Mikko Räisänen, Tapani Repo, Tarja Lehto. (2009). Cold acclimation of Norway spruce roots and shoots after boron fertilization. Silva Fennica vol. 43 no. 2 article id 208. https://doi.org/10.14214/sf.208

Keywords: boron deficiency; dieback; freezing tolerance; mineral nutrition

Abstract | View details | Full text in PDF | Author Info

Boron deficiency, manifested as shoot dieback, is a problem in conifer stands growing on soils with high nitrogen availability in Fennoscandia. Earlier observations on Norway spruce (Picea abies L. Karst.) suggest that freezing tolerance is decreased by boron deficiency. Here, the effect of boron fertilization on cold acclimation of Norway spruce was studied in a young stand with initially low boron status two years after fertilization. Buds, stems, needles and roots were collected at five sampling times during cold acclimation and subsequently exposed to series of freezing temperatures. Lethal temperatures of organs were assessed by electrolyte leakage method (EL) and visual scoring of damage (VS). Freezing tolerance of buds was measured also by differential thermal analysis (DTA). The mean boron (B) concentration in needles was 4 mg kg–1 in unfertilized and 21 mg kg–1 in B-fertilized trees while critical level of B deficiency is considered to be 5 mg kg–1. The risk for increased freezing injuries in the low-B trees was not evident since all trees achieved cold hardiness that would be sufficient in central Finland. At two sampling times out of five, shoots or stem of B-fertilized trees were slightly more freezing tolerant than non-fertilized trees. However, the present study does not give strong evidence for the hypothesis that decreased freezing tolerance in B deficiency would be a triggering factor for leader dieback in Norway spruce at the B levels studied.

Räisänen, University of Joensuu, Faculty of Forest Sciences, P.O.Box 111, FI-80101 Joensuu, Finland; (present address), FAForest, FI-83480 Ahonkylä, Finland E-mail: mr@nn.fi
Repo, Finnish Forest Research Institute, Joensuu Unit, P.O. Box 68, FI-80101 Joensuu, Finland E-mail: tr@nn.fi
Lehto, University of Joensuu, Faculty of Forest Sciences, P.O.Box 111, FI-80101 Joensuu, Finland E-mail: tarja.lehto@joensuu.fi

article id 328, category Research article

Pedro J. Aphalo, Markku Lahti, Tarja Lehto, Tapani Repo, Aino Rummukainen, Hannu Mannerkoski, Leena Finér. (2006). Responses of silver birch saplings to low soil temperature. Silva Fennica vol. 40 no. 3 article id 328. https://doi.org/10.14214/sf.328

Keywords: biomass; Betula pendula; photosynthesis; electrical impedance; mineral nutrients; soil temperature; stomatal conductance; water relations

Abstract | View details | Full text in PDF | Author Info

Two-year-old silver birch (Betula pendula) saplings were grown for a third growing season in controlled-environment rooms (dasotrons) at three soil temperatures (5, 10, and 20 °C). All trees grew the first flush of leaves, but the growth of the second flush was almost completely inhibited at the two lower temperatures. The dry weight of the second-flush leaves was 50 times larger at 20 °C than at 5 and 10 °C, with about 100 times more nitrogen. Root growth was less affected than shoot growth. Chlorophyll content, net assimilation rate and stomatal conductance were lower at low soil temperatures. The value of the cytoplasm resistance estimated from the electric impedance spectra was lower at 5 °C than at 10 or 20 °C. Leaf water potential was highest at the lowest soil temperature, and intercellular carbon dioxide concentration was only slightly lower in saplings growing in cooler soil. We conclude that the effect of long-term exposure to cold soil on net assimilation and growth was not caused by stomatal closure alone. It is likely to be additionally mediated by the limited nitrogen acquisition at the low soil temperatures, and perhaps additionally by some other factor. As the growth depression of aboveground parts in response to low soil temperature was more significant in silver birch than what has earlier been found in conifers, the relative changes in air and soil temperature may eventually determine whether birch will become more dominant in boreal forests with climate change.

Aphalo, University of Helsinki, Department of Biological and Environmental Sciences E-mail: pja@nn.fi
Lahti, The Finnish Forest Research Institute E-mail: ml@nn.fi
Lehto, University of Joensuu, Faculty of Forestry, Box 111, FI-80101 Joensuu, Finland E-mail: tarja.lehto@joensuu.fi
Repo, The Finnish Forest Research Institute E-mail: tr@nn.fi
Rummukainen, University of Joensuu, Faculty of Forestry, Box 111, FI-80101 Joensuu, Finland E-mail: ar@nn.fi
Mannerkoski, University of Joensuu, Faculty of Forestry, Box 111, FI-80101 Joensuu, Finland E-mail: hm@nn.fi
Finér, The Finnish Forest Research Institute E-mail: lf@nn.fi

article id 532, category Research article

Pedro J. Aphalo, Anna W. Schoettle, Tarja Lehto. (2002). Leaf life span and the mobility of “non-mobile” mineral nutrients – the case of boron in conifers. Silva Fennica vol. 36 no. 3 article id 532. https://doi.org/10.14214/sf.532

Keywords: needle age; conifers; model; boron; leaf life span; nutrient mobility; toxicity

Abstract | View details | Full text in PDF | Author Info

Nutrient conservation is considered important for the adaptation of plants to infertile environments. The importance of leaf life spans in controlling mean residence time of nutrients in plants has usually been analyzed in relation to nutrients that can be retranslocated within the plant. Longer leaf life spans increase the mean residence time of all mineral nutrients, but for non-mobile nutrients long leaf life spans concurrently cause concentrations in tissues to increase with leaf age, and consequently may reduce non-mobile nutrient use efficiency. Here we analyze how the role of leaf life span is related to the mobility of nutrients within the plant. We use optimality concepts to derive testable hypotheses, and preliminarily test them for boron (B), a nutrient for which mobility varies among plant species. We review published and unpublished data and use a simple model to assess the quantitative importance of B retranslocation for the B budget of mature conifer forests and as a mechanism for avoiding toxicity.

Aphalo, Faculty of Forestry, University of Joensuu, P.O. Box 111, FIN-80101 Joensuu, Finland; Current address Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, FIN-40351 Jyväskylä, Finland. E-mail: pedro.aphalo@jyu.fi
Schoettle, Rocky Mountain Research Station, 240 West Prospect Road, Fort Collins, CO 80526, USA E-mail: aws@nn.us
Lehto, Faculty of Forestry, University of Joensuu, P.O. Box 111, FIN-80101 Joensuu, Finland E-mail: tl@nn.fi

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