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`Beauregard' sweetpotatoes (Ipomoea batatas L. Lam) were stored under a continuous flow of 0%, 1%, 1.5%, 2%, 5%, 10%, or 21% O2 (balance N2) for 14 days. Respiration rate was significantly lower at 1.5%, 2%, 5%, and 10% O2 compared with 21% O2, while respiration at 0% and 1% O2 was higher than at 1.5%, 2%, 5%, and 10% O2. Respiration rate at 0% O2 remained high for several days after exposure to air while that at 1.5%, 2%, 5%, and 10% O2 increased rapidly to equal that of 21% O2. Ethanol and acetaldehyde accumulated rapidly at 0% and 1% O2 but were lower at the other O2 levels. Ethanol increased 16- and 4-fold after 14 days of storage at 0% and 1% O2, respectively, compared to 21% O2. In addition, acetaldehyde increased 11- and 8-fold at 0% and 1% O2 respectively, compared to 21% O2. Sucrose and total sugar concentration increased under low O2 concentration while reducing sugars (fructose and glucose) and pH decreased.
The glucose-6-phosphate dehydrogenase (G-6-PDH) and glucose oxidase methods are commonly adapted for plant invertase assay. A disadvantage of the G-6-PDH assay is the relatively high cost of the coupling enzymes and cofactors. A disadvantage of the glucose oxidase method, which uses a glucose kit (Sigma, 510-A), is the presence of high activities of acid invertase and alkaline invertase in the PGO enzyme formula (peroxidase and glucose oxidase), which gives a falsely high invertase activity value. An alternative and inexpensive coupled assay was developed for enzymatic assay of plant invertases. In this assay, ADP produced from phosphorylation of glucose and fructose (hydrolysis products of invertases) is coupled to oxidation of NADH by the enzymes pyruvate kinase and lactate dehydrogenase in presence of phosphoenolpyruvate and NADH. This method was compared with the glucose-6-phosphate dehydrogenase method by using protein preparations derived from plant materials of three different species. Statistical analysis indicated that the alternative assay was similar in accuracy to the glucose-6-phosphate dehydrogenase method, with an advantage of reducing the cost from $0.85 to $0.35 per assay.
`Beauregard' sweetpotato (Ipomoea batatas L. Lam) roots were maintained under different controlled atmospheres ranging from 0% to 21% O2 at 22 °C in two separate trials for 14 days to study changes in activities of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH). Trial I showed no difference in activities of PDC and ADH between 0% and 1% O2, or among 2%, 5%, and 21% O2. Both PDC and ADH activities were significantly higher at 0% and 1% O2 compared to the 2%, 5%, and 21% O2 atmospheres. In trial II, both enzyme activities were lower at 1.5% O2 than at 0% O2, but higher than at 10% and 21% O2 atmospheres. The combined data of the two trials showed a very strong correlation between PDC and ADH activities (R 2 = 0.86). In addition, a strong correlation existed between PDC activity and acetaldehyde concentration (R 2 = 0.95). The maximal activities were at pH 6.5 for PDC and at pH 8.5 for ADH in the direction of acetaldehyde-to-ethanol. The results suggest that 1.5% O2 is the critical point for the transition from aerobic to anaerobic metabolism in CA storage of sweetpotato roots, and PDC is the key enzyme in alcoholic fermentation.
Floral morphology and differentiation of `Sharpblue' southern highbush blueberry (Vaccinium corymbosum L.) were studied under natural growing conditions. There was no rest period during floral development of `Sharpblue' blueberry in Louisiana. Basal florets were already present within a racemic inflorescence in early September. All floral and reproductive organs were clearly visible in early December. Microspores and pollen grains were observed in mid- and late-January, respectively. Megasporocytes, two-cell, four-cell, and seven-cell embryo sacs were found to be simultaneously present in developing ovules in late January, suggesting that megasporogenesis and megagametogenesis in `Sharpblue' blueberry are asynchronous.
Regenerated spinach (Spinacia oleracea L.) maintained under a 10-h photoperiod (65 uE m-2 s-1) after an incubation period on a GA-containing medium were induced to flower in vitro. The plantlets were regenerated from callus initiated on MS medium with 2.0 mg L-1 kinetin and 0.5 mg L-1 2,4-D and were subsequently transferred to a medium containing 2.0 mg L-1 kinetin, 1.0 mg L-1 GA, and 0.01 mg L-1 2-4,D. While on the regeneration medium, the cultures were exposed to a long-day photoperiod. Regenerants were transferred to an IBA-containing medium for rooting, after which flowering was observed. In vitro flowering plantlets exhibited male and female flowers depending on the sex of the explant donor. Female plantlets developed seeds in the culture vessels. This method of seed production from regenerants can eliminate time-consuming steps in acclimation, transplanting to soil, and plant maintenance.
