| 1. |
- Eklund, Leif, et al.
(författare)
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Enhanced growth and ethylene increases spiral grain formationin Picea abies and Abies balsamea trees
- 2003
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Ingår i: Trees. - : Springer. - 0931-1890 .- 1432-2285. ; 17:1, s. 81-86
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Tidskriftsartikel (refereegranskat)abstract
- Spiral grain angle in Norway spruce (Piceaabies) trees and balsam fir (Abies balsamea) seedlingswas investigated in relation to growth rate, endogenousand applied ethylene. Trees from stands of Norwayspruce, which were irrigated and fertilised in order to enhancegrowth, and trees having different growth rates innon-treated stands were studied. Stem growth rate at thestand level (m3 ha–1 year–1) was measured annually, orby means of microscopy on stem sections as the numberand size of tracheids produced. Enhanced growth increasedethylene evolution and maintained a high levelof left-handed spiral grain angle in comparison to slower-growing trees. An increased number of earlywoodtracheids in fast growing trees was correlated to a moreleft-handed spiral grain angle. Ethrel, applied to stems ofbalsam fir seedlings, increased the internal ethylene levelsin parallel with increased left-handed spiral grain angle.The results indicate that ethylene regulates the extentof spiral grain angle.
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| 2. |
- Eklund, Leif, et al.
(författare)
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The influence of wind on spiral grain formation in conifer trees
- 2000
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Ingår i: Trees. - : Springer. - 0931-1890 .- 1432-2285. ; 14, s. 324-328
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Tidskriftsartikel (refereegranskat)abstract
- The correlation between spiral grain formationand crown asymmetry was investigated in 18 Scots pine(Pinus sylvestris L.) and 17 Norway spruce [Picea abies(L.) Karst.] trees selected from clones of each speciesgrowing in the south of Sweden. The angle between thelongitudinal direction of the tracheids in the outermostyear ring compared to the longitudinal direction of thestem was measured by scribing lines which followed thedirection of the tracheids. The crown asymmetry wasmeasured by taking photographs of the trees followed bya simple picture analysis of the tree. Wind data for thegrowing seasons of 1997 and 1998 were obtained fromthe Swedish Meteorological and Hydrological Institute.The results showed a significant correlation between theangle of the tracheids compared to the stem longitudinaldirection going from a left-handed angle if the trees hada crown projected to the north towards a right-handedangle the more the crown projects to the south.
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| 3. |
- Hjelm, Ulrika, et al.
(författare)
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Photosynthetic responses to short-term and long-term light variation in Pinus sylvestris and Salix dasyclados
- 2004
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Ingår i: Trees. - : Springer Science and Business Media LLC. - 0931-1890 .- 1432-2285. ; 18, s. 622-629
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Tidskriftsartikel (refereegranskat)abstract
- Trees-Structure and Function: 2004 18:622-629 Pinus sylvestris and Salix dasyclados, which differ in leaf longevity, were compared with respect to four aspects of photosynthetic light use and response: high light acclimation, photoinhibition resistance and recovery, lightfleck exposure and use and chloroplast acclimation across leaves. The first two aspects were examined using seedlings under controlled conditions and the other two were tested using trees in the field. When exposed to high light, shade leaves of Pinus acclimated completely, achieving the same photosynthetic capacities as sun leaves, whereas shade leaves of Salix did not reach sun leaf capacities although the absolute magnitude of their acclimation was larger. Shade leaves of Pinus were also more resistant to photoinhibition than those of Salix. Much of the direct light supplied within the canopy was in the form of rapid fluctuations, lightflecks, for Pinus and Salix alike. They exploited short lightflecks with similar efficiency. The greater proportion of diffuse light in the canopy for Pinus than Salix seems to lead to a lesser degree of differential intra-leaf acclimation of chloroplasts, in turn leading to lower efficiency of photosynthesis under unilateral light as reflected by a lower convexity, rate of bending, of the light-response curve. The differences in light use and responses are discussed in relation to possible differences in characteristics of the long and short-lived leaf.
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| 4. |
- Jönsson, Anna Maria, et al.
(författare)
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Frost hardiness in bark and needles of Norway spruce in southern Sweden
- 2001
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Ingår i: Trees. - : Springer Science and Business Media LLC. - 1432-2285 .- 0931-1890. ; 15:3, s. 171-176
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Tidskriftsartikel (refereegranskat)abstract
- Bark necrosis and resin flows in Norway spruce have increased in southern Sweden over the last few decades. Frost damage late in spring has been suggested as a possible cause, but other factors besides the climate may have contributed to the damage. The nutrient status influences the hardening processes and plants with poor nutritional conditions have an increased sensitivity to frost. In this study the sensitivity to frost of bark and the hardiness status of needles of Norway spruce were compared with the nutrient status at two sites with different soil fertility. The trees were 30-40 years old. The hardiness status of the bark and needles was negatively affected by low concentrations of P and Mg.
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| 5. |
- Uddling, Johan, 1972, et al.
(författare)
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Measuring and modelling leaf diffusive conductance in juvenile silver birch, Betula pendula
- 2004
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Ingår i: Trees-Structure and Function. - : Springer Science and Business Media LLC. - 0931-1890. ; 18:6, s. 686-695
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Tidskriftsartikel (refereegranskat)abstract
- Leaf diffusive conductance for water (g(l)) and twig xylem pressure (psi(xt)) was measured in juvenile silver birch, Betula pendula, under field conditions in southern Sweden. Data from one site were used to parameterise two different multiplicative models for g(l) (dependent data), and measurements from another site were used to validate these models (independent data). In addition, experiments were performed in controlled environments to validate the g(l) response functions used in the models. The driving variables in the D-model were photosynthetic photon flux density, air temperature and water vapour pressure deficit of the air (D-a), while the DH-model also included the accumulated hours after sunrise each day with D-a above a certain threshold (H). Both models satisfactorily predicted the variation in g(l) in dependent as well as in independent data, and the g(l) response functions used were supported by the experiments in controlled environments. The DH-model was more successful in predicting g(l) than the D-model by accounting for the observation that g(l) was lower at higher H under similar weather conditions. There was a considerable variation in maximum g(l) during the season, as well as between the two sites. On relatively warm and dry days psi(xt) rapidly declined during the morning and then stabilized around a constant value until the late afternoon, with the stomatal regulation effectively preventing psi(xt) from decreasing below this value. We suggest that these models could be used to simulate the g(l) in juvenile birch if maximum g(l) is locally estimated and if the response functions are not extrapolated beyond the climate range for this study.
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