Ablation article and method

An ablation article, such as a conical heat shield, having an ablating surface is provided with at least one discrete area of at least one seed material, such as aluminum. When subjected to ablation conditions, the seed material is ablated. Radiation emanating from the ablated seed material is detected to analyze ablation effects without disturbing the ablation surface. By providing different seed materials having different radiation characteristics, the ablating effects on various areas of the ablating surface can be analyzed under any prevailing ablation conditions. The ablating article can be provided with means for detecting the radiation characteristics of the ablated seed material to provide a self-contained analysis unit

Spatial-scale dependencies in the predation of seeds by rodents

Summary 1. Previous studies have shown rates of seed predation in deciduous woodland to be high (on average 60%) and extremely variable in space and time. 2. Post-dispersal seed predation by forest rodents was examined simultaneously in five areas of deciduous woodland surrounding Durham City, Co. Durham. 3. This study investigated the influence of seed density, seed burial and seed species in determining the rates of seed encounter and exploitation by rodents of both native and exotic seed. The effect of within- and between-sites differences were also examined. 4. Live-trapping studies and the use of exclosure treatments revealed that Apodemus sylvaticus and Clethrionomys glareolus were the major seed predators. Together, they were responsible for removing between 55-80% of the experimental seed supply. 5. Seed burial accounted for a high proportion of the variation and significantly reduced the frequency of rodent encounter compared to surface seeds at both seed densities. Furthermore, it increased the variation in encounter due to density, species and site effects. It had no significant influence, however, on the extent to which groups of ten seeds were exploited once encountered. 6. Variations in the frequency of seed encounter and exploitation were both strongly affected by changes in seed density, with high densities increasing the chance of seed detection and removal. Significant species effects were also detected for seed encounter and exploitation. 7. Seed predation was spatially patchy, between and within experimental sites, possibly reflecting variation in the spatial distribution of seed predators. 8. The selective nature of the seed predators, plus the relative patchiness of predation intensity in space, suggest that post-dispersal seed predation may play an important role in determining the distribution and/or abundance of deciduous woodland plants

Aspects of seed transfer within a direct drilling coulter (opener) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Agricultural Mechanisation at Massey University

A number of laboratory and field experiments were conducted in order to identify and quantify seed and seedling spacing variations produced by an experimental direct drill. Seed contact with both stationary and moving components of the coulter assembly was considered to contribute to the increased variability of seed spacing that resulted from the positioning of a chisel direct drilling coulter beneath a "Nodet Gougis" seed selection mechanism. Alternatives for transferring the seeds from the seed selection mechanism to the soil were considered. The simplest of these alternatives, a seed-transfer tube, was tested in a number of different shapes and positions. It was found that the seeder required modifications to its release characteristics in order to satisfactorily incorperate the tube transfer system. A number of deflector plates were fitted to the seeder to control seed release trajectory. A 40 degree seed deflector plate was found to produce a seed path that was most compatible with a straight vertical seed-transfer tube. A video recording technique was used to assess the effects of seeder modifications on seed release trajectory. The modified seeder and the tube transfer system were combined with the chisel direct drilling coulter, and seed spacing performance was retested. Seed spacing variability was found to be considerably less than with the original experimental drill in the laboratory, although field performance was not improved to the same extent. It was considered that this effect may have been attributable to the effects of soil flow with the direct drilling coulter and the manner with which the seed was released into the soil, which differed with the tube system compared with the unmodified coulter tested initially

Shrubs indirectly increase desert seedbanks through facilitation of the plant community

The mechanisms supporting positive ecological interactions are important. Foundation species can structure desert biodiversity by facilitating seedbanks of annual plants, but the direct and indirect mechanisms of shrub effects on seedbank have not been experimentally decoupled. We conducted the first test of shrubs increasing seedbank densities through direct effects on the seedbank (i.e. shrub seed-trapping, animal-mediated dispersal) and indirect effects by facilitating the annual plant community (i.e. seed deposition, annual seed-trapping). Two distinct desert ecosystems were used to contrast transient seedbank densities in shrub and open microsites by manipulating annual plant density and the presence of the persistent seedbank. We measured transient seedbank densities at the end of the growing season by collecting soil samples and extracting seeds from each respective treatment. Transient seedbank densities were greatest in shrub canopies and with relatively higher annual plant densities. The persistent seedbank contributed to transient seedbank densities only in one desert and in the open microsite. Shrubs indirectly increased seedbank densities by facilitation the seed production of the annual plants. Therefore, shrubs are increasing seedbank independently of the annual plant community, likely through trapping effects, and dependently by facilitating seed production of the annuals. These findings provide evidence for a previously undescribed mechanism that supports annual seedbanks and thus desert biodiversity. We also identify shrubs as being significant drivers of desert plant communities and emphasize the need to consider multiple mechanisms to improve our ability to predict the response of ecosystems to change.York University Librarie

Performance of carrot and onion seed primed with beneficial microorganisms in glasshouse and field trials

