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.

Adventitious root growth from the crown of red clover constitutes a major portion of the root system in older stands. Two 2 yr old production fields and 3 yr old research plots were sampled in springs of 1988 and 1989 to determine the relationship between spring vigor and two root types of red clover. A higher average spring vigor rating was generally associated with the presence of well developed adventitious roots. / Five hundred and fifty-six red clover plants were dug in the fall of 1988 from a space planted (1 x 1 m centers) nursery established in the spring of the same year. Two divergent populations of 55 clones each were produced based on either a low or high score for adventitious root growth. The progeny of 32 single-crosses made within and between the two populations was evaluated for flowering habit and root types under spaced planting conditions during the 1989 growing season. / Six red clover cultivars were established in solid seedings to monitor adventitious root growth at three sampling dates.

The model plant Arabidopsis thaliana has been very successful thus far as a tool for understanding and studying the genetics of plant development. Analysis of its sequenced genome revealed the occurrence of duplicated chromosome blocks, resulting in duplicated genes. Duplicated genes, high in sequence and/or structure similarity, form gene families. One such family, of BRX-like genes, is presented in this thesis. All members contain a characteristic "BRX" domain that is required for BRX activity in planta. BRX (BREVIS RADIX), is a novel regulator of root growth in Arabidopsis. However, analyses of Arabidopsis single and double mutants with other gene family members, suggests that BRX is the only member with a dominating role in root development. Interestingly, BRXL1, although having BRX activity in the root, does not act redundantly with BRX in vivo, presumably because it is expressed at much lower levels than BRX. These two gene family members demonstrate the uncommon phenomenon of unequal genetic redundancy in plants. Another gene family member, BRXL4, although non-redundant with regards to BRX activity in the root, did display novel shoot-related phenotypes when over-expressed. In these lines the lateral shoots and hypocotyls showed increased Gravitropic Set-Point Angles resulting in the downward growth of the adult lateral shoots and a wide range of growth directions in the hypocotyls. Over-expression lines of BRXL4 also displayed seedling agravitropism. Auxin-induced transcription as monitored by the DR5::GUS reporter, is altered in these lines compared to wild-type. Additionally, hypocotyl curvature, stem bending and amyloplast localization profiles in response to a change in gravity vector, are also altered in these over-expression lines and in the brxl4 mutant compared to wild-type.

This investigation confirmed that plant reaction to Al was directed through the disruption of intercellular co-ordination existing between the cell populations comprising the root meristem. The first detectable response to A1 in the root involved disruption of Golgi apparatus function in the cap periphery. Ultrastructural changes in the cap periphery coincided with the presence of A1 in these cells. Conspicuous physiological changes involving cell enlargement, cell metabolism and root elongation were identified in cells initially remote from the site(s) of A1 uptake. Communication between A1-damaged peripheral root cap cells and the cell populations of the cap and proximal meristems, quiescent centre and region of cell growth was therefore indicated. A decrease in amyloplast numbers in response to increasing AI concentration coincided with diminished Golgi apparatus activity in the peripheral cap. These changes preceded detectable reductions in mitotic activity, indicated by decreases in cap volume and root length, and it was consequently suggested that control of intercellular activities in the root meristem may be directed through polysaccharide metabolism. Low concentrations of A1 (≤ 1,25 mg dm ¯³) produced a positive growth response in the primary root. This coincided with an increase in mean cap volume and these events were interpreted as an A1-induced release of the proximal meristem from growth inhibition originating in the cap. Experiments which followed the effect of decapping on the morphology of quiescent centre cells in the presence and absence of A1 supported the existence of a Golgi apparatus-derived morphogen involved in the control of Golgi apparatus secretory activity and plastid differentiation. In contrast to the controls (0 ABA). treatment of decapped roots with 2 X 10[-4] and 5 X 10[-5] M abscisic acid inhibited the development of Golgi apparatus secretory activity and plastid differentiation. It is postulated therefore, that an early response to AI may involve inhibition of the basipetal movement of an endogenous growth inhibitor originating in the cap, which may be ABA. The presence of A1 in the nutrient solution caused an efflux of H[+] from the root. Some of the more adverse plant responses to AI were initiated at A1 concentrations where the molar ratio of charge between Ca[2+] and A1[3+] favoured A1. An hypothesis for an electrophysiological plant response to A1 involving membrane hyperpolarisation by Al ions is developed. Chemical analysis of plant fractions did not connect A1-induced nutrient disorders with the primary expression of A1 toxicity. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1986.

