Vulnerability to embolism in citrus species: hydraulic characteristics, seasonal variation and relationships between canopy and rootstock

• Grant number: 18/09834-5
• Support type: Scholarships in Brazil - Doctorate
• Effective date (Start): January 01, 2019
• Effective date (End): December 31, 2021
• Field of knowledge: Agronomical Sciences - Agronomy
• Principal Investigator: Rafael Vasconcelos Ribeiro
• Grantee: Marcela Trevenzoli Miranda
• Home Institution: Instituto Agronômico (IAC). Agência Paulista de Tecnologia dos Agronegócios (APTA). Secretaria de Agricultura e Abastecimento (São Paulo - Estado). Campinas , SP, Brazil

Abstract

The practice of grafting affects the plant susceptibility to water deficit since rootstock and canopy exhibit different resistance to drought. In xylem vessels, the tension generated by transpiration can cause formation of embolism, which reduces the ability of plants to carry water. The vulnerability of branches to embolism varies throughout the growing season of plants as well as after a drought event. This study aims to evaluate the water relations of citrus species under field conditions and to reveal the structural and functional bases of embolims susceptibility, as well as to evaluate the association of these characteristics with the tolerance to drought in citrus. As hypotheses, we have that species and varieties of canopies grafted on the same rootstock present different hydraulic characteristics; rootstock species changes the susceptibility to embolism of canopies; hydraulic conductivity and vulnerability to embolism vary throughout the year, and the branches of trees with growing fruits have higher hydraulic conductivity. For this, we will do a study of hydraulic characterization of different canopy/rootstock combinations with importance for Brazil, besides a study of the seasonal variation of these characteristics in plants in the field. The hydraulic conductivity, hydraulic safety margin, anatomy, contribution of aquaporins to water transport, water potential and leaf gas exchange in orange trees of the Valencia, Pêra and Hamlin varieties, of Ponkan mandarin and of Tahiti lime based on Rangpur lime and Valencia sweet orange grafted on Rangpur lime, citrumelo Swingle and citrandarin. The selection of drought tolerant materials could be anticipated by understanding the characteristics that induce greater embolism resistance, this may be a tool used in citrus breeding programs. (AU)