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  • Author or Editor: D. J. Weber x
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Petioles were gathered at bloomtime in four trials, one each of `Chardonnay and `Zinfadel' and two of `Cabernet Sauvignon' over 2 years, 1993 and 1994. In each trial, scions were grafted onto 12 to 14 rootstocks. Petioles were analyzed for NO3-nitrogen, NH4-N, K, P, and Mg. NO3-N levels differed among rootstocks by as much as 16-fold (126 to 2064 μg·g–1), NH4-N by as much as 4-fold (253 to 1-28 μg·g–1), K, P, and Mg by about 3-fold (9.7 to 30.6 mg·g–1, 1.8 to 6.3 mg·g–1, and 2.9 to 7.5 mg·g–1, respectively). `Freedom' had the highest levels of NO3-N. `Salt Creek' had moderate levels of NO3-N, but had the highest levels of NH4-N. The rootstock 420A Mgt was consistently low in NO3-N, NH4-N, and K. Freedom was among the highest in K content. The rootstock 44-53 Malègue' had high levels of K and low Mg. Implications for vineyard fertilization programs will be discussed.

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Successful in vitro propagation of white rubber rabbitbrush [Chrysothamnus nauseosus (Pallas) Britt, ssp. albicaulis] was achieved using both stem segments and axillary shoot explants. Medium stem segments (2–3 mm diameter) were more successfully cultured than either small (0.8–1 mm diameter) or large (4–5 mm diameter) explants. Axillary shoot explants (10–15 mm long) began to form roots within 1 week after placement in media containing 5–10 μM (1–2 mg/liter) indolebutyric acid (IBA) or 5.3–10.6 μM (1–2 mg/liter) naphthalene-acetic acid (NAA). Root growth was accelerated in the presence of IBA. In the presence of 8.9 μM (2 mg/liter) benzyladenine (BA) and 0.53μM (0.1 mg/liter) NAA, both medium stem segments and axillary shoots rapidly produced numerous side shoots that were rooted easily on media containing IBA. In vitro culture appears to be a feasible means for the mass multiplication of this potentially important rubber-producing shrub.

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