Requirement for far‐red light to maintain secondary needle extension growth in northern but not southern populations of Pinus sylvestris (Scots pine)

Abstract

Extension growth of secondary needles is under photoperiodic control in Pinus sylvestris. To test for the effects of far-red light on maintaining this extension growth, seedlings of six populations originating from latitudes between 57 degrees and 67 degrees N were raised for 11 weeks in continuous incandescent (metal halogen) light at 300 &mgr;mol m-2 s-1 and 20 degrees C and then transferred at the same temperature to a daily regime of 8 h incandescent light (230 &mgr;mol m-2 s-1) followed by a 16 h day extension with cool white fluorescent light (40 &mgr;mol m-2 s-1, R/FR ratio 7.5) or with incandescent lamps (20 &mgr;mol m-2 s-1, R/FR ratio 2.0). For the seedlings from the three populations north of 64 degrees, needle extension growth over 42 days in the FR-poor day extension treatment was lower by up to 40% than in the FR-rich day extension treatment, whereas for the seedlings from the three southern populations the needle extension growth was similar in both day extension treatments. The requirement for FR in day extensions is characteristic of 'light-dominant' photoperiodic control mechanisms. It appears that P. sylvestris changes from dark-dominant night timekeeping to light-dominant day timekeeping with increasing latitude, as with the photoperiodic control of budset in Picea abies.

The optimal selective logging regime and the Faustmann formula

“…However, in countries at mid-range latitudes like Spain natural reproduction requires that older trees protect young trees against heat and water stress in the summer (personal communication by C. Gracia, University of Barcelona, Department of Ecology and CREAF, the Centre for Ecological Research and Forestry Applications). This finding is supported by field experiments reported by Clapham et al (2002) and Sanchez-Gomez et al (2006).…”

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

“…Differences in FR light requirement for growth extension were shown by latitudinal ecotypes of Salix pentandra (Junttila and Kaurin, 1985), Picea abies (Clapham et al 1998) and Pinus sylvestris (Clapham et al 2002). When the day-length was extended with FR-poor lamps, the southern ecotypes (south of 61 -64ºN) continued to grow while the northern ones ceased growth.…”

Light and temperature sensing and signaling in induction of bud dormancy in woody plants

“…Studies using light sources enriched in red (R) or far-red (FR) light demonstrated a demand for FR light to sustain growth in angiosperms as well as gymnosperms (Håbjørg 1972;Junttila and Kaurin 1985;Clapham et al 1998aClapham et al , 2002. This trait also shows a clinal variation.…”

“…Accordingly, similar to photoperiodic control of flowering, both phyA and phyB probably act in photoperiodic control of shoot elongation. Like SD plants, southern ecotypes of woody species respond to night breaks in a R-FR reversible manner (Clapham et al 1998a(Clapham et al , 2002. Thus, since low fluence R/FR reversibility is a characteristic for light stable phytochromes, such as phyB, a domination of a phyBlike-based system in southern ecotypes can be hypothesized.…”