Thermal Biology of Liorhyssus hyalinus (Hemiptera: Rhopalidae) and Nysius simulans (Hemiptera: Lygaeidae), Fed on the Milky Stage of Maize Grains

When quinoa, Chenopodium quinoa Willd., is cultivated in South America outside of its Andean origin, the heteropterans Liorhyssus hyalinus (Fabricius) and Nysius simulans Stål may emerge as important pests. Here we studied the development and reproduction of both species at different constant temperatures in the laboratory. Egg and nymphal development were investigated at 18, 22, 26, 30, 34, and 36°C. For both species, egg incubation time significantly decreased as the temperature increased. Nymphs did not successfully develop at 18°C and the total nymphal time significantly decreased as the temperature increased from 22 to 36°C. Based on a linear day-degree (DD) model, the lower developmental threshold (LDT) temperatures for eggs and nymphs were estimated to be 16.0 and 17.9°C for L. hyalinus, and 16.1 and 19.7°C for N. simulans, respectively. Thermal requirements for egg and nymphal development were 68.6 and 114.8 DD for L. hyalinus, and 77.7 and 190.3 DD for N. simulans, respectively. Reproduction and adult longevity were studied at 22, 26, 30, and 34°C. For both species preoviposition time decreased as temperature increased, and the oviposition period was longest at 26°C. The highest fecundity and egg viability were observed at 30°C, whereas longevities were higher at 22–26°C than at 30–34°C. As the lowest tested temperatures were not suitable to both heteropterans and 30°C was found to be the optimal temperature for development and reproduction, peak densities are expected in warm areas and seasons.     

The effect of different concentrations of linseed oil or fish oil in the maternal diet on the fatty acid composition and oxidative status of sows and piglets

N‐3 polyunsaturated fatty acids (PUFA) are essential for foetal development. Hence, including n‐3 PUFA in the sow diet can be beneficial for reproduction. Both the amount and form (precursor fatty acids vs. long chain PUFA) of supplementation are important in this respect. Furthermore, including n‐3 PUFA in the diet can have negative effects, such as decreased arachidonic acid (ARA) concentration and increased oxidative stress. This study aimed to compare the efficacy to increase eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) concentrations in the piglet, when different concentrations of linseed oil (LO, source of precursor α‐linolenic acid) or fish oil (FO, source of EPA and DHA) were included in the maternal diet. Sows were fed a palm oil diet or a diet including 0.5% or 2% LO or FO from day 45 of gestation until weaning. Linoleic acid (LA) was kept constant in the diets to prevent a decrease in ARA, and all diets were supplemented with α‐tocopherol acetate (150 mg/kg) and organic selenium (0.4 mg/kg) to prevent oxidative stress. Feeding 0.5% LO or 0.5% FO to the sows resulted in comparable EPA concentrations in the 5‐day old piglet liver, but both diets resulted in lower EPA concentrations than when 2% LO was fed. The highest EPA concentration was obtained when 2% FO was fed. The DHA level in the piglet liver could only be increased when FO, but not LO, was fed to the sows. The 2% FO diet had no advantage over the 0.5% FO diet to increase DHA in the piglet. Despite the constant LA concentration in the sow diet, a decrease in ARA could not be avoided when LO or FO were included in the diet. Feeding 2% FO to the sows increased the malondialdehyde concentration (marker for lipid peroxidation) in sow plasma, but not in piglets.     

黄瓜根腐病致病病原的鉴定

在天津市及周边地区采集病株进行组织分离，同时分离到两类病原菌，经初步的生物学特性鉴定表明，引起黄瓜根腐病的主要病原菌为甜瓜疫霉、尖孢镰刀菌和茄病镰刀菌。经接种试验，认为甜瓜疫霉为主要致病菌。     

Landscape and habitat filters jointly drive richness and abundance of specialist plants in terrestrial habitat islands

Context

Landscape and habitat filters are major drivers of biodiversity of small habitat islands by influencing dispersal and extinction events in plant metapopulations.

