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Em 29 de outubro de 2025, Alan Novaes dos Santos, aluno 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 CAPES, por meio de videoconfer\u00eancia consequ\u00eancia, defendeu sua Disserta\u00e7\u00e3o de Mestrado intitulada, \u201cA influ\u00eancia dos ciclos de hidrata\u00e7\u00e3o descont\u00ednua em sementes no desempenho fotossint\u00e9tico de plantas de Sarcomphalus joazeiro<\/em> (Mart) Hauenschild submetidas a d\u00e9ficit h\u00eddrico\u201d<\/p>\n Drought is one of the primary abiotic factors directly affecting plant metabolism, causing molecular, anatomical, and morphophysiological changes that impact species growth and productivity. Under climate change scenarios, alterations in rainfall distribution patterns and intensity are expected to increase the frequency of drought events. Many plant species from semi-arid environments exhibit diverse strategies to ensure their survival throughout all developmental stages. Some species from the Brazilian dry forest display a physiological response known as seed hydration memory, which confers an important ecophysiological advantage in coping with irregular rainfall. Sarcomphalus joazeiro <\/em>Mart., a woody plant native to this environment, has been reported in the literature as exhibiting this strategy. Therefore, this study aimed to evaluate the potential influence of intermittent hydration (IH) on seeds of Sarcomphalus joazeiro <\/em>Mart. and its effects on photosynthetic performance during the early growth of plants cultivated under different water availability regimes. The seeds underwent chemical scarification with sulfuric acid for 120 minutes and were subjected to different IH cycles (0C and 3C), corresponding to 15 hours of hydration and 120 hours of drying, as determined by hydration and dehydration curves. Seeds were germinated in four replicates of 25 seeds per treatment, totaling 100 seeds for the 3 IH cycles and 100 seeds for the control (0 cycles). After germination, seedlings were acclimated in a greenhouse for 180 days and then subjected to different watering treatments: control (daily irrigation), suspension of irrigation for 28 days, followed by rehydration after 7 days, totaling 35 days of experimentation. Throughout the irrigation suspension period, analyses of soil and plant water status, photosynthetic parameters, and antioxidant enzyme activity were conducted. Results indicated that IH in seeds induced a photosynthetic strategy in seedlings under drought, characterized by controlled reductions in gross and net CO\u2082 assimilation rates, stomatal conductance, and electron transport rate during stress. This physiological adjustment likely functioned as a protective mechanism, preventing excess energy accumulation and reactive oxygen species generation, thereby preserving the integrity of photosynthetic complexes and associated biochemical apparatus. Consequently, plants derived from seeds with hydration memory induced by ID exhibited a faster and more efficient photosynthetic recovery after rehydration. These findings reinforce the role of hydration memory as a potential adaptive mechanism for Caatinga species, especially in the context of increased frequency and severity of prolonged drought events predicted under climate change.<\/p>\n Keywords<\/strong>: Seed hidratation memory, water stress, gas exchange, Caatinga.<\/p>\n A seca \u00e9 um dos principais fatores abi\u00f3ticos que afeta diretamente o metabolismo vegetal, provocando altera\u00e7\u00f5es moleculares, anat\u00f4micas e morfofisiol\u00f3gicas, com reflexos no crescimento e produtividade das esp\u00e9cies. Nos cen\u00e1rios de mudan\u00e7as clim\u00e1ticas, as altera\u00e7\u00f5es nos padr\u00f5es de distribui\u00e7\u00e3o e intensidade das chuvas, tendem a intensificar a ocorr\u00eancia desse fen\u00f4meno. Muitas esp\u00e9cies vegetais oriundas de ambientes semi\u00e1ridos apresentam diversas estrat\u00e9gias para garantirem a sua sobreviv\u00eancia em todas as fases