`Saturn', `Mars', and `Reliance' were compared based on their different Vitis vinifera and V. labrusca compositions. Disks (10 mm) from young leaves were placed abaxial side down on a standard media containing NAA or 2,4-D at 0.0, 1.0, and 2.0 mg/L with BAP at 0.0, 0.1, and 0.2 mg/L. Each treatment was replicated in 10 culture tubes and incubated at 25 ± 1C under cool-white fluorescent light for 10h photoperiods. Calli were compared by size, color, and occurrence of morphogenesis. NAA generally produced a larger callus by cultivar than 2,4-D. A greater quantity of callus was generally produced with the increase of the V. labrusca component. Callus produced on 2,4-D medium was round, compact and light to dark green in color. However, callus produced on NAA medium was amorphous, friable, and ranged in colors. Rooting occurred on some calli produced on NAA media.
Callus, induced in the dark from leaf tissue of spinach (Spinacia oleracea L. cv. Fall Green) on Murashige and Skoog (MS) medium supplemented with (in mg·liter -1) 2 kinetin and 0.5 2,4-D regenerated shoots upon transfer to a medium containing 2 kinetin, 0.01 2,4-D, and 1 GA3. Complete plants were established by stimulating rooting of the shoots with 1 mg IBA/liter and transferring them to potting soil; survival was 60%. Chemical names used: N-(2-furanylmethyl)-1H-purin-6-amine (kinetin); 2;4-dichlorophenoxy acetic acid (2,4-D); gibberellic acid (GA3); 1H-indole-3-butanoic acid (IBA).
Scarification treatments (a control, a 10-minute vacuum, or a 1.5-minute ultrasound), different media (modified Norstog and Van Waes) and growth regulators [benzyladenine (BA) at 0, 1, 1.5, or 2 mg·L-1 and 6-(r,r-dimethylallylamino)-purine riboside (2iPR) at 0, 1, 1.5 or 2 mg·L-1] were used in combination to increase seed germination of Cypripedium calceolus var. parviflorum. Seeds treated with ultrasound had higher germination (58.0%) than those treated with vacuum (27.4%) or controls (19.2%). Germination rates increased with 2iPR level and reached a maximum between 1.5 and 2 mg·L-1. Seeds on Van Waes medium, which were not transferred to fresh medium after germination, had a severe browning problem causing many protocorms to die. Those on Norstog medium continued to grow into seedlings with less browning. Germination rates of Calopogon tuberosus × Calopogon `Adventure' and Liparis liliifolia were determined on the different media and growth regulator treatments. Multiple shoots of Calopogon developed from single seeds on media containing growth regulators. Flower buds formed in vitro on Calopogon in media containing 1 mg·L-1 or higher BA 5 months after germination. L. Iiliifolia seeds in Norstog medium had a higher proportion of germination than those in Van Waes medium.
The objective of this study was to determine the efficacy of Agrobacterium tumefaciens in transforming spinach (Spinacia oleracea L.) callus. Callus was induced from leaf disks of `Baker' on Murashige and Skoog (MS) medium supplemented with 2 mg L-1 kinetin and 0.5 mg L-1 2,4-D. Callus was cut into 2-mm pieces, and 0.5 g of callus was placed in each 250-ml flask which contained 20 ml of MS liquid medium. The suspension cultures were inoculated with 100 μl of an overnight culture of A. tumefaciens harboring pMON 9749 (provided by S. Rogers, Monsanto Co., St. Louis), a plasmid cointegrated with kanamycin resistance and β -glucuronidase (GUS) genes. After coculturing for 2 days at 22C with shaking at 100 rpm, the medium was replaced with selection medium containing (in μg/ml) 75 kanamycin, 100 cefotaxime, and 200 carbenicillin and maintained for 3 weeks. Transient expression of GUS gene in transformed cells was detected with X-glu assay. This method resulted in a high level of transformation and provides the first report of transformation in spinach. This study was funded by a grant (92-B-32) from the Arkansas Science & Technology Authority.