Beneficial microorganisms (Clonostachys rosea IK726, Pseudomonas chlororaphis MA342, Pseudomonas fluorescens CHA0, Trichoderma harzianum T22 and Trichoderma viride S17a) were successfully applied to carrot and onion seed during a commercial drum priming process. Applied microorganisms were recovered above the target of at least 1 × 105 cfu g−1 seed following subsequent application of pesticides to the seed according to standard commercial practices of film-coating carrot and pelletting onion seed. Two glasshouse experiments consistently showed that priming improved emergence of carrot seed and that C. rosea IK726 further improved emergence time. Priming improved emergence of onion seed in one glasshouse experiment, but had an unexpected negative effect on emergence in the second experiment, possibly due to the proliferation of an unidentified indigenous microorganism during priming, becoming deleterious in high numbers. In this experiment, the application of beneficial microorganisms during priming negated this effect and significantly improved emergence. For each crop, a series of field trials was also carried out over three years, at two different sites each year. Although some positive effects of different seed treatments were seen on emergence or yield in individual field trials, no consistent effects were found for primed or microorganism-treated seed across all sites and years. However, a combined analysis of data for all years and sites indicated that pesticide application did consistently improve emergence and yield for both carrot and onion. This is the first comprehensive study assessing glasshouse and field performance of carrot and onion seed primed with beneficial microorganisms during a commercial process of drum priming in the UK

Compensating damage effects of seed-borne Fusarium culmorum and Microdochium nivale in winter wheat by increased seeding rates

Fusarium culmorum and Microdochium nivale are considered important seed-borne diseases of wheat in Denmark. Their damage effects consist in reducing seed germination and plant emergence which leads to reduced plant density, panicle numbers/area and yield. The aim of this study is to find out whether and to what degree these damage effects can be compensated by increased seeding rates. A trial was therefore conducted in 2004 in which seed lots of three winter wheat varities (Ritmo, Bill and Boston) having various degrees of infection by F. culmorum and Microdochium nivale were sown at various seeding rates. Seed contamination of the two pathogens was determined by counting the number of discoloured roots in the seed batches (Doyer method). Plant emergence was determined by counting the number of plants/area at seedling stage. A general linear model based on a term for [variety x pathogen] and a term for [variety x pathogen x germinating seeds/m2 x fraction of healthy seeds] explained ca. 70% of the variation in plant emergence. All parameters in the model were highly significant (p £ 0,005) and the R2 values of the individual variety x pathogen combinations ranged from 0.47 (Boston x M. nivale) to 0.85 (Ritmo x F. culmorum). The parameters of the model indicate that Boston was most responsive to an increasing seeding rate and/or healthy seed fraction, followed by Ritmo and Bill. This suggests that recommendations regarding the compensation of damage effects of seed-borne F. spp. and M. nivale by increasing seeding rates should be variety-specific. Supplemental results are expected from detailed analyses of the yield data and from an ongoing field trial. Further work will also include the development and use of molecular diagnostic tools to distinguish between various Fusarium spp. and M. nivale on contaminated seeds

Changes in seed dispersal processes and the potential for between-patch connectivity for an arid land daisy

Dispersal is a major and critical process in population biology that has been particularly challenging to study. Animals can have major roles in seed dispersal even in species that do not appear specifically adapted to animal-aided dispersal. This can occur by two processes: direct movement of diaspores by animals and modification of landscape characteristics by animals in ways that greatly influence dispersal. We exploited the production of large, persistent dispersal structures (seed heads, henceforth) by Erodiophyllum elderi (Asteraceae), a daisy from arid Australia, to further understand secondary dispersal. Seed head dispersal on and off animal tracks in eight E. elderi patches was monitored for 9.5 months by periodically recording the location of marked seed heads. Sites were located inside a reserve that excludes sheep but not kangaroos, and in a nearby area with both kangaroos and sheep. The distance moved and likelihood of seed head movement was higher in areas with sheep, and especially along animal tracks. There was clear evidence that seed heads were channeled down animal tracks during large rainfall events. Seed head dispersal away from patches occurred to a limited extent via their physical contact with sheep and potentially via wind dispersal. Thus, the advantages of this study system allowed us to demonstrate the two postulated effects of herbivores on dispersal via direct movement of seed heads, and two distinct indirect effects through landscape modification by herbivores from the creation of animal tracks and the denudation of vegetation.Louise M. Emmerson, José M. Facelli, Peter Chesson, Hugh Possingham, and Jemery R. Da

Seed Mass and Morphology in Outcrossing and Selfing Species of Clarkia (Onagraceae): An SEM Study

Seeds from three pairs of outcrossing-selfing sister taxa from the genus Clarkia (farewell-to-spring, Onagraceae)—Clarkia unguiculata, Clarkia exilis, Clarkia xantiana ssp. xantiana and ssp. parviflora, and Clarkia concinna ssp. concinna and ssp. automixa—were studied to assess the effects of contrasting mating systems on seed mass and seed morphology. For each outcrossing-selfing comparison, the seed mass of the selfing taxon was less than that of the outcrossing taxon. Seed mass typically differed significantly among populations within a taxon. Scanning electron microscopy showed that the seeds from all these taxa share several characteristics: a bullet to shield shape, a reticulate exotesta pattern, presence of crystals in the seed coat, and a seed coat that varies in thickness over the length of the seed. No morphological feature reliably distinguished seeds of outcrossing taxa from those of selfing taxa. The lack of morphological differences in conjunction with the consistent differences in seed mass between selfing and outcrossing seeds in these taxa supports the hypothesis that evolutionary forces have acted only on seed mass and not on seed morphology