Temperature effect on fructan storage and regeneration of Canada thistle (Cirsium arvense (L.) Scop)

Organic farming is challenged by perennial weeds such as Canada thistle. The increasing CO2 concentration levels causing temperature increase may lead to an increased photosynthesis and as a consequence elevated storage in underground perennating organs. In this study, we analyzed fructan, the main storage in Canada thistle, in juvenile and mature plants treated with different temperatures. Low temperatures caused higher concentrations of fructan in four weeks old plants. Proximal root fragments had higher amount of fructan than distal fragments. Regenerative ability from roots with different fructan concentrations was also associated to temperature and age. This implies that the timing of root fragmentation in autumn should occur earliest four weeks before low temperatures for each location. Otherwise, new shoots would accumulate fructan causing sprouting the subsequent spring

Effect of Mesotrione and Nicosulfuron Mixtures With or Without Adjuvants

ABSTRACT: In Field experiments, a logarithmic sprayer was used to screen the efficacy of 28.5% mixture of nicosulfuron and mesotrione, and the herbicides applied separately. Three adjuvants were also used to assess how they affected the potency of the mixture. The objectives were to test whether a mixture was enhancing or detracting the effect relative to ADM (Additive Dose Model). The test plants were canola and barley. The 28.5% nicosulfuron mixture was acting antagonistic, irrespective of plant species. The antagonistic effect of the nicosulfuron mixture decreased the more developed the plants became; for barley, it almost disappeared 40 days after treatment. For both canola and barley, one adjuvant stood out as being highly effective in decreasing ED50 of the mixture. Antagonism was not alarmingly high, which is found for many herbicides. Results are discussed in relation to the practice of testing mixtures in the literature and the requirements for getting mixture patents

Dose-Response Analysis Using R

Dose-response analysis can be carried out using multi-purpose commercial statistical software, but except for a few special cases the analysis easily becomes cumbersome as relevant, non-standard output requires manual programming. The extension package drc for the statistical environment R provides a flexible and versatile infrastructure for dose-response analyses in general. The present version of the package, reflecting extensions and modifications over the last decade, provides a user-friendly interface to specify the model assumptions about the dose-response relationship and comes with a number of extractors for summarizing fitted models and carrying out inference on derived parameters. The aim of the present paper is to provide an overview of state-of-the-art dose-response analysis, both in terms of general concepts that have evolved and matured over the years and by means of concrete examples