root-restricted conditions in DFT systems and their growth and nutritional values were investigated. Cylindrical plastic tubes 100 mm tall and 20, 25, and 30 mm in diameter were used for root restriction. Growth of all the species was retarded, as the roots were restricted. Pak-choi and edible chrysanthemum showed the greater reduction in growth compared with chicory and endive. Percentage of dry matter, C:N ratio, and ascorbic acid and anthocyanin contents increased in the root-restricted treatments. Changes in mineral contents as affected by root restriction were not consistent among tested species. Optimized root volumes to improve the nutritional values and to reduce the retarding of growth varied according to species of leafy vegetables. Tubes of Φ25mm × 10cm and Φ30mm × 10 cm gave the best results in chicory, endive, and lettuce, and edible chrysanthemum and pak-choi, respectively. Results indicate that nutritional values of hydroponically cultured leafy vegetables can be improved by root restriction using plastic tubes.

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Xin Zhao*, Janice E. Young, Ted Carey and Weiqun Wang

Organic vegetables have been suggested to produce higher levels of phytochmemicals, which play active roles in disease prevention. We measured total phenolic and aglycone flavonoid (apigenin, kaempferol, luteolin, and quercetin) contents in leaves of organically- and conventionally-grown lettuce (`Kalura' and `Red Sails'), collards (`Top Bunch') and Pak Choi (`Mei Qing') greens during spring and summer trials, using the Folin assay and HPLC, respectively. Postharvest changes in phenolic contents of organic and conventional lettuce were also investigated after 17-day storage at 4 °C. Production system did not cause a significant difference in total phenolic levels of lettuce and collards in either trial, but total phenolics were significantly higher in organic Pak Choi in the summer trial, possibly due to greater flea beetle damage in the organic plots. Organic production did not affect the aglycone flavonoid levels of lettuce and collards in the spring trial except that apigenin increased in organic samples. In the summer trial, however, concentrations of kaempferol, luteolin and quercetin tended to increase in organic lettuce and collards; only luteolin showed promising increase in Pak Choi. Species and cultivars both had significant effects on total phenolic and flavonoid contents. After 17-day storage, total phenolic content significantly increased in both organic and conventional lettuce although the concentrations of aglycone flavonoids remained relatively constant. Total phenolic content was higher in organic `Red Sails' at a marginal significance level after storage, while it did not differ between organic and conventional `Kalura'. We noted a dominant presence of glycoside flavonoids in lettuce before and after storage, which warrants further study.

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Charles F. Forney and Michael A. Jordan

Methanethiol (MT) is a volatile compound responsible for the strong off-odor that is evolved when fresh broccoli is held under anaerobic atmospheres. Inductive atmospheres can develop in modified-atmosphere packages, resulting in reduced quality. To determine if related vegetables are capable of producing MT, 12 different vegetables from the genus Brassica were cut into ready-to-eat forms. Fifty-gram samples of these cut vegetables were sealed in 500-ml glass jars and flushed with N2. After flushing, jars were held for 24 h at 20C in the dark. Headspace samples from the jars then were analyzed for MT and other volatiles using a GC-MS> The concentration of MT was greatest in jars containing broccoli florets. Broccoli flower buds removed from florets produced 40 times more MT than peduncle and stem tissues (38.3 vs. 0.87 mmol·m–3). Headspace concentration of MT (mmol·m–3) in jars containing these different vegetables was: broccoli florets, 22.7; pak choi leaf blades, 17.8; savoy cabbage, 12.4; broccoflower, 7.5; green storage cabbage, 5.2; red cabbage, 2.7; kale, 0.81; Brussels sprouts, 0.36; pak choi petioles, 0.28; rutabaga root, 0.26; cauliflower florets, 0.18; Chinese cabbage, 0.03; and kohlrabi tubers, 0.02. In addition to MT, ethanol, dimethyl disulfide, and dimethyl trisulfide were detected in the headspace over each of the 12 vegetables. The contribution of these induced compounds to off-odor development in packaged, precut vegetables will be discussed.

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J. Anderson and D. Creech

The population of U.S. Asians will increase by 41% and reach 12 million by the year 2000. Chinese cabbage, Pak Choi, Daikon, and Bitter melon have moved out of the ethnic market and are now in mainstream outlets. This study targeted a diverse range of cool and warm-season crops. Besides those listed above, this study evaluated varieties of Asian greens, Chinese brocolli, Allium, edible soybeam, melon, squash, cucumber, edible Chrysanthemum, amaranth, winged bean, yard-long bean, and edible soybean. A randomized complete block design was utilized, with three replications of row length, varying from 10 to 33 feet, depending on species tested. Direct seedlings of cool-season crops in February and September, 1989 resulted in good market quality and yield of many varieties. Work in 1990 will focus on width of the market window, market information, and grower access to markets.

