Old Plants (old + plant)

Distribution by Scientific Domains

Selected Abstracts

Aggregate sources and supplies in Jamaica

Peter W. Scott
Abstract Aggregate resources in Jamaica are sand and gravel found in active river systems, and limestone. Other rocks in Cretaceous inliers and elsewhere are generally too weathered at the surface or too remote from centres of population to be considered suitable as significant sources of aggregates. Sand and gravel generally supplies the south of the country with limestone production and markets being concentrated along the northern coastal areas. Limestone aggregates are produced by ripping and crushing, blasting being uncommon. Sand and gravel are often simply processed using a single screen, although fixed crushing and screening plant are used in some operations. The aggregate industry operates inefficiently, generally utilizing old plant, although an economic assessment shows it to be very profitable. Substitution of sand and gravel by limestone would help mitigate the negative environmental impact of extraction of aggregates from active river systems, but would considerably distort the supply of aggregates throughout the country. Copyright 2008 John Wiley & Sons, Ltd. [source]

Infection of Blackcurrant Leaves by Drepanopeziza ribis in Relation to Weather Conditions and Leaf Position

Xiang Ming Xu
Abstract Drepanopeziza ribis causes the leaf spot disease of blackcurrant (Ribes nigrum) and may lead to severe premature leaf-fall. Artificial inoculation studies were carried out to investigate infection of leaves by D. ribis conidia in relation to environmental conditions and leaf position (age) on cvs. Baldwin and Ben Hope in April and July 2007. All leaves on a number of selected extension shoots on potted three-year old plants were inoculated with conidia and then incubated under different conditions: 10, 17.5 and 25C each with five wet periods (4, 8, 12, 24 and 30 h). Number of infected leaves was determined. The two cultivars differed significantly in their susceptibility to conidial infection: cv. Baldwin was much more susceptible than cv. Ben Hope. Older leaves on extension shoots were more susceptible to conidial infection than younger leaves. Increasing length of wetness duration led to increasing incidence of leaves infected, particularly when inoculated in July. However, the effects of temperature were inconclusive and generally very small in comparison with other factors. Field epidemics were monitored over three years (2005,07). Field data confirmed the main findings from controlled inoculation studies: severe disease was associated with very wet conditions and older leaves. Furthermore, they also suggested that significant disease increase only occurred from late July onwards. [source]

When and Why do Plants Comply?

LAW & POLICY, Issue 2 2005
Paper Mills in the 1980s
This paper uses census data for 116 pulp and paper mills over the period 1979,1990 to examine the determinants of compliance with air pollution regulations. Several plant characteristics are significant: large plants, old plants, and pulp mills comply less frequently, as do plants with water pollution or OSHA violations, but firm characteristics generally are not significant. Enforcement activity increases compliance, but in a heterogeneous way: pulp mills are less sensitive to inspections, while plants owned by larger firms are less sensitive to inspections and more sensitive to "other" enforcement actions, consistent with the authors' expectations and prior research results. [source]

Efficacy of the R2 resistance gene as a component for the durable management of potato late blight in France

F. Pilet
Many race-specific resistance genes to potato late blight are overcome in France, but the disease appears later on genotypes carrying the R2 gene. This study examined whether R2 could contribute to durable late-blight control in France, and analysed the conditions of its performance. Plants grown from tubers of different physiological ages showed no difference in R2 expression in field and climate-chamber experiments, demonstrating that the delay in epidemic onset provided by R2 was not the result of gene inactivation in old plants. Among isolates collected at one site, those virulent on R2 were classified into three AFLP profiles. AFLP-VII comprised exclusively isolates virulent to R2, whereas AFLP-IV and AFLP-V included both virulent and avirulent isolates. No significant aggressiveness differences were observed between virulent and avirulent isolates from AFLP-V; however, isolates from AFLP-VII were significantly less aggressive than virulent isolates from AFLP-V. These results indicate that: (i) the delayed onset of epidemics on R2 cultivars is the result of the breakdown of R2 by virulent isolates; (ii) aggressiveness of isolates virulent to R2 depends primarily on the genetic background of the pathogen where the mutation to virulence occurs; and (iii) this mutation does not lead per se to lower pathogenic fitness. It is suggested that R2 is unlikely to make a lasting contribution to late-blight control in France, and that diversification strategies such as cultivar mixtures might not considerably increase its durability. [source]

Effect of plant variety, plant age and photoperiod on glandular pubescence and host-plant resistance to potato moth (Phthorimaea operculella) in Lycopersicon spp.

Summary The effect of plant age and daylength on glandular pubescence was determined for two lines of tomato derived from Lycopersicon hirsutum (BTN 979 and LA 1777A) and a variety of L. esculentum (N 91-1-1-1-1). Densities of type I, IV, VI and VII glandular trichomes were lowest in N 91-1-1-1-1 and, over all varieties, were more dense on plants aged greater than 6 wk. Daylength interacted with variety to significantly affect densities of type VII trichomes only. Host-plant resistance to Phthorimaea operculella was determined in preliminary tests using insects cultured from founders from a potato crop and in confirmatory tests using (less readily available) insects recovered from foliage of a tomato crop. Mortality of ex-potato neonates on LA 1777 A and BTN 979 foliage was higher 18 h after placement than for N 91-1-1-1-1, with no effect of day length or plant age. Mortality for ex-tomato neonates followed a similar trend. Ten days later, two-thirds of ex-tomato larvae had established mines on N 91-1-1-1-1 but fewer (16.7%) were live on other varieties. Stepwise multiple regression using variety as the sole factor was significant (P<0.001) in accounting for 61.4% of the variation in ex-tomato larval survival but addition of other factors to the regression model was not significant. BTN 979 supported fewer, smaller adults to develop than did N 91-1-1-1-1, whilst no adults developed on LA 1777 A. In a non-choice test using ex-potato adults, significantly more eggs were laid on N 91-1-1-1-1 than on L. hirsutum varieties and 9-wk-old plants were preferred over plants three weeks older or younger. The same variety and plant age trends were evident in a free-choice test using ex-tomato adults. [source]