Thesis (M.S.)--Ohio State University, 1985. / Includes bibliographical references (leaves 72-79). Available online via OhioLINK's ETD Center

Thesis (Ph. D.)--University of Chicago. / "Private Edition, Distributed by The University of Chicago Libraries." "Reprinted from the Botanical gazette, Vol. LXIV, No. 3 (September 1917)". Includes bibliographical references. Also available on the Internet. Also issued online.

Thesis (Ph. D.)--Cornell University, 1916. / "Reprinted from Memoir no. 14, August, 1918, of Cornell university agricultural experiment station." Bibliography: p. 135-138.

Root development in Picea glauca seedlings was studied anatomically during the first year after germination. The cyclic pattern of elongation of individual roots was established about three months after germination. With progressing development, root hairs gradually diminished and colonization of roots by mycorrhizal fungi increased. The development of primary tissues in long roots, relative to the distance from the root tip, appeared to be related to their rate of root elongation. In these roots, the development of Casparian bands in the endodermis often occurred several millimeters away from the root tip. In elongating short roots, endodermal cells attained their primary state only 2-4 cells away from the proximal part of the apical meristem. In non-elongating roots, the secondary-state endodermis was connected to the metacutis just above the apical meristem. The development of Casparian bands was always prior to the maturation of the first xylem elements. The endodermis did not develop past the secondary state. Through the presence of passage cells, it remained functional until its disruption by secondary growth. Low frequency of plasmodesmata in the endodermis indicated that the plasma membrane - cell wall - plasma membrane type of transport was the main means of molecule exchange between the cortex and the stele in white spruce roots. Undifferentiated tissues of the root near the apical meristem were almost impermeable to fluorescent dye tracers Sulforhodamine G and fluorescein diacetate. The metacutis and the endodermis at the primary and secondary state were impermeable to the apoplastic tracer Sulforhodamine G. Roots and root systems were structurally and physiologically affected by cultural treatments such as pruning and fertilizer application. Roots of seedlings grown at low nitrogen (N) supply were thin and their tracheids were narrow. Excess N did not significantly increase root diameter and tracheid dimensions, compared to the optimum supply. Dimensions of bordered pits were not significantly affected by the N level. The secondary development in roots advanced basipetally but exceptions were found indicating that cambial growth of roots could vary along the root regardless of the position relative to the root tip. Seedlings with different root systems modified by nursery culture exhibited different pattems of root growth after planting. Root elongation and root surface area increases immediately after planting were greater in container-grown than in mechanically box-pruned seedlings but this was unrelated to the longer-term performance of these seedlings. The initially low hydraulic conductance of root systems in box-pruned seedlings increased significantly 6-8 weeks after planting while it remained unchanged or declined in container-grown seedlings. Root pressure, comparable to that reported for angiosperm seedlings, was found in white spruce seedlings during the first few weeks after planting. This is contrary to the general notion that conifers do not develop notable root pressure. The initiation and elongation of roots in unfertilized organic compartments was poor compared to root growth in unfertilized mineral compartments, especially in mechanically pruned seedlings whose roots proliferated in the latter compartments. The growth of roots in the organic substrates was enhanced by the addition of slow-release fertilizer to that substrate. The growth response of roots to slow-release fertilizer added to the mineral substrate was restricted to that compartment but root growth in both soil compartments was affected by the addition of slow-release fertilizer to the organic substrate. Root development in different types of planting stock was differently affected by the soil substrate type and the addition of the slow release fertilizer. / Graduate

Eucalyptus dunnii exhibits fast growth, low lignin and high cellulose contents, traits that are highly desirable for pulp production and are therefore favoured by the paper industry. In this study, E. dunnii roots were produced by the various methods practiced by commercial forestry viz. macrocuttings, microcuttings and seedlings. Roots produced were compared and characterized in order to understand the distinctions between Eucalyptus roots produced by these methods. Seedlings and clonal mini-cuttings were sourced from the Trahar Technology Centre, Mondi (South Africa). Plant shoots were established in culture and multiplied before the induction of roots in vitro. An optimal growth medium was determined for E. dunnii multiplication, which was 4.42g.l-1 MS (with vitamins), 25g.l-1 sucrose, 0.2g.l-1 benzyl aminopurine, 0.01g.l-1 naphthaleneacetic acid, 0.1g.l-1 biotin, 0.1g.l-1 calcium pantothenate, and 3g.l-1 gelrite (pH of 5.6-5.8). Due to the high (68%) levels of vitrification, tests were conducted to reduce or reverse this phenomenon with no success. Only healthy material was selected for rooting experiments. In vitro rooting was tested on medium containing 1.105 g.l-1 MS (with vitamins), 15 g.l-1 sucrose, 0.1 g.l-1 biotin, 0.1 g.l-1 calcium pantothenate, 4 g.l-1 gelrite and pH of 4.5-5.8 and 0.1-1mg.l-1 IBA without success. In vitro rooting (4%) was achieved on peat:vermiculite (1:2) probably due to less humidity. Comparison of micropropagated plantlets and seedlings of the same height range showed that root architecture of main roots, main side roots, number of side root and shoot masses were all statistically similar. Mini-cuttings underwent treatments before placement into seedling tray inserts containing coir:perlite (1:2). With the first treatment, the lower excised end of the shoot was dipped in 20mg.l-1 IBA, for 48 hours while being incubated in a dark and humid environment; the cutting was then placed into the insert. With the second treatment, mini-cuttings were placed directly into the prepared inserts for four weeks. Thereafter, the shoots were carefully removed and underwent the same process as with treatment one. The third treatment involved dipping mini-cuttings in Seradix 1 0.1% IBA) and placement into the prepared inserts. Treatment 4 involved three pulse treatments which were tested by placing mini-cuttings into various concentrations of IBA (20mg.l-1, 200mg.l-1, 2000mg.l-1) in solution for 150 seconds before placement into the insert. Mini-cuttings devoid of any treatment had approximately the same percentage success (26%) as those treated with Seradix 1 (25%). Mini-cuttings that underwent the 200mg.l-1pulse treatments showed the greatest percentage success (30%). Mini-cuttings treated with Seradix 1 and seedlings of various sizes (7.5-70cm) were obtained from the Trahar Technology Centre and the root architecture was analyzed and quantified. Mini-cutting derived plantlets and seedlings of the same size had approximately the same shoot:root ratio. Mini-cutting plantlets had a shoot:root ratio of 2.2:1 and seedlings, 2.8:1 in the 5-7cm height range. In the 7.1-9cm height range, cutting plantlets had a shoot:root ratio of 2.5:1; and seedlings, 2.4:1. The number of lateral roots of both seedlings and mini-cutting derived plantlets in each height range was found to be statistically similar. In the comparison of seedlings of the same height range as the mini-cutting plantlets sampled, it was observed that the root architecture differed in root length and structure. With the comparison of shoot and root growth of different heights (20 to 70cm, increasing in increments of 10cm) of E. dunnii seedlings, the length of the main roots of seedlings within all height ranges were found to be similar. The same trend was noted in lateral-root lengths and numbers. While some shoot dry masses were not significantly different from others. Shoot dry mass of seedlings gradually increased in accordance with an increase in the height of shoots. With every 10cm increase in shoot height, shoot mass would increase by approximately 50%. Although in vitro plantlets, mini-cutting plantlets and seedlings of the same height range seemed similar in shoot:root ratios and root lengths, no direct comparisons could be drawn from the study due to the varying growth conditions of the samples before analysis, as well as restrictions on root growth by containers. To fully understand root architecture and growth patterns, it is suggested that more field work is required to obtain an accurate representation at different stages of growth.

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