Latitudinal cline of requirement for far‐red light for the photoperiodic control of budset and extension growth in Picea abies (Norway spruce)

Abstract

To test for the effects of far‐red light on preventing budset in Picea abies, seedlings of six populations originating from latitudes between 67°N and 47°N were grown for 4–8 weeks in continuous incandescent (metal halogen) light at 300 µmol m−2 s−1 and 20°C and then transferred, at the same temperature, to a daily regime of 8 h incandescent light (300 µmol m−2 s−1) followed by 16 h cool white fluorescent light (40 µmol m−2 s−1). (Cool white lamps are deficient in far‐red light, with a R/FR ratio of 7.5 compared with 2.0 for the incandescent lamps.) All the seedlings from 67° and 80% of those from 64° stopped extension growth and set terminal buds within 28 days of the change of regime. The seedlings from 61° and further south continued growing, as did control seedlings from 67° grown as above but with incandescent light at 20 µmol m−2 s−1 replacing cool white illumination. To distinguish between a clinal and ecotypic pattern of variation, the interval between 64° and 59° was investigated by growing populations originating from that area in the same regimes as before. After 28 days in the cool white day‐extension regime, the percentage budset was 86 for the population from 64°, 0 for the population from 59° and 25–50 for the intermediate populations; i.e. the populations showed a clinal variation in requirement for far‐red light according to latitude. Thus northern populations of Picea abies appear to behave as ‘light‐dominant’ plants for the photoperiodic control of extension growth and budset, whereas the more southern populations behave as ‘dark‐dominant’ plants.

Clinal Variation at Phenology-Related Genes in Spruce: Parallel Evolution in FTL2 and Gigantea?

“…As a matter of fact, the northernmost populations collected along the Yenisei river at 66°N and 67°N grew on much poorer soil and had a significantly smaller dominant height than populations below latitudes 62°N. It could also reflect differences in the perception of light: Norway spruce populations from latitudes between 49°N and 64°N exhibited a clear latitudinal cline in their requirement of far-red light to prevent growth cessation and bud set, with a clear increase north of latitude 61°N (Clapham et al 1998). It would be interesting in future studies to sample more densely between 62°N and 67°N and to characterize more finely the environmental conditions.…”

Short-day photoperiods affect expression of genes related to dormancy and freezing tolerance in Norway spruce seedlings

“…The dates for start and termination of SD treatment are important because bud dormancy is promoted if the natural critical night length (i.e., night length known to promote bud set of a given provenance) is reached by the end of treatment (Kohmann and Johnsen 2007) and this prevents reflushing Granhus 2010, 2013). The required natural critical night length varies by provenance, whereby northern provenances and those from high altitudes need shorter night lengths to induce dormancy compared to southern provenances from lower altitudes (Dormling 1973;Heide 1974;Dormling 1979;Dormling and Lundkvist 1983;Clapham et al 1998). This suggests that different provenances will respond variably to different timing and durations of SD treatments.…”

Growth responses of Betula pendula ecotypes to red and far-red light

“…Such perception depends on the light requirement of those plants under consideration. Latitudinal ecotypes of northern tree species have different responses to light quality (Håbjørg, 1972;Junttila and Kaurin, 1985;Clapham et al 1998), which could indicate differences in composition of their phytochrome systems. In experiments using light sources enriched in R or FR light, differences in FR light requirement by latitudinal ecotypes have been indicated.…”