1,721,057 research outputs found
On visions and new approaches Case studies of organisational forms in organic plant breeding and seed production
No full textThe report is an exploratory study of the social, financial and legal organisation, and technology applied in five initiatives in the sector of biological seed production and plant breeding in the Netherlands, Germany and Switzerland. The experiences of the studied initiatives are relevant in a period in which interest for organic seed and plant breeding is increasing. A number of the actors in the organic sector consider organic breeding a guarantee the availability of suitable seeds and varieties for the organic sector in terms of agronomic and quality traits. An important requirement is that seeds are produced and developed with technologies that are accepted in the organic sector. In addition, the organic sector is interested in breeding strategies that aim not only at economic, but also at social sustainability
Participatory approaches and institutional changes in the field of genetic resources management
No full textOn flowering and botanical seed production in potato (Solanum tuberosum L.)
No full textThe use of true potato seed (TPS) as a propagule for potato tuber (Solanum tuberosum L.) production is a viable alternative to the use of seed tubers. For this technology to be successful, efficient production of high- quality botanical seed is crucial. The objectives of the research reported in this thesis were to define production practices that maximise quantity and quality of botanical seed produced, and to contribute to the understanding of above-ground development in potato.The first part of the study describes experiments on seed production under field conditions in three contrasting agro-ecological zones in Peru. Seed production is described as a function of number of flowers produced, berry set and number of seeds produced per berry. Hundred-seed weight is used as seed-quality parameter. In the second part of the thesis, flower production is analysed as a function of inflorescence production, number of flower primordia initiated per inflorescence and flower primordia survival.The results of the field experiments indicated that generally, later-produced inflorescences on a shoot or in a field, and later-produced flowers in an inflorescence have a lower berry set and produce fewer and smaller seeds per flower. The effect of the position of the flower in the inflorescence does not affect seed size in all cultivars. Hundred-seed weight of production from primary inflorescences was increased when later-produced inflorescences were not used for seed production, but this could not compensate for the reduction of seed yield. Increasing plant density reduced the number of inflorescences per shoot and the number of flowers per inflorescence. Flower production per m2 increased with plant density in two of the three cultivars used. Berry set, number of seeds per berry and 100-seed weight were reduced when comparing flowers at similar positions on the shoot. However, because increasing plant density shifted the flower production from later- to earlier- formed flowers, the effect on average berry set, number of seeds per berry and seed size of the total seed production was relatively small. The effect of plant density on seed production was largely determined by the effect on flower production. Artificial extension of the photoperiod and interruption of the night with incandescent light increased the flower production under warm tropical conditions. This effect was principally a result of an increased inflorescence production. Photoperiod treatments did not affect the seed production per flower.Experiments in controlled conditions showed that increasing photoperiod and temperature increased the production of inflorescence positions per shoot, number of flower primordia per inflorescence and flower primordia survival in the temperature range of 15-25 °C (24-h average). Shoot development and flowering in potato were quantified as functions of rates and durations of leaf and flower primordia initiation, and of stem production. Effects of increasing temperature and photoperiods on shoot development and flowering were a result of increasing thermal durations of stem production, and leaf and flower primordia production of individual stems. The effects on individual stems were, however, small compared to the effects on stem and inflorescence production.Conclusions from the study for practical TPS production are that the last produced flowers in a field have a strongly reduced potential for seed production and that seed production can be best increased by increasing flower production through longer photoperiods and higher temperatures
Flowering and true seed production in potato (Solanum tuberosum L.). 2. Effects of stem density and pruning of lateral stems.
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Photothermal response of sympodial development and flowering in potato (Solanum tuberosum L.) under controlled conditions.
No full textIn two phytotron experiments with different potato cultivars (experiment 1: cv. Atzimba and Van Gogh; experiment 2: cv. Spunta and Desiree), a study was made of the effects of temperature (15-27 degrees C) and photoperiod (long day, LD, or short day, SD) on sympodial development and shoot, leaf and flower production. In experiment 1, data on the entire shoot were collected, whereas in experiment 2 only leaf and flower production of the main and secondary stems were measured. In experiment 1, increasing the temperature in both SD and LD treatments, and increasing the photoperiod at 15 degrees C increased the number of lateral shoots, and the numbers of inflorescences and leaves of the sympodium and of the entire shoot. In experiment 2, the number of flower primordia and survival of flower primordia of individual inflorescences increased with the photoperiod and with temperature up to 23 degrees. At 27 degrees, flower development was suppressed. Total leaf and flower production per plant were largely a function of lateral shoot production. Increasing temperature and photoperiod increased the number of leaves of individual shoots in most treatments. However, the effects on leaf and flower production of individual shoots were relatively small, except for the effect of a temperature increase from 23 to 27 degrees in experiment 2. The photoperiodic response of the time till flowering of individual shoots was facultative SD or daylength-neutral, depending on the cultivar and stem position
Flowering and true seed production in potato (Solanum tuberosum L.) 1. Effects of inflorescence position, nitrogen treatment, and harvest date of berries.
No full textBiodiversiteit in de plantenteeltwetenschappen. Over het behouden, beheersen, beheren en benutten van diversiteit in agro-ecosystemen.
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