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Gloria McIntosh and Gerald Klingaman

Spunbonded polyester or polystyrene row covers were used as additional cold protection for spinach (Spinacia oleracea), kale (Brassica oleracea), pak choi (Brassica rapa) and P-types of lettuce (Lactuca savita) grown in ground beds under unheated polyethylene tunnels during the fall and winter of 1991 and 1992 in climatic zone 6. Temperatures inside poly tunnels averaged 2.4C warmer than outside. Average temperatures were 1.9C warmer than control under polystyrene and 1.5C warmer under spunbonded polyester. Average hourly temperatures showed both row covers offered significantly more cold protection than the greenhouse covering alone; but the two row covers offered similar protection from the cold. Row covers did not result in fresh weight differences in most of the species tested, except kale which had greater fresh weight in control. It may be concluded that during a similar mild winter, these cool season vegetables could be grown under unheated polyethylene tunnels with no additional protection necessary. When temperatures are lower, row covers could provide the protection required to produce these crops.

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Jan M. Kossowski and David W. Wolfe

Long- and short-term physiological responses of pak choi (Chinese cabbage, Brassica campestris cv. `Hypro') to elevated CO2 and light environments were evaluated in the series of growth chamber experiments. Plants were grown hydroponically (Nutrient Film Technique) at 25/18°C (day/night) temperature, a 16-h photoperiod, and at three CO2 levels (350, 700, 1400 ppm) and two light levels (200 and 400 μmol·m–2·s–1 PPFD). Relative to 350-ppm CO2 treatment, the final total plant dry mass in low light increased by 37% and 38% at 700 and 1400 ppm CO2, respectively. In high light the increase was 7% and 13% at 700 and 1400 ppm CO2, respectively. Light response curves showed a positive CO2 effect on light compensation point, a slight increase in quantum yield and increase in maximum Pn rates at elevated CO2. Carbon dioxide response curves (measured at saturating PPFD of 1600 μmol·m–2·s–1) showed no effect of growth light treatment on the CO2 compensation point, but a 20% to 30% higher maximum Pn rate at saturating CO2 in plants grown at the higher light level. Overall, the highest Pn rates and the highest plant dry mass at final harvest were found in plants grown at the 400 μmol·m–2·s–1 PPFD and 1400 ppm CO2. Relative beneficial CO2 effects, however, were the most pronounced in low light conditions.

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J. Mitchell McGrath and Carlos F. Quiros

Morphology and fertility were characterized for 22 intersubspecies hybrids within B. campestris L. Nine subspecies, representing crop types from different geographical areas, were used as pollen donors on three different seed parents. Stability of scored morphological characters was divided into four classes based on their appearance in F1 hybrids; i) constant (present in all hybrids when the character was present in one of the parents, e.g., enlarged hypocotyl, divided leaf), ii) variable (present in some hybrids when the character was present in parent types, e.g., petiole color, pubescence), iii) novel (appearing in hybrids but not present in parents, e.g., anther tip spot, self-compatibility), and iv) reciprocal differences. Constant characters are assumed to have a strong genetic component, variable characters may result from heterozygosity in parents, an allelic series, or polygenic inheritance, and novel characters may arise through mutation or altered gene or physiological interactions. Reciprocal crosses revealed morphological components controlled by the maternal parent, and were most striking in pak-choi (ssp. chinensis) by turnip [ssp. rapifera (Metzg.) Sinsk.] hybrids. Pollen and seed fertility of hybrids was generally reduced when Indian oilseeds [ssp. dichomata (Roxb.) Olsson; ssp. trilecularis (Roxb.) Olsson] were used as parents. Inheritance of the enlarged hypocotyl character was tested in one F2 population. Segregation of the enlarged hypocotyl trait was consistent with a hypothesis of a dominant Mendelian locus. Various novel characters appeared in this F2 population that were not evident in the parents of the hybrid, some of which also showed Mendelian segregation. Genetic differentiation of nuclear or plastid genomes may account for these observations.

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Theodore J.K. Radovich, Archana Pant, Ian Gurr, Ngyuen V. Hue, Jari Sugano, Brent Sipes, Norman Arancon, Clyde Tamaru, Bradley K. Fox, Kent D. Kobayashi and Robert Paull

of pak choi under compost fertilization ( n = 4). Means followed by the same letter are not significantly different ( P < 0.05) within each growth medium; ACT = aerated vermicompost tea, ACTME = aerated vermicompost tea with microbial enhancer, NCT

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Brian A. Kahn, Niels O. Maness, Donna R. Chrz and Lynda K. Carrier

higher phenolic concentrations for pak choi ( Brassica rapa L. Chinensis group) compared with conventional fertilization with mineral fertilizers. The application of sanitized sewage sludges to pepper ( Capsicum annuum L.) plants improved yield without

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Norman Q. Arancon, Archana Pant, Theodore Radovich, Nguyen V. Hue, Jesse K. Potter and Chad E. Converse

-based vermicompost tea also suggests the possibility of hormonal effects on seed germination and better root growth. Pant (2011) and Pant et al. (2012 ) found a positive effect of GA4 on root and shoot growth of in vitro-cultured pak choi with similar