Comparative phytotoxicity of aqueous extracts of centaurea maculosa and melilotus officinalis on germinability and growth of wheat

Weed incursion in cultivated fields is a serious biological problem, which causes considerable yield losses of economically important field crops through allelopathy and competitive interactions. Spotted knapweed (Centaurea maculosa) and yellow melilot (Melilotus officinalis) are among the most prevalent weeds in cultivated fields of Pakistan, particularly in wheat fields. Like many other weeds, they may pose allelopathic and competitive challenges to field crops. The objective of this study was to evaluate allelopathic potentials of the two weeds on germination and seedling growth of wheat under laboratory conditions. Amounts of 15, 20, 25 and 30% concentrated leaf aqueous extracts of C. maculosa and M. officinalis were prepared and tested for their effects on germination percentage, radicle and coleoptile lengths of wheat. Germination, radicle and coleoptile lengths of test crop declined significantly at higher concentration (25-30%) of the extracts of two weeds. However, concentration of M. officinalis up to 20% had either no effect or stimulatory effects on the studied growth characteristics of wheat. Highest germination inhibition and decreased seedling growth were caused by leaf extracts of C. maculosa at 30% extract concentration. Growth inhibition was generally dependent on the extract concentration. The study indicated that both plant exhibited allelopathic activity and growth inhibitory effects on wheat at higher concentration; however, extracts of C. maculosa were more phytoinhibitory than M. officinalis. The weeds could serve as potent allelopathic plants for management of other weeds

Allelopathic effects of sheesham extracts on germination and seedling growth of common wheat

Interactions between plants represent an important aspect of ecology, which enables them to properly utilize the available resources in the given environment. The interactions are mediated by different mechanisms, among which allelopathy is a significant one. During allelopathic interactions, plants tend to suppress competitors plants or stimulate those which can help them adjust in the environment in a better manner. Such interactions are triggered by the release of chemical compounds termed, as allelochemicals, which have an important role in agricultural modulation. The objective of this experiment was to evaluate the allelopathic effects of leaf and bark extracts of sheesham (Dalbergia sissoo L.) on germination data of wheat (Triticum aestivum L.) cv. Auqab. Different concentrations (7 g/l, 14 g/l, and 21 g/l) of sundried leaf and bark extracts, obtained after 12, 24 and 36 h of soaking duration were tested for germination %, mean germination time (MGT), plumule and radicle length and seedling dry weight. It was observed that germination % was negatively affected by 21 g leaf and bark extract concentration at 36 h soaking duration, but not by lower concentration or soaking durations. MGT was significantly increased by leaf and bark extracts at three concentration levels, as well as soaking durations. Plumule and radicle length responded negatively to both leaf and bark extracts at higher concentration and when soaking duration was increased. Seedling dry weight was increased by 7 g leaf extracts at 36 h, but reduced by 21g at 12 and 24 h soaking durations. On the other hand, 21 g of bark extracts at 12, 24 and 36 h soaking duration resulted in significantly increased dry biomass. These results suggest negative allelopathy of Sheesham on studied germination parameters of wheat, except radicle length and dry biomass

Ready for testing: ensuring conformance to industrial standards through formal verification

The design of distributed, safety-critical real-time systems is challenging due to their high complexity, the potentially large number of components, and complicated requirements and environment assumptions that stem from international standards. We present a case study that shows that despite those challenges, the automated formal verification of such systems is not only possible, but practicable even in the context of small to medium-sized enterprises. We considered a wireless fire alarm system, regulated by the EN 54 standard. We performed formal requirements engineering, modeling and verification and uncovered severe design flaws that would have prevented its certification. For an improved design, we provided dependable verification results which in particular ensure that certification tests for a relevant regulation standard will be passed. In general we observe that if system tests are specified by generalized test procedures, then verifying that a system will pass any test following those test procedures is a cost-efficient approach to improve the product quality based on formal methods. Based on our experience, we propose an approach useful to integrate the application of formal methods to product development in SME.</p