The objective of this study was to examine the effects of different culture media used for maturation of bovine oocytes on in vitro embryo development following in vitro fertilization. Oocytes were aspirated from 2-5 mm follicles of ovaries collected at a local abattoir. The oocyte-cumulus complexes (OCCs) were cultured for 23-25 h in one of seven commercially available media supplemented with 6 mg/ml bovine serum albumin (BSA), 0.25 mM pyruvate, 10 micrograms/ml luteinizing hormone (LH), 0.5 microgram/ml follicle-stimulating hormone (FSH), and 1 microgram/ml estradiol. After maturation for 23-25 h, all eggs were subjected to the same in vitro fertilization protocol using modified TALP medium and subsequently cultured in the same serum-free embryo culture medium (HECM-1/BSA) for 8 days, after which embryo development was assessed. Five media (SFRE, MEM alpha, TCM199, MEM alpha/+, RPMI:MEM alpha) better supported normal oocyte maturation as determined by embryo development to the two-cell (76-82%), morula/blastocyst (25-32%), and blastocyst (12-19%) stages. Oocytes that were matured in Waymouth's medium MB 752/l or Ham's F-12 had a significantly reduced incidence of cleavage to the two-cell stage (52% and 37%, respectively), which was not attributed to failure of fertilization. Of the eggs that did cleave to the two-cell stage in these two media, 27% and 9% developed to morulae/blastocysts but only 6% and 3%, respectively, developed into blastocysts.(ABSTRACT TRUNCATED AT 250 WORDS)
The construction of dams significantly alters flow and sediment regimes with subsequent deleterious effects on the morphological and ecological character of rivers.Effective experimental floods can ameliorate the downstream geomorphic impacts of dams. The traditional view is that large floods are required to perform effective geomorphic work, and the geomorphic outcomes of small floods are often overlooked. Many river restoration frameworks do not consider small floods. Yet, there is evidence that the hydrological characteristics that ameliorate specific geomorphic impacts in a river are unique to each river, and a customised approach to setting the right mix of floods (including small experimental floods) is needed. In this study, we modify an existing flood effectiveness model developed for large floods, for determining the geomorphic effectiveness of small floods in a highly regulated Australian river. Two flood classes were added to the model (medium peak stream power and moderate total energy expenditure), and the flood power characteristics were rescaled to reflect the relative difference in the magnitude of the small floods and the magnitude of the geomorphic work performed. Using a step-wise approach, this customised model determined the geomorphic effectiveness of small floods.The best flood for ameliorating the geomorphic impacts of flow regulation had medium to long duration (10 to 51 days), high peak unit stream power (77 to 123 Wm −2 ) and moderate to large total energy expenditure (78,600 to 342,320 × 10 3 J). This approach to determining flood effectiveness for small floods is applicable to other geomorphically impacted river channels downstream of dams and can be used to inform experimental flood releases for geomorphic outcomes.
Three floods with flood peak ratios (peak discharge/mean annual flood) ranging between 0.65 and 5.35 occurred on the lower Snowy River in Victoria between June 1997 and August 1998. The June 1998 flood was the largest event downstream of the Rodger River junction where the flood peak ratio was >4. Pre- and post-flood investigations were carried out at the three Snowy River benchmarking sites in Victoria (McKillops Bridge, Sandy Point and Bete Bolong) to determine the impact of the floods on channel-boundary sediments and morphology. Few significant changes in graphic grain-size statistics for channel-boundary sediments were found at McKillops Bridge and Sandy Point. At Bete Bolong, there were many significant changes in the grain-size statistics of both the bed material and bank sediment. The variance and mean of a number of benchfull and bankfull channel morphologic parameters (width, area, mean depth, maximum depth, width‒maximum depth ratio) did not change significantly at McKillops Bridge and Sandy Point. At Bete Bolong, benchfull mean depth and area increased significantly due to bed degradation. Floods with a flood peak ratio of at least 4 are important for mobilising channel-boundary sediments and hence modifying channel morphology on the lower Snowy River.
PHOSPHORUS‐STARVATION TOLERANCE 1 (OsPSTOL1) is a variably present gene that benefits crown root growth and phosphorus (P) sufficiency in rice (Oryza sativa). To explore the ecophysiological importance of this gene, we performed a biogeographic survey of landraces and cultivars, confirming that functional OsPSTOL1 alleles prevail in low nutrient and drought‐prone rainfed ecosystems, whereas loss‐of‐function and absence haplotypes predominate in control‐irrigated paddy varieties of east Asia. An evolutionary history analysis of OsPSTOL1 and related genes in cereal, determined it and other genes are kinase‐only domain derivatives of membrane‐associated receptor like kinases. Finally, to evaluate the potential value of this kinase of unknown function in another Gramineae, wheat (Triticum aestivum) lines overexpressing OsPSTOL1 were evaluated under field and controlled low P conditions. OsPSTOL1 enhances growth, crown root number, and overall root plasticity under low P in wheat. Survey of root and shoot crown transcriptomes at two developmental stages identifies transcription factors that are differentially regulated in OsPSTOL1 wheat that are similarly controlled by the gene in rice. In wheat, OsPSTOL1 alters the timing and amplitude of regulators of root development in dry soils and hastens induction of the core P‐starvation response. OsPSTOL1 and related genes may aid more sustainable cultivation of cereal crops.
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