Genetic variances and selection efficiencies for growth traits of white spruce (Picea glauca (Moench) Voss) were estimated from clonally replicated full-sib progeny tests established both in nursery and field environments in New Brunswick, Canada. The available data included heights at 4, 5, and 6 years in the nursery test; height at 9 years, height, DBH, and volume at 14 years in the field test. Estimated variance components were interpreted according to an additive-dominance-epistasis model. For heights in the nursery test, while both non-additive and additive variances were important sources of genetic variation, the former decreased but the latter increased with age; among the non-additive genetic variance, the epistatic variance was much more important than the dominance variance. Different from the nursery traits, for traits in the field test, additive variance accounted for an average of 81% of the total genetic variance, whereas dominance variance explained most of the remaining genetic variance. Genetic parameters and selection efficiencies for three vegetative deployment strategies: deploying half-sib families (VD_FAM HS ), full-sib families (VD_FAM FS ), and multi-varietal forestry (MVF), were compared. Heritability estimates were moderate for VD_FAM HS and VD_FAM FS (0.61-0.72), high for MVF (>0.82) for the nursery heights, and high (>0.79) for the field traits for all strategies. Genetic correlations of volume at age 14 in the field test, the target trait for improvement, were strong (>0.85) with other field traits. Genetic correlations of VOL14 with the nursery heights were also strong (>0.71) at the half-sib and full-sib family levels, but were only moderate (>0.59) for MVF. Overall, practicing MVF is the most effective deployment strategy, yielding the highest genetic gains, followed by VD_FAM FS and VD_FAM HS , regardless of traits and selection methods. Furthermore, early selections for HT9 or for HT4-HT6 were very encouraging, resulting in higher gain in volume at age 14 on a per year basis.
Photosynthesis in balsam fir (Abies balsamea (L.) Mill.) was measured in the field at two locations in New Brunswick, Canada from late winter to late spring in 2004 and 2005. No photosynthesis was detectable while the soil remained below 0 degrees C throughout the rooting zone. In both years, photosynthesis began once soil temperature rose to 0 degrees C. In potted seedlings in growth chambers, there was no photosynthesis at an air temperature of 10 degrees C if the pots were frozen. These findings suggest that, once air temperatures permit photosynthesis, it is the availability of unfrozen soil water that triggers the onset of photosynthesis. In the field, full recovery of photosynthetic capacity following the onset of soil thaw was dependent on air temperature and took 5 weeks in 2005, but 10 weeks in 2004. There were two substantial frost events during the recovery period in 2004 that may explain the extended recovery period. In 2005, recovery was complete after the accumulation of 200 growing degree days above 0 degrees C after the start of soil thaw.
The relationship between certain morphological characteristics of white spruce (Picea glauca (Moench) Voss) planting stock (STK) and post-planting seedling performance was evaluated. Root system size at planting, its expansion, and its capacity to conduct water during the first post-planting weeks were determined. These characteristics were related to the performance of STK planted on two forest sites and measured for three growing seasons and to the performance of seedlings grown in large wooden boxes buried in the soil outdoors for one growing season (grown without competition from other vegetation). The compared STK were (i) polystyroblock grown, (ii) polystyroblock grown with chemical root pruning, and (iii) peat-board grown with mechanical root pruning. After three growing seasons on forest sites, seedlings with mechanically pruned roots grew more above ground than did seedlings from polystyroblock containers. This difference in seedling growth performance was even more significant for seedlings grown in wooden boxes. Of these, the mechanically pruned seedlings grew more not only above the ground but they also produced larger root systems by the end of the first growing season. This was despite the initially significantly smaller root systems of mechanically pruned seedlings, compared with the other two STK. Early (5-7 weeks after planting) post-planting root expansion patterns in the three STK were significantly different, with the roots of mechanically pruned seedlings growing less than the roots in the other two STK. In spite of this, pressure-probe measured hydraulic conductivity and water flux through root systems increased during the first post-planting weeks in mechanically pruned seedlings while declining or changing little in the other two STK. It was concluded that root system size at planting and its early post-planting expansion did not relate well to the root system hydraulic properties or to the post-planting seedling growth performance.
Deposition of major storage substances in the megagametophyte and embryo of white spruce (Picea glauca (Moench) Voss) was studied ultrastructurally and histochemically during seed development. Lipid bodies appeared to be secreted by the smooth endoplasmic reticulum. In the megagametophyte they were deposited rapidly from the club-shaped embryo stage until the early organogenesis of the embryo. Major lipid accumulation in the embryo took place during rapid cotyledon development and simultaneously with the buildup of protein bodies. Formation of protein bodies in the megagametophyte and in the embryo was first detected approximately 6 and 29 days after fertilization, respectively. It is suggested that in the megagametophyte, this process proceeded by (i) deposition of amorphous protein clumps onto tonoplasts of subdividing vacuoles during early stages of protein body formation, (ii) fusion of small cytoplasmic vesicles possibly derived from the rough endoplasmic reticulum, and (iii) deposition of protein around dense, membrane-bound vesicles attached to tonoplasts. The third process was not observed in the embryo. During advanced formation, fusion of cytoplasmic vesicles into developing protein bodies was the only process observed in the megagametophyte and in the embryo. White spruce seed protein bodies contained a variable number of crystalloids and globoid cavities except in the embryo in which only single globoid cavities were observed. Key words: Picea, ultrastructure, histochemistry, megagametophyte, embryo, seed.
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