Objectives

We assessed the effects of landscape and habitat filters on the species richness, abundance and trait composition of grassland specialist and generalist plants in small habitat islands. We studied traits related to functional spatial connectivity (dispersal ability by wind and animals) and temporal connectivity (clonality and seed bank persistence) using model selection.

Methods

We sampled herbaceous plants, landscape (local and regional isolation) and habitat filters (inclination, woody encroachment and disturbance) in 82 grassland islands in Hungary.

Results

Isolation decreased the abundance of good disperser specialist plants due to the lack of directional vectors transferring seeds between suitable habitat patches. Clonality was an effective strategy, but persistent seed bank did not support the survival of specialist plants in isolated habitats. Generalist plants were unaffected by landscape filters due to their wide habitat breadth and high propagule availability. Clonal specialist plants could cope with increasing woody encroachment due to their high resistance against environmental changes; however, they could not cope with intensive disturbance. Steep slopes providing environmental heterogeneity had an overall positive effect on species richness.

Conclusions

Specialist plants were influenced by the interplay of landscape filters influencing their abundance and habitat filters affecting species richness. Landscape filtering by isolation influenced the abundance of specialist plants by regulating seed dispersal. Habitat filters sorted species that could establish and persist at a site by influencing microsite availability and quality.

     

Effects of CO2 on leaf conductance and canopy transpiration of greenhouse grown cucumber and tomato

The effects of carbon dioxide (CO₂) on stomatal opening and canopy transpiration were investigated in cucumber (Cucumis sativus L., cv. Jessica) and tomato (Lycopersicon esculentum Mill., cv. Calypso). Stomatal opening (i.e. leaf conductance, g) was measured with a porometer, and canopy transpiration rate (E) with weighing lysimeters on intact plants in large greenhouses. Regression analysis was applied to account for the effects of radiation, air humidity, leaf temperature and CO₂ on g. The effect of CO₂ on E, which is primarily through g and secondarily through adjusted air humidity, was investigated by combining the regression equation for g with the Penman-Monteith equation for E. The relative effect of CO₂, as calculated with the fitted regression equations, was a decrease of about 4% in g for cucumber and of about 3% for tomato, per 100 μol mol-1 increase in CO₂, in the range of about 300 to 1200 μmol mol^?1 CO₂. The effect of CO₂ on E was smaller than on g and the extent of the effect depended on the conditions, mainly ventilation rate. The ratio K (relative change in calculated E divided by relative change in calculated g) was estimated at less than 0.2, except at low radiation. In reality, K will be even lower, because feedback mechanisms enforce the reduction in g and counteract the reduction in E. So the reduction of the transpiration rate of greenhouse cucumber and tomato caused by moderate CO₂ enrichment is small and mostly negligible, except under low light conditions.     

ALCEPAS,an onion growth model based on SUCROS87.I. Development of the model

Summary

A dynamic simulation model for onion crop growth is presented that is based on SUCROS87, a Simple and Universal Crop Growth Simulator. Onion specific values of parameters and relations of SUCROS87 were established using results from field experiments. The model simulates potential crop growth when weeds, pests, diseases and soil conditions are not limiting growth and there is ample supply of water and nutrients. The model accounts for the influence of sowing date and plant density. The combined influence of environmental factors on leaf growth, bulb initiation and maturity is incorporated. The potential use of the model is discussed.     

ALCEPAS,an onion growth model based on SUCROS87. II. Validation of the model

Summary

A dynamic simulation model for onion growth at potential production level (ALCEPAS), presented in a previous paper, was validated using data on leaf area index, bulb and green leaf dry-matter production, bulb formation and day of fall-over from independent trials at four locations. The model performance in terms of bulb dry-matter production was good under environmental conditions close to the optimum, but insufficient under stress situations. The model overestimated leaf area index and green leaf dry matter. Bulb formation was simulated satisfactorily, while the time of 50% fall-over was simulated too early at low plant densities.     

