Cellular stages of root formation, root system quality and survival of Pinus elliottii var. elliottii x P. caribaea var. hondurensis cuttings in different temperature environments

Time to first root in cuttings varies under different environmental conditions and understanding these differences is critical for optimizing propagation of commercial forestry species. Temperature environment (15, 25, 30 or 35 ± 2°C) had no effect on the cellular stages in root formation of the Slash × Caribbean Pine hybrid over 16 weeks as determined by histology. Initially callus cells formed in the cortex, then tracheids developed and formed primordia leading to external roots. However, speed of development followed a growth curve with the fastest development occurring at 25°C and slowest at 15°C with rooting percentages at week 12 of 80 and 0% respectively. Cutting survival was good in the three cooler temperature regimes (gt;80%) but reduced to 59% at 35°C. Root formation appeared to be dependant on the initiation of tracheids because all un-rooted cuttings had callus tissue but no tracheids, irrespective of temperature treatment and clone

Indole-3-butyric acid accelerates adventitious root formation and impedes shoot growth of Pinus elliottii var. elliottii × P. caribaea var. hondurensis cuttings

Many plantation tree species are cloned to achieve the growth, disease resistance and wood quality characteristics required for a successful economic venture. However, clonal propagation is limited by declines in adventitious root formation with increasing stock plant age. We examined the effects of immediate or delayed IBA application on adventitious root formation and subsequent root and shoot development of cuttings harvested from 8-year-old clonal hedge plants of Pinus elliottii var. elliottii × P. caribaea var. hondurensis. IBA applied at the time of setting accelerated root formation, elevating the percentage of cuttings with roots at 13 weeks post-setting from 45 to 78% and from 83 to 93% for a low- and a high-rooting clone, respectively. Final rooting percentages for the same treatments and clones (78 and 85%, and 88 and 100%, respectively, at 20 weeks post-setting) were not significantly affected by IBA application. IBA increased the root:shoot ratio of rooted cuttings by decreasing shoot weight compared with untreated cuttings, without affecting root weight, root length, root surface area or root volume. IBA was only effective when applied at the time of setting. A simple IBA treatment for cuttings from 8-year-old clonal hedges, by accelerating root production, has potential for reducing nursery costs and increasing the root system quality of containerised pine cuttings. © 2010 Springer Science+Business Media B.V