The role of citrus rootstocks on metabolism and transport of photoassimilate in plants under water deficit

Author(s)

Simone Ferreira da Silva

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2020-07-23

Examining board members

Rafael Vasconcelos Ribeiro; Sara Adrián López de Andrade; Camila Pinto da Cunha; Neidiquele Maria Silveira; Sarah Caroline Ribeiro Souza

• Advisor: Rafael Vasconcelos Ribeiro

Abstract

An effective strategy to mitigate the impacts of water scarcity on citrus crops without affecting the vulnerability of orchards to disease is the diversified use of drought-resistant rootstocks. Studies involving Rangpur lime under water deficit seek to identify physiological mechanisms that give drought resistance to this rootstock, which represents the first step towards the development of new citrus rootstocks capable of ensure orchards good performance in periods of water shortage. The reducion of availability of water requires plants to strike a new balance between supply and demand for available resources, which can result in greater or lesser growth impairment depending on the strategy adopted by the rootstock. The reducion of availability water requires of plants a new balance between supply and demand for available resources, which can result in greater or lesser growth impairment depending on the strategy adopted by the rootstock. The allocation of photoassimilates is associated with source and sink relationship established under water deficit, and sink strength will depend on the metabolic activity of the sink organ influenced by regulatory adjustments in response to the water deficit. In this context, this study combined physiological analyzes with monitoring on the allocation of 13C-labeled photoassimilates and analysis of primary metabolite profile of source and sink organs, to assess how citrus rootstocks influence sink strength and identify which metabolites are altered in citrus plants under water deficit. Valencia orange plants grafted on Swingle citrumeleiro, Rangpur lime or Sunki mandarin were evaluated for response to water deficit and rehydration. Unlike the other species, Rangpur lime responded to initial variation in water availability by prioritizing root growth over shoot and demonstrating ability of its root system to increase the import of photoassimilates, which probably favored growth. In the roots, metabolic profile showed down-regulation of nucleotide metabolism and of shikimate and aspartate pathways, linked to the up-regulation of arginine and citrulline levels, stimulating in the aerial part a greater alternative energy supply and arginine and asparagine accumulation. In response to rehydration, it showed greater efficiency in the use of nitrogen, accumulating in greater proportion compounds with higher N/C ratio. The results suggest that greater sink strength and differentiated metabolic adjustments are involved in the resistance of the Rangpur lime to drought. Such information is essential for the direction of new studies that seek the development of new species of citrus rootstocks resistant to drought, an environmental condition that limits plant growth and productivity (AU)

• FAPESP's process: 15/14817-4 - The role of rootstocks on carbohydrate metabolism and transport in citrus species under water deficit
• Grantee: Simone Ferreira da Silva
• Support Opportunities: Scholarships in Brazil - Doctorate