This thesis reports results of a study of relationships between photosynthetic activity and developmental parameters, and cambial activity (wood formation rate), during and following the period of active wood formation in untreated white spruce seedlings, and in seedlings stressed either by extensive stem incisions, or by tilting. The approach involved the use of two non-destructive methods for measuring photosynthetic activity: chlorophyll a fluorescence using optical instrumentation, and CO₂ uptake using infrared gas exchange techniques. Photosynthetic development was examined by estimating chlorophyll a content from a specific fluorescence parameter (O-level), and by the relative occurence of specific chloroplast stroma and membrane (thylakoid) proteins using electrophoretic and immunoblotting techniques. Cambial activity was determined using digitized image analysis of prepared cross-sections of seedling stems. Several fluorescence parameters were strongly correlated to cambial activity in untreated seedlings during the period of active wood formation (in mid-summer). However, the correlations were severely diminished or non-existent when cambial activity was arrested (in late-summer and autumn). Correlations between fluorescence and cambial activity in stressed seedlings were not discernible at any time, suggesting that the induced stresses resulted in a substantial alteration in normal source:sink relationships. Carbon dioxide uptake measures, either uncorrected or corrected to estimated chlorophyll α content, were not measurably correlated to cambial activity in untreated or stressed seedlings at any time in this system. Chlorophyll α content estimated from O-level fluoresecence, was not related to cambial activity in untreated or stressed seedlings. The relative occurences of two enzymes and proteins associated with photosynthetic carbon fixation, i.e. ribulose 1,5-bisphosphate carboxylase (Rubisco) and Coupling Factor, did not appear to be influenced by applied wounding and geotropic stresses. In contrast to the strong correlations found between fluorescence parameters and current season stem vigour, pre-season seedling height and cross-sectional stem areas were not related to stem vigour. These results suggest that in unstressed white spruce seedlings, the measure of specific chlorophyll α fluorescence parameters, using the methods delineated in this study, offers an alternative and more strongly predictive means of assessing current stem vigour, than measures of seedling dimensions. The results of this study provide strong evidence for, and a degree of elucidation on, the anticipated but previously unestablished existence of a source:sink relationship between leaves and vascular cambium in conifer seedlings. This information should provide an initial foundation for the elucidation of non-invasive methodologies by which to assess stem vigour of white spruce seedlings, and to probe source:sink relationships in other conifer species. / Science, Faculty of / Botany, Department of / Graduate

In response to concern over the failure and poor growth of many interior and white spruce plantations in British Columbia the effect of storage duration and soil temperature on the photosynthetic ability of white spruce seedlings was explored. Seedlings of Picea glauca were dark freezer stored (-5°C) from 9.6 to 30.6 weeks, thawed and grown for 28 days in a growth chamber at three different soil temperatures (3,7,11°C). During this period gas exchange variables and chlorophyll fluorescence kinetics were followed. Seedlings stored for periods of 22 weeks or longer had significantly lower rates of photosynthesis dependent on the outplanting soil temperature. Stomatal conductance was initially low upon outplanting and showed a recovery period of 4-7 days duration. The level of stomatal conductance increased in seedlings after they were stored for 26.1 weeks or longer. Chlorophyll fluorescence measurements of seedlings stored from 22 to 30.6 weeks showed a recovery period in photosynthetic efficiency (Fy/Fp) related to changes in photosynthesis. A decrease in seedling Fy/Fp with increasing periods of storage was noted at day 5 after outplanting. A disproportionate increase in new root growth with the increasing soil temperatures, measured after the 28 day growth period, suggested a soil temperature threshold for root growth exists between the 7°C and ll°C. In contrast, the stomatal conductance and photosynthesis results suggest the seedling shoots were not directly affected by the cold soil temperatures. In general, the results suggest Picea glauca seedlings stored longer than 22 weeks in freezer conditions have reduced photosynthetic ability, root growth and overall vigor. Fluorescence and bud break data suggest the reduction was possibly due to freezing damage sustained in storage affecting photosynthetic electron transport through photoinhibition upon returning seedlings to the light. / Forestry, Faculty of / Graduate