do seu desenvolvimento. Algumas esp\u00e9cies da Floresta Seca brasileira apresentam em suas sementes uma resposta fisiol\u00f3gica conhecida como mem\u00f3ria de hidrata\u00e7\u00e3o de sementes, que confere uma importante vantagem ecofisiol\u00f3gica aos efeitos da irregularidade pluvial. O Sarcomphalus joazeiro <\/em>Mart., planta lenhosa nativa desse ambiente, \u00e9 reportado na literatura como sendo uma esp\u00e9cie que apresenta tal estrat\u00e9gia. Portanto, este trabalho tem como objetivo avaliar a poss\u00edvel influ\u00eancia da hidrata\u00e7\u00e3o descont\u00ednua (HD) em sementes de Sarcomphalus joazeiro <\/em>Mart. no desempenho fotossint\u00e9tico durante o crescimento inicial das plantas cultivadas sob diferentes regimes de disponibilidade h\u00eddrica, buscando tamb\u00e9m avaliar se a hidrata\u00e7\u00e3o descont\u00ednua promove altera\u00e7\u00f5es positivas na toler\u00e2ncia \u00e0 seca desta esp\u00e9cie. As sementes passaram por escarifica\u00e7\u00e3o qu\u00edmica com \u00e1cido sulf\u00farico, durante 120min, e foram submetidas a diferentes ciclos (0C e 3C) de HD correspondendo a 15 horas de hidrata\u00e7\u00e3o e 120 horas de secagem, valores determinados atrav\u00e9s das curvas de hidrata\u00e7\u00e3o e desidrata\u00e7\u00e3o. As sementes foram colocadas para germinar sendo 4 repeti\u00e7\u00f5es de 25 sementes para cada tratamento, totalizando 100 sementes para os 3 ciclos de HD, e 100 sementes para 0 ciclos. Ap\u00f3s a germina\u00e7\u00e3o, as pl\u00e2ntulas foram aclimatadas em casa de vegeta\u00e7\u00e3o por 180 dias, e ent\u00e3o submetidas a diferentes tratamentos h\u00eddricos, sendo eles: Controle- rega di\u00e1ria e Suspens\u00e3o de regas por 28 dias, seguida de Reidrata\u00e7\u00e3o ap\u00f3s 7 dias, totalizando 35 dias de experimento. Ao longo do per\u00edodo de suspens\u00e3o de regas, foram realizadas an\u00e1lises do status h\u00eddrico do solo e das plantas, de par\u00e2metros fotossint\u00e9ticos e da atividade enzim\u00e1tica antioxidante. Os resultados indicaram que a HD em sementes promoveu nas pl\u00e2ntulas submetidas \u00e0 seca, uma estrat\u00e9gia fotossint\u00e9tica, caracterizada por redu\u00e7\u00f5es controladas nas taxas brutas e l\u00edquidas de assimila\u00e7\u00e3o de CO\u2082, condut\u00e2ncia estom\u00e1tica e taxa de transporte de el\u00e9trons durante o estresse. Esse ajuste fisiol\u00f3gico parece ter atuado como um mecanismo de prote\u00e7\u00e3o, evitando o ac\u00famulo excessivo de energia e a gera\u00e7\u00e3o de esp\u00e9cies reativas de oxig\u00eanio, preservando a integridade dos complexos fotossint\u00e9ticos e do aparato bioqu\u00edmico associado. Como consequ\u00eancia, as plantas oriundas de sementes com mem\u00f3ria de hidrata\u00e7\u00e3o induzidas pela HD apresentaram recupera\u00e7\u00e3o mais r\u00e1pida e eficiente da fotoss\u00edntese ap\u00f3s a reidrata\u00e7\u00e3o. Os resultados refor\u00e7am o papel da mem\u00f3ria de hidrata\u00e7\u00e3o como um potencial mecanismo adaptativo para esp\u00e9cies da Caatinga, especialmente em um cen\u00e1rio de intensifica\u00e7\u00e3o de eventos de seca severa e prolongada previstos pelas mudan\u00e7as clim\u00e1ticas.<\/p>\n Palavras chave: <\/strong>Mem\u00f3ria de hidrata\u00e7\u00e3o de sementes; estresse h\u00eddrico; trocas gasosas; Caatinga.<\/p>\n indispon\u00edvel para consulta<\/p>\n
\nA influ\u00eancia dos ciclos de hidrata\u00e7\u00e3o descont\u00ednua em sementes no desempenho fotossint\u00e9tico de plantas de Sarcomphalus joazeiro<\/em> (Mart) Hauenschild submetidas a d\u00e9ficit h\u00eddrico<\/h3>\n
\nABSTRACT<\/strong><\/h4>\n
RESUMO<\/strong><\/h4>\n
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Alan Novaes dos Santos<\/b><\/span><\/strong>
\nA influ\u00eancia dos ciclos de hidrata\u00e7\u00e3o descont\u00ednua em sementes no desempenho fotossint\u00e9tico de plantas de Sarcomphalus joazeiro<\/em> (Mart) Hauenschild submetidas a d\u00e9ficit h\u00eddrico<\/p>\n
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