Plants were regenerated from whole embryo explants obtained from eastern white pine (Pinus strobus L.) seeds. Embryos were surgically removed and axenically cultured to induce buds in vitro on a modified Murashige and Skoog medium containing various concentrations of 6-benzylaminopurine. Embryos remained on bud induction medium for 21 days and then were transferred to the same basal medium without 6-benzylaminopurine to promote bud development and subsequent shoot elongation. The medium containing 10 μM 6-benzylaminopurine induced the greatest number of shoots per embryo. Rooting was achieved by direct transfer of the shoots to a non-sterile artificial soil mixture followed by multiple treatments with 15 nM 1-naphthaleneacetic acid. Regenerated seedlings are currently growing under greenhouse conditions.
— Quercus alba, white oak, and Quercus rubra, northern red oak, were selected to develop in vitro plantlet regeneration methods from bud and embryo explants. Various hormonal combinations were applied to explants to induce axillary bud proliferation. Maximal multiple shoot production was obtained when an intermediate micromolar range of benzyladenine (0.44-4.44 μM) was applied alone or in combination with low concentrations of naphthaleneacetic acid (1.0-100 μM). In vitro rooting of 1 Q alba microshoot was accomplished. axillary bud proliferation / Quercus / in vitro / regeneration Résumé — Prolifération de bourgeons axillaires de 2 chênes nord-américains, Quercus alba et Quercus rubra. Des méthodes de multiplication in vitro à partir de bourgeons ou d'embryons ont été développées. De nombreuses combinaisons hormonales ont été testées pour induire la prolifération de bourgeons axillaires chez les explants. Les meilleurs résultats ont été obtenus avec une solution micromolaire de benzyl adénine variant de 0,44 μM à 4,44 μM appliquée seule ou en mélange avec de l'acide naphtalèneacétique (1,0-100 μM). L'enracinement in vitro de microplants de Q alba a été obtenu. prolifération de bourgeons axillaires /Quercus /in vitro / régénération
The high rate shear of a granular material is investigated by the use of a discrete mesodynamic method. The simulation describes a Couette flow geometry without gravity. A collection of frictional and perfectly smooth particles are subjected to strain rates ranging from 2 3 ϫ10 1 to 2 3 ϫ10 4 1/s at solids concentrations ranging from 75% to 87% in a two-dimensional geometry. Normal stresses at the base of the granular sample are recorded. Large fluctuations in individual transmitted stresses are observed. The behavior of this stress profile compares well with previous experimental results. A near linear relation between normal stress and the strain rate is observed. The mechanism of stress transfer, stress chain formation, and random particle collision, through the depth of the sample, is seen to depend on solids concentration. Friction affects both the magnitudes of normal stresses and the characteristics of the granular flow.
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