Functional characterisation of arabidopsis under acidic and aluminium stresses

Jayakumar Bose

    Research output: ThesisDoctoral Thesis

    191 Downloads (Pure)

    Abstract

    [Truncated abstract] Low pH and Al3+ toxicity coexist in acid soils, affecting root growth. Thus, Al3+ toxicity is always studied at low pH. Decades of research showed that Al3+ toxicity mechanisms are complex and still unclear. The reason for such ambiguity about Al3+ toxicity may be due to poor knowledge about the accompanying low pH stress (H+ toxicity) because (i) low-pH stress alone can cause poor root growth in diverse plant species, and (ii) plants are usually grown (for a long period) or just conditioned (for a few hours) in a low-pH (4.5) medium before applying Al3+ treatments. Hence, low-pH and combined low-pH/Al3+ stresses need to be separated in order to understand stressspecific toxicity and tolerance mechanisms in plants and ultimately to breed genotypes that are more tolerant of these two stresses in acidic soils. Arabidopsis thaliana mutants differing in Al sensitivity were used in this dissertation together with the wild type (Col-0) to characterise low-pH and combined low-pH/Al3+ toxicity and multiple tolerance mechanisms. One Al-tolerant mutant, alr104, which has high rhizosphere alkalinising capacity and two Al-sensitive mutants, als3 (defective in redistribution of accumulated Al away from Al-sensitive tissues) and als5 (defective in the Al exclusion mechanism), were tested. I would write as… One Altolerant mutant, (alr104) and two Al-sensitive mutants, (als3 and als5) were tested. Tolerant genotype alr104 has high rhizosphere alkalinising capacity, whilst als3 is defective in redistribution of accumulated Al away from Al-sensitive tissues and als5 is defective in the Al exclusion mechanism. The distal elongation zone of the root is the primary zone of Al toxicity: the zone acts as ‘plant command centre’ to integrate sensory inputs caused by diverse environmental stimuli into adaptive mechanisms. In addition, the importance of the mature root zone for plant nutrient acquisition is also beyond doubt. Accordingly, all the measurements
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2010

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