Attention shift not memory averaging reduces foveal bias

AbstractTwo experiments examined which of two mechanisms, attention shift or memory averaging, reduces foveal bias. The target stimulus was a black dot presented for 80ms while observers maintained fixation. The two main conditions were ‘with’ and ‘without’ vertical and horizontal bars as landmarks, which were placed on more eccentric positions than the target stimulus. To induce attention, the landmark was flashed on for 80 ms (Experiment 1) or disappeared (Experiment 2) with a stimulus onset asynchrony of 0, 106.4, or 212.8ms in both experiments. As a control, non-flashed and non-disappeared landmark conditions were employed. The observers’ task was to point to the remembered location of the target with a mouse cursor. The results showed that the magnitudes of foveal bias were significantly lower in the flashed and disappeared landmark conditions than in the without landmark condition. Furthermore, the magnitudes in the flashed and disappeared landmark conditions did not differ from their respective control conditions. The latter finding in the disappeared landmark conditions provides evidence for ‘attention shift’ against ‘memory averaging’ as the mechanism reducing foveal bias

Design, fabrication and performance evaluation of a small drum type potato grader

Grading potatoes by size is an important operation for preparing tubers for seed and for commercial purposes. If potatoes were sold after grading, this would be beneficial to both producers and consumers. Since mechanical graders are not locally available, potatoes are graded, when necessary, by hand. This is a time consuming, costly, and inefficient method. This work concerns the development of a potato-grading machine for small-scale farmers. The grader consisted of a hopper, grading unit, prime mover and catchment tray fitted on a frame. The grader was made of locally available materials to keep the cost low. The grading unit was made up of plastic oil container, hopper and catchment tray made up of mild steel sheet and the frame was made up of mild steel angle bar. A 0.75 hp, single phase electric motor was used as a prime mover with a gear box (30:1) for reducing the rpm. Machine parameters for the evaluation included the speed of the grading unit (RPM) and inclination of the grading unit. These were tested on potato tubers taking note their influence on grading system efficiency, capacity, damaged tubers and power consumption as independent variables. Data were analyzed and the results indicated that optimum set-up of the grader was at 6 RPM speed of the grading unit, inclination of 30giving a system efficiency of 91.57 %, capacity 420.10 kghr-1, damaged tubers of 1.17 % and low power consumption of 9.30 W-hr. The cost of the grader was estimated to be Tk45,000.00 with a break-even quantity of 50 tons of tubers in one year

Diversity of weed communities under different water regimes in bertam irrigated direct seeded rice field.

Experiments were initiated at MARDI Bertam Rice Research Station in Penang in the dry season of 2004 and main season 2004/2005 to study the effect of different water regimes on diversity of weed species. Plots receiving continuous flooded treatment (T1) and flooding up to panicle initiation (T2) significantly suppressed weed population to approximately 18 – 58% and reduced weed biomass to 14 – 57% as compared to the highest values in continuous field capacity treatment (T5) at all sampling dates (30, 60 and 90 DAS) in both planting seasons. Across water regime treatments the weed composition comprised of 11 weed species in the dry season and 10 weed species in the main season. Broadleaved weeds, especially Monochoria vaginalis and Limnocharis flava were the most dominant weeds in most water regime treatments. The SDR values of broadleaved weeds in the dry season were 48.7, 46.4, 44.2, 40.7 and 35.8% for T2, T1, T3 (flooding for the first month), T5 and T4 (continuous saturation), respectively. In the main season, the SDR values for the broadleaved weeds increased to 79.5, 68.2, 62.4, 62.2, and 50.57% for T2, T1, T3, T4 and T5, respectively. Fimbristylis miliacea and Cyperus iria were dominant in the dry season with SDR values of more than 34% in all water regime treatments, but decreased to less than 23% in the main season. For grasses, comprising of mostly Echinochloa crus-galli, Echinochloa colona and Leptochloa chinensis, SDR values of more than 20% were recorded in T4 and T5 in the dry season, while in the main season SDR values of between 21 – 34% were observed in treatments T1, T3and T5

Impact of nitrogen and phosphorus fertilizer on growth and yield of bambara groundnut

