Leaf beetle grazing does not induce willow trichome defence in the coppicing willow Salix viminalis

Abstract 1 Willows are frequently attacked and defoliated by adult leaf beetles (Phratora vulgatissima L.) early in the season and the plants are then attacked again when new larvae emerge. The native willow Salix cinerea has previously been shown to respond to adult grazing by producing new leaves with an increased trichome density. Subsequent larval feeding was reduced on new leaves. This type of induced plant response may reduce insect damage and could potentially be utilized for plant protection in agricultural systems. 2 Here, we investigated if the willow species most commonly used for biomass production in short rotation coppice, Salix viminalis, also responds to adult beetle grazing by increasing trichome density. Larval performance and feeding behaviour on plants previously exposed to adult beetles was compared with that on undefoliated control plants in a greenhouse. 3 We found an overall decrease in trichome density within all the plants (i.e. trichome density was lower on new leaves compared to that for older basal leaves on S. viminalis). However, leaves of beetle defoliated plants had a higher trichome density compared to control plants. Larval growth and feeding was not affected by this difference between treatments. Larvae appeared to remove trichomes when feeding on S. viminalis, a behaviour that might explain the lack of difference between treatments.     

Factors limiting polygyny in the willow ptarmigan

Willow ptarmigan (Lagopus lagopus) usually pair monogamously and males invest more in vigilance and parental care than do males of other grouse species. I tested whether polygyny is rare because male parental care is necessary for successful reproduction. By continuous removal of males I skewed the operational sex ratio, induced polygyny, and then compared breeding success and survival of females that shared a mate and those that did not. Both groups had similar clutch sizes, laid eggs at the same time, produced young of the same weight, and fledged similar numbers of juveniles. Hens that shared a mate suffered higher losses of nests during incubation, and fewer returned to the breeding range in subsequent years. Thus, although male parental care was not essential, it did improve female reproductive success and survival. I suggest that willow ptarmigan are not polygynous because territorial females are able to prevent potential secondary hens from settling, thus securing unshared access to male investment and territorial resources.     

Effect of willow cultivar and plant age on the melezitose content of giant willow aphid (Tuberolachnus salignus) honeydew

1. The giant willow aphid Tuberolachnus salignus is an invasive pest in New Zealand, attacking over 50 species and hybrids of willow. The aphids produce copious amounts of honeydew, which is used by other insects as a food source.
2. When foraged by honeybees, T. salignus honeydew causes honey to crystallize in the comb and affects bee health; these effects are associated with the elevated melezitose content in the honeydew. The impact of host plant-related factors on T. salignus honeydew melezitose content remains unknown.
3. This study investigated the effect of willow cultivar and plant age on the melezitose content (and that of other sugars) of T. salignus honeydew. To do so, we conducted high-performance liquid chromatography analyses of honeydew samples from 13 willow clones collected in the same season (autumn) from 1- and 2-year old plants under field conditions.
4. Melezitose was the most abundant of the measured sugars in most samples, but its content did not vary significantly with willow cultivar or plant age. By contrast, sucrose was significantly affected by both factors. Fructose and glucose were significantly impacted by willow plant age and cultivar, respectively. A significant cultivar*age interaction was observed for all sugars.
5. We recommend the selection of resistant willow cultivars and further research on potential biocontrol agents to lessen melezitose-related problems in apiculture industries.

     

再论海尔蒙特的柳树实验

在讨论海尔蒙特柳树实验的基础上,比较客观地分析了海尔蒙特从事科学研究的时代背景．以及海尔蒙特的柳树实验对后来科学研究的影响和启迪。     

Evidence for solution flow in the phloem of willow

Sucrose specific mass transfer measurements were made in a translocating willow shoot (Salix viminalis L.) by a steady state labelling technique and the translocate sucrose specific activity, concentration and velocity monitored by analysis of the honeydew from two colonies of the willow aphid Tuberolachnus salignus Gmelin. The values of sucrose SMT obtained were related to the simultaneous measurements of translocate concentration and velocity and to the gradients of sucrose concentration within the stem transport path to determine if transport was a bulk flow or a diffusional analogue. Estimates of potassium ion concentration in the sieve tubes were made, using aphid honeydew, and related to the sucrose SMT measured simultaneously. Correlations were found between translocate concentration, velocity and SMT which suggested that solution flow was occurring rather than a process analogous to diffusion. Evidence was obtained that velocity of flow was a valid concept and that the measured velocity was being lowered by leakage of tracer from the sieve tubes. The analysis of potassium concentration suggested that if solution flow was occurring then potassium must be very exchangeable down the transport path. A good correlation was observed between the SMT of sucrose and the combined gradient of sucrose and potassium concentration, though this gradient was in the opposite direction to transport in some cases.Abbreviations SMT Sucrose specific mass transfer rate - SAR Specific activity ratio - OP Osmotic pressure     

