Home About us Contact
|
Home About us Contact | ||
|
|
||
Shoot Apex (shoot + apex)
Selected AbstractsSomatic embryogenesis and multiple-shoot formation from seed-derived shoot apical meristems of rhodesgrass (Chloris gayana Kunth)GRASSLAND SCIENCE, Issue 3 2007Takahiro Gondo Abstract High-frequencies of somatic embryogenesis and multiple-shoot formation were achieved with seed-derived shoot apical meristems of rhodesgrass (Chloris gayana Kunth). Shoot apices as initial explants were isolated from aseptically germinated seedlings, and cultured in vitro. Embryogenic calli and the multiple shoots were induced and maintained on MS basal medium with various combinations of 2,4-dichlorophnoxyacetic acid (2,4-D) and 6-benzylaminopurine (BAP), the two most effective treatments being 2.0 mg L,1 2,4-D and 0.1 mg L,1 2,4-D + 2.0 mg L,1 BAP. These embryogenic calli and multiple-shoot formations could be used as alternative regenerable target tissues for genetic transformation using particle bombardment of rhodesgrass. [source] Optimization of culture conditions for plant regeneration of Panicum spp. through somatic embryogenesisGRASSLAND SCIENCE, Issue 1 2010Mi-Suk Seo Abstract We developed a rapid and efficient shoot regeneration system for Panicum spp. by adjusting the regeneration medium and studying the responses of different genotypes and the influence of explant types (mature seed, immature embryo and shoot apex). We used Panicum meyerianum (Nees) and Panicum longijubatum (Stapf) which were shown to perform well, to select the optimal medium for shoot regeneration. The highest frequency of shoot regeneration was obtained on Murashige and Skoog medium supplemented with 30 g L,1 maltose and 1 mg L,1 N-phenyl-N,-[(1,2,3-thidiazol-5-yl) urea]. The callus formed green spots after 1 week of culture and showed primary green shoots after 2 weeks. In this system, the calli derived from mature seed of nine Panicum genotypes showed large variation in shoot regeneration ability: from 0 to 69.9% in the frequency of shoot formation and from 0 to 8.4 in the number of shoots per callus. Guineagrass (Panicum maximum Jacq.) showed no ability and switchgrass (Panicum virgatum L.) showed low ability to regenerate from mature seed-derived calli; however, both were able to be regenerated from immature embryos and calli derived from shoot apices. We developed an efficient protocol for high shoot regeneration of various Panicum genotypes which provides a foundation for efficient tissue culture and genetic improvement of Panicum. [source] Response of Faidherbia albida (Del.) A. Chev., Acacia nigrescens Oliver. and Acacia nilotica (L.) Willd ex Del. seedlings to simulated cotyledon and shoot herbivory in a semi-arid savanna in ZimbabweAFRICAN JOURNAL OF ECOLOGY, Issue 2 2010Sijabulile Dube Abstract Woody plant seedling establishment is constrained by herbivory in many semi-arid savannas. We clipped shoots and cotyledons of three woody species 5-day (=,early') or 28-day (= ,late') post-emergence to simulate herbivory. Seedlings had shoot apex, one or two cotyledon(s) removed, or were retained intact. Survival rates were ,80%, ,40% and ,20% for Acacia nilotica, Acacia nigrescens and Faidherbia albida respectively. F. albida mobilized stored cotyledon reserves faster and consequently shed the cotyledons earlier than the two Acacia species. Cotyledons were shed off as late as 70 days post-emergence with 5-day shedding earlier than 28-day and cotyledon life-span decreasing with intensity of defoliation. Shoot apex removal 28-day resulted in higher compensatory growth than 5-day in all three species. Cotyledon removal had no effect on shoot length, while shoot apex removal reduced shoot length. In F. albida root growth was stimulated by shoot apex removal. We conclude that potential tolerance to herbivory in terms of seedling survival was of the order A. nilotica > A. nigrescens > F. albida, timing of shoot apex and cotyledon removal influenced seedling growth in terms of biomass and that shoot apex removal stimulated compensatory growth which is critical to seedling survival. Résumé L'établissement de jeunes plants ligneux est contrarié par l'herbivorie dans de nombreuses savanes semi arides. Nous avons coupé les pousses et les cotylédons de trois espèces ligneuses à 5-j (= tôt) ou à 28 j (= tard) après leur émergence pour simuler l'herbivorie. On coupait l'apex de la tige et un ou deux cotylédons, ou on les laissait intacts. Le taux de survie était , 80%, , 40% et , 20% pour Acacia nilotica, Acacia nigrescensetFaidherbia albida respectivement. F. albida mobilisait plus rapidement les réserves stockées dans les cotylédons et par conséquent perdait les cotylédons plus tôt que les deux espèces d'acacia. Les cotylédons étaient perdus jusqu'à 70 jours après leur apparition, les 5-j les perdant plus tôt que les 28-j, et la durée de vie des cotylédons diminuait avec l'intensité de la défoliation. L'enlèvement des cotylédons n'avait pas d'effet sur la longueur de la pousse, tandis que celui de l'apex la réduisait. Chez F. albida, la croissance des racines était stimulée par l'enlèvement de l'apex. Nous concluons que la tolérance potentielle à l'herbivorie, en termes de survie des jeunes plants, suit cet ordre-ci : A. nilotica > A. nigrescens > F. albida; que le moment de l'enlèvement du bourgeon apical et des cotylédons influence la croissance des jeunes plants en termes de biomasse; et que l'enlèvement du bourgeon apical stimule une croissance compensatoire qui est critique pour la survie du jeune plant. [source] Florigen: One Found, More to Follow?JOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 6 2006Xuhong Yu Abstract