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Keywords:

  • Leucaena leucocephala;
  • VA mycorrhiza;
  • water relations;
  • leaf orientation;
  • droughr avoidance;
  • nutrient absorption

Summary

Plant growth characteristics, nutrient absorption and water relations were compared for plants of Leucaena leucocephala (Larn.) de Wir that were non-mycorthizal and those that were infected with the vesicular-arbuscular (VA) mycorrhizal fungus Glomus fasciculatum (Thaxter sensu Gerd.) Gerd. and Trappe. Mycorrhizal plants had substantially greater shoot and root dry weight, leaf area and root length than non-mycorrhizal plants, and alsos greater P, K, and Ca uptake. Leaf area was over five times greater and leaf conductance to water vapour diffusion was nearly twice as great for mycorrhizal plants, yet the difference between xylem pressure potential and soil water potential were considerably less in mycorrhizal plants than in non-mycorhizal plants. Stomatal responses to the humidity deficits of the air during the day were nearly twice as great in mycorrhizal plants. Leaflet folding and orientation responses to avoide direct sunlight during the day were also much greater in non-mycorrhizal plants. Lower leaf conductances and increased leaf folding leading to less absorption of sunlight may contribute significantly to the reduction in growth rate observed in non-mycorrhizal plants.