On the ultrastructure of differentiating secondary xylem in willow

Summary Studies of differentiating xylem inSalix fragilis L. show the immediate cambial derivatives to be ultrastructurally similar. The Golgi apparatus is important at all stages of wall synthesis, possibly producing (amongst other substances) hemicellulose material which is carried to the wall in vesicles or multivesicular bodies. The endoplasmic reticulum also contributes one or more components to the developing wall: at some stages during differentiation the endoplasmic reticulum produces electron opaque bodies which appear to be guided towards the wall by microtubules. Compact structures formed from concentric membranes (myelin-like bodies) have been found joined to rough endoplasmic reticulum, but their presence is not explained.Two types of plasmalemma elaboration occur: invagination of the plasmalemma itself to form vesicles which may contain cytoplasmic material; and vesicles between the plasmalemma and cell wall which are the result of single vesicles or multivesicular bodies traversing the plasmalemma. Both systems provide a means for transporting cytoplasmic material across the plasmalemma.Microtubules have been seen associated with all vesicles derived from the cytoplasm which appear to be moving towards the wall. The presence of microtubules may generally be explained in terms of orientation of vesicles, even if they also happen coincidentally to parallel the supposed orientation of microfibrils in the wall itself. It is possible to resolve connections between the microtubules and the plasmalemma.     

Phytoferritin in plastids of the cambial zone of willow

Summary Crystalline and paracrystalline arrays of electron-opaque granules have been found in plastids of the cambial zone and its immediate derivatives in crack willow (Salix fragilis L.). These granules have a diameter of 55 to 70 Å and, when in crystalline arrangement, show a centre to centre spacing of 100 Å with adjacent, slightly curved, or linear rows running parallel. The 70 Å particles have a substructure of four to six subunits 15 Å in diameter. These units are arranged around an electron-translucent core 20 Å diameter. It is suggested that this complex is phytoferritin. It is assumed that the electron-translucent area around the opaque granules represents the proteinaceous shell characteristic of both plant and animal ferritin as described by other authors. The phytoferritin is commonly found spread in a thin, regular, array over the surface of plastoglobuli in the plastids.It is further suggested that the phytoferritin is an iron-protein complex which allows the plant to store iron in non-toxic form. This theory would be in accord with the presence of phytoferritin in plastids which appear to be morphologically mature but which, on account of their position within the stem, would not be expected to be photosynthetically very active.     

Postemergence herbicides in Swedish willow stands

Eleven herbicides were tested for postemergence use in newly established stands of Salix viminalis and Salix dasyclados. Spraying was carried out at two rates and at two stages of growth (shoot lengths 5–7 cm and about 15 cm respectively). Effects on Salix plants were estimated by regular observations of damage symptoms during the growing season and by measuring the biomass production up to the first winter after planting. Significant differences were found between the treatments. Cyanazine could be sprayed at early and late stages of development at both rates without reduction of biomass production. Metamitron, 3,6-dichloropicolinic acid and bentazon also showed promising results. Bromofenoxim, linuron and metribuzin reduced biomass production. Damage to Salix plants was generally most pronounced at late spraying. Time of spraying was more significant in terms of the effects on the plants than was the rate of herbicide application.     

Abiotic induction of susceptibility in insect-resistant willow

Plants are mosaics of resource quality to insect herbivores. Some leaves are superior to others, resulting in variable insect performance. Certain Salix viminalis L. (Salicaceae) genotypes show an unusually strong resistance to the gall midge Dasineura marginemtorquens Bremi (Diptera: Cecidomyiidae). A few leaves are frequently galled on such resistant willows, whereas on the great majority of leaves all larvae die before any galls are formed. We performed a series of greenhouse and field experiments in order to understand in more detail the observed intraplant heterogeneity. First, we tested whether random events (biotic or abiotic) can induce a susceptibility that is expressed later (next season), i.e., delayed induced susceptibility. Second, we performed a combined field and greenhouse experiment to test the possibility that susceptibility was induced by abiotic factors at the time of gall induction (within days), i.e., rapid induced susceptibility. We found support for rapid induced susceptibility, but not for delayed induced susceptibility. Although resistance remained strong, significantly more leaves with surviving larvae and galls were found on potted plants moved to the field compared with identical plants that remained in the greenhouse. Potted field plants were exposed to field conditions during a very short period in connection with gall initiation. Thus, we can exclude soil moisture, nutrient availability, and the history of the plant as factors explaining the induction of susceptibility. We tentatively suggest that radiation interferes with the expression of resistance. Our findings suggest that plasticity in plant resistance may be linked to ambient light conditions, and that heterogeneity in leaf suitability can be of ecological significance in plants that are considered resistant.     

Conservation of montane willow scrub in Scotland

Summary

The community known as montane willow scrub has been almost totally destroyed in Scotland by human activities. The species of montane willows are not regarded as threatened by the conventional criteria, but the continued effects of grazing, combined with their sparse distribution in suboptimal habitat and dioecious habit, suggest that the long term threat to some species may have been underestimated. Conservation measures are needed urgently if we are to restore areas of montane willow scrub. It will be necessary to use fencing to provide protection from grazing, and also it may well be necessary to do some planting to provide enough individuals for effective pollination and regeneration to occur.     

