Navegando por Autor "Perez, Junior Pastor Molina"

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Impacts of drought on coffee: integrating physiological and morphological processes from the leaf to the whole-plant scale
(Universidade Federal de Viçosa, 2018-04-09) Perez, Junior Pastor Molina; Matta, Fábio Murilo da
The water deficit negatively impacts plant growth and development through morphophysiological alterations, either at the leaf level or at the whole plant level. This study focused on the dynamics of ecophysiological and canopy architecture traits of two coffee cultivars, cv. RUBI MG1192 (Rubi: drought sensitive) and cv. IAPAR59 (I59: drought tolerant). The trials were conducted over two years; three irrigation treatments were applied (irrigated and non-irrigated during the dry seasons, and irrigated during the second dry season only). Samplings and measurements were performed at six times (7- 10 plants per treatment combination, totalling 211 plants). The following parameters were evaluated: relative growth rate, net primary productivity, leaf composition (C, N, and Δ13C), water-use efficiency, phenotypic plasticity, leaf water potential (ΨL), sap flow (SF), canopy conductance (gC), total soil-to-leaf hydraulic conductance (gL), branch setting (number and length), number of phytomers, leaf shedding and renewal, dynamics of leaf area and internode length; in addition, the patterns of light intercepted by the canopy was modelled. The cultivar which retained its leaves under severe drought (I59) proved to be more isohydric and more plastic for hydric functioning (SF, gC, and gL), demonstrating precocious adjustments to drought. In contrast, the leaf-shedding cultivar (Rubi) was more anisohydric and more plastic for late reactions to drought through, e.g. an increased root dry mass-to-leaf area ratio and leaf shedding with faster leaf renewal due to greater number of branches of second order. Despite marked differences in their hydric functioning, the two cultivars expressed similar vegetative growth, yield and recovery. Overall, drought had effects on all of the studied variables but no architectural trait appeared to be specifically responsive to water stress. Rubi displayed a greater proportion of higher order branches allowing a fast recovery of its leaf area from drought. This was associated with a high number of phytomers that in turn supported faster development of axillary buds (leaves and/or floral buds). The fitness of coffee plants submitted to climatic events depends on the adequacy of physiological and organo-morphogenetic features and, consequently, these aspects should be accounted for in breeding programs aimed at improving drought tolerance in coffee.