دانلود رایگان ترجمه مقاله دمای مورد نياز برای جوانه زنی و رشد جوانه، تعیین زمان رویش جوانه سه تک لپه ای – Academic 2008
دانلود رایگان مقاله انگلیسی نیاز دما برای رویش بذر و رشد جوانه، تعیین زمان بندی روش جوانه سه تک لپه ای، ژنوتیپ های بهاره جنگل های مرطوب به همراه ترجمه فارسی
عنوان فارسی مقاله: | نیاز دما برای رویش بذر و رشد جوانه، تعیین زمان بندی روش جوانه سه تک لپه ای، ژنوتیپ های بهاره جنگل های مرطوب |
عنوان انگلیسی مقاله: | Temperature Requirements for Seed Germination and Seedling Development Determine Timing of Seedling Emergence of Three Monocotyledonous Temperate Forest Spring Geophytes |
رشته های مرتبط: | زیست شناسی و کشاورزی، علوم گیاهی، علوم باغبانی، فیزیولوزی و اکولوژی گیاهان زراعتی، علوم و تکنولوژی بذر |
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نشریه | Academic |
کد محصول | f243 |
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بخشی از ترجمه فارسی مقاله: اهداف و پیش زمینه : |
بخشی از مقاله انگلیسی: Background and Aims The optimal period for seedling emergence depends on factors such as habitat preference, life cycle and geographical distribution. This research was performed to clarify the role of temperature in regulating processes leading to seedling emergence of the European continental Scilla bifolia and the Atlantic Narcissus pseudonarcissus and Hyacinthoides non-scripta. † Methods Experiments in natural conditions were performed to examine the phenology of embryo growth, seed germination in the soil and seedling emergence. Effects of temperature conditions on embryo growth, seed germination, seedling growth and leaf formation were studied in temperature-controlled incubators. †Key Results In nature, embryo growth of all three species was initiated from the moment the seeds were dispersed in spring and continued during summer. A sequence of high temperature followed by a lower temperature was required to complete embryo growth and initiate germination. Seeds of H. non-scripta and N. pseudonarcissus germinated in autumn once they attained the critical E:S ratio, while seeds of S. bifolia started germinating when temperatures were low in winter. Seedlings developed normally, but slowly, only when placed in low temperature conditions (5 or 10 8C), resulting in a time lag between the moment of radicle protrusion and seedling emergence in the field. †Conclusions A continuous development of the embryo and seedlings of the three species was observed from the moment the seeds were dispersed until seedlings emerged. A sequence of high summer temperatures followed by decreasing autumn and winter temperatures was required for all developmental processes to be completed. Although a time lag occurs between radicle protrusion and seedling emergence, the term ‘epicotyl dormancy’ does not apply here, due to the absence of a period of developmental arrest. Timing of first seedling emergence differed between the three species and could be related to differences in geographical distribution. INTRODUCTION An embryo that does not entirely fill the seed is a common feature in ripe seeds of several Angiosperm taxa (Martin, 1946). A large number of these species have an underdeveloped embryo at the moment of dispersal, meaning that it has to grow within the seed before germination can occur (Grushvitzky, 1967). These seeds are termed morphologically dormant (MD) or morphophysiologically dormant (MPD), where there is an additional physiological block preventing germination (Nikolaeva, 1977). So far, eight types of MPD have been defined, based on temperature requirements for embryo growth and physiological dormancy break, and on the ability of gibberellic acid to overcome dormancy (Baskin and Baskin, 2004). According to Martin (1946), the level of embryo development in ripe monocotyledon seeds varies from underdeveloped rudimentary embryos to fully developed linear embryos. Genera that include species with underdeveloped embryos are especially common in Liliales and certain Asparagales families. An overview of dormancy types in Liliaceae s. str. shows that five out of eight types of MPD are known to occur in this group (Kondo et al., 2006). Although dormancy has been studied in other monocotyledon taxa, data on embryo growth requirements are particularly scarce. Timing of seedling emergence is a crucial event in a plant’s life cycle, affecting the plant’s chances of becoming established and reaching the reproductive phase (Harper, 1977). Seedlings of most species emerge shortly after the seed has germinated in the soil. Thus, timing of seedling emergence is mainly regulated by dormancy breaking and germination requirements of the seed. In some other species, a considerable time lag exists between the moment of radicle protrusion in the field and emergence of the seedling (e.g. Baskin and Baskin, 1985). In most cases these seeds show epicotyl dormancy, meaning that a physiological block prevents further growth of the epicotyl (Barton, 1933). A time lag between germination and seedling emergence can, however, also result from a reduced seedling growth rate (Karlsson et al., 2005). In general, dormancy is considered a mechanism to avoid periods that are favourable for germination but unfavourable for subsequent seedling establishment (Vleeshouwers et al., 1995). The most favourable period for seedling establishment can vary according to the geographical distribution and climatic conditions. Differing climatic conditions are, therefore, often reflected in dormancy breaking requirements of seeds (Skordilis and Thanos, 1995). Habitat preference and life cycle of the species are other factors determining the optimal period for seedling emergence and thus affecting seed behaviour (Nikolaeva, 1999). In the present study temperature requirements for germination and seedling emergence of Hyacinthoides non-scripta, Scilla bifolia (Hyacinthaceae) and Narcissus pseudonarcissus (Amaryllidaceae) were compared. These three species have a very similar ecology, being long-lived spring geophytes growing in temperate deciduous forests (Blackman and Rutter, 1954; Barkham, 1980; Keller, 2004). Although vegetative reproduction through formation of daughter bulbs occurs regularly, formation of seeds is also an important means of propagation (Knight, 1964; Barkham, 1992). The main difference in ecology between the studied species is found in their geographical distribution. Hyacinthoides nonscripta and N. pseudonarcissus both have a European Atlantic distribution, while S. bifolia has a European continental distribution. Hyacinthoides non-scripta grows abundantly on the British Isles and the western parts of Belgium and France, while scattered populations occur up to North-western Germany and the Alps (Thompson and Cox, 1978). Native populations of N. pseudonarcissus occur from England up to Western Germany, Switzerland and Northern Italy (Caldwell and Wallace, 1955). Scilla bifolia, on the other hand, is distributed throughout Central and Southern Europe, its range extending westwards to France and Belgium and eastwards up to the Caucasus and Turkey (Hegi, 1975). Seed morphological traits such as embryo size and seed coat impermeability undoubtedly affect seed dormancy. Amongst related taxa these traits can be considered fairly conservative (e.g. Corner, 1976). As a consequence, when comparing seed germination syndromes of different species, the phylogenetic relatedness of these species should not be neglected (Nikolaeva, 1999). Studies based on molecular data strongly support inclusion of Hyacinthaceae and Amaryllidaceae in the Asparagales group (Chase et al., 2000; Tamura et al., 2004). Hyacinthoides and Scilla are both included in the Hyacintheae tribe and can thus be regarded as closely related genera (Pfosser and Speta, 1999). The aim of this study was to elucidate and compare timing of embryo growth, seed germination in the soil and seedling emergence in natural conditions of the three spring geophytes H. non-scripta, S. bifolia and N. pseudonarcissus. A series of experiments in controlled conditions was performed to test how temperature regulates: (a) embryo growth; (b) germination; and (c) seedling development. Since these three species have a very similar ecology, an attempt was made to explain how biogeographical differences result in interspecific variation in timing of germination and emergence. |