Bambara groundnut (Vigna subterranea) is an indigenous African crop which belongs to the family fabacea and sub-family of faboidea. It seeds contain 63% carbohydrate, 19% protein and 6.5% oil and good source of fibre, calcium, iron and potassium. Hence, this study aimed to determine the effect of nitrogen (N) and phosphorus (P) on growth and yield bambara groundnut. A pot experiments was conducted in ladang 15 at the Faculty of Agriculture; Universiti Putra Malaysia. The experiment was performed Randomized Complete Block Design (RCBD). The size of the pot was 65.94 cm2. The experiment was conducted in a factorial design with four levels of N (0, 10, 20, 30 kg/ha) and P (0, 20, 40 and 60 kg/ha). In this study, N and P fertilizer was played dominating role for vegetative growth of the plant. Plant height (20.65 cm), leaves number (262), leaf area (2140.54 cm2), number of pod (47.25) and pod weight (22.8 g) increased with the application of level of N and P. Vegetative growth and yield of the plant was better at N30P60 kg/ha than the all other treatments. It can be concluded that by using N30P60 kg/ha growth and yield of bambara groundnut is maximum

Effect of water regimes on germination of weed seeds in a Malaysian rice field

The effect of different water regime treatments on the viability of weed seeds in direct-seeded rice field was evaluated. Five water regime treatments were used namely, continuous flooding condition until maturity, early flooding until 55 DAS (day after sowing) followed by saturated condition until maturity, early flooding until 30 DAS followed by saturated condition until maturity, continuous saturated condition until maturity, and continuous field capacity condition throughout the experimental period. Total weed seed population in soil sampled from March-May. The results showed that weed population dominated by broadleaved weeds (90625 seeds m-2), mainly Hedyotis corymbosa, Monochoria vaginalis and Ludwigia hyssopifolia, followed by sedges (34257 seeds m-2), mostly F. miliacea and Cyperus iria. The grasses, predominantly Leptochloa chinensis, recorded the lowest number in all water regime treatments (20647 seeds m-2). In soils sampled from September-November, sedges (53041 seeds m-2) mainly Fimbristylis miliacea along with broadleaved weeds (54624 seeds m-2), predominantly Monochoria vaginalis and Ceratopteris pteridoides, dominated in most of the water regime treatments, while grasses, mainly Leptochloa chinensis and Panicum repens, recorded the lowest number (24935 seeds m-2). Ten weed species, which were not observed in the field trials, were recorded from the same soils used in the weed seedbank study. The results showed that differences in water regime treatments did not significantly reduce the viability of weed seeds in the soil. However, a small reduction in seed viability (approximately 8%) was observed in soil samples during the September-November period

Allelopathic effects of Batawali (Tinospora tuberculata) on germination and seedling growth of plants.

A study was undertaken to explore the effects of methanol extracts (100,50, 25, 12.5 and 6.25 g/l) from the dried powders of aerial parts of Batawali (Tinospora tuberculata) on emergence and initial growth of rice, radish, lettuce and carrot as represented by germination percentage, radical and hypocotyle length. Results indicated that both stem and leaves of Batawali markedly raised the suppression of germination and primary growth of all examined crops when plants were exposed to increasing the methanol extract concentrations from 6.25to 100 g/l of distilled water. The half-inhibitory concentrations that inhibit germination (ECg50), radicle (ECr50) and hypocotyle (ECh50) growth weredetermined for both the extracts. According to these values, an index (Re) was calculated in order to establish a ranking of the most sensitive plants and most effective extract. It was observed that the leaves extract was more active than the stem extract and caused the greatest negative effect on germination and early growth of plants. All tested plants differed in their sensitivity to T. tuberculata extracts. Higher reduction in plant growth parameters was observed in carrot. The tested extracts inhibited mainly the growth of radicle more than the growth of the hypocotyle and germination percentage in all examined crops, except carrot. According to the study, it could be concluded that T. tuberculata extracts had a significant herbicidal activity which depended on the extract concentrations, plant parts and the target crops

HR Award II. na UK - KA7

Příspěvek představí aktivity open access univerzitní knihovny chystané v projektech výzvy Rozvoj kapacit pro VaV (MŠMT)

Effects of Tinospora tuberculata leaf methanol extract on seedling growth of rice and associated weed species in hydroponic culture

