Source‐sink patterns on coffee trees related to annual climate variability: An approach through stable isotopes analysis

Abstract

Stable isotopic determination constitutes a useful tool to identify the processes that control the dynamics of the carbon and nitrogen flow in plants, unraveling the mechanisms of their differential investment under different environments. This work aimed to evaluate the spatiotemporal variation of source‐sink patterns of coffee trees under field conditions in response to climatic conditions through the assessment of stable isotopes. For this purpose, stems, leaves, and fruit samples from coffee trees were collected following a temporal pattern based on the region's climatic characteristics and the plant's phenology and a spatial pattern considering different parts of the canopy. The carbon and nitrogen percentage content, the C/N ratio, and the carbon and nitrogen isotopic compositions (δ13C and δ15N) were determined for all samples. The basal portion of the orthotropic branch was also considered for the isotopic analysis of the tree's growth rings. The results obtained were correlated with the climatic variables of the region through a Pearson correlation analysis (p<0.05). Coffee plants showed traditional δ13C values of C3 plants. Temporal δ13C variation was associated with the different growth rates between phenological stages and the use of substrates produced at different times under different environmental conditions leading to differences in photosynthetic discrimination. Spatial δ13C variation was observed with heterotrophic tissues isotopically heavier than leaves, with a significant decrease trend in δ13C values from the top (upper third) to the bottom (lower third), associated with ecophysiological differences between the canopy, isotopic fractionation processes downstream of photosynthetic carbon discrimination, and the fixation of C from other pools. Temporal δ15N variation was associated with the precipitation rates in the region and the fertilization distribution across the tree, while the spatial variation was with the plant's nitrogen assimilation and translocation patterns. The tree growth rings isotopic analyses showed isotopic differences between growth rings of the same plant addressed by the climatic conditions, with precipitation being the primary climatic determinant influencing the fixation and discrimination against 13C. Our results highlight the importance of using stable isotope analysis as a reference point for coffee ecophysiological studies to characterize how the temporal and spatial patterns of δ13C and δ15N emerge and signal the influence of climate on the source‐sink relationship of coffee trees under field conditions.This article is protected by copyright. All rights reserved.

Increased fruit load influences vegetative growth, dry mass partitioning, and bean quality attributes in full-sun coffee cultivation

“…These results can serve as a guide to understanding the impact on the growth of coffee trees established in full-sun field conditions, particularly in years with high production during the crop production cycle (Flórez et al, 2016;Rendón, 2020). By manipulating the sink organs through varying fruit load intensities, it becomes apparent that fruits are dominant sinks with a high capacity for importing photoassimilates, especially when compared to other functional sink organs like expanding leaves and vegetative branches (Almeida et al, 2021;Toro-Herrera et al, 2023).…”

“…Coffee is a C3 perennial species, and various climatic, genetic, and nutritional factors influence its growth under tropical conditions (DaMatta, 2004;León-Burgos et al, 2022;Toro-Herrera et al, 2023). A negative correlation has been shown to exist between the growth of reproductive organs, specifically fruits, and vegetative shoot growth (Rakocevic et al, 2020).…”