Rose flower production as related to plant architecture and carbohydrate content: Effect of harvesting method and plant type

Summary

The dependence between flowering cycles and woody stem parts of a rose crop was studied, with respect to plant architecture and carbohydrate content. Two harvesting methods (“control” versus “flush”) and two plant types (“control” versus “one stemmed”) were compared. Crop growth and partitioning of dry matter were studied as influenced by crop management during 18 months of culture. For a full-productive year, flush harvesting generally promoted bud break as compared with continuous harvesting but at the same time, also due to lower light interception, blind-shoot formation was enhanced and the individual flower weight reduced. Numbers of basal shoots were hardly related to flower production over a full cropping year. Flower production was much more sensitive to the number and diameter of branches at the height of cutting the flowers. The treatments did not affect carbohydrate allocation in the plant. Total carbohydrate storage was much too low to argue a clear role for the possible use of movement of carbohydrate reserves towards new growth. Maximum starch concentration was found at the beginning of summer and gradually dropped to a minimum in December and then increased again to a spring maximum. A cold treatment did increase the total non-structural carbohydrate (TNC) concentration but no positive influence on new basal-shoot formation was observed. No starch gradient was found in basal stem parts.     

Low seed/nut productivity in cashew (Anacardium occidentale): Effects of self-incompatibility and honey bee (Apis mellifera) foraging behaviour

Summary

The roles of self- versus cross-pollination and honey bee (Apis mellifera L.) foraging behaviour in low nut yield of cashew (Anacardium occidentale L.) were studied in NE Brazil in 1997 and 1998. It was shown that both self- and cross-pollination can set fruits in cashew, but most of fruits originating from self-pollination are shed 9–15 d after pollination, and fruits harvested are primarily from cross-pollination. Honey bees display foraging behaviour in cashew orchards conducive to cross-pollination, but in plantations originating from clonal material they failed to increase fruit yield despite cashew's dependence on insect pollination. It is concluded that cashew has a mechanism of selective abortion through which it discards self-pollinated fruits and that honey bees can contribute to increased fruit yield only when cashew trees of genetically diverse origin are found in the same orchard.     

Effect of different rates of composted organic amendment on urban soil properties,growth and nutrient status of three Mediterranean native hedge species

Increasing green space, especially in densely built-up areas is considered to be a valuable climate change adaptation response in order to reduce the threat of high temperatures to human health and comfort and to controlled global greenhouse gas emissions. Practical responses to climate change, under urban conditions, in order to avoid or reduce trees and shrubs vulnerability, can be considered drought resistant planting approaches, as the addition of organic amendeds to soil. The improvement of physical–chemical soil quality is a key step for carrying out xeriscaping programs of urban green spaces in Mediterranean semiarid areas. Organic amendments, particularly compost, have been receiving a renewed attention not only in horticulture but also in the context of restoring disturbed urban soils to address environmental issues as well as to improve trees and shrubs growth. The influence of increasing rates (0, 15, 30, and 45%) of composted sewage sludge (SSC) placed in the plantation hole on both urban soil properties and growth for three native Mediterranean woody hedge species was monitored over a 2-year period after planting. The experiment was supported by a xerogardening project in an urban context under semi-arid conditions. The results indicate that the urban soil physical characteristics were positively influenced by the addition of SSC: the 45% rate showed an increase in both moisture and infiltration values, thereby increasing the volume of plant-available water in the soil. The chemical properties of the amended soils were also directly affected by the SSC rate, but the effect of the compost on organic matter, nitrogen and potassium contents decreased over time. Our results prove that the hedge growth response to the compost treatments is also highly dependent on the rate of compost used. At the end of the trial, in Rhamnus and Myrthus plants 30% compost level guarantees the best performance; in fact, the further addition of 15% of compost led to a significant decrease in hedge and diameter values, in particular in Myrtle. This could be explained by the high pH at 45% compost, which would seem not to suit the physiology of the two species. On the other hand, in Phillyrea plants, the rate of 45% compost gives high performance equal to that of 30%; it would therefore seem that the high pH at 45% compost does not influence the nutritive elements’ absorption and, as a consequence, the growth. The use of composted sludge as an amendment for sclerophyllous could be feasible and, what is more, helpful to mitigate the environmental impact of organic waste disposal. Moreover more natural vegetation can be introduced into urban parks and green spaces in semi-arid environments to encourage sustainable landscaping and xerogardening.