Fisiologia Vegetal
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/185
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Resultados da Pesquisa
Item The Tick Tock of Biological Clocks on Crop Domestication and Plant Environmental Responses.(Universidade Federal de Viçosa, 2022-02-25) Siqueira, João Antonio Batista de; Araújo, Wagner L.; http://lattes.cnpq.br/4599642186886817Timing governs practically all processes documented, and thus since is extremely complex to alter temporal dynamics. Meanwhile, precise mechanisms to monitor the time are fundamental to ensure life on Earth. Organisms naturally develop differential abilities to monitor the time, wherein the biological chronometers regulate spatiotemporal dynamics, ensuring the emergence of new cells and allowing the organism can anticipate unfavorable environmental conditions. In this context, the biological clocks are highlighted due to their ability to timekeeping the circadian rhythms, development, and metabolism. This thesis is largely focused on the investigation of the functions of biological clocks in the context of plant growth and stress response as well as on investigating the functional role of the photoperiod to mediate aluminum (Al) tolerance. To this end, several complementary approaches were undertaken to understand: (i) the significance of biological clocks on crop domestication; (ii) the diel regulation of the Al tolerance in plants; and (iii) the specific behavior of root clock and its implication on plant yield. Firstly, it was demonstrated that tomato domestication apparently synchronized the distinct biological clocks of this species. Notably, the results demonstrate how this synchronization has contributed to the increased yield of cultivated tomatoes yet reduced their ability to tolerate abiotic stresses in comparison with wild tomatoes. In an attempt to demonstrate this, it was investigated the significance of water supply at different periods of the day in tomatoes. To this end, Solanum pennellii and S. lycopersicum (cv. M82) plants were exposed to different watering regimes: at dawn, dawn/dusk, and dusk. I was noted that the dusk watering treatment promoted a significant reduction in the number of leaves only in M82, whereas the other watering treatments did not alter the plant height in both genotypes. By analyzing the height and number of leaves in the different genotypes (MT, SFT ox , and SP5G pen ), it was observed an overall trend, revealing that dusk watering treatment resulted in smaller plants with fewer leaves than dawn and dawn/dusk watered plants. In conclusion, the analyses of the impacts from differentperiods of watering during the day suggested that watering tomatoes near dusk can significantly improve crop yield. Next, and mostly based on recent evidence, it was discussed that modifications of the DNA and metabolic checkpoints can mediate Al tolerance. Accordingly, mitochondrial organic acid metabolism and the genetic manipulation of DNA checkpoints were demonstrated to be not sufficient to promote plant survival under high Al concentrations. Compelling evidence showed that DNA checkpoint alterations are coupled with significant changes in mitochondrial metabolism. Thus, it was suggested that interactions between both mechanisms can occur in plants with elevated Al tolerance, supporting their growth even in soils with excessive Al levels. Following, it was demonstrated that photoperiod is closely associated with Al responses, wherein short-days (SD) favor the Al tolerance and long- days (LD) are related to Al sensitiveness. Genes involved in DNA checkpoints are induced specifically under LD conditions, arresting cell divisions and root elongation. Likewise, it was described how the photoperiodic regulation shapes Al tolerance in plants, which can contribute to developing a stable tolerance to Al in crops. Furthermore, the evidence suggested the occurrence of unique developmental phases for roots, in which these would be uncoupled from shoot phases. Altogether, it was indicated new frontiers to be pursued in plant biology, which have enormous potential to enhance nutrient use efficiency and reduce the use of chemical fertilizers in the next generation of crops. Keywords: Domestication. Biological clocks. Energetic stress. Metabolism.Item Efeitos do alumínio sobre o metabolismo foliar e morfologia radicular em genótipos de milho contrastantes para a tolerância à seca(Universidade Federal de Viçosa, 2016-05-20) Siqueira, João Antonio Batista de; Ribeiro, Cleberson; http://lattes.cnpq.br/4599642186886817Plantas cultivadas frequentemente são acometidas pela toxidez desencadeada pelo alumínio (Al) no solo. Esse estudo foi conduzido de modo a examinar os efeitos do Al sobre a fisiologia de genótipos de milho com susceptibilidade (BRS1010) e tolerância (BRS1055) a seca, uma vez que as respostas a esses estresses são correlacionadas. Com esse intuito, plantas de milho (Zea mays L.) após 5 dias de germinação foram expostas a 0 ou 100 µM de Al por até 120 horas (h). O alongamento radicular (AR) foi reduzido em BRS1010 após 72 h de exposição ao Al, enquanto BRS1055 apresentou redução somente em 120 h de exposição ao Al. Inversamente, o alongamento caulinar (AC) e foliar (AF) foram incrementados em BRS1055 após 72 h da imposição ao estresse. Enquanto que em BRS1010 o AF se manteve constante, ocorrendo a redução no AC após 72 h de estresse por Al. Raízes de BRS1010 apresentaram danos morfológicos mais intensos que BRS1055, explicados pelos maiores níveis de Al na região da coifa e pelo maior engrossamento dos ápices radiculares. Folhas de BRS1010 exibiram acúmulo de glicose, sacarose, amido, aminoácidos e proteínas, indicando que o crescimento foi comprometido por limitações relacionadas a utilização desses metabólitos. A taxa de respiração no escuro (R E ) foi superior em folhas de BRS1055 em condições de estresse, assim, foram encontrados menores níveis de fumarato nesse genótipo. Enquanto, os níveis de malato foram superiores em folhas de BRS1010 diante da toxidez por Al. Dessa forma, o acúmulo de malato, possivelmente estaria condicionando BRS1010 a menores taxas de R E em condições de estresse por Al. Parâmetros fisiológicos e de crescimento exibiram baixas correlações em BRS1055, enquanto em BRS1010 esses parâmetros foram altamente correlacionados. Os resultados sugerem que os mecanismos de tolerância ao Al em BRS1055 estão relacionados a manutenção do crescimento por meio de ajustes metabólicos alternativos em folhas.