Bud burst in Norway spruce (Picea abies): preliminary evidence for age-specific rest patterns

Abstract

This study examines the effect of chilling and photoperiod on rest completion and bud burst in Norway spruce [Picea abies (L.) Karst.] using twigs from both 15-year-old ("young trees") and 56-year-old ("old trees") trees. The material was transferred between September and May from outdoors to experimental forcing conditions with four different photoperiods. The bud burst percentage of the twigs from young trees generally increased in all photoperiods until the end of the year. After that it decreased until vernal equinox (March 20) and then increased steeply towards spring. This new observation of transient rest completion during autumn suggests that young trees have (I) a transient time window during late autumn when ontogenetic development is possible, and (ii) a secondary rest culminating approximately at the time of vernal equinox. In twigs from old trees the transient rest completion was much weaker as the bud burst percentages generally remained under 20 during autumn and winter. At vernal equinox there were no burst buds in twigs from the old trees in any photoperiod and after that the bud burst percentage increased basically in the same manner as in the young trees. The bud burst percentage of the twigs from young trees was generally higher as the photoperiod increased. However, no evidence for absolute long photoperiod requirement of rest completion was observed.

The Annual Phenological Cycle

“…Thus Linkosalo et al's (2006) hypothesis does not provide an adequate solution to the paradox (Table 3.5). Partanen et al (2005) found that the pattern of bud burst percentage, BB%, obtained with 15-year-old Norway spruce trees was different from both the typical pattern observed earlier with seedlings and the other pattern observed by Partanen et al (2005) with older trees. The BB% of the 15-year-old trees first increased in autumn, basically similarly to that observed with seedlings ( Fig.…”

“…3.20). These deviant findings obtained with differentially aged trees led Partanen et al (2005) to hypothesize that the environmental regulation of rest break and bud burst changes as the trees get older. This hypothesis is physiologically motivated, since several aspects of the seasonality of trees change with ageing (Ununger et al 1988;Vitasse 2013).…”

“…Similarly to the studies with long-term historical data sets, Hannerz (1999) found that simple temperature sum models that assumed rest completion on Hänninen et al (2007) 19 Fu et al (2012) a fixed calendar day predicted the timing of bud burst more accurately than more complicated models that also addressed the effects of chilling. Partanen et al (2005) studied the rest completion of naturally growing 56-year-old Picea abies trees by transferring twigs detached between September and May into forcing conditions in a greenhouse. Regardless of the night length applied in the forcing conditions, bud burst consistently occurred only in transfers made after mid-April (Fig.…”

Modelling the timing of Betula pubescens budburst. I. Temperature and photoperiod: a conceptual model

“…Various studies have shown an interaction between photoperiod and duration of exposure to chilling conditions on budburst timing (Heide 1993, Myking & Heide 1995, Partanen et al 2005, in which LDs promoted growth in birch after partial chilling exposure. Myking & Heide (1995) hypothesised that LDs acted as a substitute for chilling in partially chilled plants.…”

Significance of the root connection on the dormancy release and vegetative bud burst of Norway spruce (<i>Picea abies</i>) seedlings in relation to accumulated chilling

“…Therefore, in addition to young seedlings, branches detached from the trees have been commonly used in forcing experiments. Partanen et al (2005) for instance found that the bud burst percentage of detached twigs of Norway spruce trees varies during winter, and depends on the age of the tree. However, detaching the twig may affect its physiology.…”