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Wayne A. Sargent and Zong-Ming Cheng

Hybrid aspen is a major source of fiber in the north-central United States. One major problem for utilizing genetically improved aspen, and a variety of other woody species, is the difficulty in rooting hardwood cuttings. The objective of this project was to construct and confirm the function of genetic transformation vectors with two rooting genes (iaaM from Agrobacterium tumefaciens and rolB from A. rhizogenes) using three promoters (CaMV35S, soybean heat shock-inducible and poplar wound-inducible promoters). The gene constructs can be used to transform aspen for improvement of rooting hardwood cuttings and to elucidate rooting mechanisms. Each of these six gene constructs was inserted contiguously upstream from the promoter-less-glucuronidase (GUS) gene in the plasmid pBI 101. The engineered plasmids were transformed into A. tumefaciens strain LBA 4404 by electroporation. The functions of the genes were confirmed by transforming Nicotiana tabacum with these constructs. In plants transformed with iaaM and rolB under the CaMV35S promoter, the GUS gene expressed constitutively. These plants were also morphologically abnormal, with callus (and sometimes root) formation on stem tissue. The plants transformed with heat shock and Win6 constructs had no root formation and little or no GUS expression, without induction. After induction with heat shock (42°C for 1 hr per day for 7 days) or wounding (wounding the plants daily for 7 days), root formation occurred and GUS expression increased significantly with each gene, respectively. No roots developed in the non-transformed control shoots. The transformed plants with the regulatory promoters appeared morphologically normal. These constructs are currently being tested in hybrid aspen.

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Gerald A. Tuskan, Emile J. Poisson and Wayne A. Sargent

Benzylaminopurine and chlorflurenol were applied to 2-1 nursery stock of Scots pine and ponderosa pine and 2-0 nursery stock Colorado blue spruce and Black Hills spruce to determine if crown morphology was influenced by varying combinations of the two plant growth regulators. Four levels of benzylaminopurine, 0, 250, 750 and 1250 ppm, and two chlorflurenol levels, 0 and 1% (v/v) were tested. Morphological response to treatments was significantly enhanced when treatments were applied to open, elongating buds. Benzylaminopurine significantly increased bud and shoot formation, while chlorflurenol significantly reduced height and increased branch length at species dependent concentrations. The two plant growth regulators lacked positive synergistic effects.

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Gerald A. Tuskan, Emile J. Poisson and Wayne A. Sargent

Benzylaminopurine and chlorflurenol were applied to 2-1 nursery stock of Scots pine and ponderosa pine and 2-0 nursery stock Colorado blue spruce and Black Hills spruce to determine if crown morphology was influenced by varying combinations of the two plant growth regulators. Four levels of benzylaminopurine, 0, 250, 750 and 1250 ppm, and two chlorflurenol levels, 0 and 1% (v/v) were tested. Morphological response to treatments was significantly enhanced when treatments were applied to open, elongating buds. Benzylaminopurine significantly increased bud and shoot formation, while chlorflurenol significantly reduced height and increased branch length at species dependent concentrations. The two plant growth regulators lacked positive synergistic effects.