Sitka spruce (Piceasitchensis (Bong.) Carrière) seedlings were cultured using two nursery methods of blackout (short photoperiod) application: static treatment (constant day length of 14.28 h) and dynamic treatment (day length varying over length of experiment, with a mean of 14.28 h). Both methods when compared with a control (natural day length) reduced seedling height by inducing terminal bud set, increased seedling root weight, and decreased shoot to root and sturdiness ratios. Both static and dynamic blackout treatment seedlings had 26 and 30% lammas flush, respectively. Compared with control, both methods accelerated cold hardiness acquisition. After winter storage at −2 °C, treated seedlings flushed sooner than did control stock under light:dark temperatures of 25:20 °C. Under a cooler regime, 15:5 °C, differences among treatments were not significant. After planting in a common garden trial, terminal bud phenology had a range of treatment responses. Control seedlings flushed later and set bud sooner. Dynamic treatment seedlings' bud set phenology was nearest to that of controls. At a common garden trial and a reforestation site, blackout-treated seedlings had greater first-season terminal height increment. Planting check was observed for all treatments in the field during the second and third growing seasons. After five field seasons there was no height difference among treatments, and survival averaged 87%. Groundline stem diameter was never different among treatments. Biologically, the dynamic treatment is intermediate between the static and control treatments, but the static treatment is recommended because it is easier to apply in the nursery, and differences between the dynamic and static treatments were minimal.
Differences between shoots of normal and stagnant 20-year-old lodgepole pine were assessed in an attempt to elucidate possible causes of stagnated growth. Leaves of the stagnant plants are relatively short, narrow and few, and the intemodes between fascicles are short. At least on the site studied, foliar mineral concentration was the same for the two types of plant. Long shoot apical meristems are relatively small in height and diameter. The possibility that the differences reside in the apical meristem, i.e., are epigenetic rather than directly environmentally induced, was tested. Reciprocal grafts of vigorous and stagnant scions onto the two types of rootstock showed, however, that growth assumed that typical of the rootstock by the third growing season, and this was maintained in the subsequent season. This result, and the strong resemblance of stagnant shoots to those resulting from transplant shock, suggest that differences in the form and activity of the root systems is a potential cause of stagnation in lodgepole pine.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.