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Em 30 de setembro de 2022, Maria Fernanda da Costa Oliveira, aluna de mestrado do Programa de P\u00f3s-Gradua\u00e7\u00e3o em Biodiversidade Vegetal e Meio Ambiente do Instituto de Pesquisas Ambientais de S\u00e3o Paulo, bolsista CNPq, por meio de videoconfer\u00eancia em consequ\u00eancia do isolamento social causado pela pandemia do COVID-19, defendeu sua Disserta\u00e7\u00e3o de Mestrado intitulada, \u201cAvalia\u00e7\u00e3o da hidrata\u00e7\u00e3o descont\u00ednua em sementes de Sarcomphalus joazeiro <\/em>Mart. Hauenschild (Rhamnaceae) e sua influ\u00eancia nas respostas de pl\u00e2ntulas submetidas ao d\u00e9ficit h\u00eddrico\u201d.<\/p>\n A banca examinadora foi presidida pelo seu orientador Emerson Alves da Silva (Instituto de Pesquisas Ambientais \u2013 IPA) e composta pelo Dr. Marcos Vinicius Meiado (Universidade Federal de Sergipe \u2013 UFS) e pela Dra. Ana Karla Moreira Lobo (Lancaster University, UK).<\/p>\n A baixa disponibilidade h\u00eddrica afeta diretamente o banco de sementes presente na Caatinga e a sua capacidade de germina\u00e7\u00e3o. Assim, sendo a \u00e1gua um fator abi\u00f3tico essencial para o processo de embebi\u00e7\u00e3o, diversas esp\u00e9cies da Caatinga apresentam nas suas sementes uma estrat\u00e9gia fisiol\u00f3gica reportada na literatura como mem\u00f3ria h\u00eddrica, utilizada para mitigar os efeitos da irregularidade pluvial existente nesse ambiente. Sendo assim o objetivo do presente trabalho foi avaliar a ocorr\u00eancia de mem\u00f3ria h\u00eddrica em sementes de Sarcomphalus joazeiro <\/em>atrav\u00e9s da an\u00e1lise das altera\u00e7\u00f5es bioqu\u00edmicas em sementes submetidas a ciclos de hidrata\u00e7\u00e3o e desidrata\u00e7\u00e3o \u2013 HD e \u00e0 hidrata\u00e7\u00e3o cont\u00ednua e sua influ\u00eancia em plantas jovens oriundas dessas sementes submetidas a d\u00e9ficit h\u00eddrico, atrav\u00e9s de an\u00e1lises de par\u00e2metros ecofisiol\u00f3gicos, bioqu\u00edmicos e anat\u00f4micos. As sementes passaram por escarifica\u00e7\u00e3o qu\u00edmica com \u00e1cido sulf\u00farico, durante 120min, e foram submetidas a diferentes ciclos (0, 1, 2 e 3) de hidrata\u00e7\u00e3o e desidrata\u00e7\u00e3o \u2013 HD, correspondendo a 12 horas de hidrata\u00e7\u00e3o e 48 horas de secagem, valores determinados atrav\u00e9s das curvas de hidrata\u00e7\u00e3o e desidrata\u00e7\u00e3o, e \u00e0 hidrata\u00e7\u00e3o cont\u00ednua por um per\u00edodo de 183h, foram utilizadas 310 sementes por tratamento, o experimento foi realizado tr\u00eas vezes, sendo assim uma triplicata biol\u00f3gica. Foram realizadas coletas em cada ponto dos ciclos de hidrata\u00e7\u00e3o e desidrata\u00e7\u00e3o e ao longo do per\u00edodo de hidrata\u00e7\u00e3o cont\u00ednua e em diferentes intervalos de tempo (controle, 13h, 61h, 74h, 122h, 135h e 183h), ap\u00f3s o in\u00edcio da hidrata\u00e7\u00e3o das sementes, totalizando 7 coletas, sendo 30 sementes coletadas em cada uma, posteriormente foram congeladas com nitrog\u00eanio l\u00edquido e mantidas em ultrafreezer a -80\u00baC para posteriores an\u00e1lises bioqu\u00edmicas. As demais sementes dos tratamentos de\u00a0 hidrata\u00e7\u00e3o descont\u00ednua e hidrata\u00e7\u00e3o cont\u00ednua foram colocadas para germinar, sendo 4 repeti\u00e7\u00f5es de 25 sementes cada para cada tratamento, totalizando 100 sementes por ciclos de HD\u00a0 e 100 sementes provenientes da hidrata\u00e7\u00e3o