Importância do cálcio na mitigação dos efeitos da restrição hídrica em eucalipto
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2022-05-11
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Universidade Federal de Viçosa
Resumo
O cultivo de eucalipto está entre as atividades do setor florestal mais importantes para a economia brasileira e mundial. Recentemente, o déficit hídrico tem sido o fator abiótico que tem mais afetado o crescimento e a sobrevivência dessas florestas. Por este motivo, a seleção de clones mais tolerantes à seca tem sido uma das principais estratégias adotadas nos novos plantios. No entanto, é necessário compreender os mecanismos responsáveis pela tolerância à seca nessas plantas e a influência dos nutrientes nesses processos. Diversos estudos têm dado foco ao nutriente cálcio (Ca), como importante mitigador da tolerância à seca em plantas. Assim, o objetivo desta tese foi identificar a importância do Ca nos mecanismos de tolerância à seca e os mecanismos e efeitos do suprimento deste nutriente na expressão dos transportadores de Ca (MCA1 e ACA11) e das proteínas intrínsecas de membranas (PIP) em raízes de eucalipto. Para atingir esses objetivos, mudas do clone de eucalipto VM01 (E. urophylla × camaldulensis), caracterizado como tolerante à seca, foram cultivadas em sistema hidropônico na presença ou ausência de Ca e submetidas à restrição hídrica pelo uso de polietilenoglicol 6000. Os resultados obtidos mostram que a restrição hídrica aumenta a expressão do ACA11 (transportador de Ca do vacúolo) e diminui a expressão do MCA1 (transportador de Ca na endoderme). Isso resulta em maior concentração de Ca nas raízes do clone VM01 em condições de seca. Esse fato favorece o crescimento de raiz e maior relação raiz/parte aérea, importantes caraterísticas que favorecem a sobrevivência das plantas em condições de déficit hídrico. As plantas cultivadas na presença de Ca sob restrição hídrica apresentaram maior hidratação, menores danos oxidativos e maior atividade de enzima antioxidante. Além disso, observou-se que em geral no início da seca houve regulação positiva das PIP (aquaporinas), uma estratégia importante para aumentar a absorção de água. Por outro lado, com aumento do tempo de seca a regulação gênica foi negativa, estratégia também importante para evitar a perda de água. Dessa forma, espera-se que o trabalho auxilie na identificação de mecanismos para a seleção de clones tolerantes a seca, contribuindo para proteção e manejo de plantios de eucalipto. Palavras-chave: Tolerância à seca. Nutrição. Aquaporinas. Transportadores de cálcio
Eucalyptus plantations is among the most important activities in the forestry sector for the Brazilian and world economy. Recently, water deficit has been the abiotic factor that has most affected the growth and survival of these forests. For this reason, selecting of drought tolerant clones has been one of the main strategies for new plantations. However, it is necessary to understand the drought tolerance mechanisms and the influence of nutrients on drought tolerance processes. Thus, the objective of this thesis was to identify the importance of Ca in the mechanisms of drought tolerance and the mechanisms and effects of the supply of this nutrient on the expression of Ca transporters (MCA1 and ACA11) and intrinsic membrane proteins (PIP) in roots of eucalyptus. To achieve these objectives, seedlings of eucalyptus clone VM01 (E. urophylla × camaldulensis), characterized as drought tolerant, were grown in a hydroponic system in the presence or absence of Ca and subjected to water restriction using polyethylene glycol 6000. The results showed that water restriction increases the expression of ACA11 (carrier of Ca in the vacuole) and decreases the expression of MCA1 (carrier of Ca in the endodermis). This results in a higher concentration of Ca in the roots of clone VM01 under drought conditions. This fact favors root growth and a greater root/shoot ratio that are important characteristics to plant survival under water restriction. That plants that are grown in the presence of Ca under water restriction have greater hydration, less oxidative damage and greater antioxidant enzyme activity. In addition, it was observed that, in general, at the beginning of the drought there was positive regulation of PIP, an important strategy to increase water absorption. On the other hand, with increased drought time, gene regulation was negative, which is also an important strategy to avoid water loss. Thus, it is expected that this work helps identifying and selecting drought-tolerant clones and contribute to the protection and management of eucalyptus plantations. Keywords: Drought tolerance. Nutrition. Aquaporins. Calcium transporters
Eucalyptus plantations is among the most important activities in the forestry sector for the Brazilian and world economy. Recently, water deficit has been the abiotic factor that has most affected the growth and survival of these forests. For this reason, selecting of drought tolerant clones has been one of the main strategies for new plantations. However, it is necessary to understand the drought tolerance mechanisms and the influence of nutrients on drought tolerance processes. Thus, the objective of this thesis was to identify the importance of Ca in the mechanisms of drought tolerance and the mechanisms and effects of the supply of this nutrient on the expression of Ca transporters (MCA1 and ACA11) and intrinsic membrane proteins (PIP) in roots of eucalyptus. To achieve these objectives, seedlings of eucalyptus clone VM01 (E. urophylla × camaldulensis), characterized as drought tolerant, were grown in a hydroponic system in the presence or absence of Ca and subjected to water restriction using polyethylene glycol 6000. The results showed that water restriction increases the expression of ACA11 (carrier of Ca in the vacuole) and decreases the expression of MCA1 (carrier of Ca in the endodermis). This results in a higher concentration of Ca in the roots of clone VM01 under drought conditions. This fact favors root growth and a greater root/shoot ratio that are important characteristics to plant survival under water restriction. That plants that are grown in the presence of Ca under water restriction have greater hydration, less oxidative damage and greater antioxidant enzyme activity. In addition, it was observed that, in general, at the beginning of the drought there was positive regulation of PIP, an important strategy to increase water absorption. On the other hand, with increased drought time, gene regulation was negative, which is also an important strategy to avoid water loss. Thus, it is expected that this work helps identifying and selecting drought-tolerant clones and contribute to the protection and management of eucalyptus plantations. Keywords: Drought tolerance. Nutrition. Aquaporins. Calcium transporters
Descrição
Palavras-chave
Eucalipto - Resistência à seca, Plantas - Efeito do cálcio, Déficit hídrico
Citação
BARROS, Patricia Ramalho de. Importância do cálcio na mitigação dos efeitos da restrição hídrica em eucalipto. 2022. 89 f. Tese (Doutorado em Solos e Nutrição de Plantas) - Universidade Federal de Viçosa, Viçosa. 2022.