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Em 13 de dezembro de 2022, a aluna \u00darsula Caroline Salvaterra Batista, do programa de P\u00f3s-Gradua\u00e7\u00e3o em Biodiversidade Vegetal e Meio Ambiente do Instituto de Pesquisas Altera\u00e7\u00f5es clim\u00e1ticas dr\u00e1sticas t\u00eam sido previstas para o final deste s\u00e9culo, com um decl\u00ednio de chuvas em diversas regi\u00f5es do globo, e aumento na frequ\u00eancia e intensidade de eventos extremos, como a seca, em regi\u00f5es tradicionalmente \u00famidas. A Mata Atl\u00e2ntica \u00e9 um hotspot<\/em> mundial que abriga um grande n\u00famero de esp\u00e9cies vulner\u00e1veis e amea\u00e7adas de extin\u00e7\u00e3o e seu cont\u00ednuo desmatamento, associado \u00e0s mudan\u00e7as do clima, p\u00f5e em risco a biodiversidade deste bioma. Mais de 70% das brom\u00e9lias ocorrem na Mata Atl\u00e2ntica, dentre elas a esp\u00e9cie alvo deste estudo, Acanthostachys pitcairnioides<\/em>, end\u00eamica dessa regi\u00e3o. A. pitcairnioides<\/em> \u00e9 uma brom\u00e9lia ep\u00edfita pertencente \u00e0 subfam\u00edlia Bromelioideae. Nas brom\u00e9lias ep\u00edfitas, as folhas s\u00e3o o principal meio de Palavras-chave:<\/strong> CAM; Ep\u00edfita; Mata Atl\u00e2ntica; Osmorregula\u00e7\u00e3o; Seca<\/p>\n Drastic climate changes have been predicted for the end of this century, with a decline in rainfall in several regions of the globe, and an increase in the frequency and intensity of extreme events, such as drought, in traditionally humid regions. The Atlantic Forest is a global hotspot that is home to a large number of vulnerable and endangered species and its continuous deforestation, associated with climate change, puts the biodiversity of this biome at risk. More than 70% of bromeliads occur in the Atlantic Forest, among them the target species of this study, Acanthostachys pitcairnioides<\/em>, endemic to this region. A. pitcairnioides<\/em> is an epiphytic bromeliad belonging to the subfamily Bromelioideae. In epiphytic bromeliads, leaves are the main means of obtaining and Keywords:<\/strong> Atlantic Forest; CAM; Drought; Epiphyte; Osmoregulation<\/p>\n
\nAmbientais (IPA), bolsista CAPES, defendeu a disserta\u00e7\u00e3o de mestrado intitulada: \u201cRespostas morfofisiol\u00f3gicas e metab\u00f3licas de Acanthostachys pitcairnioides<\/em>(Mez) Rauh
\n& Barthlott (Bromeliaceae) ao d\u00e9ficit h\u00eddrico\u201d. A banca examinadora foi presidida pela orientadora Mar\u00edlia Gaspar (IPA) e contou com a participa\u00e7\u00e3o de Catarina Carvalho Nievola (IPA) e de Kleber Resende Silva (Instituto Tecnol\u00f3gico Vale). A defesa foi realizada no formato remoto\/virtual, por meio da Plataforma Teams.<\/p>\n![\"\"](\"https:\/\/smastr16.blob.core.windows.net\/pgibt\/sites\/242\/2024\/07\/ursula_caroline_salvaterra_batista_ms.jpeg\")
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\nRespostas morfofisiol\u00f3gicas e metab\u00f3licas de Acanthostachys pitcairnioides<\/em> (Mez) Rauh & Barthlott (Bromeliaceae) ao d\u00e9ficit h\u00eddrico<\/h3>\n
\nRESUMO<\/strong><\/h4>\n
\nobten\u00e7\u00e3o e armazenamento de carbono, nutrientes e \u00e1gua, esta \u00faltima na forma de neblina ou \u00e1gua da chuva. Embora A. pitcairnioides<\/em> seja classificada como tendo metabolismo fotossint\u00e9tico do tipo C3, em fun\u00e7\u00e3o de an\u00e1lises de dC13 (Crayn et al. 2015), a esp\u00e9cie, al\u00e9m da proximidade filogen\u00e9tica com A. strobilaceae<\/em> e outras brom\u00e9lias CAM, apresenta caracter\u00edsticas foliares de plantas suculentas e outras adapta\u00e7\u00f5es visando evitar a perda de \u00e1gua. Em fun\u00e7\u00e3o do aumento de secas intermitentes previsto pelo IPCC em seu ambiente natural de ocorr\u00eancia, n\u00f3s hipotetizamos que A. pitcairnioides<\/em> apresente toler\u00e2ncia \u00e0 seca e que o CAM seja um dos mecanismos induzidos nestas condi\u00e7\u00f5es. Tendo em vista que a disponibilidade de \u00e1gua \u00e9 o fator mais limitante para o crescimento e sobreviv\u00eancia das ep\u00edfitas, o presente estudo objetivou avaliar as respostas morfol\u00f3gicas, fisiol\u00f3gicas e metab\u00f3licas de A. pitcairnioides<\/em> \u00e0 seca, assim como as respostas de recupera\u00e7\u00e3o da esp\u00e9cie ap\u00f3s a reidrata\u00e7\u00e3o, simulando um evento extremo de seca com posterior ocorr\u00eancia de chuva. Para tal, plantas cultivadas em casa de vegeta\u00e7\u00e3o foram submetidas a 42 dias de seca por suspens\u00e3o de rega, sendo reidratadas ap\u00f3s esse per\u00edodo. Mesmo com a completa extin\u00e7\u00e3o da \u00e1gua do solo e queda do teor relativo de \u00e1gua da folha para 47%, a esp\u00e9cie foi capaz de tolerar o estresse h\u00eddrico imposto. A seca causou a plasm\u00f3lise do par\u00eanquima aqu\u00edfero, mas n\u00e3o do par\u00eanquima clorofiliano, sugerindo a ocorr\u00eancia de um transporte de \u00e1gua entre esses tecidos, que preservou o aparato fotossint\u00e9tico e o metabolismo da planta. Queda significativa do potencial osm\u00f3tico foliar foi observada somente no 42\u00ba dia de seca, que coincide com as concentra\u00e7\u00f5es aumentadas de importantes osmorreguladores, como sacarose, mio-inositol, galactinol, xilitol e prolina. O ac\u00famulo de acidez titul\u00e1vel, de oxaloacetato e malato refor\u00e7am o metabolismo CAM
