Características morfológicas de frutos, acúmulos de reservas em sementes e aclimatação fotossintética de populações de Myrsine coriacea (PRIMULACEA) ao longo de um gradiente de altitude
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Data
2021-09-01
Autores
Moreira, Vinicius Ferreira
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Universidade Federal do Espírito Santo
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Our objective was to analyze the morphological responses and accumulation of reserve compounds in fruits and seeds of populations of Myrsine coriacea from different altitudes, as well as to evaluate the photosynthetic acclimatization potential of seedlings of the species submitted to contrasting climatic scenarios. The study was conducted in two stages. In the first stage (Chapter 1), the hypothesis is being hypothesized that fruits and seeds of M. coriacea present smaller size and increase in the accumulation of more energy reserves with increasing altitude. For this purpose, fruits were collected from matrices of ten populations along an altitude gradient of 1521 m (639 to 2160 m). After collection, the morphological and biochemical characteristics of seeds and pericarp were determined. Our result showed that fruit size (diameter and dry mass) decreased with increasing altitude. While the pericarp and seed showed greater accumulation of total soluble phenols with increasing altitude, corroborating the hypothesis that fruits and seeds of M. coriacea are smaller and increase in the accumulation of more energy reserves with increasing altitude. In the second stage (Chapter 2), the hypothesis was tested that M. coriacea matrices located at higher altitudes, compared to those at lower altitudes, present seedlings with less capacity for photosynthetic acclimatization under conditions of higher temperature and pressure deficit of steam (high atmospheric demand). For this purpose, seedlings of seven populations of M. coriacea were produced. located along an altitude gradient of 1135 m (639 to 1774 m). Initially, seedlings from the seven populations were cultivated in pots under two contrasting thermal conditions (AD - high atmospheric demand and BD - low atmospheric demand), established in greenhouses (140 m altitude). After four months of cultivation, four individuals from each population cultivated in AD were transferred to BD (ADBD) and vice versa (BDAD), establishing four heat treatments (AD, BDAD, BD and ADBD). Gas exchanges and chlorophyll a fluorescence was determined during 24 h, starting at 04:00 h and measurements were performed at 3 h intervals. Seedlings from all evaluated populations showed the same ability to acclimatize the photosynthetic machinery to heat treatments. The higher altitude population (MAC - 1774 m) showed chronic photoinhibition (lower Fv / Fm ), lower photosynthetic capacity ( A and A g ), higher proportion of energy dissipation in photorespiration in relation to gross photosynthesis ( R p / A g ) and higher oxidative pressure in chloroplasts ( REE / A g ), regardless of heat treatments. In BD, seedlings (BD and ADBD) showed lower stomatal opening (lower gs ) and higher intrinsic water use efficiency ( A / g s ), regardless of population. The results show that populations of M. coriacea located at high altitudes are locally adapted and, under climatic conditions imposed by a scenario of global warming, may be more threatened. We highlight the need to adopt strategies for the preservation and sustainable management of tropical forests due to their greater sensitivity to temperature increases as a result of climate change.
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Compostos fenólicos , estresses , floresta tropical , fotorrespiração , temperatura