Growth and physiological responses of teak (Tectona grandis Linn. f.) clones to Ca, H and Al stresses in solution and acid soils

Abstract

The adaptation of teak to acid soils was tested by studying physiological responses of teak clones to varying concentrations of Ca, H (pH) and Al in solution and soil culture. Nutrient solutions containing 0.05, 0.8 or 10 mM Ca were adjusted to pH 4, 5, 6, or 7. Overall, the greatest growth was obtained with nutrient solutions containing 0.8 mM Ca at pH 6. Foliar Ca deficiency symptoms developed at 0.05 mM Ca. Sensitivity of teak clones to Al was tested at pH 4 and 0, 50 or 300 µM Al by staining of roots. Roots that were stained with Chromezurol S (CAS) also stained with hematoxylin, but not necessarily with Eriochrome Cyanine R (ECR). On the other hand, roots that stained with hematoxylin did not necessarily stain with CAS or ECR. This indicates that hydrolysis of Al (as detected by CAS) leads to membrane damage which is detected by hematoxylin. A selection of clones were grown in split pots containing either limed or non-limed soil, and Al activity in the soil solution related to root biomass. Five clones were identified as Al resistant in the solution screening, and two clones were Al resistant in the soil screen, with two clones resisting low pH and Al toxicity in soil and solution screens. This study revealed that some teak clones tolerate low pH soils and moderately toxic 25 µM {Al3+} activity, and may be suitable for poor soils, but soils used in Australia for teak plantations are often too hostile and would require amelioration.