Tree Physiology Advance Access published online on December 5, 2008
Tree Physiology, doi:10.1093/treephys/tpn016
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Root proliferation of Norway spruce and Scots pine in response to local magnesium supply in soil
1 College of Resources and Environmental Sciences, China Agricultural University, Beijing 100094, P.R. China
2 Corresponding author (junlingz{at}cau.edu.cn)
3 Institute of Plant Nutrition, Hohenheim University, Stuttgart, Germany
4 Department of Plant Nutrition, Institute of Crop Sciences, Humboldt University of Berlin, 14979 Grossbeeren, Germany
5 Leibniz – Institute of Vegetable and Ornamental Crops Theodor-Echtermeyer-Weg, 14979 Grossbeeren, Germany
 |
Abstract |
|---|
Nutrient sources in soils are often heterogeneously distributed. Although many studies have examined the root responses to local N and P enrichments in the soil, less research was conducted on root responses to Mg patches. New roots of pre-grown Mg-insufficient and Mg-sufficient plants of Norway spruce (Picea abies [L.] Karst.) and Scots pine (Pinus sylvestris L.) seedlings were allowed to grow into four other pots of equal size, which were placed under the tree-bearing pot. Soils in the lower pots were either unfertilised, or supplied with Mg, or NPK or a mixture of NPKMg sources. Plants were harvested after 9 months of growth. Compared to the corresponding controls (Mg versus unfertilised and NPKMg versus NPK), Mg additions did not have a significant effect on either root dry matter, total root length (TRL) or specific root length (SRL), irrespective of tree species and plant Mg nutritional status. In contrast, NPK and NPKMg additions significantly increased the root dry matter and TRL in the nutrient-rich soil patch, and decreased SRL in Norway spruce. However, the observed root morphological changes did not occur in Scots pine. Root Mg concentrations were increased in Mg-rich soil patches, but those accumulations varied with tree species. Mg accumulation in a marked patch was measured only in newly grown roots of Mg-sufficient Norway spruce, whereas a more homogenous distribution of Mg concentration was observed for all newly grown roots in Mg-insufficient trees in the four soil treatments. In Scots pine, Mg accumulations occurred in both Mg-insufficient and Mg-sufficient plants. These results suggest that Mg patches in the soil may not lead to a local increase in root growth, but to Mg uptake and root Mg accumulation. Tree roots react differently to Mg patches in comparison to their response to N or P patches in the soil.
Keywords: coniferous tree, nutrient concentrations, nutrient-enriched soil, nutrient patches, plant nutritional status, root growth, root plasticity