Anther and tissue culture-induced grain chalkiness and associated variants in rice

Rice, Oryza sativa, plants regenerated from anther culture with and without in vitro selection pressure were evaluated for chalky seed. Progeny evaluated included 21 spontaneously doubled haploids selfed 4 times, progeny from plants regenerated from S-aminoethylcysteine resistant callus selfed 4 times and backcrosses of both types to the parental type. All lines with in vitro histories had higher seed chalkiness than the controls both in the intensity of chalkiness and in the number of seeds expressing the character. The full range of intensity and amount of chalkiness was expressed in the progeny. The average intensity of anther/tissue culture-derived progeny was 4–5, based on a scale of 1 (translucent) to 10 (fully opaque), and the average amount of chalkiness within plants sampled was 50–75 percent. The chalky characteristic is transmitted from parent to offspring into a range of identifiable F₂ segregants. Disclaimer statement Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the USDA, and does not imply its approval to the exclusion of other products that may also be suitable.     

Effect of growth temperature on the morphology and performance ofZymomonas mobilis ATCC 29 191 in batch and continuous culture

Summary Increasing the temperature in chemostat culture ofZymomonas mobilis ATCC 29 191 with low and high glucose concentrations was found to result in a decreasing frequency of septation leading to the formation of long filaments and in increasing outer membrane blebbing. Whether this effect is strain specific or universal inZymomonas is, unknown. Improvements in the fermentation kinetics could be achieved at elevated temperatures, with an optimum at 33°C. Temperatures >30°C induced uncoupled growth in chemostat cultures ofZ. mobilis ATCC 29 191. The results of this study emphasize the importance of temperature regulation in optimizing the performance of continuous fermentations withZymomonas.Nomenclature D Dilution rate, 1/h - _max Maximum specific growth rate, 1/h - S _R Initial substrate concentration, g glucose/1 - S Amount of glucose consumed, g glucose/1 - S ₀ Effluent substrate concentration, g glucose/1 - X Biomass concentration - g cells/1 - [P] Amount of product formed, g ethanol/1 - [P] Product concentrations, g ethanol/l - Y _x/s Growth yield, g cells/g glucose used - Y _p/s Product yield, g ethanol/g glucose used - O _s Specific rate of glucose uptake, g glucose/g cells/h - Q _p Specific rate of ethanol formation, g ethanol/g cells/h - VP Volumetric productivity, g ethanol/1/h - t Fermentation time, h Corresponding author     

Relationship between the cytoplasm and the vacuole phosphate pool in Acer pseudoplatanus cells

The Pi concentration of Acer pseudoplatanus cells in the two major intracellular compartments, the cytoplasm and the vacuole, has been studied using 31P NMR. For sycamore cells containing approximately 2 mM of total Pi, the cytoplasmic Pi and the vacuolar Pi concentrations were approximately 6 and 1.5 mM, respectively. When the cells were transferred to a phosphate-deficient medium, the vacuolar Pi decreased rapidly while the cytoplasmic Pi decreased slowly during the first 48 h, indicating that Pi in the cytoplasm was maintained at the expense of the vacuolar Pi. When the Pi-starved cells (i.e., those containing less than 0.5 mumol of total Pi/g wet wt) were transferred to a medium containing 300 microM Pi, Pi entered the cells rapidly and accumulated in the cytoplasm. Once the cytoplasmic Pi pool was filled, Pi was taken up in the vacuole until the vacuole Pi pool was filled. On the contrary when the non-Pi-starved cells were transferred to a phosphate-rich medium (i.e., containing 45 mM Pi), Pi entered the cells slowly by diffusion and accumulated in the vacuole but not in the cytoplasm. These results demonstrate that the Pi content of the cytoplasm is maintained at the expense of the vacuolar Pi pool when sycamore cells are transferred to either a phosphate-deficient or a phosphate-rich medium.