BIOLOGIA PLANTARUM 64: 20-31, 2020 DOI: 10.32615/bp.2019.070 20 This is an open access article distributed under the terms of the Creative Common Common BY-NC-ND Licence Biochemical and morphophysiological strategies of Myracrodruon urundeuva plants under water deficit L.M. SOUZA 1 *, M.R. BARBOSA 1 , M.B. MORAIS 2 , L. PALHARES NETO 1 , C. ULISSES 1 , and T.R. CAMARA 1 Programa de Pós-Graduação em Botânica, Universidade Federal Rural de Pernambuco, Dois Irmãos, 52171-900, Recife-PE, Brasil 1 . Programa de Pós-Graduação em Ciências Naturais, Universidade do Estado do Rio Grande do Norte, Mossoró/RN, 59600-000, Mossoró-RN, Brasil 2 Abstract In view of the ecological, social, and economic importance of Myracrodruon urundeuva Allemão, the objective of this study was to investigate the strategies of this species under drought during its initial phase of development. Two-month- old plants were cultivated under continuous irrigation or no irrigation for 20 d. After this period, the water-stressed plants were rehydrated for 20 d. Physiological, biochemical, and anatomical variables were evaluated on 20 th and 40 th day. Water deficit (25 and 85 % leaf relative content) caused senescence followed by leaf abscission. Growth in height was negatively affected by water deficit (37 % reduction). A decrease in the thickness of the mesophyll was accompanied by a decrease of the total chlorophyll content. Water deficit affected saccharide metabolism and altered cellular component dynamics. Enzyme activities were higher during the rehydration period than during the water stress. There was no increase in lipid peroxidation in plants subjected to water deficit. A reduction in the stomatal opening during water stress was a strategy of reducing water loss through transpiration. Additional key words: APX, CAT, chlorophyll, growth, leaf anatomy, relative water content, ROS, SOD, sugars. Submitted 21 December 2018, last revision 17 April 2019, accepted 24 April 2019. Abbreviations: APX - ascorbate peroxidase; CAT - catalase; LRB - leaf relative balance; MDA - malondialdehyde; ROS - reactive oxygen species; RWC - relative water content; SOD - superoxide dismutase. Acknowledgments: The authors are grateful to the Universidade Federal de Pernambuco and the National Institute of Semi-Arid for financial support, and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior for a scholarship to the first author. * Corresponding author; e-mail: lindomarsouza.ufrpe@gmail.com Introduction The ecogeographical domain of Caatinga is characterized by having sedimentary soils with poor water retention capacity, irregular rainfall, and a short warm and rainy period that is ideal for plant reproduction, and a dry period with almost no rainfall for 8 to 10 months per year (Amancio Alves et al. 2009, Santos et al. 2014, 2017). Because of its particular characteristics, Caatinga contains plant species that are adapted to water deficit by having xerophilous and deciduous leaves, a well developed root system, and closed stomata during the hottest periods of the day, which reduces transpiration (Moura et al. 2016, Maia et al. 2017). Other mechanisms used by plants under conditions of water scarcity are variations in epicuticular wax composition, stomatal density, water storage tissues, and the presence of trichomes (Barros and Soares 2013, Santos et al. 2014, Maia et al. 2017, Meira et al. 2017, Ribeiro et al. 2017) Under conditions of water deficit, plants adjust their sugar, protein, amino acid, chlorophyll, and carotenoid content in order to protect cells. For example, sugars and amino acids may affect osmotic adjustment by acting as osmoprotectants or serve as signaling molecules to prevent oxidative stress (Nishizawa et al. 2008, Vieira et al. 2017). Plant responses to various environmental factors are related to plants ability to control oxidants content, which is highly correlated with their tolerance to environmental stresses (Munné-Bosch et al. 2013). An increase in the production of reactive oxygen species (ROS) can cause a partial or total oxidation of cellular components including membrane lipids and DNA, and photosynthetic damage by inducing changes in the cellular redox status (Anjum et al. 2011, Kar 2011). Because of the multifunctional effects of ROS, cells need to control the accumulation of these molecules to prevent oxidative damage, so plants have developed an antioxidant defense system. Enzymatic components, such as superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT), and non-enzymatic components, such