Analysis of flowering dynamics heritability in the perennial warm‐season grass Paspalum dilatatum

Understanding the flowering cycles of perennial warm‐season grass species may be very important to the design of management practices and breeding. However, developmental dynamics are not well understood. As most plant traits associated with flowering dynamics do not follow a normal distribution, the use of general linear models to describe and compare these variables might be misleading. The aims of this study were (i) to find a methodology to compare panicle accumulation curves and (ii) to estimate heritabilities for flowering curve attributes. Panicle counts were recorded during a complete flowering cycle on a diverse collection of dallisgrass (Paspalum dilatatum). We compared the efficiency of different linear mixed models based on whole plot or individual plant data; then, we adjusted nonlinear regression curves for individual plants to estimate several curve attributes and compared this approach to the area under the curve. Finally, we calculated the broad‐sense heritabilities of the estimated curve parameters. The following reproductive curve attributes were obtained: panicle production potential, panicle accumulation rate and days until 3, 5, 10 and 15 panicles. We found that monitoring individual plants is more efficient when studying flowering attributes. Significant differences among genotypes for several flowering cycle attributes were found. Heritabilities were very high for all flowering cycle initiation and duration attributes. We also showed that the number of days until the emergence of a given low number of panicles can be used as a highly heritable measure to characterize flowering cycles.     

Sowing date and nitrogen supply determine the outcome of competition between dallisgrass (Paspalum dilatatum Poir.) and tall fescue (Festuca arundinacea Schreb.) in the Pampas region of Argentina

The effects of sowing date and nitrogen (N) fertilizer on the inter‐specific competition between dallisgrass (Paspalum dilatatum Poir.) and tall fescue (Festuca arundinacea Schreb.) in the humid Pampas of Argentina were investigated in two pot experiments where a constant soil moisture content was maintained. Tall fescue and dallisgrass seeds were sown either in the spring (October 2000) or in the autumn (March 2001) in mixed and mono‐specific stands with 0 or 100 kg N ha^?1. In the spring, competition from tall fescue depressed dry‐matter (DM) yield of dallisgrass from 1·53 to 0·36 g DM per plant and tiller number from 9·4 to 3·7 tillers per plant in mixed and in mono‐specific stands, respectively, while tall fescue had 3–4 times higher DM yields in mixed stands. Leaf extension rate (LER) of tall fescue was higher (1·3 mm d^?1) than that of dallisgrass (0·53 mm d^?1). In the autumn, inter‐specific competition did not affect DM yield of dallisgrass and N fertilizer increased DM yield from 0·53 to 2·07 g DM per plant, tiller number from 6·8 to 14·2 tillers per plant and LER at the beginning of autumn from 1·2 to 2·12 mm d^?1 in both species. As temperature decreased, LER was reduced in both species to 0·31 mm d^?1 by late autumn. The number of leaves per tiller was not affected by treatment. Nitrogen fertilizer increased N concentration of above‐ground tissues of both species (18 g kg^?1 DM in autumn and 20 g kg^?1 DM in spring). It was concluded that a productive mixed pasture of dallisgrass and tall fescue can be obtained by sowing early in the autumn. The application of N fertilizer in this season is essential to ensure a high herbage yield and quality.     

紫斑病对大豆室内发芽特性的影响

通过紫斑病对大豆室内发芽特性的影响研究,结果表明,大豆感染紫斑病后,种子的发芽势、发芽率、活力指数明显降低,不同感染级别种子的发芽势间存在明显差异,因此,大豆种子感染紫斑病后会因播种品质显著降低而不适于大田用种.     

轮叶党参种子中萌发抑制物质活性的研究

以白菜和小麦种子作生物测定,研究了轮叶党参种子中萌发抑制物质的活性。结果表明,轮叶党参种子中存在着活性较强的抑制物质,且抑制物质的活性随着提取液浓度的增加而增加。采用不同溶剂提取轮叶党参抑制物质的活性不同,以甲醇提取液抑制活性最强,乙醚次之,水提取液抑制作用不明显。采用去翅处理和温水浸种能有效去除大部分抑制物质。     

Changes in starch,oil, protein and amino acids in developing seeds of okra (Abelmoschus esculentus L. Moench)

The okra seeds of variety Pusa sawani were analysed for protein, non-protein nitrogen, total free amino acids, lysine, and tryptophan from the 7th day to the 42nd day after flowering. Starch, total sugars and oil percent were also estimated in these seeds. During the early stages of maturation, the soluble components (non-protein nitrogen, free amino acids and total sugars) were found in higher quantities than in the later stages. Protein, oil and starch contents increased gradually from day 7 to day 42. The rate of accumulation of oil was found to be at the highest level between 21–28 days after flowering, while the rate of protein deposition was greatest between days 35–42. Inditiation of seed maturation seems to start 21 days after flowering in okra seeds.     

The presence and inactivation of trypsin inhibitors,tannins, lectins and amylase inhibitors in legume seeds during germination. A review

During the germination of legume seeds, enzymes become active in order to degrade starch, storage-protein and proteinaceous antinutritional factors. The degradation of storage-protein is necessary to make peptides and amino acids available in order to stimulate seed growth and early plant growth. Proteinaceous antinutritional factors such as amylase inhibitors, lectins and trypsin inhibitors are present in legume seeds and protect them against predators. However, during germination, they degrade to a lower level by the action of several enzymes. The effect of germination on the content and activity of amylase inhibitors, lectins, tannins and trypsin inhibitors is discussed.