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    Root Morphological and Physiological Bases to Understand Genotypic Control of Mineral Acquisition in Rice Grains

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    CHITTOORI-DISSERTATION-2012.pdf (5.764Mb)
    Date
    2012-11-28
    Author
    Chittoori, Ratnaprabha 1982-
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    Abstract
    Rice (Oryza sativa L.) supports half of the human population. However, predominant rice consumption leads to malnutrition due to mineral deficiencies. The research goal was to support identification of genes responsible for the uptake/accumulation of potassium (K), iron (Fe), zinc (Zn) and molybdenum (Mo), thus promoting the breeding for rice with high grain concentrations of these elements. Prior studies identified rice genotypes with high grain-K, -Fe, -Zn or -Mo concentrations that were hypothesized to be due to differences in root traits. The research objective was to identify root traits associated with these elements. These traits could be bases for identifying genes. The first study determined if these genotypes showed similar accumulation patterns in leaves as in grains, which would hint at influences of the roots and enable identifying distinct root traits and possible genes in vegetative growth stages. The second study determined if root traits of high grain-Mo genotypes displayed an acid-tolerance mechanism as these genotypes originated from Malaysia where acidic soils strongly adsorb Mo making it unavailable for plants. The third study identified root trait differences of high grain-K, -Fe, -Zn and -Mo genotypes in hydroponics media, while the fourth determined root trait differences in these genotypes in sand-culture media including a 1-Naphthalene Acetic Acid (NAA) seed treatment for perturbation. The first study identified several high grain-Mo genotypes with similar Mo accumulation patterns in V4 to V6 stage-leaves as in grains, suggestive of a root influence. The second study established that gross morphological and physiological root traits of a high grain-Mo genotype were not part of an acid-tolerance mechanism. Neither the third nor fourth study identified root traits related to shoot K, Fe, Zn or Mo concentration, however positive associations of seedling vigor traits with several beneficial elements, including K, and negative associations with numerous toxic elements were established. Lack of correlation with root traits suggests other mechanisms (e.g. active uptake transporters) instead control the observed grain accumulation differences. Based on the fourth study, either direct effects of NAA on element uptake/transfer or indirect effects on soil pH and redox potential altered tissue Fe and Zn levels.
    URI
    http://hdl.handle.net/1969.1/148287
    Subject
    oryza
    imaging
    Photocapture 360
    WinRhizo
    ionome
    ionomics
    element
    nutrient
    mineral
    grain
    leaf
    rice
    genotype
    phenotype
    physiology
    morphology
    Root
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    • Electronic Theses, Dissertations, and Records of Study (2002– )
    Citation
    Chittoori, Ratnaprabha 1982- (2012). Root Morphological and Physiological Bases to Understand Genotypic Control of Mineral Acquisition in Rice Grains. Doctoral dissertation, Texas A&M University. Available electronically from http : / /hdl .handle .net /1969 .1 /148287.

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