Florigen(s) are molecules that are synthesized in response to appropriate photoperiods and transmitted from leaves to shoot apices to promote floral initiation. It has been recently discovered in Arabidopsis that mRNA of the FT gene acts as a florigen. In Arabidopsis, cryptochromes and phytochromes mediate long-day promotion of CO protein expression, which activates FT mRNA expression in leaves. FT mRNA is transmitted to the shoot apex, where it acts together with FD to activate transcription of floral meristem identity genes, resulting in floral initiation. The discovery of the molecular nature of a florigen was a major scientific breakthrough in 2005. (Managing editor: Li-Hui Zhao) [source] Frost Injury as a Possible Inciting Factor in Bud and Shoot Necroses of Fraxinus excelsior L.JOURNAL OF PHYTOPATHOLOGY, Issue 9 2005P. M. Pukacki Abstract Large numbers of European ash have died in Poland in all age classes during the last ten years. The characteristic symptom occurring on shoots of planted and self-sown seedlings was bark necroses starting from the shoot apex, necrotic buds, or leaf and twig scars. The results showed that in the bud tissue of cold acclimated European ash extracellular and intracellular ice formation occurred at approximately ,9 and ,32°C, respectively. In deacclimated plants in spring water supercooling is limited by the heterogenous ice nucleation temperature and consequently the cold tolerance is ,9 to ,4°C for bud tissues and ,13 to ,9°C for shoots. Isolations of fungi were performed from dead buds and from necroses occurring on the main stem. Alternaria alternata, Fusarium lateritium and Phomopsis scobina were among the fungi occurring in both these organs at frequencies of more than 7%. Cylindrocarpon heteronemum, Diplodia mutila and Tubercularia vulgaris from necroses were only isolated in frequencies; 3.3, 1.2 and 5.4%, respectively. It seems likely that freezing injury is the inciting factor, which combined with fungal colonization manifests itself as fatal damage to European ash buds and shoots. [source] Optimization of culture conditions for plant regeneration of Panicum spp. through somatic embryogenesisGRASSLAND SCIENCE, Issue 1 2010Mi-Suk Seo Abstract We developed a rapid and efficient shoot regeneration system for Panicum spp. by adjusting the regeneration medium and studying the responses of different genotypes and the influence of explant types (mature seed, immature embryo and shoot apex). We used Panicum meyerianum (Nees) and Panicum longijubatum (Stapf) which were shown to perform well, to select the optimal medium for shoot regeneration. The highest frequency of shoot regeneration was obtained on Murashige and Skoog medium supplemented with 30 g L,1 maltose and 1 mg L,1 N-phenyl-N,-[(1,2,3-thidiazol-5-yl) urea]. The callus formed green spots after 1 week of culture and showed primary green shoots after 2 weeks. In this system, the calli derived from mature seed of nine Panicum genotypes showed large variation in shoot regeneration ability: from 0 to 69.9% in the frequency of shoot formation and from 0 to 8.4 in the number of shoots per callus. Guineagrass (Panicum maximum Jacq.) showed no ability and switchgrass (Panicum virgatum L.) showed low ability to regenerate from mature seed-derived calli; however, both were able to be regenerated from immature embryos and calli derived from shoot apices. We developed an efficient protocol for high shoot regeneration of various Panicum genotypes which provides a foundation for efficient tissue culture and genetic improvement of Panicum. [source] In vitro chromosome doubling of Miscanthus sinensisPLANT BREEDING, Issue 5 2002K. K. Petersen Abstract The aim was to develop an efficient chromosome doubling method for Miscanthus sinensis to enable the production of triploids and so avoid seed dispersal to the environment. Antimitotic treatments with colchicine or oryzalin were tested in M. sinensis cl. MS-88-110 on: (1) in vitro shoots and plants established in soil; (2) during propagation of embryogenic callus; and (c) during the initial stages of callus induction. All systems produced chromosome-doubled plants. A higher percentage of tetraploids was found after antimitotic treatment at the explant or callus level compared with treatment of in vitro shoots or plants established in soil. In general, oryzalin was more toxic to plant material than colchicine. A higher frequency of chimeras was found among plants with altered ploidy level when the target was formed shoot buds compared with adventitious shoot formation from callus. Antimitotic treatment of embryogenic callus from shoot apices also resulted in a high degree of albinism. [source] A morphological study of the development of the second inflorescences in strawberry (Fragaria×ananassa Duch.)ANNALS OF APPLIED BIOLOGY, Issue 4 2005T KUROKURA Summary To clarify the timing of the differentiation of the first and second inflorescences in strawberry (Fragaria × ananassa Duch.), morphological changes on shoot apices during short day and low night temperature treatments were observed by scanning electron microscopy (SEM) and optical microscopy. Axillary buds just below the first inflorescence (axillary bud 1) became visible when sepal primordia of the primary flower were differentiated. By this time, other axillary buds had already developed. Axillary bud 1 developed four leaf primordia, and then a differentiated inflorescence at its summit. The phase transition of shoot apices from the vegetative to the reproductive phase may therefore trigger the differentiation of axillary bud 1 which is destined to develop into extension crowns. [source] | ||||||||||