Sugar maple trees were fertilized in June 1988 on an individual tree basis in an attempt to improve tree vigour. Fertilizers included K$ sb2$SO$ sb4$, a phosphate and base cations mix, and a commercial organic mix (Maplegro). No effect of fertilization was found on foliar nutrient concentrations and water status of trees during the 1990 growing season. This is possibly the result of dilution in tree biomass, the addition of non limiting nutrients or the experimental design. A positive effect of fertilization on growth was found for one site and, at another, fertilization was found to impair growth. Thus fertilization requirements of declining sugar maple are site specific. Soil Mg was higher around trees fertilized with Maplegro, and trees fertilized with K$ sb2$SO$ sb4$ had low leaf buffering capacities.

Studies were undertaken to determine the effects of fertilizer and liming materials on soil and fine root chemistry and fine root biomass, and on the starch content of larger diameter sugar maple (Acer saccharum Marsh.) roots. Responses in fine root biomass, fine root chemistry, and soil chemistry were observed using root-free ingrowth cores containing an organic based fertilizer (3-4-8 plus dolomitic limestone at a rate of 800 kg/ha), an inorganic fertilizer (0-3-29 plus calcite and dolomite at a rate of 1370 kg/ha), or no fertilizer. The cores were installed in three mature sugar maple stands for one year. Significant differences (p $ leq$ 0.05) in many root and soil chemical properties existed among sites. Greatest treatment response in soil and fine root chemistry occurred at the site with the poorest nutrient status. Fine root biomass decreased due to treatment at one site. No other response in fine root biomass was observed. / Larger diameter roots were sampled at two sites from sugarbush fertilization plots treated with base rich fertilizers. At one site, an acidifying treatment was also applied. Significant differences (p $ leq$ 0.05) in root starch content were observed between the acidifying treatment and the most base enriched treatments several years following fertilization.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1972. / Bibliography: leaves 228-234. / xii, 234 l illus., maps, tables

Proefschrift--Nederlandsche Handelshoogeschool, Rotterdam. / Bibliography: p. [319].

Thesis (M.S.)--Oregon State University, 2001. / Typescript (photocopy). Includes bibliographical references. Also available online.

Thesis--Nantes, 1974. / Includes index. Bibliography: p. 703-721.

Proefschrift--Wageningen. / Includes bibliographical references (p. 32-346).

Proefschrift--Nederlandsche Handelshoogeschool, Rotterdam. / Bibliography: p. [319].

Thesis (M.S.)--Montana State University--Bozeman, 2007. / Typescript. Chairperson, Graduate Committee: Vincent H. Smith. Includes bibliographical references (leaves 87-89).

Internodes 5-8, 10, 13 and 15 of Saccharum sp. var. NCo376 were examined for evidence of symplasmic phloem unloading of sucrose from the phloem, via the bundle sheath to the storage parenchyma. The vascular bundle possesses wellisolated phloem comprised of large diameter sieve elements and small diameter companion cells. A layer of phloem parenchyma surrounds the phloem, except where the phloem abuts the crushed protophloem. Outside this is a sclerenchymatous sheath, directly endarch to a parenchymatous bundle sheath, which is surrounded by storage parenchyma. The bundle sheath is interrupted at the centrifugal pole of the vascular bundle by a phloem fibre cap. Scanning Electron Microscopy revealed plasmodesmal fields throughout the bundle sheath and pith tissue. Transmission Electron Microscopy studies provided evidence of plasmodesmal occlusion, but not in all tissues. Aniline blue reactions under UV light indicate the presence of occluded plasmodesmal fields at the phloem parenchyma / sclerenchymatous sheath interface, and in localised regions of cells which are smaller than the surrounding storage parenchyma cells. This suggests a symplasmic transport pathway at these locations, and, based on these positive aniline blue reactions, with regulation via callose-mediated transplasmodesmal transport. Osmotic stress experiments, which included the addition of Ca2+, did not reveal further callose occlusion in the parenchyma, suggesting that the plasmodesmata in these regions may be closed via a noncallosic mechanism. Dye-coupling studies, using Lucifer Yellow (LYCH), which was iontophoretically injected following turgor-pressure equalisation, showed only rare, limited symplastic transport, usually only between the injected cell and one adjacent cell. Most injections did not result in transport of LYCH, suggesting either a lack of plasmodesmal connectivity, occlusion, or gating of any plasmodesmata present. This limited symplasmic transport, combined with the presence of occluded plasmodesmata at the phloem parenchyma / sclerenchymatous sheath interface suggests the presence of a two-domain phloem-unloading pathway. While symplastic transport may occur from the phloem to the sclerenchymatous sheath, further sucrose transport to the storage parenchyma appears to proceed apoplasmically from the sclerenchymatous sheath / bundle sheath interface, and into storage parenchyma cells across the cell wall and cell membrane via specialised sucrose transporters.