Phenological stages of willow (Salix)

The practice of uniform recording of biological plant growth stages or events has long been practiced in agricultural production. In this study the BBCH (Biologishe Bundesanstalt, Bundessortenamt and CHemical Industry) code has been applied to four precocious species of willows to define growth stages important to this group. The studied taxa represent varieties of potential importance in the Floral Industry. A new BBCH code is proposed where the annual cycle of willows is divided into clearly recognisable and easily distinguishable developmental phases which include eight principal stages, 30 secondary stages and six mesostages. Photographs illustrate the physical appearance of select stages. This proposed BBCH code shows a unified approach which may be applied to a large number of Salix species.     

Oils activity against Melampsora epitea on willow

Willow trees cv. Iwa growing in open field conditions in the sandy soil and naturally infected with Melampsora epitea were used. Effectiveness of paraffin oil (Atpolan 80 EC) and plant oils (Olejan 85 EC, rape and sunflower) in the control of pathogen was evaluated. When first uredinia were seen on the lower leaf surface, plants were sprayed 2-times at 7-day intervals with tested compounds at concentration from 0.25 to 2%. Also Surfactant Tergitol (TM) 15-S-9 at conc. 0.3% was added to plant oil suspension. After 2 sprayings a number of uredinia per leaf and number of browned and destroyed uredinia were counted. In the first trial Atpolan 80 EC suppressed uredinia formation about 2-4-times whereas rape or sunflower oil about 1.8 to 3-times. Additionally about 11 to 30% of uredinia were dried. In the next trials effectiveness of tested oils was higher than in previous experiment. After 2-weeks of willow trees protection with Atpolan 80 EC formation of uredinia was inhibited from 7 to 17-times, whereas Olejan 85 EC suppressed their production about 4 to 14-times. Additionally about 9-62% (Atpolan 80 EC) or 10-25% (Olejan 85 EC) of uredinia were browned and dried depend on used concentration. In the third experiment after 2-week-protection of plants with Atpolan 80 EC inhibition of uredinia formation varied from 6 to 10-times. In the case of Olejan 85 EC about 2 to 10-times less uredinia were observed on protected plants than on control, untreated leaf blades. About 48-72% (Atpolan 80 EC) or 17-61% (Olejan 85 EC) of uredinia were dried.     

Salix martiana,a regularly hermaphrodite willow

Sex distribution in a neotropical willow,Salix martiana Leybold, has long escaped the attention of botanists. Its catkins are regularly composed of female, hermaphrodite and male flowers. The present paper discusses some aspects of its possible morphological and/or evolutionary significance.     

The ten year cycle of the willow grouse of Lower Kolyma

Summary The effects of defoliation on growth and nitrogen (N) nutrition were examined in populations of Agropyron smithii (western wheatgrass) collected from a heavily grazed black-tailed prairie dog (Cynomys ludovicianus) colony (ON-colony) and a nearby lightly grazed, uncolonized area (OFF-colony). Defoliated and nondefoliated plants were grown at low soil N availability with similar sized defoliated individuals of A. smithii from a grazing-exclosure population as a common competitor. Sequential harvests were made over 24 days following defoliation. Growth analysis plus biomass and N yield and distribution data were used to identify features which may contribute to plant defoliation tolerance. Defoliation reduced total production 34% across populations. Defoliated plants produced as much new blade tissue, but only 67% as much new root biomass as did nondefoliated controls. Plants from prairie dog colonies accumulated biomass at a faster relative rate than did plants from uncolonized sites, in part, because of a 250% greater mean relative growth rate of blades and more than 200% greater rate of biomass production per unit blade biomass. Total N accumulation was significantly greater in defoliated ON- than OFF-colony individuals. The mean relative accumulation rate of N was increased by defoliation in ON-colony plants, but reduced by defoliation in OFF-colony plants. The mean rate of N accumulation per unit root biomass was more than 300% greater in the ON- than OFF-colony population. Colony plants initially had a greater proportion of biomass and N remaining after defoliation in roots. Initial differences between populations in the distribution of biomass and N were eliminated as colony plants concentrated 24-day accumulation of biomass and N in aboveground structures. The data suggest that the combination of growth, N nutrition, and biomass and N distribution characteristics of the colony population likely confer a high rate of resource capture on heavily grazed prairie dog colonies.     

Genetic and soil-nutrient effects on the abundance of herbivores on willow

The effects of soil-nutrient environment, plant genotype, and the interaction between the two on the resistance of the willow, Salix sericea, to insect species in a diverse herbivore community was measured. We found that soil-nutrient environment influenced plant growth and the abundance of most herbivores of S. sericea. However, environmental effects on herbivore abundance were often modified by plant genetics; the abundance of four of seven herbivores exhibited significant genotypeby-environment interaction effects. Pure genotype effects were mostly small and non-significant. The effects of fertilization differed among herbivores. Several herbivores were more abundant on fertilized plants, one was less abundant, and the abundance of others did not change. We found that feeding guild was a poor predictor of herbivore response. Finally we found significant phenotypic and genetic correlations among growth rate, internode length, and the abundances of several herbivores.