Partially expanded male catkins of swamp white oak (Quercus bicolor Willd.) and red oak (Quercus rubra L.) were cultured on Murashige and Skoog (MS) medium supplemented with BA or 2,4-D. Explants on 2,4-D produced a yellow embryogenic callus originating from the junction of the pedicel and peduncle. Subsequent transfers to MS with BA and then MS without growth regulators resulted in callus proliferation. After 10 to 14 weeks in culture, white embryoids developed from the callus of Q. bicolor. Separated and individually cultured embryoids underwent direct, repetitive embryogenesis. Upon transfer to l/2-strength MS, embryoid germination and plant regeneration occurred. Callus of Q. rubra degenerated after 5 months in culture, failing to yield embryogenic structures. Chemical names used: dichlorophenoxyacetic acid (2,4-D); benzyladenine (BA).
Partially expanded male catkins at the pre-pollen shedding stage of Quercus rubra L. and Quercus bicolor Willd. were cultured on MS medium supplemented with BA or 2,4D Explants on 2,4D produced a yellow embryogenic callus, seeming to originate from the pedicels. Subsequent transfers to BA and then, MS without growth regulators, resulted in callus proliferation. After ten weeks in culture, white embryoids developed from the callus of Q. bicolor. Separated and individually cultured embryoids underwent direct, repetitive embryogenesis. Upon transfer to ½-strength MS, embryoid germination and plant regeneration occurred, Callus of Q. rubra degenerated after five months in culture, failing to produce embryogenic structures.
Sunflower (Helianthus annuus L. ‘Mammoth’) and poplar (Populus × ‘Androscoggin’ H.) plants were grown in a medium containing one of five Cd concentrations, ranging from 0.13 to 13.20 μg·g−1 and watered with one of five simulated rain treatments (pH 3.2-5.2) to determine the effects of precipitation acidity on Cd mobilization and resulting effects on plant growth. Treatment rain acidity was insufficient to lower the medium solution pH to levels conducive to high Cd desorption. Plants accumulated < 1% of the total Cd applied (as CdCl2) for all Cd treatments. Root and foliar Cd concentrations increased with Cd treatment levels. Poplar accumulated proportionally more Cd in foliage than in roots for all treatments. Sunflower accumulated proportionally more Cd in leaves than in roots for the 0.29, 0.62, and 3.20 μg·g−1 Cd treatments and in roots for the 0.13 and 13.20 μg·g−1 Cd treatments. Cadmium treatments and Cd concentrations in the medium, roots, and foliage were not related to changes in plant dry weights, heights, or essential element concentrations in media, roots, or foliage of either species.
Suspension cultures of five elm selections (U. americana A, 680, 8630 and Del 2 and U. pumila S) exhibiting a range of susceptibility responses to the Dutch Elm Disease fungus (Ophiostoma ulmi) have been successfully established for future elicitor/phytoalexin studies. Calli initiated from foliar tissues of mature, greenhouse-grown trees cultured on a solid modified MS medium containing 2,4-D and BA were adapted to a liquid modified MS medium containing BA and either IAA or NAA. Cells were grown in either the presence or absence of light with continuous agitation. Uniform, rapidly dividing cell cultures were achieved when friable white or tan calli were grown in the medium containing 1 mg/l each NAA and BA in darkness. Cultures yielding an abundance of phenolic compounds exhibited decreased cell uniformity and proliferation. Increased phenolic production was associated with the presence of phenolics in the initial callus tissue, exposure to light and the use of IAA as the auxin source.