Search

Quinoa is a potential new seed crop for protein feed and human consumption in Europe, with tolerance to a range of abiotic stresses. For this purpose the study was planned to analyse the effect of important agronomic strategies like nitrogen level, N application strategy, row spacing and harvest time on yield and quality of quinoa. The experiments took place in the field of the experimental station of the Faculty of Science, University of Copenhagen. Three levels of organic nitrogen from slurry was used (60, 120 and 180 kg N ha−1), supplied either all at once at sowing, or split between sowing and beginning of the reproductive phase. The effect of row spacing and harvest time was studied by harvesting seeds at seed maturity, which occurred 2-3 weeks prior to the mechanical harvest by threshing, and a couple of months after. Yield increased significantly (P ≤ 0.05) with an application up to 180 kg N ha−1, reaching 2200 kg ha−1. Increasing N also caused a significantly increased seed weight (up to 3.3 mg) and protein content (up to 17 %). N level did not affect number and amount of weeds. Split application with part of the N applied at bud formation did not have a significant effect on yield. Delayed harvest had a negative influence on seed weight, whereas protein content was stable after harvesting even a month after seed maturity. A late harvest significantly reduced seed germination, being reduced by 50 % after a 2-month delay. A conclusion from this study is that both yield and protein content of seed can be manipulated by N level and application strategy. Harvest time is important for securing a high seed quality measured as seed germination, seed weight and protein content. A fast germination of quinoa is an important characteristic demonstrating that the crop has good possibilities for being well-established in the field when free from weeds at the time of sowing. The choice of row spacing is important and depends on weed control method. Weed control strategy should be developed based on modern precision tools. [ABSTRACT FROM AUTHOR]

Drought adaptation strategies of two bambara groundnut landraces, Uniswa Red and S19-3, collected from contrasting environments in Africa, were compared. Our objectives were to investigate the relative significance of effective stomatal control induced by the abscisic acid (ABA) signalling and osmotic adjustment in regulating plant water relations in general for this legume species. The ABA concentration [ABA] in the leaf increased linearly with declining relative leaf water content, and there were significantly higher [ABA] in Uniswa Red compared with S19-3 at the final harvest in the drought-stressed plants. Estimated by a linear-plateau model, S19-3 initiated the reduction in transpiration at a significantly lower soil water threshold (FTSW = 0.50 ± 0.024) than Uniswa Red (FTSW = 0.69 ± 0.023) indicating that the latter was more sensitive in reducing plant water use in response to soil drying. A similar trend was found for stomatal closure during soil drying, although the soil water thresholds at which relative stomatal conductance ( g) started to decline were not significantly different between the two landraces. By an early closure of stomata and hence an early reduction in transpiration rate during soil drying, Uniswa Red could be defined as a 'water-saver' such that it maintains leaf water status to a great extent of soil water deficit. This strategy is important for survival during intermittent drought. While S19-3 could be defined as a 'water-spender' with a late closure of stomata, hence a late declining of transpiration rate during soil drying allowed the landrace to maximize its water use despite giving up its leaf water relations. Such drought response together with a fast phenological development of S19-3 indicates that the landrace is capable of escaping from terminal drought while maximizing its water use and productivity when soil water is available. [ABSTRACT FROM AUTHOR]

The effects of nitrogen fertilizer on the growth and density of natural weed populations to spring barley (Hordeum vulgare L.) and winter wheat (Triticum aestivum L.) were investigated in the absence of herbicide. An increased level of applied nitrogen did not enhance: weed germination, tended to decrease the total weed biomass and had a differential effect upon the biomass of individual weed species in both wheat and barky. In competition with barley, Chenopodium album L. and Lamium spp. had lower nitrogen optima than the crop, while Urtica urens L. had a higher nitrogen optimum. In competition with wheat, Stellaria media (L.) Vill., Lamium spp. and Veronica spp. had lower nitrogen optima than the crop. The systematic changes in nitrogen effect with time were analysed by fitting orthogonal polynomials to the growth and density curves. The methodology could be recommended for other studies in which time or other systematic factors are included, as it supplies information which a traditional analysis of variance cannot provide. Since seed production is positively correlated with biomass, so nitrogen level affects seed production and, hence, the seed pool and future weed population, suggesting that fertilize r usage can be exploited in an integrated programme of crop/weed management. A trend towards lower N fertilizer application owing lo concerns about the environment will favour most of the weed species investigated in these experiments and change the composition of weed populations. [ABSTRACT FROM AUTHOR]

A set of simple sequence repeat (SSR or microsatellite) markers was used to discriminate a collection of 33 Spinacia oleracea hybrid cultivars from seven different breeding stations all over the world. All SSR markers were genic microsatellite markers located in coding or non-coding regions of genes of known function. Cluster analysis based on 13 of the SSR markers showed that the spinach hybrids grouped into three clusters. The first two clusters consisted of European spinach types, which were well discriminated according to their origin from different breeding stations. The third cluster was a mixture of Asian as well as European types of spinach. Subclusters in this group did not reflect differences in morphology, earliness or company origin. The data show that genic microsatellites are a powerful tool for discrimination of spinach cultivars. [ABSTRACT FROM AUTHOR]

Kinetic studies on a microsomal fraction from oat roots (Avena sativa) indicate that the MgATP complex is the primary substrate for the ATPase. Free ATP was a weak competitive inhibitor. Free Mg2+ appeared to be either a competitive or noncompetitive inhibitor. [ABSTRACT FROM AUTHOR]