I used a data-set of 986 plant species (from 493 genera in 195 families) obtained from a literature search and a new data collection for 58 tropical tree species (from 31 genera in 18 families) growing in two contrasting forest types in Brunei Darussalam: mixed dipterocarp forest on moderately infertile ultisols and fluvisols, and heath forest on acidic and nutrient-poor spodosols. I provide statistical evidence for the existence of discreet groups of species representing Al accumulators and non-Al accumulator based on foliar Al concentrations. The threshold foliar Al concentration was higher for tropical plants (range 2.3-3.9 mg Al g<sup>-1</sup>) than temperate plant (1.1 mg Al g<sup>-1</sup>). Species’ mean log foliar Al concentration was also higher for tropical (0.73 ± 1.11 mg Al g<sup>-1</sup>) than temperate plants (0.16 ± 1.07 mg Al g<sup>-1</sup>). I used the tropical Al accumulating shrub <i>Melastoma malabathricum </i>L. as a study species to test the hypotheses that growth would be stimulated by Al addition. Growth of <i>M. malabathricum </i>seedlings was stimulated by Al addition when the external supply of macronutrients was very low, and this growth response was associated with an increase in net assimilation rate and specific leaf area. Foliar Al concentration was positively correlated with foliar concentrations of Ca and Mg across 16 Al accumulator species sampled in the field study in Brunei Darussalam, while foliar Al and K concentrations were correlated positively in <i>M. malabathricum </i>seedlings growing in the solution culture experiments. These positive correlations contradict the hypothesis that Al inhibits the uptake of nutrient cations and they may contribute to the positive growth response to Al addition in Al accumulator plants.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:540338 |
| Date | January 2010 |
| Creators | Metali, Faizah Haji |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=165794 |
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