Source-sink patterns on coffee trees related to annual climate variability: an approach through isotopes,
carbohydrates, and spectral analysis
Coffea arabica. Resource allocation. Carbon / Nitrogen Flow. Metabolic Flux Vision
The coffee tree is subject throughout the year to adversities resulting from climatic events that can affect
the development and productivity of the crop. One of the processes highly influenced by climate is the
allocation and partitioning of carbon, with changes in the export/import of resources between source and
sink tissues. Thus, unraveling the mechanisms of differential allocation as well as the source-sink
relationship under different climatic conditions is of great relevance for management, agroecological and
socioeconomic issues. A quick and straightforward approach to assessing a plant's carbon status is to
measure the size of its overall non-structural carbon stock in periods of variable demand. However, longterm studies with this approach are scarce, making it difficult to understand the physiological processes and
controls involved. Thus, this thesis proposes the use of three analytical methods to address the spatiotemporal variation in source-sink relationship in coffee plants in field conditions: stable isotopic analysis,
carbohydrate profile analysis and near infrared spectroscopy (NIRS) analysis. The analysis of stable
isotopes constitutes a useful tool to identify the processes that control the dynamics of the carbon (C) and
nitrogen (N) flow. The isotopic ratio values reflect the interaction between all aspects of the relationship’s
carbon/water and plant nitrogen, allowing to know the chemical, physical and biological processes that
generate specific isotopic proportions. In turn, carbohydrate profile analysis is a tool that allows
determining the stock of the main non-structural compounds in plant organs. These compounds are the
main substrates for the primary and secondary metabolism of the plant and are determined in order to
improve the understanding of the processes of fixation, storage and remobilization of carbon and nitrogen
in the plant. Finally, the spectral analysis it is based on the absorption of electromagnetic radiation in the
near infrared region, collecting information about the relative proportions of C-H, N-H and O-H (S-H)
bonds, which are the primary constituents of organic compounds of plant tissue. Provides results with highrepeatability, requiring minimal sample preparation and allowing the evaluation of large samples. These
methods were used to achieve a "metabolic flux" vision that would allow us to understand the carbon and
nitrogen flows/allocation in response to the plant's phenology (alternating between vegetative /
reproductive cycles) and especially in response to the climate.