Functional Significance of Al hyper-accumulation in Tropical Forest Trees

Numerous plant species take up and store high concentrations of Al from the soil system, despite the toxicity of Al3+ to plant metabolism. One example is Tea (Camelia sinensis), which contains approximately 1% Al in mature leaves. The physiological mechanisms and ecological function of Al hyper-accumulation are unknown, but there has been recent evidence published that the trait may help to regulate soil pH in the rhizosphere to enhance uptake of essential plant nutrients, and speculation that high Al concentrations in plant tissues act as a chemical defence against herbivores or pathogens. We have developed the tropical shrub Melastoma malabathricum as a model species for conducting experimental work on Al accumulation based on growing plants in a hydroponic system which allows tight control of the nutrients supplied to the plants. The aim of this PhD studentship project would be to test competing hypotheses relating plant tissue Al concentration to regulation of soil pH vs deterrence and performance of herbivores or plant pathogens. The experimental work will be supplemented by fine-scale measurement of the distribution of Al in plant tissues using fine-scale microscopy and exploration of tropical forest floras to discover and map the biogeography and evolution of this key under-explored plant functional trait.

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