Biomass allocation in response to light and nitrogen availability: roles for gibberellin and auxin

• Ano de defesa: 2020
• Autor(a) principal: Henschel, Juliane Maciel
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Plantas - Reguladores; Biomassa vegetal; Hormônios vegetais; Fisiologia de Plantas Cultivadas
• Link de acesso: https://locus.ufv.br//handle/123456789/27905

Gibberellins (GAs) and auxins are plant hormones that regulate plant growth and development, as well as their responses to environmental conditions. GAs modulate the biomass allocation in root vegetables, and low levels of GAs induce root growth instead of shoots. Thus, it was investigated whether low levels of GAs, caused by the application of paclobutrazol (PAC), induce biomass allocation to roots of radish plants, increasing their production. In addition, it was investigated whether the increased biomass allocation to shoots 1n response to high-density (HD) of plants and to low light intensity (LL) can be reversed by the application of PAC. The results show that low levels of GAs (PAC treatment) inhibited the growth of radish plants, with stronger growth inhibition 1n shoots than roots. In addition, GAs regulated radish growth 1n response to LL, but not in response to HD of plants. The biomass allocation of radish mn response to LL was modulated by GA levels, which regulated the expression of genes related to auxin biosynthesis and cell expansion (EXP and XTH). Still, low levels of GAs altered the biomass allocation, contributing to the nutritional quality of tuberous roots of radish. Another important aspect of root growth 1s the modulation of root architecture in response to nitrogen availability. As auxins are central regulators of root growth, 1t was investigated how auxin transport, mediated by ABCB transporters, regulates root growth of Arabidopsis thaliana m response to different nitrogen sources and levels. It was observed that root growth mm response to nitrogen availabihity 1s a result of auxin redistribution instead of global auxin levels 1n roots. In addition, auxin transport mediated by ABCBI/ABCBI19, regulates the inhibition of lateral root emergence and root bending 1n response to ammonium and glutamine, whereas ABCB6/ABCB20 regulate root bending regardless of nitrogen source. This study provides new perspectives on the role of GAs and auxins on root growth and development mn response to irradiance and nitrogen availability. Keywords: Arabidopsis. Auxin. Biomass allocation. Light. Nitrogen. Gibberellm. Radish.