Elongation, rooting and acclimatization of micropropagated shoots from mature material of hybrid larch

Factors were defined for elongation, rooting and acclimatization of micropropagated shoots of Larix x eurolepis Henry initiated from short shoot buds of plagiotropic stecklings serially propagated for 9 years from an 8-year-old tree. Initiation and multiplication were on Schenk and Hildebrandt (SH) medium supplemented with 5 μM 6-benzyladenine (BA) and 1 μM indole-butyric acid (IBA). Stem elongation was obtained in 36% of the shoots on SH medium containing 0.5 μM BA and 63% of the remaining non-elongated shoots initiated stem elongation after transfer on SH medium devoid of growth regulators. Rooting involved 2 steps: root induction on Campbell and Durzan mineral salts and Murashige and Skoog organic elements, both half-strength (CD-MS/2), supplemented with 1 μM of both naphthaleneacetic acid (NAA) and IBA, and root elongation following transfer to CD-MS/2 medium devoid of growth regulators. Repeating this 2-step sequence yielded up to 67% rooted shoots. Acclimatization of plantlets ranged from 83% to 100%. Over 300 plants were transferred to the greenhouse; some showed plagiotropic growth

A means of accelerating red oak genetic tests

Half-sib seedlings from 19 mother trees were grown in containers under intensive cultural practices for 1 year and then field planted. Field growth was measured for 2 growing seasons. Height averaged 122 cm in containers and 189 and 190 cm the 1 and the 2nd years in the field. There were significant family differences for all growth characteristics. Narrow-sense individual tree heritability (17 families) for field height was extremely high, 0.89 in 1990 and 0.60 in 1991. First year growth characteristics, number of flushes, duration of shoot elongation (in days), and growth during the continuous flushing phase were measured and correlations developed with subsequent field height. Growth characteristics during the continuous elongation phase, number days of stem elongation, shoot length and growth rate, were significantly correlated with field height growth. Container production has the potential to speed genetic testing of northern red oak by rapidly producing large, high quality planting stock for field testing and by reducting confounding variation associated with seedling establishment.Une méthode rapide de mise en place de tests comparatifs de chêne rouge. Des semis de demi-frères issus de 19 arbres mères ont été élevés durant une saison dans des conteneurs dans des conditions de culture intensive, puis transférés en forêt. Des mesures de croissance ont été effectuées durant 2 saisons de végétation. La croissance moyenne était de 122 cm durant la première saison dans les conteneurs, puis de 189 et 190 cm au cours des 2 saisons passées en forêt. Des différences significatives ont été observées pour tous les caractères de croissance. Les héritabilités au sens strict de la hauteur totale (17 familles) étaient très élevées, 0,89 en 1990 et 0,60 en 1991. Les mesures durant la première saison (en conteneur) ont porté sur le nombre de pousses, la durée de l'élongation (en jours), et la croissance durant la phase d'élongation de la tige; elles ont été corrélées avec les caractères mesurés en forêt au cours des 2 saisons suivantes. Les caractères de croissance durant la phase continue d'élongation, la durée d'élongation, la longueur de la pousse et le taux de croissance étaient corrélés significativement avec la croissance en forêt. L'élevage en conteneur a l'avantage d'accélérer la mise en place des plantations comparatives de chêne rouge grâce à la production rapide de plants de taille importante et de bonne qualité. Elle tend également à diminuer la variation due à la crise de transplantation

Productivity differences among loblolly pine genotypes are independent of individual-tree biomass partitioning and growth efficiency

Genetic differences in individual-tree biomass partitioning, growth efficiency, and stem relative growth rate (RGR) could confer intraspecific productivity differences and might strongly influence forest ecosystem carbon storage. We examined the relationship between genotype productivity (stem volume), whole-tree biomass partitioning, growth efficiency (stem wood production per unit leaf area), and stem RGR among nine different loblolly pine (Pinus taeda L.) genotypes from three different genetic groups of contrasting inherent genetic homogeneity: three open-pollinated (half-sib) families, three mass-control pollinated (full-sib) families, and three clonal varieties. We hypothesized that genotype productivity would be positively associated with increased partitioning to stem wood relative to other plant parts, higher stem RGR, and enhanced growth efficiency. After 3 years under plantation conditions, genotypes showed significant differences in stem volume, percent stem wood, percent branch wood, and partitioning to fine roots, yet no differences in stem RGR or growth efficiency. Furthermore, genotypic differences in stem volume were independent of genotypic differences in biomass partitioning, and overall, we found no evidence to support the hypothesized relationships. Even so, the observed variation in biomass partitioning has implications for forest C sequestration as genotypes which partition more biomass to long-lived biomass pools such as stems, may sequester more C. Moreover, the lack of a genetic relationship between stem volume and belowground partitioning suggests that highly productive genotypes may be planted without compromising belowground C storage