The study was conducted to evaluate the responses of rice and rice weed seedlings (barnyardgrass and weedy rice) at the three-leaf stage to Tinospora tuberculata leaf methanol extract (3.12, 6.25 and 12.5 g L−1) under hydroponic culture. It shows that the leaf methanol extract had various degrees effects depending on target plant species and each tested index (biomass, root length, shoot length, transpiration volume, chlorophyll a, chlorophyll b and carotenoid contents). The effective concentration of the leaf extract capable of reducing 50% of rice growth was higher than those of target weed species. Moreover, the root length was more tolerant to leaf methanol extract in comparison to the other plant parameters measured. A greater reduction was observed in chlorophyll a content compared to chlorophyll b and carotenoid. The results revealed that the reduction of transpiration volume closely coincided with the magnitude of growth inhibition of tested plants. Ultra-fast liquid chromatography analysis revealed 11 of 32 peaks in chemical profile, including benzoic acid, caffeic acid, chlorogenic acid, isoorientin, isovitexin, orientin, p-anisic acid, syringic acid, trans-cinnamic acid, trans-ferulic acid, and vitexin have the same retention time with those peaks of the extract. The amount of compounds was present in the range of between 4 817 and 115.5 mg kg−1 dry weight (DW). The concentration-response bioassay of all 11 individual compounds and their equimolar mixture against the seeds of barnyardgrass revealed their contribution in the allelopahic activity of T. tuberculata leaf extract. The examined compounds and their combination exhibited various degrees of growth inhibitory effects on the early growth of barnyardgrass. Therefore, the specific number, concentration, combination and inhibitory activity of bioactive compounds leads to allelopathy activity of T. tuberculata leaves which could be employable directly as a natural herbicide and its growth inhibitor compounds can be used as a template for producing new herbicides

Allelopathic effect of methanol extracts from Tinospora tuberculata on selected crops and rice weeds

Herbicidal potential of aerial parts of Tinospora tuberculata on germination and seedling growth of seven test plant species, namely rice (Oryza sativa L.); two rice weeds, barnyardgrass (Echinochloa crus-galli L.) and weedy rice (O. sativa f. spontanea); and four vegetable crops, lettuce (Lactuca sativa L.), tomato (Solanum lycopersicum L.), carrot (Daucus carota L.), and cucumber (Cucumis sativus L.) were evaluated. Six concentrations of methanol extract (3.12, 6.25, 12.5, 25, 50, and 100 g L−1) were compared with the control (distilled water). The rate of seed germination and the radicle and hypocotyl length of 7-day-old test plant seedlings were reduced as the concentration of extracts increased compared to the control. Generally, the degree of toxicity of extracts derived from the leaves was more than the extracts derived from the stem. Cluster analysis and the concentrations required for 50% inhibition (defined as EC50) of all parameters showed that radicle growth was more suppressed than germination and hypocotyl growth. Lettuce and carrot were observed as the most sensitive plants while rice showed the highest tolerance to both extracts. Moreover, the dicot target plants were affected more severely than the monocots when treated with leaf extract. The chemical composition of the T. tuberculata methanolic extracts was analyzed by a GC–MS system. A total of 92 and 22 constituents (not previously identified) were found in the leaves and stem, respectively. The results showed that 17 of the 92 components in the leaves, as compared to 4 of 22 compounds in the stem, are known as toxic compounds. These results suggest that T. tuberculata contains a significant source of plant growth inhibitors with potential for the development of future natural herbicide

Screening of potential salt tolerant turfgrass species in Peninsular Malaysia.

The need for salinity tolerance of turfgrasses is increasing because of the augmented use of effluent or other low quality water (seawater) for turfgrass irrigation. Diverse populations including 34 entries of 16 turfgrass species were screened for salt tolerance from Peninsular of Malaysia under sand culture system. Irrigation seawater of different salinity levels (0, 24, 48, and 72 dS m-1) were applied to turfgrass species grown in a plastic pots filled with a mixture of sand and peat (9:1). The different species of grasses were ranked for salinity tolerance on the basis of shoot and root growth, leaf firing, turf colour and turf quality. The most salt tolerant turf species was 'P. vaginatum' (UPM), 'P. vaginatum' 'local', 'Z. matrella, Z. japonica, C. dactylon' 'satiri' , 'C. dactylon' (Kuala Muda) which were able to tolerate high levels of salinity 48 dS m-1, while, the least tolerant group (24 dS m-1) consisted of 'E. ophiuroides', (UPM), 'P. notatum' (UPM), 'A. compressus' 'cowgrass' (UPM), 'A. affinis' (UPM), and 'A. compressus' 'pearl blue' (UPM). The results indicate the importance of turfgrass varietal selection for saline environments