\npara a esp\u00e9cie, descrito anteriormente por an\u00e1lises de \u03b413C. Foi observada uma limita\u00e7\u00e3o fotoqu\u00edmica \u00e0 medida que a seca se tornou mais intensa, com diminui\u00e7\u00e3o do conte\u00fado de clorofilas, da m\u00e1xima efici\u00eancia qu\u00e2ntica do fotossistema II e da taxa de transporte de el\u00e9trons aos 42 dias. Entre 28 e 42 dias de seca, foi observado ac\u00famulo de compostos antioxidantes, como caroten\u00f3ides, \u00e1cidos graxos, \u00e1cido asc\u00f3rbico e \u00e1cidos fen\u00f3licos. Embora os experimentos tenham sido conduzidos em casa de vegeta\u00e7\u00e3o, a presen\u00e7a de diversas adapta\u00e7\u00f5es morfofisiol\u00f3gicas e a ativa\u00e7\u00e3o de diferentes mecanismos de prote\u00e7\u00e3o indicam alta toler\u00e2ncia de A. pitcairnioides<\/em> \u00e0 seca e sugerem que a mesma seja capaz de se adaptar e sobreviver \u00e0 intensifica\u00e7\u00e3o de epis\u00f3dios de seca intermitente ao qual a esp\u00e9cie est\u00e1 sujeita em seu ambiente natural.<\/p>\nABSTRACT<\/strong><\/h4>\n
\nstoring carbon, nutrients and water, the latter in the form of fog or rainwater. Although A. pitcairnioides<\/em> is classified as having type C3 photosynthetic metabolism, based on dC13 analyzes (Crayn et al. 2015), the species, in addition to its phylogenetic proximity to A. strobilaceae<\/em> and other CAM bromeliads, presents foliar characteristics of succulent plants and other adaptations aimed at preventing water loss. Due to the increase in intermittent droughts predicted by the IPCC in its natural environment, we hypothesize that A. pitcairnioides<\/em> presents drought tolerance and that CAM is one of the mechanisms induced in these conditions. Considering that water availability is the factor more limiting for the growth and survival of epiphytes, the present study aimed to
\nevaluate the morphological, physiological and metabolic responses of A. pitcairnioides<\/em> to drought, as well as the recovery responses of the species after rehydration, simulating an extreme drought event with subsequent occurrence Of rain. To this end, plants grown in a greenhouse were subjected to 42 days of drought by suspending irrigation, being rehydrated after this period. Even with the complete extinction of soil water and a drop in the relative water content of the leaf to 47%, the species was able to tolerate the water stress imposed. The drought caused plasmolysis of the aquifer parenchyma, but not of the chlorophyll parenchyma, suggesting the occurrence of water transport between these tissues, which preserved the photosynthetic apparatus and the plant’s metabolism. A significant drop in leaf osmotic potential was observed only on the 42nd day of drought, which coincides with increased concentrations of important osmoregulators, such as
\nsucrose, myo-inositol, galactinol, xylitol and proline. The accumulation of titratable acidity, oxaloacetate and malate reinforces the CAM metabolism for the species, previously described by \u03b413C analyses. A photochemical limitation was observed as the drought became more intense, with a decrease in the chlorophyll content, the maximum quantum efficiency of photosystem II and the electron transport rate at 42 days. Between 28 and 42 days of drought, an accumulation of antioxidant compounds was observed, such as carotenoids, fatty acids, ascorbic acid and phenolic acids. Although the experiments were conducted in a greenhouse, the presence of several morphophysiological adaptations and the activation of different protection mechanisms indicate high tolerance of A. pitcairnioides<\/em> to drought and suggest that it is capable of adapting and surviving the intensification of episodes of intermittent drought to which the species is subject in its natural environment.<\/p>\n
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<\/a>Ursula Caroline Salvaterra Batista<\/strong><\/a>
\nRespostas morfofisiol\u00f3gicas e metab\u00f3licas de Acanthostachys pitcairnioides<\/em> (Mez) Rauh & Barthlott (Bromeliaceae) ao d\u00e9ficit h\u00eddrico<\/a><\/p>\n
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