cont\u00ednua, as plantas oriundas das sementes submetidas \u00a0a hidrata\u00e7\u00e3o cont\u00ednua n\u00e3o apresentaram germina\u00e7\u00e3o suficiente para obten\u00e7\u00e3o de plantas para a montagem do experimento, as que\u00a0 foram oriundas de sementes que passaram pelos ciclos de HD foram submetidas a diferentes ciclos de suspens\u00e3o de rega (Controle- rega di\u00e1ria, E7- a cada 7 dias, E14- a cada 14 dias, E21 a dada 21 dias e RE- plantas que depois de 28 dias de suspens\u00e3o de rega foram reidratadas). An\u00e1lises bioqu\u00edmicas foram realizadas, al\u00e9m de an\u00e1lises dos par\u00e2metros fotossint\u00e9ticos, status h\u00eddrico e anatomia foliar das plantas jovens. Os resultados mostraram que sementes submetidas a ciclos de HD apresentaram maior germinabilidade, maior \u00edndice de velocidade de emerg\u00eancia, menores valores de T50<\/sub> e acumularam maiores teores de prolina. As plantas jovens oriundas de 0, 1 e 2 ciclos de HD apresentaram redu\u00e7\u00e3o da assimila\u00e7\u00e3o l\u00edquida de carbono (A<\/em>) somente quando submetidas a estresse severo ap\u00f3s 21 dias de suspens\u00e3o da rega, as plantas oriundas de sementes que passaram por 3 ciclos de HD n\u00e3o apresentaram redu\u00e7\u00e3o significativa aos 21 dias de estresse h\u00eddrico para esse mesmo par\u00e2metro. As an\u00e1lises anat\u00f4micas demonstraram que em condi\u00e7\u00f5es de seca nota-se que, inicialmente nas pl\u00e2ntulas oriundas de sementes que passaram por 0, 1 e 2 ciclos de HD, apresentaram sintomas como perda de turgor nas c\u00e9lulas epid\u00e9rmicas da face abaxial e\/ou redu\u00e7\u00e3o na quantidade de gr\u00e3os de amido dos cloroplastos, ap\u00f3s reidrata\u00e7\u00e3o notou-se que nas pl\u00e2ntulas oriundas de sementes que n\u00e3o passaram pelos ciclos de hidrata\u00e7\u00e3o descont\u00ednua, as c\u00e9lulas epid\u00e9rmicas da face abaxial n\u00e3o completaram totalmente o processo de reidrata\u00e7\u00e3o plena. Os resultados obtidos comprovaram que os ciclos de HD das sementes conferiram uma maior toler\u00e2ncia \u00e0 seca nas plantas comprovando a exist\u00eancia de mem\u00f3ria h\u00eddrica nas mesmas.<\/p>\n Palavras-chave:<\/strong> Caatinga, trocas gasosas, potencial h\u00eddrico, anatomia foliar, sementes.<\/p>\n Low water availability directly affects the seed bank present in the Caatinga and its germination capacity. Thus, as water is an essential abiotic factor for the imbibition process, several Caatinga species present in their seeds a physiological strategy reported in the literature as seed hydration memory, used to mitigate the effects of rainfall irregularity existing in this environment. Thus, the objective of this work was to evaluate the occurrence of water memory in Sarcomphalus joazeiro<\/em> seeds through the analysis of biochemical changes in seeds submitted to cycles of hydration and dehydration – HD and continuous hydration and its influence on young plants from these seeds subjected to water deficit, through analysis of ecophysiological, biochemical and anatomical parameters. The seeds underwent chemical scarification with sulfuric acid, for 120 minutes, and were submitted to different cycles (0, 1, 2 and 3) of hydration and dehydration – HD, corresponding to 12 hours of hydration and 48 hours of drying, values determined through of hydration and dehydration curves, and continuous hydration for a period of 183h, 310 seeds were used