The use of growth rings dimensional parameters has been an important tool for the understanding of growth, biomass allocation and climatic characterisation of forest species. However, its potential is unknown in perennial crops of socio‐economic importance, such as coffee. This work aimed to understand how the analysis of the growth rings can be used as a proxy to understand the climatic determinants of vegetative growth and biomass allocation in the different organs of coffee trees. The work was carried out in the southern region of Minas Gerais, Brazil. The structure of the growth rings of cross sections of the orthotropic stem of coffee trees (Coffea arabica L. cv. Arara) were analysed from 2011 to 2018, using standard dendrochronological techniques. Each year in that period was characterised climatically and by its bienniality. Pearson correlation statistical analysis was used for mapping the relation among annual radial growth rates of the trees and other assessed parameters as primary growth data, accumulated biomass and the climatic characteristics of the region on an annual and intra‐annual scale. During the study the water balance (conditioned by its components, Prec and ETo) and the maximum temperature were the main determinants of the characteristics of the formed ring and the plant biomass allocation. These growing characteristics were also influenced by the phenology that modulates the vegetative/reproductive growth cycles and in turn the biennial production cycles. The results show the potential of tree rings and dendrochronology as a tool that allows indirect, but long‐term, assessment of biomass allocation and growth in coffee trees.

Limited water availability in reforestation areas can compromise plant growth and development, especially for plants at early stages. In this context, the exogenous application of growth regulators, such as brassinosteroids (BRs), can be used to mitigate the negative effects of water restriction. The aim of this study was to evaluate the effect of the application of BRs (90% brassinolide + a brassinosteroid) on initial growth, gas exchange, leaf water potential and leaf anatomy in yellow Ipê (Handroanthus serratifolius), under water restriction conditions. Throughout the experimental period, plants were maintained in two different water regimes: WR1-plants maintained at 100% of the pot capacity; WR2-plants rehydrated with 50% of the evapotranspiration from the previous day. BRs were applied on three occasions during the experimental period, in five concentrations: C1, 0 g/L (application of distilled water); C2, 0.25 g/L; C3, 0.5 g/L; C4, 0.75 g/L; and C5, 1.00 g/L. The dry mass, root:shoot ratio, water status and leaf anatomy traits were evaluated at the end of the experimental period and were analysed in two-level factorial scheme (2WR  5BRs concentrations). The plant height, number of leaves, gas exchange and leaf chlorophyll content were evaluated four times during the experimental period and were analysed in a split-split-plot design (two WR  five BRs concentrations  four evaluation times). The differences between the means were evaluated by analysis of variance (ANOVA). Pairs of means were separated using the standard error of the difference between the means (SED) and the Fisher's protected least significant difference test (LSD) at p < .05. In addition, all variables were subjected to regression analysis, being the variables evaluated over time, analysed through a two-stage modelling approach. The results obtained indicate that the water deficit led to reductions in growth and gas exchange parameters, regardless of the exogenous application of the regulator; therefore, higher concentrations (C4 and C5) were the most harmful for the maintenance of metabolic and photosynthetic activity. The exogenous application of BRs in H. serratifolius plants attenuated the effects of water limitation on the leaf water potential, but was not able to mitigate for the negative effects in growth, gas exchange and leaf anatomy.

Rainfall exclusion experiments allow us assessing the effects of environmental stresses such as long-term water limitations on both leaf and canopy structural traits. This work aimed to evaluate how leaf anatomical traits and canopy development of productive coffee trees change when submitted to more dry conditions in the southern region of Minas Gerais -Brazil. The experimental plots have been set up in a plantation area in which is growing Coffea arabica L. cv. Mundo Novo-IAC 379-19, in a completely randomized arrangement, composed by three treatments: Control (C) -no gutter system; Control plus roof (Ĉ) and Exclusion system (E). Leaf anatomical and canopy traits were determined within a year at the end of each season: late Spring-2015 (Sp), and late Summer (Su), late Autumn (Au) and late Winter (Wi) -2016. During the studied period the rainfall exclusion condition led to a reduction in the relative water content (RWC) of leaves. In the leaf-level, as the dry condition increase, the leaves invested in thicker cuticles, reduced xylem and phloem areas and smaller stomata, especially with the rainfall exclusion. In the canopy-level, there was a remarkable reduction in leaf area index (LAI) especially in the winter as a strategy of reduction of transpiratory area, when the availability of water decreased around 25%. In a context of reduced water availability due to effects of climate change, coffee trees may be able to present modifications at both levels, to cope with the effects of this abiotic stress.

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