To test the hypothesis that red-osier dogwood cuttings from a more stressful edaphic environment (dry site) would have a greater salinity tolerance compared with cuttings from a less stressful environment (moist site) a greenhouse experiment was designed. Cuttings collected from three sites in southeastern Manitoba varying in edaphic conditions (moisture) were exposed to 0, 25, 50, or 100 mM NaCl in hydroponics. After four weeks of treatment, physiological parameters were measured. No differences in salinity tolerance were observed between the sites; nevertheless, this study supported previous results suggesting that red-osier dogwood can limit the transport of Na+ from the root to the shoot. To determine the presence of barriers to ion movement, the roots of red-osier dogwood exposed to NaCl were sectioned and observed using brightfield and fluorescence techniques. A modified outer cortical layer was observed suggesting the presence of an exodermis, which would be an additional barrier to Na+ and Cl- movement. Furthermore, the maturation of the endodermis and exodermis occurring closer to the root tip could also contribute to limiting the transport of Na+ to the shoot.

Root disease is a serious concern for the softwood timber industry. This thesis reports on the development of a root disease detection procedure that applies lidar data integrated with imaging spectrometer data. Photosynthetic pigments are frequently cited as one of the most responsive indicators of vegetation stress. This study estimated pigment content from needle and canopy reflectance and characterized the sensitivity of these pigments to a fungal-mediated stress. Samples were collected from the Greater Victoria Watershed District on Vancouver Island, BC, Canada. Lab reflectance measurements were made and pigments were extracted. Reflectance spectra were transformed into derivative spectra and a continuum removal band depth analysis was conducted. Reflectance metrics were generated and used in modeling pigment content. Chlorophyll-a was found to be significantly affected by the disease in the needle level portion of this study. The predictive power of reflectance attributes were assessed and yielded strong coefficients of determination (R2>0.80). Samples exhibiting stress responses affected by root disease were discriminated. It was determined that younger trees were more severely affected by the root pathogen than mature colonized trees. In the canopy level component of the study, chlorophyll-a was estimated through the application of partial least squares regression and achieved an R2 value of 0.82. Continuum removal metrics, which proved to be good estimators at the needle level, were found to be insufficient at the canopy level. Through the use of hyperspectral forest chemistry products, potential root disease sites can be identified. / Graduate

Roots are essential for plant anchorage and nutrient uptake. Although root system architecture is genetically determined, its high level of plasticity allows rapid as well as long term adaptation to the plants' environment. To confer such adaptability, favorable alleles have been selected within species to endow them with an optimized root system. The identification of such favorable alleles is therefore a central component of research in plant breeding. / In an attempt to isolate novel factors that modulate root development, we exploited natural genetic variation in the model plant Arabidopsis thaliana. Tissue culture analysis of 44 accessions led to the identification of a line, Uk-1 (Umkirch-1), whose root system differs significantly from average accessions. A short primary root and an increased number of lateral and adventitious roots are typical for the Uk-1 root system, while the average Arabidopsis root system consists of a predominant primary root and few lateral roots. The major locus responsible for the Uk-1 phenotype, BREVIS RADIX (BRX), was successfully isolated by map-based cloning. Quantitative trait locus (QTL) analysis revealed that BRX is responsible for ca. 80% of the variance of the observed primary root length difference as compared to an average control accession. / BRX controls the extent of cell proliferation and elongation in the growth zone of the root tip and is a member of a novel, small family of proteins that contain three distinct and highly conserved domains of unknown function. BRX is a low abundant, nuclear protein, which is expressed in the phloem and the pericycle at the phloem poles. BRX is also expressed in the columella. Since BRX is not expressed in the root meristem, it must affect root growth in a secondary manner, likely by modulating responses to the plant hormone auxin. / Transcriptional profiling in root tissues revealed that BRX does so by maintaining optimal expression of the brassinosteroid biosynthesis gene CPD, and thereby optimal endogenous levels of the plant hormone brassinosteroid. Further analysis identified BRX as a central component of the interdependency of brassinosteroid signaling and auxin signaling.

Photocopy (positive) of typescript. / Thesis (Ph. D.)--University of Hawaii, 1964. / Bibliography: leaves 158-161. / xi, 171 l illus., tables

Copies of author's previously published articles inserted. / Bibliography: leaves 93-107. / viii, 108, 69 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Provides evidence for a specific, regulated, high affinity mechanism for entry of calcium and other divalent cations into the roots of wheat. / Thesis (Ph.D.)--University of Adelaide, Dept. of Botany, 1996?

Thesis (Ph. D.)--University of Adelaide, Dept of Soil Science, 1987. / Includes bibliographical references (leaves 207-222).