per treatment, the experiment was carried out three times, thus being a biological triplicate. Samples were taken at each point of the hydration and dehydration cycles and throughout the period of continuous hydration and at different time intervals (control, 13h, 61h, 74h, 122h, 135h and 183h), after the beginning of seed hydration, totaling 7 collections, with 30 seeds collected in each one, subsequently frozen with liquid nitrogen and kept in an ultrafreezer at -80\u00baC for further biochemical analysis. The other seeds from the discontinuous hydration and continuous hydration treatments were placed to germinate, with 4 repetitions of 25 seeds each for each treatment, totaling 100 seeds per HD cycles and 100 seeds from continuous hydration, the plants originating from the seeds subjected to hydration continuous did not show enough germination to obtain plants for the experiment, those that came from seeds that went through the HD cycles were submitted to different water suspension cycles (Control- daily watering, E7- every 7 days, E14 – every 14 days, E21 at 21 days and RE- plants that were rehydrated after 28 days of withholding water). Biochemical analyzes were performed, in addition to analyzes of photosynthetic parameters, water status and leaf anatomy of young plants. The results showed that seeds subjected to HD cycles showed greater germinability, higher emergence speed index, lower T50<\/sub> values and accumulated higher proline contents. Young plants from 0, 1 and 2 HD cycles showed a reduction in net carbon assimilation (A<\/em>) only when subjected to severe stress after 21 days of water suspension, plants from seeds that underwent 3 HD cycles did not showed a significant reduction after 21 days of water stress for the same parameter. Anatomical analyzes showed that under drought conditions, it was noted that, initially, seedlings originating from seeds that underwent 0, 1 and 2 cycles of HD, showed symptoms such as loss of turgor in the epidermal cells of the abaxial surface and\/or reduction in the amount of starch grains from chloroplasts, after rehydration it was noted that in seedlings originating from seeds that did not go through discontinuous hydration cycles, the epidermal cells of the abaxial face did not completely complete the full rehydration process. The results obtained proved that the HD cycles of the seeds conferred a greater tolerance to drought in the plants, proving the existence of seed hydration memory in them.<\/p>\n Keywords<\/strong>: Caatinga, gas exchange, water potential, leaf anatomy, seeds.<\/p>\n![\"\"](\"https:\/\/smastr16.blob.core.windows.net\/pgibt\/sites\/242\/2024\/07\/maria-fernanda-da-costa-oliveira-ms-550x351.jpg\")
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\nAvalia\u00e7\u00e3o da hidrata\u00e7\u00e3o descont\u00ednua em sementes de Sarcomphalus joazeiro<\/em> Mart. Hauenschild (Rhamnaceae) e sua influ\u00eancia nas respostas de pl\u00e2ntulas submetidas ao d\u00e9ficit h\u00eddrico<\/h3>\n
\nRESUMO<\/strong><\/h4>\n
ABSTRACT<\/strong><\/h4>\n
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<\/a>Maria Fernanda da Costa Oliveira<\/strong><\/a>
\nAvalia\u00e7\u00e3o da hidrata\u00e7\u00e3o descont\u00ednua em sementes de Sarcomphalus<\/em> joazeiro<\/em> Mart. Hauenschild (Rhamnaceae) e sua influ\u00eancia nas respostas de pl\u00e2ntulas submetidas ao d\u00e9ficit h\u00eddrico<\/a><\/p>\n
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